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*
/
UNITED STATES DEPARTMENT OF AGRICULTURE
\
FOREST
FIRE
NORTHERN
SBRVICB
CONTROL PLANNING
I N THE
ROCKY MOUNTAIN REGION
BY
L. G. HORNBY
Senior S i l v i c n l t n r i s t
NORTHERN ROCKY MOUNTAIN
FOREST AND RANGE EXPERIMENT STATION
MISSOULA, MONTANA
PROGRESS REPORT
NUMBER I
SEPTEMBER
1936
FOREST FIRE CONTROL PLANNING
IN THE
NORTHERN ROCKY MOUNTAIN REGION
By
L. G. Hornby
The cooperative planning project described in this
report was financed largely by the Division of
Operation, Forest Service, Region One. Development
of planning methods and supervision of plan work on
national forests were in charge of the author, a
staff member of the Northern Rocky Mountain Forest
and Range Experiment Station.
September, 1936
Typical conditions of forest and topography in unburned areas of
the western white pine type.
CONTENTS
Page
Introduction
*
P a r t I . General d i s c u s s i o n of p l a n work, f a c t o r s i n v o l v e d , and r e s u l t s
Preplanning c o n s i d e r a t i o n s . . . . .
D e s c r i p t i o n of r e g i o n
•
P e r s o n n e l problem i n f i r e c o n t r o l
•
F u e l s and a f u e l - r e d u c t i o n program
F i r e - c o n t r o l o b j e c t i v e s and a c t i o n r e q u i r e d
Economic, o r l e a s t P • S •+• D o b j e c t i v e
Permissible—percentage-of—burned-area o b j e c t i v e
O b j e c t i v e of c o n t r o l wf.tb.in t b e f i r s t work—period
C o n s i d e r a t i o n s i n a p p l i c a t i o n of o b j e c t i v e . .
I n f l u e n c e o f i n t e n s e a c t i o n on c o s t , damage, and a r e a burned
General
O b j e c t i v e adopted i n p l a n n i n g
P l a n n i n g t b e f i r e — c o n t r o l system
Services necessary
Fire prevention.
P e r s o n n e l management
Fire-danger forecasting
Action on f i r e s
Fuel r e d u c t i o n
Research
Loads f o r which t o p r e p a r e
Peak l o a d s
Annual number of f i r e s and a r e a burned
A b i l i t y to carry l o a d s
Annual i n c r e a s e s i n f i r e - c o n t r o l c o v e r a g e s
F a c t o r s of personnel e f f i c i e n c y
Speed of a c t i o n
R a t e s of work
Number, u s e , and h o u s i n g of temporary f o r c e
Training in f i r e control
F i e l d work
Mapping seen—areas, road r o u t e s , and v a l u a t i o n zones
Mapping f u e l s
S t a n d a r d s adopted and t h e i r b a s e s
P r e p a r e d n e s s f o r worst c o n d i t i o n s .
Dual r e s p o n s i b i l i t i e s of firemen and crews
M u l t i p l e u s e s of roads
V i s i b i l i t y d i s t a n c e and seen—area.
T r a v e l t i m e and s t r e n g t h of a t t a c k ( T r a n s p o r t a t i o n p l a n n i n g )
Heavy r e i n f o r c e m e n t s e r v i c e . . . , .
Light reinforcement s e r v i c e
I n i t i a l a t t a c k (Smokechasing s e r v i c e )
ru
j
^
2
5
X9
x5
xg
±>j
2.8
3x
33
3a
a6
a6
•
27
27
27
27
27
27
28
28
28
28
32
33
33
38
38
38
44
44
49
49
49
56
56
56
57
57
60
61
6a
63
Page
Methods of
s e l e c t i n g man—power l o c a t i o n s
and r o a d s
68
S i l h o u e t t e s of coverage
_
7^
S e e n - a r e a s i l h o u e t t e s and c o m p o s i t e s .
Smokechaser s i l h o u e t t e s
Reinforcement
<7!
and c o m p o s i t e s
71
coverage composites
7^
R e l a t i v e danger r a t i n g s
Fuels worse than average
75
76
T e n - y e a r o c c u r r e n c e map
Damage v a l u a t i o n s
77
77
Coverage according to burning c o n d i t i o n s
78
Coverage in
79
relation
Detection
t o number o f
s t a t i o n s manned
coverage
79
Smokechasing and g r a d a t i o n i n t o l i g h t
Completeness of coverage
Prot ection
Summary
Part I I .
that
reinforcement
coverage
80
83
corresponds with danger
84
87
D e t a i l e d p r o c e d u r e s i n p l a n work
I n s t r u c t i o u s for
Selection
89
f u e l - t y p e mapping
89
and t r a i n i n g o f m a p p e r s
89
F u e l s and c o n d i t i o n s c o n s i d e r e d
Rate of spread.
90
91
I n f l u e n c e of t r e e o r brush cover
I n f l u e n c e o f s l o p e and t o p o g r a p h i c
Influence of f o r e s t type
I n f l u e n c e of p r e v i o u s b u r n i n g ,
9X
94
shelter
cutting,
95
97
a n d blow—down
Resistance to control
98
S t a n d a r d r a t i n g s of 43 t y p i c a l
conditions
99
Legend end i l l u s t r a t i o n s
104
Scale....
104
Field
suggestions
104
Current posting
105
R a t e and c o s t o f m a p p i n g
X05
Inspection
Instructions
Potential
«
for
detection
Definition
Number o f
105
seen—area mapping.
of
109
s t a t i o n s from w h i c h t o map
"detection
109
station"
109
stations
I n f l u e n c e of f o r e s t
xio
type
xio
I n f l u e n c e o f t o p o g r a p h y and v i s i b i l i t y . . . .
110
I n f l u e n c e of smokechaser t r a v e l time
Influence of frequency of f i r e , f u e l s ,
1x1
xn
and v a l u e s
Road p a t r o l s t a t i o n s . . .
P r e p a r a t i o n s f o r f i e l d work
ij.1
11a
P o t e n t i a l — p o i n t s map and b a s e map
11.2
W r i t t e n i n s t r u c t i o n s t o mappers
Equipment
O r g a n i z a t i o n , p e r s o n n e l , and t r a i n i n g
F i e l d work.
Methods of mapping seen a r e a s
Mapping from t r e e t o p s
••••
>
IV
•
•
xia
1x2
X13
113
X13
xxs
Page
13X1^
Mapping s c a l e and s y m b o l s
A c c u r a c y and r e f i n e m e n t o f n a p p i n g
P e r p e t u a t i o n o f napping s t a t i o n s
lx
R e c o r d o f c o n d i t i o n s a t t i m e o f mapping
xx8
P r o g r e s s map
•••
C o l l e c t i o n o f improvement p l a n d a t a . ,
xx8
Xx8
F o l l o w - u p work a t s i t e s c h o s e n f o r o c c u p a n c y
Check o f
o b s e r v a t o r y h e i g h t and l o c a t i o n . . .
xxo.
xxo
Scheduling p a t r o l s for g r e a t e s t
efficiency
xxg
S u p e r v i s i o n and i n s p e c t i o n
R a t e and c o s t o f seen—area mapping. . . » „
...
Method o f
Initial
Current
action
2.96
reinforcement
determining allowable travel
attack
X35
X35
(Small crew a c t i o n )
Method o f w o r k i n g o u t l i g h t
coverage
x«7
times
x«8
(Smokechaser a c t i o n )
132
a c c o r d i n g t o s i z e and a g g r e s s i v e n e s s o f f i r e .
R e l a t i o n s between t r a v e l
l a a
l g a
D e t a i l s of transportation planning
Heavy r e i n f o r c e m e n t s (Heavy s e c o n d l i n e d e f e n s e ) . .
Light reinforcements
g
t i m e , man p o w e r ,
X3«
and f u e l . . .
132
Night at tack s
X33
Midday a t t a c k s
133
D e r i v a t i o n o f t r a v e l t i m e formul a
Application of
Contents of p l a n s .
Part I I I .
Statistics
travel
X35
time formula
for individual
137
•
forests
national
and o t h e r s u p p o r t i n g d a t a . . .
R e l a t i o n b e t w e e n f i r e p e r i m e t e r and a r e a .
148
j.50
X75
Literature cited
X73
TABLES
PART I
T a b l e x*
A v e r a g e f l o w and d r a i n a g e a r e a o f C o l u m b i a R i v e r and t r i b u t a r i e s
r e l a t i o n to national
in
f o r e s t s o f R e g i o n One
6
Table 3.
Land u s e and p o p u l a t i o n i n r e g i o n
studied
Q
Table 3.
P l a n t s p e c i e s i m p o r t a n t from t h e s t a n d p o i n t o f f i r e
control
commonly
found i n timber t y p e s o f w e s t e r n f o r e s t s o f Region O n e . . .
Table 4.
F o r e s t — t y p e a r e a s i n w e s t e r n f o r e s t s o f R e g i o n One:
t o t a l s b u r n e d i n xoax—30, and t o t a l
Table 5.
Numbers o f f i r e s ,
suppression
totals
xx
existing,
burns p e r m i s s i b l e
costs,
xo
and a c r e a g e s b u r n e d on w e s t e r n
f o r e s t s o f R e g i o n One i n x o a i ~ 3 0 and i n xj)3x~33
Table 6.
S u p p r e s s i o n t i m e and c o s t s ,
and a c r e a g e s o f f i r e s on w e s t e r n
o f R e g i o n One i n x o a x - 3 0 and i n xo3X — 33
T a b l e 7.
Number o f man h o u r s u s e d t o c o r r a l
One i n
T a b l e 8«
forests
•
f i r e s on w e s t e r n f o r e s t s o f
25
Region
X931-30 an* i 9 3 i ~ 3 3 * • • •
Average i n i t i a l
in IQ34J
T a b l e Q.
25
kv- f u e l
rates of fire
41
s p r e a d i n w e s t e r n f o r e s t s o f R e g i o n One
classification
54
Time a l l o w e d l i g h t — r e i n f o r c e m e n t
crews f o r assembly p l u s t r a v e l
b u r n i n g c o n d i t i o n s a r e "maximum".
V
when
63
Page
Values used i n t r a v e l - t i m e formula f o r "maximum" c l a s s o f burning
c o n d i t i o n s corresponding t o c l a s s 5 of t h e Danger Meter
65
Smokecha3er t r a v e l time and number o f men required i n i n i t i a l attack
f o r i n d i c a t e d f u e l types when burning c o n d i t i o n s are "maximum".......
66
Smokechaser t r a v e l times required i n i n i t i a l a t t a c k , f o r i n d i c a t e d
f u e l t y p e s , when burning c o n d i t i o n s are "average"
66
Coverage? made p o s s i b l e by roads, t r a i l s , and l a n d i n g f i e l d s i n
westfc.n f o r e s t s of Region One
74
Table X4-
Percentage of f u e l s worse than average in each western national f o r e s t of Region One c o v e r e d hy each s e r v i c e of f i r e c o n t r o l as planned
for '•maximum" burning c o n d i t i o n s . ,
85
Table xs«
Form used in summarizing c o s t s o f f i r e
88
Table
10«
Table
n.
Table i a .
Table 13.
control
PART I I
Table 17*
Table
x 8-
Moisture content of wood c y l i n d e r s and r a t e of wind movement accord-r
ing to d e n s i t y of timber stand, at P r i e s t Fiver Experimental F o r e s t . .
ga
C l a s s i f i c a t i o n of 43 fuel c o n d i t i o n s , t y p i c a l for the northern Rocky
Mountain region, as to probable r a t e o f f i r e spread and probable
r e s i s t a n c e o f f i r e to c o n t r o l
ioo
Table 19"
Number of men needed in n i g h t reinforcement action to c o n t r o l i n a c t i v e
f i r e s of d i f f e r e n t s i z e s before xo 01 clock of t h e next forenoon
X3X
Table
SO'
Number o f men required f o r vidda.y a t t a c k s according t o t r a v e l time and
f u e l c o n d i t i o n s when danger meter r a t i n g at f i r e i s the average o f
c l a s s 4. . . . . . . . . . . . . . . . . . .
X45
Table
3X«
Number of men required for midday a t t a c k s according t o t r a v e l time and
f u e l c o n d i t i o n s when danger meter r a t i n g at f i r e i s the average of
cl a s s 5
146
Number of men required for midday a t t a c k s according to t r a v e l time and
f u e l c o n d i t i o n s when danger meter r a t i n g at f i r e i s the average o f
class 6
•
• •.•
••
147
Table
PART I I I
Table 23.
Timber type acreages i n i n d i c a t e d n a t i o n a l f o r e s t s
151
Table 34,
Actual area burned, allowable burn and d i f f e r e n c e by t y p e s for
i n d i c a t e d national f o r e s t s .
15;
Table
ac.
Allowable
forests.
153
Table
a 6«
Area burned, and a l l o w a b l e burn i n each timber type and year i n
i n d i c a t e d national f o r e s t s
154
Hen a v a i l a b l e , s t a t i o n s , housing o f firemen s t a t i o n s ,
teaiporary personnel
, , -.
x6a
Table 37.
burn in xo years by timber t y p e s for i n d i c a t e d n a t i o n a l
and u s e o f
Table
2 8«
Total f o r c e s Brat****!*, inc.! .idijig C i v i l i a n Conservation Corps men, i n
seasons 7.933-35- . . . . . . .
Table
ag.
Total f o r c e s a v a i l a b l e , e x c l u s i v e o f C i v i l i a n Conservation Corps men,
i n season.? igsrt.—35* •
••
•
VI
•
163
164
Page
T a b l e 30*
Table 3 1 .
Table 33.
R e g u l a r temporary f i r e — c o n t r o l f o r c e p r o v i d e d f o r b u r n i n g c o n d i t i o n s
c l a s s e d as average
R e g u l a r firemen p r o v i d e d i n each y e a r of p e r i o d 1991-31
c o n d i t i o n s c l a s s e d as a v e r a g e
x6s
for burning
166
S t a t i o n s o c c u p i e d by firemen when b u r n i n g c o n d i t i o n s were c l a s s e d as
a v e r a g e i n 1921-31 and i n i934~35
167
Table 33.
Fireman s t a t i o n s a t which d w e l l i n g s were p r o v i d e d i n 1921-30 and 1934—
T a b l e 34.
35
Emergency g u a r d s employed i n 1921-35.
168
169
Table 35.
Men i n p r o j e c t crews a v a i l a b l e f o r f i r e duty i n 1921-35
170
T a b l e 36*
P r o j e c t crews a v a i l a b l e f o r f i r e duty i n 1921-31
Table 37.
T o t a l s t a t i o n s o c c u p i e d f o r any k i n d of work
173
Table 38.
P e r i m e t e r of f i r e c o r r e s p o n d i n g with a r e a e n c l o s e d
X76
•
••
171
FIGURES
PAET I
F i g u r e 1,
A.
B.
C.
F i g u r e 3*
Burned a r e a and two i m p o r t a n t i n f l u e n c e s
Figure 3.
I n f l u e n c e of i n t e n s i t y of a t t a c k on s u p p r e s s i o n t i m e and on a v e r a g e
c o s t and acreage p e r f i r e
23
I n c i d e n c e of c o n s p i c u o u s l y s e v e r e s e a s o n s i n 1903-34* i n c l u s i v e ,
peak l o a d s o f l i g h t n i n g f i r e s 1921-30
•
30
F i g u r e 4.
N a t i o n a l f o r e s t s and l a r g e f i r e s
P r o f i l e of region
V e a t h e r s t a t i o n s and minimum p r e c i p i t a t i o n s of July—August i n c h e s .
7
7
7
^
and
Figure 5.
lightning—fire concentration areas.
31
F i g u r e 6*
Man-caused f i r e s . Number, and t o t a l a c r e a g e b u r n e d , by c a u s e i n each
y e a r o f p e r i o d 1910— 34> i n c l u s i v e
34
Man—caused, l i g h t n i n g , and t o t a l f i r e s .
year
35
F i g u r e 7.
F i g u r e 8»
Development
A. Seen by
B. Reached
C. Reached
Number, and a c r e s burned p e r
of c o v e r a g e s
d e t e c t o r s of average season o r g a n i z a t i o n
by smokechasers, a v e r a g e - s e a s o n t r a v e l s t a n d a r d s
i n 6 . 5 h o u r s from c i t i e s of over 9000 p o p u l a t i o n
1910 t o 1933
36
36
36
F i g u r e 9.
Development of a c c e s s i b i l i t y ,
F i g u r e io»
F i r e c o n t r o l o p e r a t i o n s completed w i t h i n p e r i o d s i n d i c a t e d
40
Figure n .
R a t e s o f work a c c o r d i n g t o age and d e n s i t y of s t a n d . . .
43
F i g u r e 12*
Number o f men a v a i l a b l e f o r f i r e d u t y
45
Figure 13.
Man power, s t a t i o n s , and housing" of r e g u l a r f i r e - c o n t r o l f o r c e
46
F i g u r e 14.
Uses of r e g u l a r temporary f o r c e
A. P e r c e n t a g e of f o r c e u s e d f o r o v e r h e a d and s e r v i c e of supply
B. Average number of firemen p e r s t a t i o n
47
47
VII
37
Page
48
F i g u r e \$.
Fire control training record......
F i g u r e x6«
F i e l d f u e l map
gx
F i g u r e x6 - A.
F u e l s i n burned a r e a s
Fuel of high, r a t e o f s p r e a d and h i g h r e s i s t a n c e t o c o n t r o l i n t h e
western white p i n e type
3 . Fuel of h i g h r a t e of s p r e a d and extreme r e s i s t a n c e t o c o n t r o l i n
t h e c e d a r , hemlock, w h i t e f i r t y p e
53
x.
_B
F i g u r e x6 «
x«
3.
Flashy f u e l s
G r a s s on g e n t l e s l o p e i n p o n d e r o s a p i n e t y p e
Continuous c h e a t g r a s s
53
55
55
F i g u r e x7«
D i s t r i b u t i o n of f i r e s as t o s i z e and i n i t i a l r a t e o f s p r e a d .
64
F i g u r e x8«
I n i t i a l r a t e s of s p r e a d i n d i f f e r e n t
69
F i g u r e xo«
I n i t i a l r a t e s of s p r e a d as c l a s s i f i e d f o r p l a n n i n g p u r p o s e s
F i g u r e 30•
D e t e c t i o n coverage
A. Method of s o r t i n g seen—area s i l h o u e t t e s
B. P e r c e n t a g e o f c o v e r a g e o b t a i n e d a c c o r d i n g t o number o f s t a t i o n s
manned p e r m i l l i o n a c r e s
Smokechasing c o v e r a g e of f u e l s worse t h a n a v e r a g e a c c o r d i n g t o
s p a c i n g of man—power s t a t i o n s
F i g u r e 3X«
timber types
70
73
73
83
PART I I
Figure 33.
Average h o u r l y w e a t h e r r e a d i n g s d u r i n g week August xo—x6> 1031*
a c c o r d i n g t o d e n s i t y of t i m b e r s t a n d
g3
Figure 33.
B r a c k e t f o r f a s t e n i n g map board t o t r e e t o p
xx7
Figure 34.
Method f o r d e t e r m i n i n g l o c a t i o n and e l e v a t i o n of l o o k o u t
X31
Figure 35.
Method of d e t e r m i n i n g t r a v e l t i m e s f o r l i g h t r e i n f o r c e m e n t crews
X39
F i g u r e 36.
R a t e of work and c o r r e s p o n d i n g t r a v e l t i m e l i m i t s r e q u i r e d t o c o n t r o l
f i r e s o f i n d i c a t e d r a t e s of s p r e a d
X36
"1°ure
Number of men and c o r r e s p o n d i n g t r a v e l time l i m i t s r e q u i r e d t o c o n t r o l
f i r e s of i n d i c a t e d r a t e s of s p r e a d and r e s i s t a n c e s t o c o n t r o l . . . . . . . .
X39
a
^*
F i g u r e z&,
A.
B.
C.
I n f l u e n c e of crew s i z e on r a t e of work.
I n f l u e n c e of r a t e of s p r e a d on r a t e of work
P e r c e n t a g e o f f i r e s t h a t o c c u r r e d i n f u e l s of e x t r e m e , h i g h ,
medium, and low r a t e of s p r e a d c l a s s i f i c a t i o n s
X43
X4a
X4«
PART I I I
Figure
ag.
F i g u r e 30^
F i g u r e 3x«
Days of J n l y and August x92i—25* i n c l u s i v e , on which xo o r more
l i g h t n i n g f i r e s o c c u r r e d i n one o r more o f t h e i n d i c a t e d n a t i o n a l
forests.
X55
Days o f J u l y and August X9«6~30j i n c l u s i v e , on which xo or more
l i g h t n i n g f i r e s o c c u r r e d i n one o r more of t h e i n d i c a t e d n a t i o n a l
forests.
•
•
X56
Discoveries within x hour in i n d i c a t e d n a t i o n a l f o r e s t s ,
inclusive.
*«.«
..
•
X5?
VIII
X931— 34*
Page
Figure 33. Reports within 15 minutes in indicated national forests, 1991—34,
inclusive
•
...»
Figure 33.
Figure 34.
Figure 35.
Figure 36.
^g
Get-aways within 5 minutes in indicated national f o r e s t s , 1931-34,
inelttaire.
159
Travel times within 3 hours, in indicated national forests, 1931—34,
inclusive
x6o
Fires corralled within 1 hour and within 34 hours, in indicated
national forests, 1931—34, inclusive
x 61
Perimeter of f i r e corresponding with area enclosed
x^g
IX
I
INTRODUCTION
In the northern Rocky Mountain region a high degree of protection
from fire is necessary to perpetuate forest yields and communities industrially dependent upon them. On rugged and inaccessible areas a green,
healthy forest cover is needed for recreation, erosion control, and regulation of water resources. Immense conflagrations continue to challenge the
forester. In this and other forest regions of the United States fire conditions have been analyzed and the analyses have been made the bases of
systematic planning to reduce burned acreage.
As systematic planning naturally followed the collection and examination of evidence, the literature on results of forest fires is older
and more voluminous than that on satisfactory forest fire control measures.
The earliest compilation of forest fire statistics for the whole United
States was made by C. S. Sargent for the year 1880 and was published in
the Tenth Census. Later census reports by decades were made by the
Division of Forestry. Plummer (15) 1/, writing the third decade report in
1912, listed the well-known years and localities of great drought and heat
in the United States beginning with 1662, and in Europe beginning with
1303. He gave the date, size, and location of twenty-one "historic" fires
of the United States and Canada (1800-1910 inclusive), the ten largest of
which ranged from 450,000 to 3,000,000 acres 2/. Writing also in 1912,
Adams (1) gave considerable information on methods of fire prevention and
suppression, much of which has not become obsolete.
In 1914 Dubois (5J published for the use of forest officers in
California a comprehensive treatise on all phases of fire-control planning, giving Roy Headley particular credit for assistance. He assigned
the duties of detection and initial attack to separate units of organization, discussed distribution of fire-control personnel in relation to
localities of high danger, and advocated giving every forest area an integrated danger rating. He did not propose any method of combining the factors of frequency and occurrence, character of fuel, and damage. In the
work described here an integration of these factors was made and applied
to planning.
Publications of Show and Kotok (16, 17, 18), issued in 1923-29, present findings as to the nature of the fire-control problem in California
for different forest types and discuss the objectives of fire control.
j
A/
Italic numbers in parentheses refer to Literature Cited, P- 173*
2/
whether these large fires developed from one or several small fi
is not stated by Plummer.
2
FIRE CONTROL PLANNING—NORTHERN ROCKY MOUNTAIN REGION
These authors credit Roy Headley 3/ with originating the concept of the
minimim-cost objective (least total cost of presuppression, suppression
and damage, called "P+ S + D"), which he described in the California
regional suppression manual of 1916. In 1924 they advocated (ij) a
minimum-damage objective, and in 1929 they stated (18) that the maximum
damage allowable is burning of 0.2 percent of the region's area per year.
In 1930 the Washington conference of regional foresters accepted (22) the
theory of a maximum allowable percentage of burned area per year and set
up such an objective for each forest type of the United States. In 1930
Show and Kotok announced (ig) standards of detection and travel-time
allowance for initial attackers (designated by them as "hour control")
for each California forest cover type.
In 1930 Norcross and Grefe (14) worked out a method of determining
the least cost of providing firemen and roads (or trails) that would
satisfy travel-time requirements. This method was applied in a large
amount of planning for the national forests of California, in which the
locations of detectors were assumed to be unrelated to the locations of
initial attackers and their road facilities. This method is inapplicable
where the combined duties of detection and initial attack are assigned to
the personnel of every station. For this reason it was not usable, except
as a partial guide, in national forests of Oregon and Washington. In the
northern Rocky Mountain region it was not used.
From the beginning of systematic planning in every region, it has
been advocated that fire-control organizations be increased and decreased
during the fire season according to number of fires to be fought and
severity of burning conditions. In 1931, in developing methods of planning under the project described here, several degrees or steps of preparedness were specified to correspond with degrees of danger. It was evident that only through combining all factors of danger into a single rating for a particular day and locality could the corresponding degree of
preparedness be put into effect in widely separated localities. In 1928
Gisborne (8) described methods of measuring separately some of the factors
of danger. In the years 1932-1934 he developed (gt 10) a "fire danger
meter" that integrated probable combinations of factors into seven classes
of danger corresponding to the steps in preparedness being used in firecontrol planning. As a guide to judgment the "danger meter" was increasingly relied upon, and in 1935 its use by forest officers in Region One
was required. The term "danger" has been used inconsistently. The number of factors included has varied, and the important factor of probable
damage, although it influences current practices, has not been recognized
in a systematic way either in current or long-period plans.
a/
About 1317 this objective was developed independently by Elers Kocn in
the northern Rocky Mountain region, District One of the Forest Service.
INTRODUCTION
3
In the northern Rocky Mountain region fire-control research and
planning, expansion of fire-control organization, and speed and strength
of attack on fires developed rapidly, with increasing appropriations,
after the disastrous season of 1910. Each of the succeeding severe seasons 1914, 1919, 1926, 1929, 1931, and 1934 stimulated analysis, which in
each case brought about restatement of requirements. In 1931 a study
more comprehensive than any of its predecessors was instigated by Regional
Forester Kelley and was undertaken by Gisborne and Hornby t±J on the basis
of a ten-year accumulation of detailed facts begun in 1920. The results
of this study have guided the more complete planning of a desired firecontrol system than was attempted previously.
Logically, fire-control plans are formulated for periods of five
or ten years and for the current year. This report deals with periodic
plans. More specifically it deals with the location and quantity of man
power and the facilities required. Commonly recognized facilities for
satisfying requirements as to speed and strength of attack include roads,
trails, landing fields, means of communication, towers and other structures, as well as equipment and supplies. The Forest Service construction program of the region involving several million dollars worth of
fire-control improvements was based to a large extent on the planning
described here.
Although fire-control planning is not new, the methods described
here are original in several respects. Requirements for detection were
correlated with those for initial attack. A road system was designed to
satisfy the combined needs of initial attack, light reinforcement, and
heavy reinforcement with the least expense. So far as authority delegated to the planners permitted, the road requirements of general administration and utilization of forest products were correlated with firecontrol needs. Other new features were the mapping of fuels according to
probable rate of spread and resistance to control, and the use of classes
of fuel rather than general cover types to determine requirements of
speed and strength of attack. Man-power locations and road locations
were selected through sorting combinations of individual coverage silhouettes over glass-top tables lighted from beneath. The integration of
all danger factors into ratings of areas was used for the first time.
One of the most important and satisfactory developments was that five
years of plan work, 1931-35, covering 15 million acres, was consumated
by actual construction, to a large extent without change. Equally
valuable is the training of men in systematic methods of procedure. The
supervisor of every forest and more than 100 other men of the region
participated actively in the plan work. These men will continue to substitute analyzed facts for personal opinions and to recognize necessary
interrelations among all the factors of fire control, and will carry
this analytic habit into other work.
Fire Control Objectives and Practices in the Northern Rocky Mountain
Region, x93i.
Unpublished-
H
FIRE CONTROL PLANNING—NORTHERN ROCKY MOUNTAIN REGION
This presentation of f i r e facts and planning procedures i s regarded
as a report on progress up to the dates shown. In several cases the data
c o n s t i t u t e the only records available of conditions existing in the e a r l i e r
years. In order to determine trends data were compiled to as early a year
as dependable records permitted. Such charted trends do not become obsol e t e , in f a c t , if entered currently as contemplated, they provide a continuously improving guide to action. Although data have been entered in a
few of the t a b l e s and charts to 1934, i n c l u s i v e , a more complete analysis
to determine the continuation of trends since 1931 i s needed.
I t i s necessary to recognize that through the l a r g e increases in f i r e control effort put into effect during recent years additional measures and
costs of preparedness have been spread over a very large area for the purpose of catching the occasional d i f f i c u l t f i r e s that previously escaped from
i n i t i a l a t t a c k s . Thus, the opportunity for obtaining a reduction of burned
area proportional to increased expenditures has continually become l e s s and
l e s s , and small gains now are as i n d i c a t i v e of efficiency and progress as
large ones were in the e a r l i e r years of f i r e c o n t r o l . Under these condit i o n s , current i n v e s t i g a t i o n s and analyses for the purpose of determining
the most e f f i c i e n t procedures rank in importance with the measures of p r e paredness and control put into effect.
In considering the contents of t h i s report and the p r a c t i c a b i l i t y of
applying the methods described, i t should be kept in mind that experience
has been made the b a s i s for drawing conclusions. After working with f i r e control f a i l u r e s , and some successes, for 20 years, the a u t h o r ' s approach
i s that of endeavoring to show s p e c i f i c methods that have a chance of being
successful and are s t i l l economically j u s t i f i a b l e .
5
PART I
GENERAL DISCUSSION OF PLAN WORK,
FACTORS INVOLVED, AND RESULTS
PREPLANNING
CONSIDERATIONS
DESCRIPTION OF REGION
The information presented here applies to the 23 million acres of
forest land lying in Montana west of the Continental Divide, in Idaho
north of the Salmon River, and in Washington east of the Pend Oreille
River. The analyses of experience apply specifically to the 16 million
acres of this region protected from forest fires since 1906 by the Forest Service of the United States Department of Agriculture. Figure 1, A,
shows the geographical position of the protected areas. Throughout this
publication, these protected areas are referred to as "western forests of
Region One."
The national policy that for many years governed the disposal of
public-domain lands resulted in private ownership of the most productive
and most accessible timberlands of the region. This left only the more
remote and rugged forest areas for national forests. With the reverse
ownership trend now well under way, owing to tax delinquency and to gifts
and sales of cut-over land, public responsibility for fire control is
increasing in the localities where forest soils are of highest value.
In general, the region consists of forest-covered mountains rising
higher and more ruggedly eastward to the Continental Divide from the
Columbia plateau, the major part of which is in Oregon and Washington.
Altitudes range from 700 feet on the Snake River, at Lewiston, Idaho, to
10,000 feet on peaks of the Bitterroot Range and Continental Divide.
Figure 1, Bt shows a profile of the region from southwest to northeast in
the direction of prevailing winds.
The headwaters of the following large tributaries of the Columbia
River lie entirely or partially within the region; Kootenai, Clark's Fork,
Flathead, Spokane, Clearwater and Salmon. Table 1 shows rough approximations of the average discharge of each of the larger rivers and their
drainage areas. These data were collected by Regional Forester Kelley in
1935 f° r use as a guide in determining the importance of national forest
areas is regulating streamflow, erosion, and silting of navigable streams
within the Columbia Basin. The table shows the approximate drainage area
of each stream that lies within the indefinite limits of Region One
territory, the portion that lies within the exterior boundaries of national forests, and the percentage this last area is of the Columbia River
drainage area that lies above the Dalles. The large area, and influential
I though small) percentage, that lies within national forests of other
regions was not determined, but is included in the figures of column five.
e boundaries of
on One forests
: Percent of Colum; bia drainage area
FIRE CONTROL PLANNING—NORTHERN
T3
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FIRES LARGER THAN 10,000 ACRES, 1911-34 •
NATIONAL FORESTS UNDER CONSIDERATION
12000 Ff.
II 0 0 0
10000 £
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FORESTED
NON-FORESTED
PROFILE ALONG LINE A - B
WEATHER STATION AND ABSOLUTE MINIMUM PRECIPITATION OF JULY-AUGUST IN INCHES
FIGURE I
A -
NATIONAL
B-
PROFILE
C-WEATHER
FORESTS
OF
AND
LARGE
FIRES
REGION
STATION AND M I N I M U M
OF J U L Y - A U G U S T
IN
INCHES
PRECIPITATION
©
DESCRIPTION OF REGION
8
When studying these data it is essential to keep in mind that much
more precipitation falls within the forested portions of the Columbia
Basin than in the much larger unforested portions. Also, forests defer
the date of peak discharge through shading winter accumulations of snow
and retaining in the ground large amounts of water that percolate slowly
into stream channels. For these reasons, the 12.2 percent of area contained within the national forests of Region One exert influences immensely greater than indicated by area comparisons. The relative discharges
from forested and unforested drainages are not known.
Although mining is a very important industry of the region and
uses large amounts of timber in certain localities, very little acreage is
occupied by its widely scattered activities, except in the vicinity of
Wallace and Kellogg in Idaho, and Butte and Anaconda in Montana. Agriculture is highly developed only in scattered and relatively narrow intermountain valleys. The largest continuous strip of agricultural land, that
including the Bitterroot, Missoula, and Flathead Valleys, has a length of
approximately 150 miles and irregular widths up to 30 miles. As is shown
by table 2, two-thirds of the regional area is better suited to forest and
recreational uses than to general farming and grazing, the other land uses
occupying considerable areas.
Climate and weather vary extremely. Average annual precipitation
at weather stations, all of which are at the lower altitudes, ranges from
20 to 40 inches. Probably the average at the higher altitudes is in the
neighborhood of 60 inches. July and August cover the critical part of the
fire season. In this period precipitation is less than half of normal 30
to 60 percent, of the time (21 )> Within every block as large as a 20-mile
square, the worst conditions of wind and drought that have occurred in any
other such block must be expected. Figure 1, C, shows the minima of precipitation recorded for the July-August period at weather stations well
distributed over the region. The highest minima, 0.55 inch and 0.70 inch
(those for certain areas near Glacier National Park), are far below the
quantity that can appreciably influence large runs of fires. Proof lies
in the fact that fires burning 30,000 to 100,000 acres each have occurred
around or near the stations where these minima were recorded. Figure 1
A, shows that fires larger than 10,000 acres have occurred in all parts
of the region, in spite of organized fire-control efforts.
From October to April snow covers a large part of the land in the
region that is higher than 5,000 feet. Average annual snowfall ranges
from 60 to more than 200 inches unmelted (21).
Owing to the absence of
habitations where the larger quantities of snow fall, the records available are too meager to be of much value in determining any relations that
may exist between the snowfall of a given winter and the stream flow or
burning conditions of the following fire season.
FIRE CONTROL PLANNING—NORTHERN ROCKY MOUNTAIN REGION
Table 2 .—Land use and population
in region studied
1/ 2/ •
LAND USE
Forest and -recreational
Other
Total
:
Million
acres
j
19.5
9.0
:
28.5
:
Percentage
of area
68
32
:
100
POPULATION
Locat ion
Within region
Rural areas, and c i t i e s smaller than
3,000 3 /
C i t i e s largei- than 3,000
Total
C i t i e s l a r g e r than 9,000 - ' within
130 miles of region v i a ]road
:
:
Population
Number
: Percent
:
:
144,164
44,562
:
188,726
:
•
217,568
:
:
76
24
100
406,294
Grand t o t a l
Cities ^ l a r g e r t h a n 9,000
7/ithin region
Missoula
Adjacent
Spokane
Lewiston
Butte
Anaconda
Helena
Great F a l l s
Total
:
;
:
14,657
;
115,514
9,403
39,532
12,494
11,803
28,822
;
j
;
j
232,225
:
1/
Boundaries of region a r e shown in f i g . 1 .
2/
Data from U. S. Forest Service land-use study made i n 1934 and
from U. S. Census of 1930. Data are for whole counties lying
e n t i r e l y or p a r t l y v/ithin the region.
3/
Existing c i t i e s f a l l n a t u r a l l y into c e r t a i n size class groups.
The ranges of such groups were used.
4/
Locations of c i t i e s l i s t e d are shown in f i g . 1 .
DESCRIPTION OP REGION
10
Severe lightning storms are normally to be expected between June
15 and September 15. If fuels have previously been dried to such a
dsgree that they are inflammable, such storms frequently start large numbers of fires. (This subject is further discussed under the heading
"Peak Loads. ")
Tree species, forest types, age classes, and fuel conditions are
highly intermixed, particularly where the older classes predominate.
Fires are responsible for a great deal of this intermixture. The standard
classification of timber types, and the plant species most important from
a fire-control standpoint that are commonly found in each, are shown by
table 3.
The region contains approximately 16,000 million board feet of merchantable western white pine, which constitutes 65 percent of the existing
timber of this species and 18 percent of the white pine of all species in
the United States. For lumber production this species has been, and
probably will continue to be, the most valuable in the region. Ponderosa
pine occupies a position of intermediate value between western white pine
and the other timber species, the present stumpage values of which, even
near main routes of transportation, are very low, or negative. In the
form of poles western red cedar has about the same value per unit of volume as the lumber of western white pine, and the species, though constituting only a small part of any extensive stand, is more widely distributed
through the region.
Although pure stands do not occupy large areas in the region, each
of the trees listed in table 3 except western red cedar predominates over
a considerable area in some part of it. Western red cedar invariably
develops in the shelter of associated trees, which may be of any species
occurring in the region. In considering fire control in the western white
pine type, it is necessary to bear in mind that only 15 percent of white
pine, by volume, is required to classify a stand as of this type. Frequently the majority of trees in a mature stand of the white pine type are
of other species. In various mixtures, the species associated with white
pine may be any of the trees listed except mountain hemlock and whitebark
pine. Within a white pine area of only a few acres it is not unusual to
find most of this species' common associates.
The frontispiece shows typical conditions of forest and topography
in the western white pine type. Conditions on burned areas are discussed
on page 15 and under Fuel Mapping, illustrations are shown in figure 16-A.
II
FIRE CONTROL PLANNING—NORTHERN ROCKY MOUNTAIN REGION
Table 3.—Plant species
important from the standpoint
of fire
xj commonly found in timber types of western forests
Region One.
Common name
Trees
Western white p i n e
Ponderosa p i n e
Lodgepole p i n e
Whitebark pine
Western l a r c h
Douglas f i r
Lowland w h i t e f i r
Alpine f i r
Engelmann spruce
Western hemlock
Mountain hemlock
Western r e d cedar
Shrubs
Ceanothus
Huckleberry
Nine bark
Ocean spray
Service-berry
Rocky mountain maple
Willow
Alder
Menzezia
Yew
Grasses
Cheatgrass
Others
Tree Moss
Staghorn l i c h e n
2/
Timber Type Zj
S c i e n t i f i c name
P i n u s monticola
P i n u s ponderosa
Pinus contorta
Pinus a l b i c a u l i s
Larix occidentails
Pseudotsuga t a x i f o l i a
Abies g r a n d i s
Abies l a s i o c a r p a
P i c e a engelmanni
Tsuga h e t e r o p h y l l a
Tsuga m e r t e n s i a n a
Thuja p l i c a t a
(Ceanothus v e l u t i n u s
(Ceanothus sanguineus
Vaecinium s p .
O p u l a s t e r malvaceus
Sericotheca discolor
Amelanchier a l n i f o l i a
Acer glabrum
Salix spp.
Alnus s p p .
Menzezia f e r r u g i n i a
Taxus b r e v i f o l i a
Western white pine
Ponderosa pine
Lodgepole pine
Larch-Douglas fir
Douglas fir
White fir-cedar
Cedar-hemlock
Spruce
Subalpine
Brush
Grass
Species
control
of
X
X
X X
X
X X X
X X X X X X
X
X
X X X X X X X
X X X X X X X
X
X X X X X
X
X
X X
X X X
X
X
X
X X
X X X
X
X
X X X
X
X X
X X X
X
X
X X X
X
X X X X
X X
X
X X X X
X X
X
X X X X
ac
X X
X X
X
X
X
X X
X X
X
X
X X X X X X
X X
X X
X X
X
X X
X X X
X X X
X X X
X X
X
X
X X X X
X X X X
X X X X
X X X
X X X
Bromus s p p .
X
X X X X X X
A l l e c t o r i a , or Unsea s p p .
X X X X X X X X X
1 / C o n d i t i o n of f r o s t e d v e g e t a t i o n not c o n s i d e r e d .
2/ S p e c i e s confined t o s t r e a m bottoms e x c l u d e d .
2>/ Occurrence of s p e c i e s i s i n d i c a t e d by " x " .
X X
X
X
X
X
X
X X X X
12
PERSONNEL PROBLEM IN FIRE CONTROL
Personnel management is a major consideration in planning fire control. No degree of effectiveness in other phases can offset handicaps
existing in it.
The industries and population of the region have an important bearing on the fire problem, aside from being sources of fires. Fire control
is concerned with location, quantity, and experience of man power available
for the regular seasonal organization and for sudden calls to large fires.
While the rural population is the best source, the seasonal peak of rural
activity coincides with that of fire control. Table 2 shows the city and
rural populations within the region and also the adjacent city populations,
from which large numbers of laborers can be drawn on short notice.
Unsettled industrial conditions make it impossible to determine what
proportion of the population is available as heavy reinforcements for fighting large fires. In the past, during the most severe fire seasons, the
supply was easily exhausted in any and all localities. Transients collected
from freight trains, hobo camps, and other sources have frequently been used,
and have been imported in large numbers from as far as Seattle. The
Civilian Conservation Corps has recently b.come an important factor.
For uniformly efficient initial attack, it is necessary that trained
and experienced men be charged with the responsibilities of detection and
smokechasing 5/ and be stationed previous to the occurrence of fire.
Development of a dependable supply of such man power has been recognized as
a vital need for many years. In spite of its importance the progress made
has been erratic and not great.
The normal task of detection, and of going as quickly as possible to
forest fires and handling efficiently the kind that cause most of the
region's burned area, ranks in difficulty and importance with recognized
skilled crafts.
No industries of the region require increased man power during winter months. The total of summer-season wages that can be accumulated in
fire control and other short-time jobs does not constitute an annual income
attractive to vigorous, ambitions men looking for permanent occupations and
agreeable living conditions.
The many jobs to be done make it necessary for a fireman to occupy
several different stations within a season, and frequently to live alone
during the peak fire-load months of July and August. In the work of detection, he must be on duty continuously day and night. As a smokechaser,
5/
A siokecliaser is a man to whom is assigned the responsibility for making
first attacks. The term "fireman'" designates both detectors (lookouts)
and snokechasers. The combined duties of detection and smokechasing
may or may not be assigned to any particular fireman.
J
3
FIRE CONTROL PLANNING—NORTHERN ROCKY MOUNTAIN REGION
when n o t away from h i s s t a t i o n f i g h t i n g f i r e , he m u s t k e e p hims e l f c o n s t a n t l y a v a i l a b l e to r e c e i v e t h e r e p o r t of a f i r e and in r e a d i n e s s
to s t a r t immediately with p r o p e r equipment. These c o n d i t i o n s p r e c l u d e t h e
p o s s i b i l i t i e s of normal community and family a s s o c i a t i o n s . No p r o v i s i o n
i s r e g u l a r l y made for s h i f t s to r e l i e v e t h e f a t i g u e of continuous d u t y , or
for r e c r e a t i o n .
Although employment p r a c t i c e s have been d i r e c t e d toward o b t a i n i n g
the b e s t men e a s i l y a v a i l a b l e , t h e s e p r a c t i c e s have not prevented t h e use
of a l a r g e number of low-grade men. The u l t i m a t e e s t a b l i s h m e n t of s t a b l e
l o c a l p o p u l a t i o n s , dependent upon growing and h a r v e s t i n g f o r e s t c r o p s ,
would help t o solve the personnel problem. U n t i l such sources of l a b o r
become a r e a l i t y , t h e r e g u l a r s e a s o n a l p e r s o n n e l might p o s s i b l y be p r o cured through l a b o r arrangements with d i s t a n t i n d u s t r i e s in which a c t i v i t i e s reach t h e i r lowest l e v e l s in summer. Men from such s o u r c e s might be
expected t o r e t u r n annually for many y e a r s .
With a s t a b i l i z e d force the e f f e c t i v e n e s s of annual t r a i n i n g would
be g r e a t l y i n c r e a s e d .
For purposes of comparison, f i g u r e 2 shows t h e burned a r e a s of
worst s e a s o n s , the year-long man power annually a v a i l a b l e for f i r e d u t y ,
and t h e t r a i n i n g given annually in the d u t i e s of f i r e c o n t r o l . Dotted
l i n e s suggest t r e n d s t h a t appear t o be c o n s i s t e n t with an attempt t o
b r i n g burned a r e a to the allowable l e v e l by t h e year 1940. ( I t i s shown
l a t e r in the d i s c u s s i o n of acreage burned p e r year t h a t burned a r e a i s a
problem of worst seasons o n l y . )
When t r a i n i n g f a l l s off r a p i d l y , as i t did a f t e r 1930, for a few
y e a r s some of t h e t r a i n e d men return to work and some of t h e s e remember
t h e i r t r a i n i n g . In graph C of f i g u r e 2 i t has been assumed t h a t t h e
i n f l u e n c e l a s t s two y e a r s . A s i m i l a r assumption, not shown, a p p l i e s t o
numbers of men a v a i l a b l e as shown by graph B.
With t h e s e c o n s i d e r a t i o n s in mind i t w i l l be noted t h a t while y e a r long p e r s o n n e l and training increased t o 1930 maxima and dropped, w o r s t season burned area decreased c o n s i s t e n t l y to a 1931 minimum and then
s h a r p l y i n c r e a s e d . Other influences on burned area whose f u n c t i o n s and
t r e n d s are c l o s e l y related to s u f f i c i e n c i e s of year-long personnel and
t r a i n i n g , are supervision, inspection and training of men at point of
duty.
In f i n a l a n a l y s i s , e f f i c i e n c y can be proved only by the organizat i o n ' s a b i l i t y uniformly to perform i t s functions with a degree of rapidi t y that approaches the highest demonstrated t o be p o s s i b l e . These
operations are discovery, report, getaway, t r a v e l , and f i r e f i g h t i n g .
{Records of annual accomplishment for each of the western f o r e s t s of
Region One are shown l a t e r in Part I I I . Annual averages for t h i s group of
f o r e s t s are shown l a t e r in f i g u r e s 10 and 11.)
1500
1400
\
I
1300
Mil
" 1 '" 1
4
• — - y
1
1
~1
I H
i
1
I
|
•
!
!
>
1*4
!
|
i
n
(A i?00
C^llOO
i
!
1
i
I
j
1
!
;
1
j
•
i
i
i
k?oo
v) 800
(A
700
A
N GOO
<
X 500
1
i
\
400
CJ 300
2o
£
^
K.,
1
°
iS.
Al o w a b l e
72,900/
\
o --•-
100
,
1
1920
I92S
1930
210
*
^
*
200
*
170
1340
1335
_ ___-- — • —— - —"" ,*'
_ _ - ** N ^
190
•
-
/
-
V
1
1
•
B
180
Vj
"*
*
^
^
1
lt>0
(• \
1^0
1
Sw ' 1
/
140
1925
1920
1935
1930
1940
4400
4000
,,-- — "".'
U.3fo00
X
|tf£-
'""
-x
^3200
fw
^2800
\2400
X2000
IfcOO
f
1T
J^ y
yd /
I920
\
'
^
\ ~\~~^~i ^
y j
J
'3
j,/y
1200
FIG. 2
S* \
I925
BURNED AREA AND
1930
TWO
IMPORTANT
-4 •
1935
INFLUENCES
A - A R E A BURNED IN WORST SEASONS ONLY
B - Y E A R - L O N G M A N POWER A V A I L A B L E FOR F I R E D U T Y
Includes regional supply m e n and one c h i e f cierk per f o r e s t
C - TRAIN ING GIVEN IN FIRE CONTROL
For d u t i e s o f f i r e m a n , f o r e m a n , and r a n k e r
Width o f r i b b o n represents two y e a r s d u r a t i o n o f influence
REGION I WESTERN FORESTS
FUEL REDUCTION
15
Study of the erratic performance of these operations in spite of
the continuous developments in numbers of men, their placement, and facilities for action (shown later by figures 8, 12, and 13) indicates that the
burned-area objectives will not be reached at the present levels of action.
After the existence of a fire is known, travel consumes part of the
time available for control, and work at the fire consumes the remainder.
Hence, allowable travel times are dependent upon rates of work that will
be put into effect after arrival. Average rates of work have been so low
that unwieldy numbers of men and excessively short travel times would
result from accepting them for the future. Higher rates, demonstrated by
the better classes of employees, have been used in forecasts applied to
the work of planning. Carrying out the plans outlined here will not accomplish the expected results until travel times and rates of work have been
brought within the specifications used in planning.
FUELS, AND A FUEL-REDUCTION PROGRAM
An important regional characteristic is that fires, of any size,
kill most of the trees within their borders. Mature ponderosa pines provide a partial exception, frequently surviving grass fires; and a few old
larches per acre, in scattered patches, usually survive crown fires.
The typical landscape for 20 years after the first burn of a mature
stand resembles the home anchorage of a sailing fleet. These snag areas,
and "blowdown" areas, constitute peak load problems.
Fuels so heavy that the most powerful attacks are sometimes ineffective exist over large areas of single burn. In their worst form these
fuels are the remnants of decadent stands of 75 to 150 trees per acre
killed by crown fires that consumed only the twigs. Within 10 years,
tangled intermixtures of reproduction, snags, and broken windfalls usually
develop. After another 10 years these change slowly into easier fuels as
snags fall, and new stands overtop the masses of rotting debris. Average
fuel conditions are approached 40 to 60 years after the fires.
The absence, almost everywhere, of single^burn refuse in stands
older than 80 years indicates that such debris has commonly been consumed
by fire before new stands were able to grow to maturity. Strong support
for this theory is found in the many failures, during the past 20 years, of
efforts to prevent vast areas of first burns from being reburned by immense
single runs of fire. Apparently a program of fuel reduction will be required if large first burns are to be prepared for satisfactory fire control.
On numerous occasions in single burns, while a smokechaser was felling a single large snag on fire in a light breeze, a disastrous spread to
other snags and to ground fuels has resulted from flying sparks. The job
presented in such circumstances to a light reinforcement crew, arriving 1
to 3 hours after call for help is made, can hardly be exaggerated. Instead
16
FIRE CONTROL PLANNING—NORTHERN ROCKY MOUNTAIN REGION
of one snag on fire, ten or more should be expected, each requiring 1 man
hour to fell it, and the tangled ground fuels normally are full of°sparks
and fires in various stages of development.
For large fires the rapidly advancing fronts of which are producing
intense heat, frequently the worst fuels are those left by single burns in
the bottoms of small valleys where growing conditions are most favorable
and where sufficient water for fire pumps flows continuously. Fires
usually die down as they run downhill out of the wind; but if there they
encounter the fuels that are the worst possible for creating strong new
convection currents carrying thousands of large sparks onto the next
ridges, increased momentum is given them in .the very places where they
could best have been fought if those fuels had been removed. The expense
of converting hundreds of these fire traps into firebreaks would be high,
but possibly not so high in the long run as the alternative costs of suppression and of damage caused by conflagrations. Such conversion is one
sure way to eliminate a large amount of burned area.
Almost every large run of fire in a burn takes a toll from adjacent
green mature stands. Thus, in addition to exposing vast areas of steep
slopes to almost free forces of erosion and making them uninviting to
recreationists, it creates new areas of single burn to continue the cycle—
mature forest to single burn, to double burn, to very slow regeneration by
periodic seeding into the vast barren areas from the mature trees of margins and from advancing bands of young trees as these become old enough to
bear germinable seeds.
Lack of preparation in 1910 left an immense inheritance of difficult
fuels—single burns. According to rough estimates the area of fuels worse
than average increased from 5 percent in 1909 to a maximum of 23 percent
in 1931, and is now slowly decreasing.
An important subject for consideration in a fuel-reduction program
is the increasing encroachment of cheat grass into abandoned fields and
over-grazed ranges adjacent to forests. This grass occupies the driest
exposures, and becomes extremely inflammable early in the summer. In many
places it forms a connecting link for spread of fires, from roadsides and
other places where fires are likely to start, to forests. Its rate of
spread is normally so fast that there is little hope of placing smokechasers with travel times short enough to meet the situation.
FIRE-CONTROL OBJECTIVES, AND ACTION REQUIRED
Fire control is one of the more important activities necessary to
maintain forest resources in condition satisfactory to the owners, public
or private. Protection may be needed for the production of wood xr of
wild life, for conservation of scenic values, for regulation of water
flows, or for other purposes. Determination of what constitutes satisfactory protection necessitates not only a forecast of the requirements of
#
OBJECTIVES
17
local and distant consumers, and forest users, but also an estimate of the
toll taken by destructive agencies other than fire. Considering the lack
of knowledge in the many factors involved, it is neither to be expected
that a definite and changeless objective could be determined in a short
period of years, nor that a specific objective would be applicable everywhere. A general objective applicable everywhere through evaluation of
existing factors was the first one developed. This has been called the
"Economic," "Least Cost," or "Least P + S + D" objective.
ECONOMIC, OR LEAST P + S + D OBJECTIVE
The essential features of this objective are, that damage, "D," is
expressed in terms of money value, and that damage is regarded as one of
the costs of fire, the other items of cost, "P + S," being incurred for
control measures. The letter "P" represents expenditures for presuppression (including prevention) and "S M represents expenditures for suppression. Up to a certain point increases in costs of preparedness and firefighting, "P + S," are more than equally repaid by reductions in damage
"D." Expenditures could, however, be increased to such an extent that
the total of expenditures and damage would be unnecessarily great. This
objective aims at applying the degree of fire control that produces the
least total of "P +• S + D." That this theory is sound can hardly be
questioned. The difficulty of application lies in evaluation of the item
"D." Appraisals to be correct must include considerations of erosion,
water regulation (for floods, irrigation and hydro-electric rower),
recreation (including scenery, fish and game), and general forest influences on climate, and on stabilization of forest communities, not for one
year but for the duration of the damage. The difficulties are obvious.
Even if the evaluation of damage had not proved elusive, cost statistics
would be lacking from which to show how much reduction of damage was
accomplished by a given increase in fire-control costs. The most economical division of cost between presuppression and suppression is open to
argument.
In 1928 Flint (6) published Forest Service statistics for this
Region, covering trends since 1910 in the relations between the three
factors of this objective. He concluded that total cost plus losses
would be most economical when 2.2 cents per acre were expended for presuppression. If the conflagrations of 1926 were left out of the calculations, he found that presuppression costs should be 1.35 cents per acre,
but if seasons of very severe burning conditions were to occur more frequently (as they have since he made his computations in 1928), expenditures for presuppression even greater than an average of 2.2 cents per
acre would produce the most economical total of "P + S + D. "
Even if these conclusions were acceptable guides, it would still
be necessary to adjust the long-period average by increasing presuppression expenditures during seasons of most severe burning conditions and
decreasing them during seasons of less than average severity. Furthermore, the correct distribution of Regional funds to localities would
remain to be determined.
18
FIRE CONTROL PLANNING—NORTHERN
?OCKY MOUNTAIN REGION
How much dependence to p l a c e on h i s c o n c l u s i o n s i s d i f f i c u l t t o
determine. Damages were based on changing s t a n d a r d s of a p p r a i s a l , and
many a p p r a i s a l s were merely rough a p p r o x i m a t i o n s . Because f u t u r e market
v a l u e s a r e unknown, weights given t o a c c e s s i b i l i t i e s and ages of s t a n d s
burned have been e r r a t i c and u n d e t e r m i n a b l e . No a p p r a i s a l s have as yet
included a l l items of damage. The evidence seems to be ample, however, to
j u s t i f y the c o n c l u s i o n t h a t much g r e a t e r e x p e n d i t u r e s f o r p r e s u p p r e s s i o n
are economical.
F l i n t ' s computations and c o n c l u s i o n s a r e probably as a c c u r a t e as
any t h a t have been a p p l i e d t o t h e "Economic" o b j e c t i v e . He concluded t h a t
"the s a f e s t simple index f o r t h e d i s t r i b u t i o n of funds i s a r e a burned
o v e r . " The rcany undeterminable v a l u e s involved in a p p l i c a t i o n of t h e
"Economic" o b j e c t i v e l e d t o adoption of a b u r n e d - a r e a o b j e c t i v e .
PERMISSIBLE
PERCENTAGE OF BURNED-AREA OBJECTIVE
To guide f i r e - c o n t r o l a c t i o n during t h e y e a r s w h i l e social demands
are changing and d e t e r m i n a t i o n s of f a c t s a r e c l a r i f y i n g i s s u e s , a temporary s t a n d a r d {22) of t o l e r a b l e average annual burned a r e a was adopted
for n a t i o n a l f o r e s t s . This statement s p e c i f i e d , f o r each f o r e s t t y p e ,
t h e maximum annual burned p e r c e n t a g e compatible with maintenance of t h e
f o r e s t cover over a long p e r i o d of y e a r s .
The r e l a t i v e p e r c e n t a g e s of burned a r e a allowed in d i f f e r e n t
were based on r e l a t i v e r a t i n g s of damage made by experienced f o r e s t
c e r s . The following f a c t o r s were c o n s i d e r e d .
types
offi-
1.
Timber v a l u e - p r e s e n t and p o t e n t i a l .
2.
D e s t r u c t i o n of s i t e v a l u e by f i r e s .
3.
The d i f f i c u l t y of r e - e s t a b l i s h i n g t h e f o r e s t following
4.
Creation of f u t u r e f i r e h a z a r d s , whicn w i l l prevent t h e maintenance
of t h e f o r e s t i t s e l f .
fires.
One-tenth of one percent (0.1%) of burned a r e a p e r year was allowed
spruce and white p i n e t y p e s , which a r e t h e o n l y ones included in the most
damaged c l a s s . Allowances f o r o t h e r t y p e s of t h e region a r e shown in
t a b l e 4. I t was e s t i m a t e d t h a t w i t h i n t h e l i m i t s of such l o s s e s i n t e n s i v e
timber management can be c a r r i e d o u t .
For watershed v a l u e s allowances v a r y i n g , with damage and i n t e n s i t y
of u s e , from 0 . 4 to 1.2 percent of a r e a burned p e r y e a r were s p e c i f i e d .
The p e r c e n t a g e of allowances a p p l i c a b l e to p a r t i c u l a r watershed v a l u e s
e x i s t i n g in t h e region have not been worked o u t .
The f o r m u l a t o r s of t h i s o b j e c t i v e did not p r o v i d e burned a r e a
allowances for r e c r e a t i o n v a l u e s , which in c e r t a i n a r e a s a r e obviously
higher than t h e h i g h e s t wood-products v a l u e s . However, i t was recognized
t h a t where high v a l u e s a r e at s t a k e , a s m a l l e r burned a r e a than the
OBJECTIVES
19
specified allowance might prove to be the most economical, considering a l l
items of cost and damage. Thus, provision was made for applying the
"Economic" objective, previously discussed.
I t should be pointed out than an amount of burned area cannot, corr e c t l y , be called "permissible 1 ' unless i t i s that amount which r e s u l t s
from the most economical t o t a l cost of control expenditures plus damage.
Hence, if a l l items of damage within the burned area allowance were
accurately appraised, t h e i r t o t a l should conform to the objective of
"Least P + S +• D" and the two objectives would be the same. Since the
allowances are maximum amounts that can be t o l e r a t e d , the word "tolerable"
more correctly describes them than "permissible," the word o r i g i n a l l y
applied.
Table 4.—Forest-type areas in western forests of Region One: totals existing,
totals burned in ig2i-$o» and total burns
permissible.
Area
Burned over in 10 years
; Total : Actual, s Permissible:Relation of actual
permissible
H 1 2/
« 3 / jand(Dver
:
Under
1921-30
:M acres M acres : M :Per- , M acres , M acres
:acres:cent
279
Western white pine t 2,116 !
300 : 21 :! 1.0
Ponderosa pine
: 1,307 :
65
: 26 , 2.0
39
Lodgepole pine
: 4,172
:
286
131 : 417 10.0
Larch-Douglas fir l 3,101 :
211 ; 78 ; 2.5
133
Douglas fir
: 1,331 :
26
: 40 I 3.0
!
14
:
545 :
55
White fir-cedar
: 11 2.0
44
:
85 :
2 ; 2.0
Cedar-hemlock
9
11 :
:
641 :
16
S 6 ! 1.0
Spruce
10
:
166
% 2,566 :
i
58
142 : 308 :12.0
Subalpine
Brush and grass
:
333 !
25 : 83 :25.0
*
514 :
524
962 : 992 : 6.1
Jl6s196 :
Total
Forest type
jj
G r o s s , e x c l u s i v e of 344, 785 meres b a r r e n and c u l t i v a t e d .
^
Annual f i g u r e s were t o t a l e d r e g a r d l e s s of a r e a o v e r l a p .
2J
esters
P e r m i s s i b l e a c c o r d i n g t o r e p o r t of Washington Conference of R e g i o n a l For1930, a p p l y i n g t h e a l l o w a n c e s s p e c i f i e d f o r t i m b e r management.
For the western national forests of Region One the relation of
burned area to t o t a l area and to the permissible-bum-objective for the
period 1921-30 i s shown in table 4 for each of the forest types present.
(Similar data are shown for each of the individual forests in Part I I I . )
2C
FIRE CONTROL PLANNING—NORTHERN ROCKY MOUNTAIN REGION
The overburn of 514,000 acres was caused by 82 f i r e s out of 12,056,
l e s s than 1 percent of a l l f i r e s . In other words, a few conflagrations
caused 2 to 14 times as much burn as i s permissible in the timber types of
highest value, in s p i t e of the fact that 99 percent of a l l f i r e s were
s a t i s f a c t o r i l y controlled.
The intermixture of types makes i t probable that e f f o r t s , which e v i dently are needed to reduce burned area in the overturned types, will proportionately decrease that in the already underburned types as well.
Hence, the permissible-burn percentages set up for the underburned types no
longer have any p r a c t i c a l significance, and in the following calculations
only overturned types are considered.
The 1921-30 r a t i o of 10-year burned acreage in a l l types to that in
the overturned types alone was 1.5 to 1. The permissible 10-year allowance
in types now overturned i s 144,000 acres. If the 1.5 to 1 r a t i o continues
through the period 1931-40, the 10-year t o t a l burn for a l l types, by d i r e c t
proportion, should not be allowed to exceed 216,000 acres. Approximately
all of t h i s may be expected to burn in three or four seasons that will
probably be classed as "worst." Burned area i s insignificant except in
"worst" seasons, two of which I1931 and 1934) have already occurred. Using
the conservativ p r o b a b i l i t y of three "worst" seasons in the 1931-40 period,
the average burned area of one "worst" season should not be allowed to
exceed one-third of 216,000 acres, or 72,000 acres. The area already burned,
1931-34 inclusive, i s 497,5000 acres, which averages 249,000 acres for each
of the "worst"seasons 1931 and 1934. Hence, the whole burned-area allowance
for the 10-year period has already been greatly exceeded in the f i r s t 4 years,
and the average burned area per "worst" season i s 3.,5 times that permissible.
Attention i s directed to the use here of burned-area allowances based
e n t i r e l y on the timber management specification of the objective. Actually
considerable portions of the areas burned l i e in the zone now c l a s s i f i e d as
permanently non-merchantable, to which the more l i b e r a l burned-area allowances of watersheds should be applied. On the other hand, i t i s not at a l l
unlikely that the 1931-40 period will contain four "worst" seasons instead
of the three used in the estimate, in which event the burned-area allowance
will probably be further exceeded.
I t i s doubtful that a closer estimate of the s i t u a t i o n could be
made. The accuracy of the present estimates i s ample to support the s t a t e ments that burned area continues to be highly unsatisfactory and that action
in a l l phases of f i r e control must be much f a s t e r , stronger, and more e f f i cient before the permissible burned-area objective needs to be subjected to
refined scrutiny.
A high degree of chance in several factors enters into the probability of a t t a i n i n g t h i s objective. These factors are number of large runs that
occur over a long period of years, number of f i r e s that die down enough to
permit control before they reach excessive s i z e , and the places, in r e l a t i o n
to intermixtures of types, where errors of action or unusual weather r e s u l t
in large runs. In the northern Rocky Mountain forests t h i s objective i s not
tangible except for long-period post-mortem examinations.
OBJECTIVES
21
OBJECTIVE OF CONTROL WITHIN THE FIRST WORK-PERIOD
r v ^ - „ ^ 6 n a U 1 9 2 1 ~ 3 0 f i r e s w e r e arranged in size classes and the c o r r e s ponding average speed and strength of attack determined, i t was found on
the b a s i s of averages, that the b e t t e r the action was the greater was'the
area burned. This apparent inconsistency i s caused by analyzing tie facts
from the wrong viewpoint, that i s , by f a i l u r e to segregate records of
ac ion according to prevailing severity of burning conSitions and according to fuels. Anyone familiar with the usual p r a c t i c e of placing men
closer to the worst fuels than to easy ones, when burning conditions are
worst, knows that large acreages of burned area accumulate in s p i t e of
f a s t , strong action. Very few of the 16,000 individual f i r e reports accumulated since 1920 t e l l how severe the burning conditions were at the f i r e
and none records fuel conditions in terms specific enough to indicate what
speed and strength of attack i s needed for success in a p a r t i c u l a r fuel.
If sufficient information were available, useful multiple c o r r e l a t i o n s probably could be worked out between the five variables severity of
burning conditions, character of fuel, speed of attack, strength of attack
and area burned.
For the reasons given, f a i l u r e must be admitted in endeavoring to
obtain, for the forest types of t h i s region, correlations between burned
area and speed of attack similar to those reported by Show and Kotok dg)
for the forest types of California. In the northern Rocky Mountain region,
such c o r r e l a t i o n s could not be r e s t r i c t e d to man-caused f i r e s as were
those of Show and Kotok: in t h i s region lightning f i r e s c o n s t i t u t e 70 percent of a l l f i r e s and cost about the same, in the t o t a l , as those caused
by man. Speed could not be measured from hour of i g n i t i o n , because 20 percent of lightning f i r e s are not discovered within 24 hours and some smoulder unknown for more than 10 days. Even for man-caused f i r e s , especially
of the camper and debris-burning c l a s s e s , the hour when spread began i s
more significant than that of i g n i t i o n .
In analyses and plan work for t h i s region, action time has been
measured from hour of discovery. This s t a r t i n g point, while open to
c r i t i c i s m , i s the most d e f i n i t e one available.
In s p i t e of the limitations mentioned, d e f i n i t e indications of
required f i r e - c o n t r o l action are not lacking. Conclusions based on analys i s of f i r e records by Gisborne and Hornby £/ are as follows: Past overburn was a l l caused by a few large conflagrations; almost every spot in the
region must be suspected as a possible s t a r t i n g point; and the objective of
permissible-percentage-of-burned-area w i l l probably not be attained if any
f i r e larger than 4,000 acres i s permitted. In each of the five forest
types assigned the lowest percentages of permissible burn, the sum of the
areas burned by a l l f i r e s smaller than 4,000 acres equaled the permissible
burn. Although in other types f i r e s l a r g e r than 4,000 acres did not cause
overburn in 1921-30, the intermixture of types and man's well-demonstrated
$f
Fire-control Objectives and Practicec in the Northern Rocky Mountain Region, i03X»
Unpublished.
22
FIRE CONTROL PLANNING—NORTHERN ROCKY MOUNTAIN REGION
inability to stop fires at any particular size or place make it necessary
to conclude that there, also, no larger fires can be permitted intentionally. The conclusions are further substantiated when attention is focused
on areas smaller than the entire region, regarding them as the entire forest to be protected, such as sustained-yield working circles and natural
units used for recreation or water regulation.
After the heat at the front of an aggressive fire becomes too great
to permit work, only a remarkable change of conditions there makes it possible to prevent unlimited spread. Effective changes may be in fuel, topography, wind, or moisture. Under such conditions, argument whether the
allowable size is 4,000 or 400 acres appears irrelevant. The opportunity
to limit spread is before a fire makes its first aggressive run. The next
opportunity comes after the fire dies down (usually at nightfall) and
before it makes another run during the next mid-day burning period. This
means that under the most severe burning conditions detection and first
attack must aim at preventing the escape of any fire. Failing this, reinforcement attacks must be planned to stop all spreads as soon as heat and
advancing fronts permit. Another definite way of stating approximately
the same objective is that when burning conditions are critical detection,
first attack, and reinforcement action must be planned to catch every fire
in the first work period. This period ends when the next mid-day burning
period begins, usually between 9 and 12 a.m. This is a tangible guide of
action rather than a post-mortem check on accomplishments. It is the
objective applied to plan work discussed here.
CONSIDERATIONS IN APPLICATION OF OBJECTIVE
Influence of Intense Action on Qost, Damage, and Area Burned
Under certain conditions least cost of fire control plus damage is
obtainable by applying a high rate of suppression work, thereby completing
the job in a short time. One of these conditions prevails in localities
where large numbers of men are available without regular cost to maintain
them. Figure 3 shows, for fires attacked at various sizes, the intensity
of attack, the length of suppression time, the average suppression cost,
and average acreage burned per fire. This figure includes all fires, within the indicated range, that occurred in Region One during the 10 years
1921-30. For all fires controlled within 36 hours, regardless of initial
size, it is evident that the stronger and faster the action the less was
the cost as well as the acreage burned. For fires that lasted beyond 36
hours the data are erratic; influences affecting these cases include fatigue,
deferred attacks, weather and fuels prevailing during the second and later
work periods.
When an attempt was made to plot comparable data to that shown by
figure 3 for the period 1931-33, inclusive, it was found that the greatly
increased intensity of action practiced could not be justified on the basis
of suppression costs alone as was the case for the average of the 1921-30
period. For fires suppressed within any given length of time the average
cost per fire since 1930 was found to be 2 to 10 times as great as before.
2
FIG.3.
3
4
5
6
7
8
9
MAN-HOURS USED PER HOUR OF
10
II
12
SUPPRESSION
INFLUENCE OF INTENSITY OF ATTACK ON
AVERAGE COST AND
SUPPRESSION
ACREAGE PER FIRE.
SIZE OF FIRE
©
*
13
14
TIME
WHEN
ATTACK
0 . 0 0 — 0 . 2 5 ACRES
0.26 — ! .00 ACRES
FIRES OF
WAS BEGUN
1.01 — 5.00 ACRES
5.01 - 2 0 . 0 0 ACRES
1921-30
REGION I WESTERN
FORESTS
15
16
TIME
AND
17
ON
18
APPLICATION OF OBJECTIVE
2H
Although the annual t r e n d has not been examined, an abrupt i n c r e a s e in
i n t e n s i t y of a c t i o n i s known to have begun in 1929. The q u e s t i o n a r i s e s ;
was the resulting reduction of damage great enough to j u s t i f y t h i s higher
average cost per fire?
In table 5 are shown the number of f i r e s , t h e i r t o t a l suppression
c o s t s , and the area burned in each period. In order to make possible a
comparison of equal numbers of f i r e s in each period, the cost and burned
area of 2,786 f i r e s , at the 1921-30 average per f i r e , are shown. The percentage of severe f i r e seasons was approximately the same in each period.
If damages in the burned area were appraised at $1 per acre, i t will
be found by addition of burned acres to suppression c o s t s , that the comparative t o t a l "S + D" costs are $208,575 in favor of the l e s s intensive action
represented by the average in effect for 1921-30, inclusive. But if damage
were appraised at $5 per acre the "S + D" t o t a l costs would be $9,229 in
favor of the more intense 1931-33 actions. I t would not be legitimate to
draw refined conclusions from t h i s rough evidence. However, the conclusion
appears to be amply supported that whenever a large supply of man power i s
available the most economical action i s to send as quickly as possible to
every f i r e enough men to insure that every part of the perimeter will be
placed under control before worse weather conditions are encountered.
In table 6, more detailed comparisons are made between comparable
data of the two periods. I t may be confusing to note that although the
average size of a l l f i r e s has been greatly reduced in recent years, a l a r g er average size occurred for every length of suppression time. A clearer
way to s t a t e the case i s that any size of f i r e has been corralled in a
shorter time in recent years than formerly. Until analyzed, the larger
average size during recent years in the longest suppression time c l a s s ,
four or more days, may s t i l l be perplexing. In recent years almost no
snail f i r e s got into t h i s c l a s s . The average size shown, 2,160 acres, i s
derived from a few large f i r e s , 28 in three years, or an average of nine
per year. In the former period, since many small f i r e s got into t h i s c l a s s ,
the average size shown, 1,360 acres, i s derived from both small and large
f i r e s , the t o t a l number being 339 in 10 years, or an average of 34. per year.
The lower the probable damage, the more d i f f i c u l t i t becomes to make
a clear showing in favor of high control c o s t s . I t also becomes more
d i f f i c u l t to determine a desirable division of control costs between p r e paredness and suppression. The degree to which preparedness expenditures
for fast reinforcement action could economically be increased i s determinable only by t r i a l . In table 6 there i s a strong indication that the
average reduction in burned acreage per f i r e i s as closely related to
quick and strong i n i t i a l attack as to l a t e r action. In comparing the percentages of f i r e s in each suppression-time c l a s s for the two periods i t
will be observed that 15 percent more f i r e s were suppressed in the 0 - 1
hour class in 1931-33 than in 1921-30; in fact, the 0 - 1 hour c l a s s i s
the only one in which a gain was made in 1931-33. Obviously the change
that occurred was removal of f i r e s and l a r g e r burned areas from each of
the longer suppression-time classes to some shorter one. Since fit st
25
FIRE CONTROL PLANNING—NORTHERN
T a b l e ,5. - - Numbers of fires,
burned on western
and in 1931-33-
ROCKY MOUNTAIN REGION
suppression
costs,
forests
of Region
and acreages
One in 1921-30
Number : T o t a l s u p p r e s - : T o t a l
j of
:
sion cost,
, acreage
.2
fires :
in dollars
burned
Item
1921-30 t o t a l
2 10,252 ;
2,447,933
1931-33 t o t a l
2,786 :
928,880
1
2,786 :
665,854
; 142,365
Expected t o t a l for 2,786
according t o 1921-30
averages p e r f i r e
:: 524,019
87,914
fires
j
:
Table 6.—Suppression time and costs,
and acreages of fires
western forests
of Region One in 1921-30 and in
if on
1931-33-
:
P e r c e n t a g e of
Average a c r e :
Average c o s t ,
Suppression :
f i r e s , in
;
in d o l l a r s ,
:
age burned
time 2 /
t o t a l number
per f i r e
;
per f i r e
: 1921-30
1931-33 i 1921-30 : 1931-33 . 1921-30 : 1931-33
0 - 1 hour
1 - 4 hours
4 - 12 "
L2 - 24 "
1 - 2 days
2 - 3
"
3 - 4
»
4 »
Total or
average
:
:
;j
j
:
jI
;:
:
j
41.1 j
29.4 :
13.8 {
5.9
:
3.8
t
1.5 :
1.1
3.4 •
100.0
s
55.8
26.4
10.5
4.0
1.3
0.6
0.3
1.1
100.0
:
:
:
:I
;
:
.
9
23
68
148
336
742
1,357
5,160
239
:
18
:
59
223
::
:
732
: 2,842
. 5,244
: 7,241
: 16,400
:
333
:
:
•
•1
s
•
:
:
1/
On which f i r s t a c t i o n was t a k e n by Forest S e r v i c e .
2/
Elapsed t i m e from work begun t o f i r e
corralled.
0.3 :
0.4
1.0
!
2.3
10.6 !{
11.7
9.2 !;
30.8
2 6 . 5 . 106.0
69.7 : 5 7 9 . 1
146.9 j 554.6
1360.0 . 2160.0
51.1
:
31.5
APPLICATION OF OBJECTIVES
26
attack is primarily involved in the o - 1 and 1 - 4 hour suppression time
classes, it appears probable that quicker and stronger smokechaser action
than has yet been practiced will do at least as much to reduce burned area
as increased reinforcement action. However, the latter is also necessary,
and indications are that its sphere of activity should be expanded by taking action on more small fires.
general
After study of errors, rates of spread, fuels, and other influences
on the larger fires of the period 1921-30, inclusive, the conclusion was
reached that a considerable number of them would have escaped even from the
stronger and faster initial attacks and light reinforcement attacks specified in present plan work. No doubt occasional conflagrations, impossible
to control within the first work period, would occur under a degree of preparedness so expensive as to be clearly uneconomical. When burning conditions are at the other extreme, minimum, man-power stations are frequently
so widely separated that control of remote fires within the first work period is impossible. Since it is most economical to permit longer control times
then, these fires might be called legitimate extra-period fires. Another
cause of extra period fires is error. It is estimated that these three factors will prevent at least two percent of all fires from being controlled
within the first, work period. Specifications used in plan work were intended
to permit the control of all other fires, approximately 98 percent, within
the first work period. The percentages of fires that became extra-period in
the years 1931-35, inclusive, are 5.6, 4.3, 6.7, 8.7, and 4.7 respectively.
It must be understood that any action requirement stated here applies
only to areas where the objectives, the forest types, and the fire histories
are as specified. If the objectives were modified for part of the region,
allowing more burned area per type, less fire-control strength would be
required there. On an area occupied by a forest type in which fires do not
make large single runs, or make them very rarely, larger fires could be
allowed and hence less strength of fire control might be required. Provision of a regular paid organization for detection or for initial attack might
be unnecessary, as is the case in some forests of eastern Montana.
The form of fire-control organization and the capacity required are
local considerations determined by the objective and by fire danger as indicated by fire history.
OBJECTIVE ADOPTED IK PLASHING
Attention is directed to the fact that no conflict exists between the
three major objectives of fire control that have been widely recognized.
Consequently, for planning purposes, the following composite objective was
used. By attempting to "Control every fire in the first work period," it is
hoped to keep burned acreage within the "Permissible-pereentage-of-burnedarea, " and ultimately to make the sum of fire-control costs and losses most
"Economical."
11
FIRE CONTROL PLANNING—NORTHERN ROCKY MOUNTAIN REGION
PLANNING THE FIRE-CONTRQL SYSTEM
SERVICES NECESSARY
Before attempting plan work i t i s necessary t o study the d i f f e r e n t
a c t i v i t i e s t h a t i n f l u e n c e burned a r e a . A l i s t of f i r e - c o n t r o l a c t i v i t i e s
c o n s i d e r e d necessary f o l l o w s . For each of those over which he has no cont r o l t h e p l a n n e r must determine i t s importance and t r e n d and assume some
l e v e l of e f f i c i e n c y for t h e f u t u r e .
FIRE PREVENTION
A degree of e f f e c t i v e n e s s equal t o t h a t now in e f f e c t was assumed
in p l a n n i n g .
PERSONNEL MANAGEMENT
Procurement, training, supervision, and inspection.
Evidence already discussed (and considered later in connection with
figures 10 and 11) strongly indicates that reasonable success and economy
demand an increase in personnel efficiency. Rates of work higher than the
average of the past have been assumed in determining allowable travel times
and strengths of attack.
FIRE-DANGER F ORECASTING
Increased efficiency through research is assumed.
ACTION ON FIRES
Eirst Line of Defense
Detection (lookouts)
Initial attack (smokechasers)
Second Line of Defense
Small mobile reinforcement crews
Their bases are communities, landing fields, and other
stations.
PEAK LOADS
26
Heavy r e i n f o r c e m e n t s
T h e i r b a s e s a r e c i t i e s with 100 or more emergency f i r e f i g h t e r s a v a i l a b l e on c a l l . Since a i r p l a n e s cannot s a t i s f y
t r a v e l - t i m e r e q u i r e m e n t s a t n i g h t , t h i s s e r v i c e i s dependent upon a road system.
The four s e r v i c e s of a c t i o n on f i r e s a r e given equal weight. A planning
p r o c e d u r e has been developed f o r each, and p e r c e n t a g e s of a r e a covered by
each have been worked o u t .
FUEL REDUCTION
E l i m i n a t i o n of t h e most d i f f i c u l t
f u e l s i s d i s c u s s e d on page 15.
RESEARCH
Increase in effectiveness through an expanded program is assumed.
LOADS FOR WHICH TO PREPARE
After study of all the information available, the conclusion has
been reached that a system planned to control approximately 98 percent of
all fires within the first work period after discovery will be the most
economical, all items of expense and damage being considered.
PEAK LOADS
Since the occurrence of fires everywhere must be expected, the most
difficult fuels, already discussed, constitute one form of peak load. Conspicuously severe fire seasons constitute another form. The increasing
frequency of their occurrence is shown in figure 4, A, by a moving number
of severe seasons that have occurred per 10-year period.
An accurate definition of the term "worst season" or most "severe
season" is impossible, and will continue to be impossible until methods are
found and adopted for evaluating and comparing the composite results of
such influences as number of days when extremely rapid spread must be expected, continuity of such days, area of prevalence, number of fires, number
that occur in difficult fuels, and concentration in number per unit of area
according to character of fuel ignited. In such seasons a high degree of
drought exists for 4-8 consecutive weeks. Other developments depend upon
the frequency of occurrence in "flashy" fuels of high resistance to control
and upon the speed and strength of attack applied. Exhaustion is a
2S
FIRE CONTROL PLANNING—NORTHERN ROCKY MOUNTAIN REGION
conspicuous c h a r a c t e r i s t i c in a cause and effect r e l a t i o n s h i p . Man power,
including detectors and overhead can stand the s t r a i n of continuous work
only a limited length of time. After mental and physical exhaustion of
the f i r s t s t r i n g " man power, anything can and usually does happen.
A third form of peak load i s caused by high r a t e of spread continuing for several hours. Continuous rates of spread have averaged as high
as 1,600 acres per hour for a 12-hour run. Perimeters produced by the
l a r g e r single runs have ranged from 30 to 90 miles. Some of the larger
runs resulted from the impossibility of making f a s t , strong attacks;
others from f a i l u r e to do so; a few f i r e s , soon after ignition or discovery, have spread rapidly in s p i t e of Quick and strong a t t a c k s .
Coincidences of a l l the most d i f f i c u l t f i r e - c o n t r o l conditions s e l dom occur. In the very severe season of 1926 lightning started 109 f i r e s
on July 12 and 37 more on July 13, within the Kaniksu National Forest,
which then had a gross area of about 700,000 acres. Examples of s t i l l
higher daily concentrations on smaller areas are 30 f i r e s on 100,000 acres
and 15 on 10,000. A daily concentration of 30 to 70 f i r e s per million
acres i s not uncommon.
Using 10 or more new lightning f i r e s as a peak daily load on any
national forest, figure 4, B, shows the number of peak loads that occurred
i n c l u s i v e , on the western national forests of Region One during the JulyAugust period of each of the years 1921-30. The 124 peak-load days of the
five-year period 1926-30 c o n s t i t u t e an increase of 91 percent over the 65
that occurred during the previous five-year period.
Figure 4, C, shows that the average number of f i r e s per peak-load
day has increased rapidly.
Peak-load days and number of f i r e s for each national forest are
shown graphically in Part I I I . These graphs show that peak loads usually
occurred on the same day on several adjacent forests and occasionally
occurred on the same day on a l l f o r e s t s , p a r t i a l l y preventing inter-change
of man power even where roads for guick delivery existed. From 75 to 100
percent of these coinciding f i r e s were stopped at sizes l e s s than onefourth acre.
In planning, special consideration has been given to areas on which
peak daily loads have recurred. Figure 5 shows the areas of the region on
which two'or more lightning f i r e s per 10,000 acres originated on at l e a s t
three days of the 10-year period 1921-30. In studying concentrations mancaused f i r e s were ignored, because i t was found that no more than three,
and usually none, of them originated on any forest on the same date as a
l i g h t n i n g - f i r e concentration. The 10,000-acre unit was chosen because i t
i s conveniently convertible and represents about the minimum acreage over
which the man oower of one s t a t i o n i s responsible for f i r s t attack. On
the shaded areas shown by figure 5 there i s a reasonable probability that
at any time during a f i r e season the man power of any s t a t i o n will have
more than one f i r e to attack on the same day. I d e n t i f i c a t i o n of these
is
A
/
™™
/
/
/
/
/
I\
1908
10
15
/
20
25
30
35
20
25
30
35
30
35
14
§
12
B
£
x
to
1908
1? *
70
^ ^ r x
5 0
p—
C
^ ^ 2 0
^ Or
X
19 38
20
25
YEAR
F I G . 4 INCIDENCE OF CONSPICUOUSLY SEVERE SEASONS IN
1908-34 INCLUSIVE AND PEAK LOADS OF LIGHTNING FIRES 1921-30
.ArAVERAGE NUMBER OF WORST SEASONS PER 10-YEAR PERIOD (VERTICALLY
ABOVE THE DIVISION BETWEEN EACH TWO YEARS, THE AVERAGE THAT INCLUDES
FIVE YEARS ON EITHER SIDE IS PLOTTED)
2 5 - NUMBER OF DAYS WITH PEAK LIGHTNING-FIRE LOAD PER SEASON (JULY-AUG.)
C - A V E R A G E NUMBER LIGHTNING FIRES PER PEAK-LOAD DAY PER SEASON
R- I WESTERN FORESTS
31
C A N A D A
FIG.5
LIGHTNING - FIRE
CONCENTRATION
AREAS
A R E A S ON WHICH TWO OR MORE F I R E S PER 10,000 ACRES
O R I G I N A T E D ON AT L E A S T T H R E E D A Y S OF T H E PERIOD 1921-30,INCL.
NUMBER OF FIRES AND AREA BURNED
32
areas makes fire control there a lesser problem than elsewhere, because
great concentrations are likely to occur almost anywhere and without
warning.
Annual and 10-year average numbers of fires per unit of area do not
indicate strain. They do, however, show how many times any area has been
threatened with fire damage and suppression costs. Where average annual
occurrence is high over an area of single burn or blowdown, the satisfaction of requirements there constitutes one of the worst possible peakload problems.
ANNUAL NUMBER OF FIRES
AND AREA BURNED
The number of fires started by man in each year since 1909 and the
areas burned in each year since 1920 are shown, under each of the standard
classes of cause, in figure 6. These data apply to the western national
forests of Region One as a unit whose area has remained approximately the
same throughout the periods specified. Similar data are given for each
forest in Part III. It will be npted that railroad, debris-burning, and
camper fires have only infrequently produced a large part of the total
burned area and have shown a continuous decline in number. Other causes
have been more erratic. Smoker fires, which have been increasing in number since 1927, seem to demand outstanding consideration in planning.
The annual numbers and burned acreages for man-caused fires, for
lightning fires, and for all fires combined are shown in figure 7. It
will be noted that the number of man-caused fires declined from 1917 to
1925 and in most of the years since then has approximated the 1925 total,
and that the areas burned by man-caused fires increased up to 1929 and
thereafter declined. The annual total number of fires, although it has
varied greatly, has sharply declined since 1929. The decrease is almost
entirely accounted for in the lightning-caused component. Tendencies
toward increased concentrations per unit of area are discussed on page 29.
Planners are seriously interested in knowing whether this decline will
continue or whether, like the decline of 1919-23, it will be followed by
a rapid increase.
No pronounced tendency in area burned annually by lightning fires
can be stated. This means that the fire-control organization has not
gotten the upper hand in the fight. In spite of conspicuous and continuous efforts to get the upper hand, it is necessary to conclude that such
efforts did not keep pace with the increasing frequency of serious burning conditions and the rate of accumulation (discussed on page 16) of
single-burn fuels.
In figure 7 the graph of total area burned annually shows that the
outstandingly severe seasons contributed most of the total. Measures of
preparedness must be designed primarily for such seasons. It must be
admitted that the classification of seasons as severe is based largely on
area burned. Burning conditions may have been equally severe for short
periods in other seasons when no fires occurred in worst fuels or none
escaped from control.
33
FIRE CONTROL PLANNING—NORTHERN
ROCKY MOUNTAIN REGION
The consistent reduction of area burned in severe seasons up to and
including 1931 constitutes a noteworthy accomplishment, p a r t i c u l a r l y in view
of the increase in frequency of peak loads shown by figure 4. The unfortunate increase in 1934 and some of the factors that influenced i t were discussed on page 13 in connection with figure 2.
ABILITY TO CARRY LOADS
ANNUAL INCREASES IN FIRE-CONTROL COVERAGES 2 /
Owing to increased appropriations, the road mileage and the number of
s t a t i o n s manned increased continually after 1910, and the area s a t i s f a c t o r i l y covered by detection, smokechasing, and reinforcement action increased.
Figure 8, A, shows percentage of area within the protection boundaries of
western national forests seen by detectors of the average-season organizat i o n . Figure 8, B, shows area reached by smokechasers under travel-time
standards now specified (table 12) for burning conditions called "average."
The coverages shown by these two graphs for the period 1910-29 should be
regarded only as good approximations. The graphs were derived from curves
showing coverages obtained when different numbers of s t a t i o n s per million
acres are occupied. The s t a t i o n s occupied from 1910 to 1919 were determined in part from the memories of forest officers.
The percentage of area reached by heavy reinforcements within present travel-time standards for t h e i r a r r i v a l from the bases of man power
now used i s shown by figure 8, C. The geographical l i m i t s reached by the
routes and methods of travel in use at the end of each five-year period,
respectively, from 1910 to 1934 were worked out on maps. Since no allowances were made for delays, the coverages shown are probably greater than
the actual.
The data for 1930 and l a t e r years shown by each of the three graphs
of figure 8 were worked out by methods of planning described l a t e r .
The influences of systematic planning on coverages in effect since
1930 are conspicuous. These coverages were accomplished by a r e d i s t r i b u tion of man power s t a t i o n s , without increasing the number, and by correlation of road construction with location of man power. In 1934 the areas
covered by detection and smokechasing were each approximately twice as
great as in 1917, and the area reached by heavy reinforcements was four
times as great.
The geographical location of developments in heavy-reinforcement
coverage accomplished by road construction during the period 1919-33>
inclusive, i s shown by figure 9. Many of the smaller areas l e f t uncovered in 1933 are reached from roads constructed since then.
2/
"Coverage" means area reached by attackers within travel—time limits, or area seen
by detectors.
RAILROADS
600
500
100
400
80
300
fcO
No Data
200
40
10
100
"-
~
r
30
1910
34
DEBRIS
200
(/) 100
ki
1
_
M j 1 _P.
1910
"I
±
± ±
~
-
1910
20
30
25
34
BURNING
40
: zr
X.
n
^.
25
20
30
34
1910
15
20
xL30 _
-_ ±
25
10
34
LUMBERING
k
200
40
100
20
rtn
1910
IB
20
25
30
34
1910
15
H
20
U
25
"T-t
30
34
INCENDIARY
80
300
foO ^)
200
40
__
100
1910
r ~ - ii 15
-
20
20
25
- ln
30
34
1910
15
20
25
30
34
0)
^
CAMPERS
1^| 300
]
40
200
20^
^ 100
—
1910
^4—
""
--.__ 15r
20
""
25
""
- - 30— E L 34
1910
15
H
25
20
30
SMOKERS
n
300
foO
V
^ 200
—
100
1910
400
34
20
*
$
^
25
SMOKERS,
MISC.AND
-UNKNOWN
30
40 k
34
1910
20
r
4
4
25
20
30
34
30
34
MISCELLANEOUS
200
100
r-i
1910
15
20
25
30
34
1910
FIG.6
15
20
YEAR
Y EAR
MAN-CAUSED
FIRES
N U M B E R , A N D T O T A L ACREAGE BURNED, BY C A U S E
IN EACH YEAR OF PERIOD 1910-34 INC.
REGION
I WESTERN
FORESTS
25
s
MAN -
F
1 *»«_
~ i_
CAUSED
—I—I—I—I—I—I—I—I—I—I—
—
_,
_
* 1
~ —
—
™"
i
•
J
M
I
~
200 - - 5
~
1910
15
20
30
25
~^
^
34
1910
—
~
15
20
i
LIGHTNING
ly
l2
°0
-
_
i
_
^
4UU
_jl
34
^
—
.
i
L
•*
F
-
_
1-
~
'
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-
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^
1
1 j_
700
j—
30
mm
r
1
«.
25
^*T
^
IltS
TS
KV\
r
^
1
i
I
S
1
__
1
1910
15
20
[
25
>
30
34
I9I0
15
(v^
U
ttU
v
-
T
20
mn
tn
o 300
_
,2e
-t
x - ±
25
30
34
^
TOTAL
i
°
1
! |
i _
111
"*J
—
n
Qft
i
1500
L
—
—
O)
_
or,r>
_
_
— —•
~|r"
— J L
-|-
m
ZUUU/
_ l
—
i
700
m
foOO
—
l
-t—
1000
400
—I
100
A
1910
FIG.7
•
15
20
YEAR
• '— A n
i
25
30
34
I9I0
IS
i~i
20
i I""
25
A
X
_n
YEAR
M A N - C A U S E D , LIGHTNING, AND TOTAL FIRES
N U M B E R , A N D ACRES B U R N E D P E R
YEAR
A. O U T S T A N D I N G S E V E R E F I R E S E A S O N S
REGION I W E S T E R N FORESTS
-100
nUi 1
A
30
^
34
k
80
A
70
DETECTION
1
('
foO
50
4-0
0)
3 0
ki
£
20
^
10
1910
o
o
o
c?
O 80
O
^ 70
15
20
25
30
35
1940
25
30
35
1940
25
30
35
19'4-0
BsMOKECHASING
,
foO
<
50
§40
kj 30
20
k io
0
1910
15
20
1
k
70
k
fo0
r>i
H EAVY
l ^ REINFORCEMENTS
k
^
4-0
30
20
10
1910
15
20
YEAR
FIG. 8
DEVELOPMENT OF COVERAGES
A . - S E E N BY DETECTORS OF AVERAGE SEASON ORGANIZATION
I B - R E A C H E D BY SMOKECHASERS, AVERERAGE-SEASON TRAVEL ST'DSC - R E A C H E D IN 8.5 HOURS FROM CITIES OF 9 0 0 0 + POPULATION
REGION I WESTERN FORESTS
37
FIG. 9
DEVELOPMENT
OF
ACCESSIBILITY
1510
TO 1933
A R R I V A L IN 8.5 HOURS FROM BASES —
SPOKANE, L E W I S T O N , MISSOULA
AND GREAT
V/////M
k'-w-.i
Area
Area
expanded
remaining
by road c o n s t r u c t i o n
unreached in 1933.
1910-1933.
FALLS
ABILITY TO CARRY LOADS
38
FACTORS OF PERSONNEL EFFICIENCY
Because the effects of an increase or a decrease in the efficiency
of man power over a period of years must be recognized in planning, it is
necessary to study trends in performance and in factors known to influence
personnel efficiency.
§££ed of Action
Efficiency of fire control is measured largely by the speed with
which fires are extinguished. Trends in speed of action for each of the
time-consuming operations of control are shown by figure 10. No explanation has been found for many of the apparent inconsistencies. The 10
percent increase since 1921, in number of lightning fires discovered within one hour, is consistent with the increase of about 50 percent in number of detection stations. Lightning fires, unless seen at the time of
strike, are likely to be invisible or inconspicuous for many hours or even
days. Get-away time to lightning fires is influenced by high concentrations
of lightning strikes per unit of area. Practice has been frequently to
defer action on fires in easy fuels, waiting for expected fires to develop
in worse fuels. The increase in percentage of lightning fires reached
within 2 hours is consistent with road developments in localities little
used by people. An increase in percentage of fires controlled within 1
hour after arrival has occurred since 1930, coincident with increases in
road mileage and number of smokechaser stations, and with more efficient
location of stations. These advantages permitted smokechasers to attack
fires at smaller size than was possible before.
After examining these data the only conclusion which can be reached
is that whatever progress has been made in fire control has resulted primarily from manning more fireman stations, and from having more firemen,
reinforcements, roads, and other facilities. Conspicuous progress in
providing man power and facilities tempts the observer to conclude that
average efficiency of men has not increased.
gates of Work
With the exception of the two phases, prevention and detection,
fire control organizations exist almost entirely for the purpose of performing a rate of suppression work that is faster than the rate of fire
spread. Hence, as much detail of that work as is usable is given here.
Considering its importance, one is naturally disappointed to find that
very little evidence of work rates according to the factors involved has
been collected.
In planning, in dispatching men to fires, and in studying the records
of performance it is necessary to recognize that rates of constructing held
fire line, per man hour, vary with a great many factors, the more important
of which are listed below without regard to order of importance.
3S
FIRE CONTROL PLANNING—NORTHERN ROCKY MOUNTAIN REGION
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
Fuel resistance to control
Method of attack
Kind of tools, equipment, and food provided
Efficiency of directing officers
Training and experience of firefighters
Physical and mental ability of firefighters
Size of crew
Size of fire
Aggressiveness and heat of fire
Prevailing atmospheric temperature
Fatigue
Darkness
On individual fire reports and in field studies the influence of
each of these factors has not been recorded. Hence, analyses for the purpose of determining relative efficiencies cannot be made, neither can anyone determine to a reasonable degree of accuracy what rate of work to
expect of a crew of particular size in any fuel. Individual fire reports
show only one of these 12 major factors, fuel, and it is recorded in terms
of forest type and age class so general that resistance to control is not
recognizable. When an attempt was made to compare rates of work in different seasons, it was found in general that rates of work were lowest in
the most severe seasons. These are the seasons in which the largest crews
were used on the largest and hottest fires.
A portion of the perimeter of most fires requires little or no'
work, due to fires dying out and to absence of fuels. For all fires of the
period 1921-30, inclusive, the sum of recorded perimeters, on which work
was done, was found to be 75 percent of the sum of total perimeters, and
this percentage was approximately the same for every size class of fire.
If (as was frequently the case) the length of perimeter worked is not correctly recorded, an error is introduced in determining the man hours used
per chain of held line.
From the standpoint of fire suppression tactics, the total labor
used, or needed, to complete all the work required on a fire may properly
be charged against the total fire perimeter to determine the number of man
hours per chain. However, only a part of this labor is needed to corral
(stop the spread of) a fire, the remainder being used for mop-up and patrol.
The efficiency of getting rid of one fire and getting men and equipment
quickly reorganized in preparation for the next fire is ommitted from this
discussion. Here the important consideration is to get every fire stopped
within the first work period, and only the labor used, or needed, up to the
point of corralling will be discussed. The labor required up to this stage
of completeness determines the number of men to be stationed at different
places and the travel time allowed between man power stations and fuel.
During the process of firefighting, it is difficult to know just
when a fire will certainly spread no further; hence, the smaller the fire
the more likely it is that the smokechaser, or foreman, reported an optimistic corralling time. Not infrequently a small fire is correctly reported
corralled at the time attack on it is begun. Reports made for fires
80
DISCOVERY
Within 1 H o u r
feO
40
oL\Jn
- — . . — —• .
<+'
"" m ^^
1920
\ ^ —•
*
*
1925
1935
1930
80
• ^ -
^L^
*
REPORT
Within 15 Minutes
feO
——^»
40
1925
1920
k
80
^
feO
Uj
0
kj
1930
1935
G E T - AWAY
Within 5 Minui es
_>
s
P ~ » - r ^ w-
r ^ *
40
^ ' - —,
"""o*
1920
^*•
"
—— —
••«*•,
1930
1925
1935
8 0
TRAVEL
Within 2 h ours
.-
C^ feO
1
40
1925
\
^v
p
1930
W i t h i n 2.4
80
s*
— «*t
* - • ^
- — " " "— —
1920
y
1935
Hours-—
ARRIVAL
TO CONTROL
bO
^ V W i t h i n I Hour
40
1920
1925
MAN-CAUSED
ALL
YEAR
1930
1935
LIGHTNING
CAUSES COMBINED
F1G.I0 FIRE CONTROL OPERATIONS COMPLETED
WITHIN PERIODS INDICATED
R- I WESTERN
FORESTS
RATE OF WORK
41
corralled within a few hours contain t h i s element of uncertainty, but
they are specific in showing the number of man hours used in construction
of held f i r e l i n e , that i s , labor used up to the point of c o r r a l l i n g .
Since the time of corralling a large f i r e usually i s in the second day, or
l a t e r , some sectors of the f i r e had previously been on a mop-up and p a t r o l
basis. In reports and analyses considerable and undeterminable amounts of
such labor have been included with, and charged against, l i n e construction
labor. Evidently the larger the f i r e and longer i t s duration the greater
i s the amount of labor incorrectly charged to construction of held f i r e
l i n e , and the l e s s comparable are average r a t e s of work per man hour derived from the reports. Comparisons of recorded r a t e s of work, disregarding efficiency, should show that they decrease with size of f i r e . Such a
decrease i s shown in table 7. Failure to recognize the uncomparability of
records frequently has resulted in conclusions that some or a l l of the 12
factors just enumerated were entirely responsible for the much higher records of efficiency of smokechasers than of crews. The weight of each
factor, and a l l those involved, must be determined before reasonably accur a t e comparisons can be made.
Table 7.—Number of man hours used to corral fires on western
forests of Region One in 1Q21-30 cind 2931-33.
, Number of man
Average number
Average size
of
fire
in
Suppression
of man hours
hours per chain
acres
time 1/ :
per fire
: of held line £f
1931-33 ; 1921-30 ; 1931-33 : 1921-30 , 1931-33
1921-30
0-1
hour
l
1-4
hours 8
4-12
"
5
12-24 "
I
1-2 days
5
2-3
"
j
3-4
"
;
4-30 M
5 i
9 !
34 :
87
221
559
922
3140
0.3 1
2 l
I
1
.0 l
11
I
1
0
.
6 :
61 i
;
9.2
:
220
26.5 i
961 \
69.7 !
3283
!
146.9
!•
1539
,
1360.0
.
3220
j/
Elapsed time from •work begun to f i r e corralled.
2}
Held l i n e was
acreage.
0.4 1 0.7
2.3 i
11.7
30.8 !
106.0 :
579.1
554.6
2160.0
0.7
0.9
2.1
3.4
5.3
6.1
6.8
;
!
:
5
!
:
0.2
0.6
1.4
3.4
7.4
10.8
5.2
5.5
assumed to be three—fourths of the perimeter that corresponds to f i r e
In table 7 it will be observed that in addition to controlling any
size of fire in a shorter time in recent years than in the former period,
about the same number of man hours were used for the same size of fire.
Consequently, the number of man hours per chain corresponds roughly with
the number of man hours per fire in either period. A considerable gain
in efficiency is shown in handling the smallest fires. No other
42
FIRE CONTROL PLANNING—NORTHERN ROCKY MOUNTAIN REGION
consistent differences in efficiency are evident. It should be kept in
mind that the rates of work are averages. Approximately four times the
number of man hours shown per chain have been used, and probably are needed,
for each fire size where fuels and burning conditions are worst.
Trends in rate of fire suppression work on large fires are given in
figure 11. It shows, according to density of stand, regardless of timber
type, average rates of work in the years 1931, 1932, and 1933 combined, and
for each of these years separately. These data are based on 102 rough
analyses made by men in charge of reinforcement crew work along selected
portions of fire lines, most of which were on large fires and during the
severe season of 1931. The total man hours included are 147,325, which
were used along a total fire line length of 28,900 chains, giving a grand
average of 5.1 man hours used per chain for the combined operations of
clearing and trenching fire line. For clearing, the grand average is 2.2,
and for trenching 2.9. Since the total of 5.1 constitutes only 85 percent
of the work done up to the time fires were reported as corralled, approximately 6 man hours per chain of line were used to corrall these sections of
fire line. The data could not be segregated for further analysis. In fact,
the segregations shown may not include comparable fuels, burning conditions,
crew sizes, crew efficiencies, and other unknown influences previously enumerated. Since the data for cut-over areas include only 79 chains of fire
line in light fuels, they should be disregarded, or considered minimum.
Because most of the samples of work were collected under the severe
burning conditions of 1931, man hours used per chain, under the ordinary
burning conditions of 1932 and 1933, accomplished by smaller crews, should
be found less, if efficiency were equal. If efficiency increased, a still
lower number of man hours per chain should be evident in figure 11. It is
necessary to conclude that efficiency as shown by these examples did not
increase consistently in the period 1931-33, inclusive. So few analyses
were made in the severe season of 1934 that the evidence does not justify
conclusions.
With large crews on large fires, where fuel resistances along perimeters vary greatly, the average production frequently is about 1 chain of
held line per man day, which is an average of about 12 man hours per chain.
After comparing this rate with the 6 man hours per chain shown by the samples of work, just discussed, the 100 percent difference should be discussed.
The 6-man-hour figure includes very little work on lost line, not much of
the lost motion that almost invariably has been characteristic of organizations at large fires, and all labor was charged to the specific kinds of
work performed. The 12-man-hour figure includes considerable work on lost
line, and all lost motion. But also important, large numbers of man hours
that were used each day, particularly after 2:00 p.m., for mop-up and patrol
are included in the average as though chargeable to construction of new
line. For these reasons the two rates of work are not comparable. However,
the difference is great enough to direct attention to the highly expensive,
non-productive, items of lost line and lost motion. Comparable methods of
firefighting that could unquestionably be improved were employed in both the
M A T U R E STANDS
OPEN
DENSE
DENSE
LITTLE
HEAVY
WINDFALL WINDFALL
b
POLE STANDS
OPEN
DENSE
BRUSH
AMU
GRASS
5
\ 3
\2
1
<>
1)
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\
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8?
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f
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r
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s.
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w
v
^
1 2 3 4AV."
1 2 3 4 AV.
1 2 3 4 AV.
1 2 3 4 AV.
1 2 3 4AV.
CLEAR//VG PLUS
TRENCH/NG
^
4
1 2 3 4AV.
DENSE REPRODUCTION
LITTLE
HEAVY
WINDFALL WINDFALL
i
0
2
N
j
L
11
C U T OVER
SLASH
SLASH
LIGHT
HEAVY
AV. A L L T Y P E S
DEAD
GREEN
STANDS
UNCUT
^>
|
jI
\
•
\ I
1
0
11
1)
^
V
/ \
V/ >
1I
CLEAR/NG
P/RE L/NE
YEAR S 1931-34 AND AVERA(3E
1
k 5
4
I
-S i
1>
V,
L
\j
<i>
>(»
If
\
A
\s
1jl
//
«i
s
8
7
\
1)
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al
/
i
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1 /
2
1
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1 2 3 4 AV.
1 1 3 4 AV.
1
1 2 3 4 AV.
s,S/(
/V
\
<J
\
\
(<
1
/
\/
U
\>
1 2 3 4 AV
IS
•vl
1 2 3 4 AV.
1 2 3 4 AV.
YEARS 1931-34 AND AVERAGE
F16.ll RATES OF WORK
ACCORDING TO A 6 E AND DENSITY OF STAND
MAN-HOURS USED PER CHAIN OF FIRE LINE
( B A S I S , A L L SAMPLES REPORTED IN 1931-34, INC.)
R-l WESTERN FORESTS
K
MAN POWER AND TRAINING
»W
6 and 12-man-hour rates. Indications are that after making the greatly increased expenditures now contemplated by the Forest Service for supervision,
and for training in methods of attack, organization, and supervision, the
average cost per comparable fire probably will be reduced. If the burned
area is more than proportionately reduced also, higher fire control expenditures of all kinds per acre could be justified on low-value areas than were
indicated on page 24 for existing levels of suppression efficiency.
Number, Use, and Housing of Temporary. Force
Figure 12 shows the annual comparison of number of men in the
regular temporary fire-control force with the number in improvement crews
available for fire duty. Except for the 20 percent reduction of regular
temporary men in 1934, it will be observed that man power has increased
greatly.
Figure 13 shows that the number of stations occupied by the
regular temporary force, and the number provided with dwellings have
increased more rapidly than the number of employees. Housing is regarded
as a factor in efficiency, especially of detectors. The annual differences between graphs A and B are shown in figure 14, A, as percentages of
the force used for overhead and service of supply. This percentage has
approximated 17.5. The annual relation of graphs B and C of figure 13
are shown in figure 14, B, as average number of regular season employees
per station. The rapid approach toward one man per station after 1927 is
conspicuous.
liaising in Iix£
Q°EIIOI
Training has been mentioned already in the discussion of figure 2.
In figure is trends in the amount of training given each year, since 1921,
are shown. Since these data are based on estimates and scanty records,
they must be regarded as good approximations only. It will be observed
that the decline in training after the 1930 peak coincided with a very
large increase in untrained seasonal personnel, shown by figure 12, and a
rapid and drastic reduction in year-long experienced personnel, shown by
figure 2, B.
45
ionnn
1 VUUU
18000
17000
IfaOOO
15000
14000
13000
12000
IIOOO
cv IOOOO
(*
9000
^
8000
/
/
\
/
7000
/
bOOO
B,
/
5000
/
4000
3000
2000
£1
1000
"~*"
19 20
1925
1930
19.35
YEARS
FIG.I2
N U M B E R OF MEN AVAILABLE
FOR FIRE DUTY
A - T O T A L INCLUDING CIVILIAN CONSERVATION CORPS
B - T O T A L EXCLUDING CIVILIAN CONSERVATION CORPS
C - REGULAR TEMPORARY FIRE-CONTROL FORCE
R-l
WESTERN
FORESTS
1000
\
\
900
\
\
800
j
A
t
\
700
foOO
kj
QQ
500
^
400
\
- "
A.
•
—
, —„,—-
x>
_D
C
300
200
D
100
19 20
1930
1925
1935
YEARS
FIG. 13 MAN POWER, STATIONS, AND
HOUSING OF REGULAR FIRE CONTROL FORCE
A - R E G U L A R TEMPORARY FORCE
B - FIREMEN OF REGULAR FORCE
C - S T A T I O N S OCCUPIED
D - REGULAR FIREMEN STATIONS
PROVIDED W I T H D W E L L I N G S
R-l
WESTERN
FORESTS
24
22
20
18
lb
k
/
/
/
/ \
v\ \
/ \
/
\
/
\
/
\
/
\
I
\
\
\
*s
l4
A
ki
£ -o
k
8
(o
4
2
1920
1925
1930
1935
YEARS
1.4-U
1.30
B
k
QQ 1.20
1.10
1920
1915
1.00
F1G.I4
1930
19.35
YEARS
USES OF REGULAR TEMPORARY FORCE
J V - PERCENTAGE OF FORCE USED FOR OVERHEAD A N D
SERVICE OF SUPPLY
B - AVERAGE NUMBER OF FIREMEN PER STATION
R-l
WESTERN
FORESTS
1200
A
s! IOOO
£
600
> feOO
^
4O0
«
200
1
^
1920
1925
1930
1935
3500
JB
3000
X 2500
\
2000
^1500
pt iooo
^
500
1.
20
X
3,0
1925
19:55
1930
C
\
\
IA
*
\
2.0
,9 20
1925
19;J5
1930
YEAR
FIG.I5
FIRE CONTROL TRAINING
RECORD
REGION ONE W E S T E R N F O R E S T S 1922-34
A - N O . M E N G I V E N T R A I N I N G IN FIRE CONTROL-^ FOR D U T I E S
- B - N O . M A N - D A Y S TRAINING G I V E N
VOF FIREMAN
C - A V . NO. DAYS T R A I N I N G G I V E N PER M A N
^FOREMANGRANGER
»9
F I E L D WORK
MAPPING SEEN AREAS, ROAD ROUTES, AND VALUATION ZONES
The field jobs done in t h i s planning project were as follows:
*•
EH£l MiffiEllig ~ The fuels on 15 million acres of national forest and
cooperative lands were mapped. The detailed i n s t r u c t i o n s used are
given in Part I I .
2.
Seen-Area Manning - Seen-area maps were made from more than 3,000
potential detection s t a t i o n s within the 15 million acres covered by
plan work. The detailed i n s t r u c t i o n s used are given in Part I I . This
work was done by men who had completed college courses in topographic
mapping and who were further trained by J. B. Yule, in charge of maps
and surveys.
3.
Examinations of Road Routes - Through field examinations Regional
Forester Evan Kelley decided the locations of some of the roads constructed and proposed. Other routes were proposed by forest supervisors and t h e i r s t a f f s . Paper locations of a l l desirable proposed
routes and additions necessary to meet travel-time standards were made
in the office by road engineer H. A. Calkins. In the field he revised
these locations, determined the b e t t e r of a l t e r n a t i v e p o s s i b i l i t i e s ,
and examined routes usable as connecting links between trunk routes.
The procedures followed in road planning are described in Part I I .
4.
M§j)T>in.£. of Valuation Zones - Existing and potential value zones for
wood products were made by logging engineer Philip Neff of the division
of forest management. Relative values for recreation were worked out
by Assistant Regional Forester M. H. Wolff.
MAPPING FUELS
A general knowledge of procedures followed in classifying and mapping fuels i s necessary to understand the methods applied in covering them
with the services of control. Disregarding timber type e n t i r e l y , fuels
were classified and mapped in terms of r e l a t i v e i n i t i a l r a t e of spread and
the resistance they offer to control. There are many precedents in
engineering practice for classifying materials to be worked in such a way.
Ratings were based on conditions at the end of a month of mid-summer
drought.
Fuel mappers received field training in groups. Each man was provided with the written instructions given in Part I I . He was required
f i r s t to place each fuel examined in one of the classes of probable r a t e
of spread, low, medium, or high, and to place outstandingly high r a t e s in
50
FIRE CONTROL PLANNING—NORTHERN ROCKY MOUNTAIN REGION
a fourth class, extreme. Estimates of rate of spread were confined to the
first 1 to 3 hours that must elapse between discovery and arrival of an
attacking force. Next he was required to designate the resistance to control, using the same general terms, low, medium, high, and extreme. Maps
were made on a scale of i inch to the mile. (For plan work, this was
reduced to one-half inch to the mile.) Classes of rate of spread were
shown by colors; resistance to control was shown by direction of colored
lines. A section of a field map is reproduced as figure 16.
Under this procedure part of the responsibility for specifying the
control action necessary is taken by the fuel mapper. While looking at the
fuel in the field he has before him the best possible array of evidence.
Each fuel class represents a composite condition of size, volume, arrangement, and exposure of material. Classification is based on such conditions
rather than on an average indicated roughly by cover type, the basis used
by Show and Kotok (18, ig), because it was found that fuel characteristics
within types have exerted 3 to 15 times as much influence on initial rates
of spread as have forest type characteristics.
The lower picture of the frontispiece shows typical fuel conditions
after logging and slash disposal in western white pine associated with
western hemlock, white fir and an understory of western red cedar. Initial
rate of spread is classified as Low where such fuels are exposed to the
north and east, and Medium where they are exposed toward the south and west
to prevailing winds and strong solar radiation. Resistance to control is
Medium. If a poor job of slash disposal, or none, had been done, rate of
spread would have been classified as more rapid.
The upper view of the frontispiece was obtained by looking toward
the east up Benton Creek within the Priest River experimental forest. Some
idea of the typical relation of topography to fire spread and a conception
of the difficulty of obtaining seen area from detection points are given by
this illustration. In this view are all the species commonly associated
with western white pine as listed in table 3 on page 11. The fuels that
govern initial rates of spread are not visible in this view and cannot be
classified without examining the area; in fact, a very wide range of fuel
classes was found there.
Fuel conditions in burned areas are illustrated in figure 16-A. All
the trees in these views are dead. Fuels such as those shown in view 1 are
common in every timber type of the region except ponderosa pine. If such
fuels lie on protected north and east exposures, initial spread is classified as Medium instead of High as designated in the illustration for south
and west exposures. Resistance to control is High.
Such fuels as those shown in view 2 of figure 16-A were discussed on
page 15 as desirable for elimination in a fuel reduction program. The dense
mass of dry grass, bark, splinters, small limbs and disintegrating trunks on
the ground are 4-6 feet deep and fully exposed to sun and wind. The picture
FIG. 16 FIELD FUEL MAP
(Section of" Kaniksu Forest)
RATE OF SPREAD
Shown by Color o f Lines
Extreme
Medium
Low
RESISTANCE TO CONTROL
Shown by Direction of Lines
l Solid l E x t r e m e
Hidh
£ ^ ^ Medium
YZ7?Z\ L o w
S c a l e o f 1 inch = 1 mile.
For plan work this and ail other maps were
r e d u c e d \o scale o f \ inch = I mile.
FIG. 16-A.—FUELS IN BURNED AREAS
Fuel of high rate of spread and high resistance to control in the western white
pine type. Such fuels are found in every tinber type.
Fuel of high rate of spread and extreme resistance to control in the cedar,
hemlock, white fir type.
'
FUELS
53
was taken about 10 years after a crown fire killed the stand. Initial rate
of spread is Extreme on exposed sites both near the ground and between broken
broom-topped snags. Resistance to control is also Extreme.
Flashy, light fuels are illustrated in figure 16-B. In open stands
of pure ponderosa pine rate of spread usually is High and resistance to control Low. This species may constitute any percentage of older stands, and
brush, logging slash, and reproduction may frequently cause resistance to
control to be Medium.
Cheat grass (Bromus tectorumj
shown in view 2 was discussed on page 16
as dangerous because of its Extreme rate of spread. No other grass was allowed this rating. Its resistance to control is lower than that of any other
fuel.
The few illustrations and the discussions are considered sufficient to
show that fuels of the northern Rocky Mountain region vary more within any one
timber type than between the averages of timber types, if indeed the average
conditions of any one type could be identified. For further ratings corresponding to described conditions, the reader is referred to the 43 examples
given under "Instructions to Fuel Type Mappers" in Part II.
It is not to be inferred that all the relationships between fuels,
weather, and control have been determined as accurately as is desirable.
Much refinement of field data and more accurate correlations between factors
remain to be worked out before fire-control managers and dispatchers are provided with the degrees of detail they need.
The question whether or not fuel has been mapped accurately, that is,
whether actual rates of spread correspond with classifications of predicted
rates is answered to some extent by table 8. The table shows the average
rates of spread of fires occurring during the 1934 season that originated in
fuels mapped as high, medium, and low, under two groups of fire danger classes
as indicated by danger-meter readings. 8/
Because of the limitations stated in footnotes to table 8, the rates
of spread shown are not to be considered averages for their respective
classes and danger ratings.
In view of the wide ranges of variation of which the averages are
shown, and the small number of cases, it is remarkable that no average is
found to be highly inconsistent. The half of the data first compiled gave
similarly consistent averages. It is evident that in general rates of
spread are being estimated consistently.
It is evident also that the ratings given by the danger meter consistently indicate differences in rates of spread to be expected, and that their
general indications can be relied upon by fire-control managers.
Q/
The "danger « t . r . « developed by Gisborne ( 9 ,
^ ^ J ^ ^ f ^ ^ ^ V j ^ h l h i X t t j
danger on the b a s i s of measurements of f u e l , moisture, wind, v x s i h i l i t y , ana P ™
dang
of l i g h t n i n g storms
5^
FIRE CONTROL PLANNING—NORTHERN ROCKY MOUNTAIN REGION
Table 8.—Average initial
ests of Region
Time of
day
:
:
:
:
:
rates if of fire spread
One in 1934, by fuel
in western
forclassification.
Rate of p e r i m e t e r i n c r e a s e , under
given burning c o n d i t i o n s , i n fuels %J
of d e s i g n a t e d mapping c l a s s i f i c a t i o n s
Moderate (danger-meter
: : Severe (danger-meter
.
c l a s s e s 3 and 4) 2/
: : c l a s s e s 5, 6, and 7) —'
: : High
Low
: High
: Medium :
: Medium : Low
: Chains , Chains : Chains : : Chains : Cha i n s : Chains
:per hour :per hour :per hour : : p e r hour :per hour :per hour
8:00 A. M.
to
4:00 P.M.
l
13.1
:
2.4
:
Other
\
3.5
i
2.0
1 0.8
:'
7.2
Average
j
8.3
2.2
:
i:
11.0
:
1.3
1.1
i:
16.4
:
28
:
37
:
13
\:
22
Other
:
28
!
41
!
14
::
31
Combined
;
56
:
78
::
27
::
53
Grand t o t a l
1
1.1
2.8
:
1.0
3.1
j
1.0
37
:
10
Number of cases included
8:00 A. M.
to
4:00 P . Um
T o t a l , by
«\
danger c l a s s
:
3.3
161
:
j1
33
j
70
8
s
18
141
302
1/
Data for f i r e s t h a t had no spread (mostly s i n g l e - s n a g f i r e s ) were
omitted from t a b l e . Data f o r f i r e s reached i n l e s s t h a n o n e - h a l f
hour were l i k e w i s e o m i t t e d , because spreads d u r i n g such s h o r t
i n t e r v a l s a r e l i k e l y not t o be r e p r e s e n t a t i v e .
2/
The refinement i n mapping i s not s u f f i c i e n t t o i n s u r e t h a t t h e
c l a s s i f i c a t i o n shown i s t y p i c a l of t h e f u e l in which the f i r e s
originated.
3/
""
The danger-meter r a t i n g s were not for s p e c i f i c exposures and a l t i t u d e s but f o r whole n a t i o n a l f o r e s t s each l a r g e r t h a n a m i l l i o n
acres.
5b
FIG. 16-B.—FLASHY FUELS
1.
Grass on gentle slope in ponderosa pine type. Because sparse grass is heavily
grazed, rate of spread is classified, as Low. Resistance to control is Low.
3.
Continuous cheat grass, classified as Extreme in rate of spread and Low in
resistance to control.
STANDARDS
56
STANDARDS ADOPTED AND THEIR BASES
In order to plan consistently and systematically it is necessary to
adopt standards. After analyzing results and trends for different localities (national forests) and after summarizing them for the region, as has
been done throughout this report, these data were used as the basis for
formulating standards. Since the standards approved by the administration
for any condition must be applied wherever and whenever that condition is
found, further useful argument is restricted to questioning the standards,
or interpretations of them. For each field and office procedure of major
importance standards were set up.
PREPAREDNESS FOR WORST CONDITIONS
Weather, fuel, and personnel efficiency determine the speed and
strength of attack needed on any fire. Preparedness for worst burning conditions requires more roads and other facilities than are needed during
less difficult times. Planning determines the stations to be occupied and
the man power to be placed at each under different severities of burning
conditions. The term "Maximum" has been applied to a range of conditions
including those that are most critical. Similarly the terms "Average" and
"Minimum" represent parts of the whole range of burning conditions.
Ten years has been selected, arbitrarily, as the period for which
it is hoped the present plans, with minor revisions, will satisfy requirements. In order to forecast the average annual cost of fire control and
damage, it is necessary to estimate the durations of different degrees of
burning severity to which preparedness and suppression costs, plus damage,
will correspond. The probability of error in these estimates is very
high, owing to changing seasonal conditions and lack of records. The
severities of burning conditions considered, with the corresponding dangermeter classes, and the estimated duration of each in a 10-year period are
as follows:
Severity of
burning conditions
Danger-meter
classes
Minimum
Average
Maximum
2
3 and 4
5, 6 and 7
Weeks of duration
with in,13^ear period
90
86
24
DUAL RESPONSIBILITIES OF FIREMEN AND CREVS
It is necessary here to state that the man power planned for every
location, whether one man or a crew, was assumed to perform the duties of
detection as well as those of smokechasing.
57
FIRE CONTROL PLANNING—NORTHERN ROCKY MOUNTAIN REGION
MULTIPLE USES OF ROADS
Duplications of total road requirements could easily result from
uncorrected developments to satisfy separate uses, such as removal of forest products, recreation, and general administration. In planning the
fire-control road system in its relation to man power, other foreseeable
road requirements were given consideration so far as the authority delegated to planners permitted doing so. The evident possibilities of such
correlations were far from exhausted.
VISIBILITY
DISTANCE, AND SEEN AREA
In discussions here, and in general usage within the region, the
term "seen area" is applied to the area that would be visible from one or
more given points if the human eye could see to an infinite distance. The
term "visibility distance" applies to the distance to which light, contrast,
and atmospheric conditions permit an observer to see a smoke or object.
During the past 5 years the Pacific Northwest, California, and
Northern Rocky Mountain Forest Experiment Stations have devoted a great
deal of research effort to determining how far detectors can be expected to
see the smokes created by fires of a size small enough to permit satisfactory suppression action by the first-line defense service. Unfortunately
the results were not available soon enough to justify revision of the standards of allowable vision distance set up at the beginning of this plan
work in 1931. Although several of the assumptions on which these standards
were based have proved to be erroneous, it is believed that the defects in
the standards have not caused any serious errors in the placement of detectors.
One of the purposes of the visibility-distance research was to produce a visibility meter that would enable detectors to keep fire-control
managers currently informed of atmospheric conditions making it desirable
to man more or fewer detection stations. Meters based on different principles have been constructed by McArdle (12J and Byram (4) at the Pacific
Northwest Station and by Shallenberger and Little at the Northern Rocky
Mountain Station.
The factors in visibility distance are highly complex. Professional
physicists disagree on the interpretation of experimental evidence. Assuming average eyesight of the observer, the more important influences determined by investigations are prevailing atmospheric obscurity, size of smoke,
and contrast with background. Under uniform conditions of atmospheric obscurity and background, the visibility distance of a standard small smoke 2/ w i t h
d
In the investigations carried on by the Pacific Northwest and Northern Rocky Mountai
Experiment Stations the sane standardized candles were used. They produced smoke of
a constant color and volume, simulating the smoke of a small forest fire.
VISIBILITY DISTANCE AND SEEN AREA
58
the sun shining on i t , according to McArdle d3), Byram (4jt Foitzik (7),
and Buck and Fons (3), i s greater in the direction of the sun than away
from i t . V i s i b i l i t y distance of smoke in the shade i s much l e s s than
that of smoke in the sun and, according to Shallenberger and L i t t l e 10/
and McArdle (i3), i s l e s s in the direction of the sun than away from i t .
Shallenberger and L i t t l e found the v i s i b i l i t y distance of shaded smokes
to vary (not by simply proportion) with the angle formed by two l i n e s running from the observer to the smoke and to the sun. When the atmosphere
i s conspicuously c l e a r , the v i s i b i l i t y distances of small shaded smokes at
4:00 p.m., for observers looking in the direction of the sun and away
from i t are approximately 10 and 15 miles, respectively. When atmospheric
obscurity i s conspicuous, but not dense, these l i m i t s are reduced to 3.5
and 6.0 miles, respectively.
Topographic shadows cover large areas in early morning and l a t e
afternoon. The period of the day from 3:30 to 7:30 p.m., called evening
period here, presents by far the most d i f f i c u l t problem in v i s i b i l i t y
distance.and, hence, in the allowable spacing of d e t e c t o r s . Approximately 32 percent of a l l the f i r e s of 1321-30 were recorded as originating in
this period. Of a l l the f i r e s that had to be fought during the dangerous
mid-day burning period, 61 percent more of them originated during the l a t e
evening hours than in any other 4-hour period outside the mid-day period
i t s e l f . The following data gives the "high l i g h t s " of a detailed study of
factors for each hour of the day and night.
5*. 30
1:30
5:30
to
7:30
A.M.
to
3'-30
P.M.
to
7:30
P.M.
Percentage of 1921-30 f i r e s discovered within
1 hour after estimated time of i g n i t i o n . . . .
26
61
50
Average discovery distance in miles for regul a r l y stationed detectors
5.7
6.5
5.7
The increases from early morning to early afternoon and decreases thereafter
show the importance of v i s i b i l i t y distance in obtaining quick discoveries,
and indicate the part that shadows and illumination plan.
Over the area that i s seen from the typical detection station a
larger area of shadow develops in the afternoon on the west side than on the
east side. Within c i r c l e s of 10-mile radius around q. representative s t a tions an average of 56 percent of the t o t a l seen area was found to be shaded
at 5:30 p.m. on August 21, and the percentage of seen area shaded averaged
1.7 times as great in the western h a l f - c i r c l e s as in the eastern halfc i r c l e s . These facts were determined by the use of p r o f i l e s plotted across
seen areas that had been mapped previously on 100-foot contour maps.
10/
Two manuscripts prepared but not yet published.
59
FIRE CONTROL PLANNING—NORTHERN ROCKY MOUNTAIN REGION
Other factors that effect allowable visibility distance indirectly,
because they interfere With smoke rise and unobstructed views of small
smokes, are height and density of tree crowns, air circulation, humidity,
and character of fuel. So far as known, no measurements of these influences have been made. It was estimated that smoke would rise into view
more rapidly in open stands typical of south exposures than in dense stands
typical of north exposures. It was also believed that lightning-struck
trees, which frequently produce smoke for a short time immediately after
being struck, are more likely to hold dormant fires in the fuels at their
bases for many more days on north exposures than on south exposures. For
these reasons longer vision distance was allowed toward the north than
toward the south in setting up standards in 1931.
For planning purposes the limits of visibility from a given observation point were represented by a figure formed by reducing and flattening the western and southern quarters of the circumference of a circle.
The shortening in the west was to allow for the effect of shadows, and that
on the south to allow for density of stands. Three sizes of this figure
were used: One for "minimum" burning conditions, when good visibility normally prevails, a smaller one for "average" burning conditions, and a still
smaller one for "maximum" burning conditions. In planning detection coverage for any one of the three degrees of burning severity, theoretically the
part of the area seen from any station that lay beyond the distance limits
applicable should have been disregarded. Practical considerations prevented doing this completely.
Around the four representative points studied the average acreage of
seen area per mile of distance from the observer was found to be as follows:
Within 4 miles, 3,500; within 6 miles, 3,093; a n d within 10 miles, 3,416.
It is evident that between distance limits of 4 and 10 miles area seen from
these four points was directly proportional to the radius, and averaged
3,336 acres per mile of radius. This figure may be regarded as a rough
index to the topography characteristic of the western white pine type in
north Idaho. For distances less than q. miles this index value given would
be too low. Typical topography in the western white pine type is shown by
the frontispiece and by figure 16-A on page 52. An area, if entirely in
view from an observer, increases in proportion to the square of the area's
radius. Examinations of the seen areas of many hundreds of lookouts brings
out the fact that beyond 10 miles the increase in seen area drops off
abruptly except in the direction of valleys, which are usually narrow. The
portion of the region not occupied by white pine type is characterized, in
general, by wider valleys, to which the index given probably is not applicable. A view of such topography is given in figure 16-B on page 55.
In plan work several factors tended toward disregard of visibilitydistance limits and toward the assumption that detection was effective
throughout seen area. The topography of the region is such that much of
VISIBILITY DISTANCE AND SEEN AREA
60
the area seen at a distance greater than 6 miles, and a considerable part
of that seen at less distance, is seen from several stations; that is,
the "tops of the world" are visible to all detectors. An overlap of 50
to 60 percent unavoidably exists when the largest number of stations is
manned for worst burning conditions. When new coverage was added in plan
work by selecting an additional station, attention was focused on making
the new seen area include the greatest possible area of country not previously covered, regardless of a distance limit. Distribution of new
stations was strongly influenced by the frequent absence of satisfactory
detection points where stations were needed. Since every detector is
also smokechaser, in locating stations some concessions were made to
travel-time standards of smokechasers.
After considering the many influences that govern visibility distance and those that make an even distribution of man-power stations
impossible, it is appropriate to question the desirability of working with
any visibility-limit lines other than concentric circles corresponding
with degrees of atmospheric obscurity. A circle is much easier to work
with than any other figure. It is doubtful that selection of stations in
present plan work would have been changed materially, if at all, by use
of circles, and their use in the future is recommended. However, in
regions of rugged mountains such as that covered by this study, where
shadows are a strong factor, the visibility distance of smokes in the sun
is not an acceptable standard. Fire control, being a problem of only a
few percent of all fires, demands in this region that the more critical
requirements of seeing small smokes in the shade and toward the sun govern
to some extent the size of circle used. A decision might correctly be
made in some cases that meeting this requirement would be more expensive
than the damage to be expected through not meeting it.
The need for promptness of discovery depends upon severity of
burning conditions; even in the absence of smoke, it is desirable to
speed up discovery as burning conditions become worse. The only way to
accomplish this (excluding considerations of personal efficiency) is to
shorten the maximum distance from detector to smoke by manning more detection stations. The results of plan work and investigations indicate that
the radii of vision-distance limits to be observed in this region when
planning the locations of detectors for burning conditions of "maximum,"
"average," and "minimum" severity should be approximately 6, 8, and 15
miles, respectively. These standards should be used as guides rather than
applied rigidly.
TRAVEL TIME AND STRENGTH OF ATTACK (TRANSPORTATION PLANNING)
For heavy and light reinforcements, the time limit within which
control must be' established is 10 o'clock of the forenoon following a
fire's escape, which is the end of the first work period. Travel is one
FIRE CONTROL PLANNING—NORTHERN ROCKY MOUNTAIN REGION
of the jobs of action that must be completed within a part of the time l i m i t .
The man power to be sent i s determined at the time. For i n i t i a l attack the
limit i s also 10:00 a.m., but further standards, specifying strength of
attack in r e l a t i o n to travel time, burning conditions, and fuels, have been
set up. They are stated by tables 11 and 12, page 66.
Heavy-Reinforcement Service
Since no spot of appreciable size could be identified at which 100
f i r e f i g h t e r s or more would not at some time be needed, every spot was assumed
to require t h e i r work. This i s called heavy reinforcement action, or heavy
second-line defense. The c i t i e s from which 100 men or more can be obtained
on short notice are Spokane, Lewiston, Missoula, Butte, and Great F a l l s .
Anaconda i s included with Butte. The locations of these c i t i e s are shown by
figure 1, and t h e i r populations by table 2. Control of f i r e s by 10:00 o'clock
a.m. was assumed to require delivery at f i r e l i n e s and the beginning of work
there by daylight. After allowing before daylight for hiring, assembling,
feeding, r e s t i n g , and organizing men ready for work, following the e a r l i e s t
probable hour of evening c a l l s for reinforcements, a travel-time allowance of
8.5 hours was decided as applicable to heavy reinforcement action.
As shown by figure 9 on page 37 several very large areas of the region
were not reachable in 1933 within the allowance of 8.5 hours. The larger
portions of two of them have not been brought within t h i s limit to date and
cannot be brought within i t by road construction even of the highest type.
For these areas only three a l t e r n a t i v e s in planning appear to be available;
establish lighted airplane routes and landing f i e l d s and provide radio bea- '
cons to overcome smoke obscurity; s t a t i o n large crews within a network of
roads; lower the travel-time standards and hope that control will be possible
within the second work period instead of the f i r s t .
The fact should be pointed out that many f i r e s have been so large
that i3o men delivered by daylight could not possibly gain control by 10:00
o'clock a.m. In fact, applying the r a t e of work frequently accomplished, by
large crews, 1 chain of held l i n e constructed per man per day, not more than
100 chains of controlled perimeter could be expected. Another fact to be
pointed out i s that 100 men, or even fewer, may be successful at some shorter distance, since a longer time before 10:00 a.m. i s available. The plan
work, as carried out for heavy second defense, went no further than to
design a system of roads that would permit delivery of crews within 8.5
hours by automobile-bus plus walking time from the c i t i e s specified. Otherwise, for the t e r r i t o r y lying outside the 8.5-hour time limit the same gener a l scheme of planning was followed.
Considering the facts discussed, i t should be obvious that d i r e c t ness of road route and high speed standards of construction are factors that
compete for importance with and may be of added assistance to number and
efficiency of f i r e f i g h t e r s , and they c o n s t i t u t e a factor that can overcome
handicaps in distance from man-power bases. Under certain conditions i t may
even cost l e s s in t o t a l to expend more per mile along a direct route than
l e s s per mile along a devious route.
REINFORCEMENTS - ROADS - LANDING FIELDS
62
Since direct trunk routes are definitely a necessity for heavy reinforcement service, and they are not necessities for light reinforcement and
first attack services, direct routes were given first consideration in
transportation phases of planning. The latter were planned as connecting
links and spur roads, respectively.
Ll£lli~E^iSl2Icemeni Service
For severe burning conditions small mobile reinforcement crews were
planned, to be stationed at strategic locations. Communities were considered man-power bases and an estimate of available man power was made for
each. A wide range of action was provided by landing fields and secondary
road links between trunk roads.
Travel times corresponding to fuel resistance and size of crew were
worked out, and are shown by table 9. Before applying the travel times to
determine the area covered by any crew, the estimated time required to
assemble the men at a community center, or to assemble and transport them
by airplane to a forest landing field, was subtracted. Details of planning
roads and landing fields are explained in Part II.
Table 9.—Time allowed light-reinforcement
crews for
assembly
plus travel when burning conditions
are "maximum. "
:
:
:
:
:
:
:
:
Fuel
resistance
to
control
Extreme
High
Medium
Low
;
Time allowed for assembly plus travel for
indicated number of men
:
:
5
8 j 10 : 16
20 : 25 : 30 : 40 : 50 :
Hours .Hours Hours:Hours .Hours :Hours: Hours:Hours :Hours:
: 0.7 2.1: 3.1: 3.5: 3.9: 4.1:
j
. 3.4. 5.1: 7.8 8.6: 9.2: 9.5: 9.8: 9.9:
8.3 ! 9.5: 10.0 10.0: 10.0: 10.0: 10.Of 10.0:
: 5.3
8.0 10.0 10.0: 10.0 10.0: 10.0: 10.0: 10.0: 10.0:
Light reinforcement action is assumed to begin in late evening,
approximately 6:00 p.m. No travel times longer than 10 hours were allowed,
because of the frequent early forenoon increases in aggressiveness of
fires when burning conditions are severe.
The size of fire which this service is expected to control is 50
acres or less. Selection of this size was based on the data shown by figure 17, A. In this figure it will be observed that only 7 percent of the
2,714 fires that occurred in the very severe seasons, 1926 and 1929, were
larger than 50 acres. By observing the sharp bend of the curve for sizes
larger than 50 acres, it becomes obvious that an attempt everywhere to control larger fires with this form of service would entail very high expenses
to maintain many more light reinforcement crews, and they would rarely be
called into action. In plan work, aimed at satisfying the travel times,
based on a 50-acre size, it was necessary to design an intensive system of
roads in addition to placing many more crews than have been available in any
locality in the past. For larger fires judgment at the time is expected to
govern the action to' be taken.
63
FIRE CONTROL PLANNING—NORTHERN ROCKY MOUNTAIN REGION
IHllL^I i l l 2 £ £ (Smok^lliiaiUjr Service)
Smokechasers are provided in plans with spur roads to t h e i r s t a t i o n s
and into areas of worst fuels.
I t will clarify matters to admit that a few f i r e s become so hot
within a few minutes after ignition that men cannot work d i r e c t l y in front
of them, and that at such a spot a hundred men are no more effective than
one. A few f i r e s spread so rapidly almost from the moment of ignition that
i t i s impossible economically to place man power close enough to overtake
t h e i r advancing perimeters. These f i r e s , if they develop into conflagrat i o n s , are part of the 2 percent considered on page 26 for which i n i t i a l
attack preparedness i s l i k e l y to be i n s u f f i c i e n t .
Under the methods described in the following paragraphs, different
allowable travel times can be determined for any r a t e of spread, depending
upon the r a t e of work applied. A limiting factor, however, i s whether
heat from the f i r e will permit the man power to control f i r e perimeter at
the r a t e assumed. Plans contemplate success of i n i t i a l attacks during midday burning periods. On days when severe burning conditions p r e v a i l , every
minute from the time of discovery to that when control i s insured i s fraught
with the p o s s i b i l i t y of a large run. Such runs may be caused by whirlwinds,
by strong direct winds (with or without the influence of slope), and by convection currents resulting from rapid production of M a t , that cause f i r e s
to climb into t r e e crowns.
With these considerations in mind, the f i r e reports were analyzed for
time used in successful attacks and a limit was set on the o v e r - a l l elapsed
time between discovery and actual c o n t r o l . This time limit designated "C"
in the following l i s t of factors v a r i e s with r a t e of spread. For i n i t i a l
attack to be successful the operations of discovery, report, get-away,
t r a v e l , and firefighting must be completed while a f i r e i s actively increasing in s i z e .
The factors of i n i t i a l attack are as follows:
C
= over-all control time between discovery and actual control,
expressed in hours.
0.25 hour m time allowed for report and get-away.
W
= r a t e of constructing held f i r e l i n e , expressed in chains per
hour. Rates accomplished by using crews are not proportional
to numbers of men in excess of 4.
p
= average r a t e of perimeter increase, from discovery to time
attack i s begun, expressed in chains per hour.
t
= t r a v e l time, the unknown and desired quantity, expressed in hours.
The i n t e r r e l a t i o n of these factors i s expressed by the following
equation:
b4
—
—
18
Ifc
i
IA
k
A
i
l
> 10
1
kj
(^
kj
l
u
5 ZE
•
8
n
8
10
12
14
Ifo
!8
20
22
24
2fo
28
30
32
34
HUNDREDS OF ACRES
/.<o
24
22
20
S.C
J5
18
lb
14
W<
///
i
RATE
_0_F
ii 0
i:10
SPREAD
12
1 0' L
8
^\
7/
<o
4
2
u
10
H.R.-CONTROL
R.
20
30
40
50
<o0
70
80
90
IC)0
C H A I N S PER HOUR
\i10
BY HEAVY R E I N F O R C E M E N T S
S.C.= CONTROL BY
L.R.= C O N T R O L BY L I G H T R E I N F O R C E M E N T S
M10
IErO
Ifcifl
I7(
SMOKECHASERS
FIG, 17.—DISTRIBUTION OF FIRES AS TO SIZE AND INITIAL RATE OF SPREAD
A, Acreages of fires of two severe seasons, 1926 and 1929. Basis, total 2,714
fires. Curve shows proportion of fires that were of designated or greater size,
B, Rates of spread of fires of 10-year period 1921-30, Basis, total 8,789 fires
for which rate of spread was recorded. Curve shows proportion of fires for which
average rate of perimeter increase between discovery and first attack was that
designated or greater,
R-l, western forests
INITIAL ATTACK
65
The derivation of this formula, and considerations essential to it,
are given in Part I^F^/i5It is assumed that only half the fire perimeter
needs to be worked within the over-all control time, "C," the remainder
being left to be worked, under less pressure, immediately thereafter.
Table i o « — V a l u e s used in travel-time
formula
of burning conditions
corresponding
Danger
Meter.
•» Resistance
• • to control
|
P
Chains
per
hour::
j Hours :
••
18
i 1 Extreme
:i 3.0 ;
10
:: High
!. 3.5 :
8
:; Medium
1l 4 # 0 5
:
6
:: Low
: 4.5
1
Rate of spread
Extreme
High
Medium
Low
i/
c
;
for "maximum"
to class 5 of
class
the
•
•
11/
•
•
:Chains per man hour
•
•
•
0.2
•
0.8
•
•
2.0
•
•
3.2
•
Applicable to each nan of crews not larger than 4 men. The method of
work is assumed to be hand labor, withont water, with the most suitable
tools. Because rates of saokechaser work according to•fuel resistance
could not be obtained from the records, 1,344 estimates covering a
wide variety of fuel conditions were obtained from experienced men.
The range of these estimates was divided into three equal parts called
Low, Medium, and High resistance; the lowest rate was assigned to
Extreme resistance.
Using the values of table 10 in the formula allowable, travel times
were worked out and are shown in table 11. The travel time and strength
of attack specifications of this table were used in plan work. Due to
subsequent small revisions in table 10, the formula now gives slightly
different results from those shown in table 11.
It should be kept in mind that the specifications of table 11 apply
only to action in localities where class 5 is indicated by the Danger
Meter. This is in the lower range of the class of burning conditions called
"Maximum." Until sufficient studies have been made to determine the length
of time fires can be allowed to burn before men cannot work directly on
their fronts, judgment must govern the speed and strength of attack to be
applied where Danger Meter ratings are in classes 6 and 7.
With fuels that require more than one man in initial attack, it
was assumed in planning that the men for any fire could come partly from
each of several stations located within the allowable travel time limits.
66
FIRE CONTROL PLANNING—NORTHERN ROCKY MOUNTAIN REGION
Table 11.—Smokechaser travel
time and number of men required
in
initial
attack for indicated
fuel types when burning
conditions
are "maximum. • j/
Rate
Of
spread
Extreme
High
Medium
Low
Requirements by class of fuel resistance to control
Extreme
:
High
:
Medium
:
Low
J Travel
Travel
Travel \
Travel ,
; time . Men time . Men : time , Men : time
Men
Hours .Number: Hours .Number: Hours Number Hours Number
:
:
:
:
0.50 J 20 :
0.50
7 ,.
0.50 :
5 .
0.50 :
1.00 :
1.00 ::
1.50 !
5 • 1.00
4 . 1.00
1.75
3
2 : 2.25
4 ]S/
3
2 :
2 :
yz
0.50
1.50
2.25
3.00:
±/
Burning conditions are represented by Danger Meter class 5.
3/
Cheat grass is the only fuel assigned this classification.
2
2
2
For burning conditions classed as "average," corresponding to
Danger Meter classes 3 and 4, each of the travel allowances of table 11
was increased 50 percent and only one man was required for attack. 'The
allowances obtained in this way are shown by table 12. The relation of
approximately 1.5 to 1 was found by studying the actual travel times that
have been in effect on several national forests where a high degree of
success was attained under average burning conditions.
Table 12.—Smokechaser travel
for indicated
fuel
'average. "
Rate
of
spread
Extreme
High
Medium
Low
times
types,
required in initial
attack,
when burning conditions
are
• Requirements by class of fuel resistance to control
Extreme
:
High
:
Medium :
Low
Travel :
Travel
:
Travel
:
Travel
time
time
:
time
time
Hours
Hours
:
Hours
Hours
;
:
:
0.75
0.75
0.75
:
0.75
1.50
1.50
2.25
!
:
1.50
1.50
2.50
3.50
:
:
0.75
2.25
3.50
4.50
The specifications shown represent steps in required action. Oneman attacks have been successful in every fuel under low degrees of burning severity. As conditions become more severe it is expected that firecontrol managers will apply gradations between these steps by increasing
the numbers of men sent to fires and the speed of action.
INITIAL RATES OF SPREAD
6/
Simply because a mathematical formuLa has been developed and used in
determining t r a v e l times, one i s not to infer that the specifications of
tables 11 and 12 are correct. The formula only places the factors in correct relation to each other. The r e s u l t s are no b e t t e r than the values
placed in the formula.
Since each f i r e report shows hour of discovery and hour of, and s i z e
a t , a r r i v a l of f i r s t man, on the assumption that size on discovery was i n s i g nificant i t i s possible to determine average i n i t i a l r a t e s of spread. The
range, d i s t r i b u t i o n , and trends of i n i t i a l r a t e s of spread were determined
from the records of the 10-year period 1921-30. Rate of spread was measured
in perimeter increase, rather than in area increase, per unit of time,
because the former indicates the r a t e at which suppression work i s i n c r e a s ing.
Figure 17, B, on page 64 shows what percentages of the 8,789 f i r e s of
the 10-year period 1921-30 spread at designated r a t e s . The two graphs of
figure 17 show that from the standpoint of both size and r a t e of spread the
c r i t i c a l problem l i e s in the worst 7 percent of cases.
Figure 18 shows, for f i r e s that originated in given timber and fuel
types, the percentages with designated average i n i t i a l r a t e s of spread. In
the analysis i t was found that the percentages for single and double burns
also f e l l within the range shown by figure 18. I t i s apparent in t h i s f i g ure that average i n i t i a l r a t e s of spread in different types of green, uncut
forests free from insect epidemics and blow-downs varied somewhat in p r o portion to openness of stand.
Figure 19, based on the same data as figure 18, shows the division of
the range of i n i t i a l r a t e s of spread that was adopted for planning purposes.
Thus, for example, the c l a s s i f i c a t i o n "Extreme" was given to fuels in which
i t was to be expected that an i n i t i a l r a t e of spread approximating 18 chains
per hour or more would occur in 16 percent of a l l cases. (As figure 18
shows, cut-over areas contained one such fuel.) Similarly, 16 percent of
f i r e s in fuels classed as "High," "Medium," and "Low" would be expected to
spread at the r a t e s of 10, 8, and 6 chains per hour or more, respectively.
These c l a s s i f i e d r a t e s of spread are the ones designated "p" in t a b l e 10.
Rough evidence indicates that these r a t e s of spread correspond approximately
with Danger Meter c l a s s 5. Hence, 16 percent of a l l f i r e s occur in Danger
Meter classes 5, 6 and 7 and many of them are expected to spread too rapidly
to be caught by application of the t r a v e l times and strengths of attack
specified for i n i t i a l attacks in table 11. For the slowest spreading 84
percent, control by i n i t i a l attack i s expected.
Figure 17, Bt shows the percentages of f i r e s estimated to require each
of the s e r v i c e s , heavy reinforcements, l i g h t reinforcements, and i n i t i a l
attack. I t must be recognized that the divisions are only approximate. Some
rapidly spreading f i r e s are stopped by changes in fuel, natural b a r r i e r s ,
and r a i n . On the other hand, slowly spreading f i r e s occasionally escape.
68
FIRE CONTROL PLANNING—NORTHERN ROCKY MOUNTAIN REGION
METHODS OF SELECTING MAN-POWER LOCATIONS AND ROADS
The work of determining locations for man power and roads would be
r e l a t i v e l y simple if the personnel of each of the services—detection,
smokechasing, and light-reinforcement action—were independent. In designing an arrangement of smokechaser s t a t i o n s , frequently i t was found that
such a s t a t i o n was needed in approximately the same place where a s t a t i o n
for detection purposes had previously been planned. If smokechasing duties
were assigned to the detector, an additional man would be made available
for placement elsewhere. If both duties were assigned to a given number of
men, s t a t i o n s for each service would be closer together than they would be
if only one of these duties were assigned to each s t a t i o n . Furthermore, i t
became apparent that a small crew located primarily for light-reinforcement
action could perform a l l three d u t i e s , and that the effectiveness of crews
to which the t r i p l e duty was assigned was greatest where the road system
had been designed to suit t h i s combination of d u t i e s . I t was found that
the t o t a l cost of men and roads necessary to satisfy a l l standards would be
much l e s s if the dual r e s p o n s i b i l i t i e s of detection and attack were assigned
to the man power of every s t a t i o n . In plan work these two r e s p o n s i b i l i t i e s
were assumed to be assigned to the man power of each s t a t i o n .
The dual-responsibility system i s most economical even if an additional man must be assigned to each of a considerable percentage of s t a t i o n s
for detection duty only when burning conditions are most severe. In many
places absence of a detector, caused by sending the only man at a station to
a f i r e , need not c o n s t i t u t e a serious disruption of service. Of the t o t a l
area seen from the s t a t i o n s manned at times of maximum burning' severity, 50
to 60 percent i s covered by two or more detectors. This overlapping i s an
unavoidable product of an endeavor not to leave more than 15 to 25 percent
of any forest unseen by any detector. Before deciding that an e n t i r e s t a tion force cannot be allowed to go to f i r e s , the planner should study the
seen area l e f t uncovered by t h i s action, p a r t i c u l a r l y as to fuels and as to
frequency and causes of f i r e s .
Assigning dual r e s p o n s i b i l i t y to every occupied s t a t i o n influences
the location of s t a t i o n s with reference to topography. I t tends to keep
firemen away from high, rugged peaks and out of the bottoms of deep-cut,
crooked v a l l e y s . With most of the s t a t i o n s located in wide valleys or at
intermediate elevations, i t was found that inexpensive roads could be
constructed to most of them, and such roads were planned.
By providing roads where only t r a i l s existed previously, each smokechaser i s enabled to cover more area within a given time, and a reduction
can be made in the number of smokechasers needed within a given area. The
Norcross-Grefe (14) method of transportation planning i s based on doing
t h i s to the extent that i t i s most economical in the t o t a l cost of roads
and smokechasers. In t h i s region removal of a smokechaser also accomplishes the undesirable removal of a detector. Topography makes i t d i f f i c u l t
to occupy enough detection s t a t i o n s to satisfy seen-area coverage standards.
The detection s t a t i o n s must be occupied regardless of road mileage provided.
LV
1!
r
i1
1
20
1
\
\
\
\
15
\
\
.1
1 \
10
5
ia^
ib
s2
1 i
4-^
10
20
30
40
CHAINS
50
k0
70
80
90
100
PER HOUR
FIG. 1 8 . INITIAL RATES OF SPREAD IN DIFFERENT TIMBER TYPES
Basis, fastest-spreading 25 percent of t o t a l 8,789 f i r e s during 10-year period
1921-30 t h a t were attacked within 12 hours and for which r a t e of spread was
recorded. Curves show percentages of f i r e s for which r a t e s of perimeter i n crease between discovery and f i r s t a t t a c k were those designated or g r e a t e r .
With the exception of w cut over," each of the types represented i s uncut
green forest of pole size or l a r g e r . The types represented, with numbers
of f i r e s i n each, are as follows:
Ia Cut over
1,103 f i r e s 4 Douglas f i r
215 f i r e s 6 Subalpine 850 f i r e s
l b Brush-grass
710
•
4 Lodgepole pine 639
•
7 White fir-172 •
2 Ponderosa pine
996
"
5 White pine
772 n
cedar
3 Larch-fir
673
"
5 Cedar-hemlock HO
*
7 Spruce
169 "
R-l western f o r e s t s .
10
20
30
40
CHAINS
50
PER
hO
10
80
90
100
HOUR
FIG. 1 9 .
INITIAL RATES OF SPREAD AS CLASSIFIED FOR PLANNING
PURPOSES
B a s i s , t o t a l 8,789 f i r e s of 1 0 - y e a r p e r i o d 1921-30 t h a t were a t t a c k e d
w i t h i n 12 hours and for which r a t e of spread was r e c o r d e d . Curves
show p e r c e n t a g e s of f i r e s f o r i & i c h a v e r a g e p a t e s of p e r i m e t e r i n c r e a s e
between d i s c o v e r y and f i r s t a t t a c k were 12iose d e s i g n a t e d or g r e a t e r .
Curves I a , l b , 2 , and 7 a r e d e r i v e d from F i g . 18 . D i v i s i o n s of range
of v a r i a t i o n a r e shown i n t e r m s t h a t were u s e d i n f u e l mapping.
R-l western f o r e s t s .
SELECTION OF STATIONS
71
Another very important consideration is that peak loads in number of lightning fires, to be expected anywhere, are likely to give more than one fire
to each smokechaser. Reducing the number of smokechasers would simply
aggravate the difficulty. In plan work the requirements of the road system were based on reinforcement action, except for providing firemen with
connections to the system and providing other roads necessary to satisfy
travel-time standards.
For many years it has been the general practice in the region to
assign smokechasing duties to detectors and in periods of emergency to
place on duty additional firemen charged with both responsibilities. However, a large number of smokechaser stations have been manned where detection work could not be performed. In plan work the most desirable arrangement of stations was sought with almost entire disregard of the locations
of existing stations.
SILHOUETTES OF COVERAGE
Seen-area Silhouettes and Composites
A map showing the area seen from each of the 3,000 points studied as
potential detection stations was copied in lacquer on a sheet of thin transparent material similar to celluloid. When such a "silhouette" was placed
over a glass table-top lighted from beneath, the seen-area could be studied
in relation to such conditions as fuel, frequency of occurrence and values
at stake, shown on overlay maps or tracings. Assuming any set of potential
stations to be occupied, by placing their seen-area silhouettes over the
light in correct geographical relation to each other, as illustrated in figure 20, A, it was possible to see what areas were covered by the detection
service, and whether they were within the vision distance limits allowed
for "maximum," "average," or "minimum" burn conditions (described under the
heading "Visibility Distance and Seen area," page 60). By coloring the seen
area within the 6-mile limit black, that lying between 6 and 8 miles red,
and that between 8 and 15 miles green, it was possible to determine the seenarea coverage in relation to allowable vision distance limits. Many different sets of silhouettes were examined over the light until the most satisfactory combination of seen areas was determined. In endeavoring to obtain
the desired degree of coverage and at the same time occupy the fewest
possible number of stations, attention was focused on having the small
unseen areas coincide with areas containing least difficult fuels and fewest numbers of previous fires.
Smokechaser Silhouettes and Comjx>si_tes
With allowable travel time placed on a tracing of each of the different fuels mapped, it was possible to determine from this tracing and the
map of existing roads and trails how far the smokechasers of each station
could reach. Over these combined maps a silhouette of smokechaser coverage
was worked out on thin transparent paper. The areas covered under travel
standards for "maximum" burning conditions specified in table 11 were shown
72
FIRE CONTROL PLANNING—NORTHERN ROCKY MOUNTAIN REGION
by black pencil and additional areas reached under standards for "average"
burning conditions, specified in table 12, were shown by red crayon. At
long distances from a station, fuels with long travel-time allowances were
covered, while those with short time allowances were uncovered, that is,
were not reached. Additional coverages obtainable by constructing additional roads and trails were determined by the same procedures. Combinations of smokechaser silhouettes were studied over a glass-top table
lighted from beneath in the same way that seen-area silhouettes were
studied for best fit together and for danger in uncovered areas.
Since every detector is also a smokechaser, it was necessary to
adjust determinations as to the stations most desirable for detection and
those most desirable for smokechasing. The procedure found most satisfactory for this purpose was alternate use of two glass-topped tables. On one
table detection coverage was built up; and on the other, smokechasing coverage. Detection coverage was given preference, because it was found that the
number of places from which detection coverage could be obtained was much
more limited than the number desirable to occupy for smokechasing purposes.
Whenever a seen-area silhouette was inserted in the detection composite being built up, the smokechasing silhouette for the same station was inserted in the smokechasing composite on the other table. In this way the
stations to be occupied were determined and tracings (composite silhouettes)
of the areas covered by each of the services were obtained. The smokechasing coverage added by occupying any particular selected station might permissibly be small if the detection coverage added was large, and vice versa.
The value of a station was determined by the sum of new coverages obtained
in each service and by the degree of danger existing in these new coverages.
("New coverage" means the area added after certain stations have been selected. Obviously, new coverage depends upon the order in which stations are
selected. )
Attempts to make mathematical ratings of new coverages to govern priority of selections was abandoned when it was found that equally accurate and
more practical selections could be made in much less time by visual methods.
It was found that when the detection and smokechasing coverages have each
been built up to approximately 60 percent, the uncovered remainder usually
consists of small disconnected patches and irregular narrow strips. In them
it is desirable to evaluate carefully any new coverage gained, for the reason that the addition is frequently so small as to be economically questionable.
Reinforcement Coverage Composites
Coverage composites for the services of light and heavy reinforcements were worked out in conjunction with road plans. For light reinforcement service the areas were shown that could be reached within the travel
times specified by table 9 for different numbers of men, available in communities or planned for placement in camps. For heavy reinforcement service, the areas that could be reached in 3.5 hours' travel from Spokane,
Lewiston, Missoula, Butte, and Great Falls were shown. In addition this
composite showed the area that could be reached in 12.5 hours* travel time,
and the area that lay within 4. hours' walking distance from the nearest
road, landing field, or man-power base. The coverages existing and planned in the different forest units of the region are shown by table 13.
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FIG. 20.—DETECTION J0VERAGE
A. Method of sorting seen-area silhouettes for desirability and best
fit together into composites.
B. Percentage of coverage obtained according to number of stations
manned per million acres.
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75
FIRE CONTROL PLANNING—NORTHERN
ROCKY MOUNTAIN REGION
For heavy and light reinforcement services table 13 shows the percentage of area reached in 1935 and that planned on each of the forests
included in plan work and under each of the conditions of arrival time and
walking that are important considerations in fatigue and control within
the first work period. Large variations in existing and planned coverages
will be observed. These variations are caused largely by exclusion of
roads from wilderness areas, by variations in distance from man-power
bases and by the impossibility of reaching within 8.5 hours the larger
areas shown in figure 9 of page 37. Mileages and costs of construction
and maintenance of existing and proposed roads were worked out and the proportions chargeable to fire control were estimated. Annual costs were
determined by amortizing investments on a 50-year-life basis.
RELATIVE DANGER RATINGS
After detection coverage has been built up (by the methods of selection just described) to about 60 percent, each new station adds a relatively small area to the total already covered. The same condition is found in
building up coverages in the services of smokechasing, light reinforcements
and heavy reinforcements. In order to justify further additions to each
coverage the planner must evaluate what is gained, and continually he must
determine whether an addition is more valuable in one place than in another.
In the areas under consideration different numbers of fires per unit of
area must be expected, fuels are different, and the values at stake vary
greatly. The decision as to relative danger cannot be based on any one of
these factors alone, but must be based on an integration of them. A method
of integration was developed and a map was made showing intensity of total
danger existing in different areas. Additions in coverage were evaluated
by multiplying the acreage added by the intensity of danger within the area.
The product expressed as so many danger points showed the relative merits of
adding a station (or road) in one place or another, no matter how far
separated the proposed stations (or roads) might be.
In working out these ratings it was recognized that the danger f~om
one fire is the sum of probable expense plus probable damage. In total, the
danger is expense plus damage multiplied by the number of times it will
happen. Expressed mathematically
(Expense + Damage per fire) x frequency of Occurrence = Danger
Damage is enclosed within a fire-perimeter along which expense is
incurred. Rate of fire spread and resistance to control, shown on fuel
maps, determine the rate at which both damage and expense will accumulate.
After arbitrarily assuming a length of burning time, the fuel maps provide
the basis for determining probable expenses according to the resulting
size of fire and resistance of fuel to control. A map showing probable
damage per acre was made by methods explained on page 77.
In working out these ratings fires were assumed, to spread 4 hours
(the average duration of uncontrolled daily spreads) at each of the rates
shown for Extreme, High, Medium, and Low in table 10. For each of the
fire sizes thus obtained the man hours of firefighting time were determined
FACTORS OF DANGER
76
for resistances to control Extreme, High, Medium, and Low. In this way
the expense of control for each size of fire was expressed in man hours.
Expense is not confined to fire-line work, and overhead, transportation, equipment, and presuppression costs must be included in order
to obtain the complete expense to add to damage. Dividing all costs of
the period 1921-30, including Regional Office overhead, by the number, of
man hours reported on actual firefighting work, the cost per man hour
was found. That cost was used in working out the probable expense of
control.
In spite of the apparent sources of error involved in making a
fire-danger map by this method, the classifications worked out seem to
correspond satisfactorily with opinions of different groups of wellinformed men regarding the relative importance of fire control on different areas. Substitution of judgment integrations of these factors for
the more laborious method used is not desirable because judgments have
failed to be consistent and have failed to refine estimates to specific
small areas. Whatever opinion is held regarding the value of danger
ratings integrated by this or any other method, it must be admitted that
each of the factors set forth becomes an important consideration in some
place and that no one factor can be selected as the sole consideration in
determining the degree of fire-control organization needed. It must also
be admitted that opinions held by administrative officers regarding
values have governed the distribution of presuppression funds. The attempt
has been made here to recognize values systematically. Nothing more is
claimed for the danger formula than that it states the natural relation
of factors to each other. Until these factors can be evaluated accurately,
it appears more correct to estimate them as accurately as possible than to
avoid such estimates.
The numbers of danger points that would be covered by use of proposed roads, trails, detectors, and smokechasers have been used as priority ratings of the sequence in which they should be established.
Fuels Worse Than Average
In building up coverages of detection and smokechasing, fuel alone
was allowed to govern the selection of stations up to the point where
uncovered areas became ragged. This procedure was found not to conflict
with the advocated use of total danger ratings. A tracing of areas where
fuels were worse than average was used continually as an overlay on coverage composites being built up. The class of fuel considered average, that
with medium rate of spread and medium resistance to control, was thrown
with all fuels given longer smokechaser travel time allowances. The fuels
classed as worse than average were found to cover 25 to 35 percent of the
areas of different forests.
77
FIRE CONTROL PLANNING—NORTHERN
ROCKY MOUNTAIN REGION
Ten-Year Occurrence Ma£
Another tracing used as an overlay showed the number of fires per
thousand acres that should be expected. In making this, a square of 1,000acre size was used over a tracing of all fires that occurred in 10 consecutive years, and whatever number of fires fell within it was written on the
tracing at that spot. After the tracing was completed for a forest, the
entire area was subdivided into parts that appeared to be approximately
uniform, and each part was labelled with the nearest whole number of fires
per thousand acres estimated reasonable to expect there in the next 10
years. No area received a rating less than 1. It should be noted that any
one of these final numbers is not the average number of fires that occurred
per thousand acres.
In this work, fires caused by railroads and brush burning were
excluded from consideration because recent trends indicate that laws and
fire-prevention efforts will make their influences insignificant. Areas
where incendiary fires were conspicuous were identified and eliminated
from general consideration. After the selection of stations was completed,
these areas were restudied, and if coverages were insufficient, added stations were determined for occupancy as long as the incendiary cause continues to be an important consideration. Fires caused by lumbering were
excluded because the area subject to them moves with logging. However,
from the standpoint of fuels, areas logged or about to be logged were given
special consideration. It was found that fires caused by smokers, campers,
and fishermen were more numerous in the vicinity of logging operations.
This was attributed to the fact that logging roads make areas more easily
accessible to recreationists. Allowances were made for changing tendencies
in these causes also. The areas, shown by figure 5 on page 31, where peak
daily loads of lightning fires have been repeated were given special consideration.
A valuable use of the 10-year occurrence tracing was in determining
the seasonal period of occupancy for each station. This tracing showed the
origin spot of every fire by a small circle colored to show the size class
of fire that developed. Within the circle a letter showed the cause, one
number showed the year and another the month, and the color of the enclosed
figures showed 10-day period of occurrence. By studying this tracing it
was possible to shorten the previous period of occupancy of many stations
and use the savings for more men or stations when and where conditions were
more critical.
Damage Valuations
The Region One Division of Forest Management worked out, by extensive field work, rough appraisals of stumpage value. Based on these
appraisals, average fire-damage valuations per acre were estimated. Site
quality was evaluated regardless of whether mature timber was present.
In appraising the values of stands it is necessary to recognize
that protection from fire is a factor of value. With a low degree of protection a given stumpage is worth less than where a high degree of protection is paid for by some agency other -that the purchaser.
COVERAGE ACCORDING TO BURNING CONDITIONS
78
If v a l u e s at s t a k e a r e used as a f a c t o r in n e c e s s a r y s t r e n g t h of
f i r e - c o n t r o l o r g a n i z a t i o n and placement of man power, t h e p l a n n e r must
r e c o g n i z e t h a t h i g h - v a l u e s t a n d s now mature w i l l w i t h i n a few y e a r s be
r e p l a c e d by r e p r o d u c t i o n .
If a s t a t i o n remained in use throughout a r o t a t i o n , t h e v a l u e s covered by t h a t s t a t i o n would vary from zero to t h a t at
m a t u r i t y . For p l a n n i n g p u r p o s e s o n e - h a l f of the a p p r a i s e d v a l u e p e r acre
of a mature stand was used as t h e average v a l u e . No v a l u e s of s a l v a g e
a f t e r f i r e s were allowed except in t h e ponderosa p i n e t y p e .
The Region One D i v i s i o n of Lands worked o u t , with f o r e s t s u p e r v i s o r s ,
rough a p p r a i s a l s of p r o b a b l e f i r e damage t o r e c r e a t i o n . C l a s s v a l u e s were
worked out and i d e n t i f i e d on maps. These v a l u e s must be regarded as r e l a t i v e and t e n t a t i v e o i l y . They c o n s t i t u t e a f i r s t attempt t o compare r e c r e a t i o n v a l u e s with wood-products v a l u e s . The v a l u e s assigned ranged from
$0.50 t o $350.00 p e r a c r e , t h e l a t t e r o c c u r r i n g in and adjacent to groups
of summer homes.
Much argument and l i t t l e agreement r e s u l t e d from a t t e m p t i n g tc e s t i mate fire-damage v a l u e s on t h e l a r g e f o r e s t a r e a s of t h e region t h a t are
too i n a c c e s s i b l e , and occupied by too scrubby s t a n d s , to have wood-products
v a l u e s and t h a t have t h e lowest p o t e n t i a l r e c r e a t i o n v a l u e .
Estimates
s o l i c i t e d ranged from $0.10 to $2.00 p e r a c r e , averaging about $ 0 . 5 0 . Since
a l l v a l u e s were rounded off t o t h e n e a r e s t d o l l a r and r e c r e a t i o n had already
been assigned a v a l u e of $0.50, t h e s e a r e a s a u t o m a t i c a l l y f e l l i n t o t h e
$1.00 p e r acre c l a s s and t h i s v a l u e was t h e lowest one used.
COVERAGE ACCORDING TO BURNING CONDITIONS
In making p l a n s for "Average" burning c o n d i t i o n s l o n g e r t r a v e l times
for smokechasers and l o n g e r v i s i o n d i s t a n c e s for d e t e c t o r s were allowed
than in making p l a n s for the most s e v e r e c l a s s of burning c o n d i t i o n s , c a l l e d
"Maximum." For "Minimum" burning c o n d i t i o n s , s t i l l l o n g e r v i s i o n d i s t a n c e s
were allowed. Coverages were worked out for each of t h e s e s e r v i c e s under
each c l a s s of burning s e v e r i t y . For t h e s e r v i c e s of l i g h t r e i n f o r c e m e n t s
and heavy r e i n f o r c e m e n t s coverages were worked out only for "Maximum" burning s e v e r i t y , using the s p e c i f i c a t i o n s d e s c r i b e d under "Travel Time and
Strength of A t t a c k , " page 6 1 . Each of t h e coverages mentioned t h a t involved
t r a v e l was worked out using e x i s t i n g roads and t r a i l s and again assuming
t h e e x i s t e n c e of proposed roads and t r a i l s . More e x a c t l y , proposed manpower placements and proposed roads and t r a i l s were worked out in d i f f e r e n t
combinations u n . i l a d e c i s i o n as t o the b e s t combinations was reached.
When the g e n e r a l burning c o n d i t i o n s over a t r a c t of 1 m i l l i o n or
more a c r e s a r e "Minimum," c e r t a i n s p o t s more exposed to drying i n f l u e n c e s
than o t h e r s develop "Average" o r even "Maximum" c o n d i t i o n s . This phenomenon i s f r e q u e n t l y e x h i b i t e d e a r l y in t h e season at lower a l t i t u d e s on south
and west e x p o s u r e s . Mature cheat g r a s s i s one fuel in which a high r a t e of
s p r e a d must be expected on any f a i r day r e g a r d l e s s of c o n d i t i o n s p r e v a i l i n g
over t h e g e n e r a l l o c a l i t y .
I t i s assumed t h a t whatever plan o r n a r t of
p l a n , a p p l i e s t o t h e s p e c i f i c burning c o n d i t i o n s in any -raai I a r e a will be
put i n t o e f f e c t .
79
FIRE CONTROL PLANNING—NORTHERN ROCKY MOUNTAIN REGION
COVERAGE IN RELATION TO NUMBER OF STATIONS MANNED
DETECTION COVERAGE
The area seen from the first point selected for occupancy is usually
larger than that seen from any point selected later. Furthermore, the
entire coverage is new and free from overlap. After 50 percent of the total area has been covered, overlap begins to accumulate rapidly. After 80
percent coverage is reached, most of the area seen from each new point
selected is overlap, and the 20 percent of total area still not covered
consists of small, scattered patches. It would require the occupancy of
about 500 points per million acres to obtain 100 percent coverage. As is
shown by figure 20, B, page 73, one-tenth of this number, 50, would cover
65 to 80 percent, varying principally with topography and the amount of
patrol detection required around each point. Each curve of figure 20, B,
shows approximately the percentage of area that would be covered in a particular kind of northern Rocky Mountain topography by occupying any number
of stations per million acres. No limit is placed on vision distance.
Patrols requiring more than 15 minutes from each main station have been
eliminated from consideration.
Detection patrol, as used, means travel from point to point with
observations of 15 minutes required at each point where a stop is made.
No detection is credited from an observer in a moving automobile unless
someone else is driving it.
Obviously, one way to obtain a high degree of detection coverage
per station is to require long patrols from each one. One man could effect
a 90 percent coverage of an enormous area if he were allowed a week in
which to do it. Although it verges on the ridiculous, that is exactly the
form of detection practiced in many of the more remote localities of this
region as late as 191s. In the plan work described here, where roads run
along ridge tops and between good observation points in valleys, patrols
and facilities for frequent communication have been planned. For "Average"
burning conditions longer patrols have been planned than for "Maximum"
burning conditions.
Neither fire-control managers nor planners should fail to recognize
that even the most efficient of detectors do not and could not observe continuously. One may as well believe in Santa Claus as to presume that detectors observe for 24 hours each day, the regular period of duty assigned to
each detector in this region. Assuming that 10 minutes is a reasonable
estimate of the relief time each detector should use between intensive
observations of his seen area, he may be able to effect more detection per
dollar of expense by using this 10 minutes moving to another point than by
walking around within the space of his observatory. A continuation of
planning now being carried on is determination of lengths and routes of
patrols (station-to-station detection) to be used.
SMOKECHASING COVERAGE
80
The most efficient detection by a given number of men is assumed
to be that which effects the largest number of hours of coverage, weighted
according to danger existing in the area covered, that is, according to
the integrated danger in fuel conditions, frequency of occurrence, and
values at stake. Values were regarded as determining in part the number
of detectors (and other factors of strength) allowed per unit of area. A
detailed study to determine for selected areas the basic principles upon
which to plan the most efficient routing and scheduling of detection
patrols is now needed.
A statement of the percentage of area covered by detection in any
locality is not complete and hence cannot be used as a basis for comparison with coverages in other localities until the extent of patrolling and
the vision distance limit used are stated.
SMOKECHASING AND GRADATION INTO LIGHT REINFORCEMENT COVERAGE
In each of the coverages obtained by smokechasers, light reinforcements, and heavy reinforcements, the first stations or roads selected
effect much greater coverage per station or mile than any of those selected
thereafter. Any one of the curves of figure 21 shows for smokechasing
coverage the rapidly diminishing returns per station after 30 stations per
million acres have been selected. This figure shows the wide range of
variation in coverage delivered by any particular number of stations per
million acres. The variation is caused chiefly by mileage of roads per
unit of area and the proportion of road mileage that can be traveled at
high speed. Each curve of figure 21, A, or 21, B, applies to a locality
in which a uniform intensity of road mileage exists. Coverage curves for
low speed areas take the shape of the lower ones while curves for high
speed areas have the shape of the upper ones in each chart.
In comparing figures 21, A, and 21, B, it will be observed that
smokechaser stations must be much closer together when burning conditions
are worst (in the Maximum class) than when they are Average. The comparative numbers of stations required to reach 80 percent of an area are
shown by the upper curves in each chart to be 60 and 30 stations per million acres respectively. The conditions under which these coverages are
possible are found in such areas as those of the Cabinet and Kaniksu forests, where the highest speeds are possible on Federal and State trunk
highways and where many tributary roads (some of them permitting relatively high speeds) make adjacent areas highly accessible.
The lowest curve of chart B shows that in localities where no
roads exist, as in parts of the Selway and Flathead forests, to reach
80 percent of the area under travel times applicable to Average burning
conditions, 145 stations per million acres are necessary. Under the
shorter travel times applicable to worst (Maximum class) burning
81
FIRE CONTROL PLANNING—NORTHERN ROCKY MOUNTAIN REGION
conditions, the lowest curve of chart A shows that more than 200 stations
per million acres are necessary. Considering that even in recent years
such areas have not been provided with more than 35 to 50 stations of all
kinds (including crews) per million acres, the very high cost and the
administrative difficulties of meeting these travel-time and man-power
requirements with trained men and without roads become evident.
Although these travel times are short enough to present a difficult problem in first attack, they still fall short of neeting the needs
of about 10 percent of all fires. It should be recalled that on pages
66 and 67 these travel times were shown to correspond with no greater
severity of burning conditions than indicated by class 5 of the Danger
Meter. To satisfy the still more exacting requirements of Danger Meter
classes 6 and 7 either of two courses may be followed. Still shorter
travel times can be worked out for each fuel, using still greater numbers of men, thus providing even more stations per million acres, or,
dependence can be placed on mobile light reinforcement crews. The
decision, which was made to follow the latter course, carries with it
the obligation to plan for and establish these light reinforcement crews
and the roads, trails, landing fields, and other facilities necessary to
make them effective. In the last two lines of table 13 on page 74 are
shown the existing and planned degrees of coverage by the light reinforcement service.
For the benefit of those now engaged in plan work in other regions
it should be pointed out that evidence of the need for a light reinforcement service in this region is shown in the following places in this
report, figure 2 on page 23, table 6 on page 25, figure 9 on page 37,
figure 17 on page 64, and the discussion on page 67 as related to figure
18 on page 69 and figure 19 on page 70. Thus through analyses the evidence accumulated, but not until sufficient plan work had been done to
construct the curves shown by figures 21, A, and 21, B, was the evidence
conclusive. The gradation from smokechaser action alone into it supported by light reinforcements probably involves the most difficult phase
of successful fire control and hence also the most difficult phase of
plan work.
T
i
r
T
• > — - — IT^— 1 --—~———
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10 20 3 0 4 0 5 0 60 70 8 0 90 100 110 120 130 140 150 160
NUMBER OF STATIONS PER MILLION ACRES
1
1 LLMjiMJJJ-^L^^y^^iS
,y ^^^\^-~—^^—•
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y ^ ^^^Z^-^"^^—T^—^~Z-^~
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/ / /
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imy
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h
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v
r
T
y
1
j
1
10 20 3 0 4 0 50 60 70 8 0 90 I00 MO 120 GO 140 150 160
NUMBER OF STATIONS PER M I L L I O N ACRES
FIG.2
SMOKECHASING
COVERAGE
OF FUELS WORSE THAN AVERAGE
ACCORDING TO SPACING OF MAN-POWER STATIONS
UNDER TRAVEL TIME STANDARDS REQUIRED A - W H E N BURNING CONDITIONS ARE IN WORST CLASS
D - ••
"
ii
it
n AVERAGE ••
DEGREE OF COVERAGE PLANNED.
83
COMPLETENESS OF COVERAGE
Several factors should be pointed out which in the p r a c t i c a l application of plans have been found to lower the standards assumed to be in
effect. One of these i s road and t r a i l maintenance. If maintenance i s
not done so as to permit the speeds of travel assumed in planning, action
w i l l be slower than planned. Telephone maintenance also i s involved in
speed of action. Another factor i s mode of t r a v e l . For a l l s t a t i o n s on
roads automobile t r a v e l was assumed in planning; if automobiles (in good
condition) are not used, the distances reached in a given length of time
will f a l l far short of those planned.
If plans for 100 s t a t i o n s per million acres have been approved and
only 80 are manned, i t i s obvious that the standards have not been met. A
similar condition, the effect of which i s not so obvious, i s encountered in
plan work. The standards may not have been met because of f a i l u r e to plan
the same degree of coverage for areas similar in danger. Any set of traveltime specifications can be modified by the f i r e - c o n t r o l manager, or by the
planner, simply by completing coverage to the degree he chooses. The important point i s that argument regarding s a t i s f a c t o r i n e s s of any travel-time
specifications can lead to no useful conclusions unless the completeness of
coverage to be worked out i s included in the argument.
The economical impossibility of seeing and of reaching within traveltime allowances 100 percent of any large area has been discussed in connection with figures 20 and 21. Planners must be given a limit of completeness at which to stop adding coverage in each of the services of control.
This i s equivalent to saying that some sort of limit must be placed on the
mileage of roads, and the number of firemen and crews allowed in different
l o c a l i t i e s . In areas where a 60 percent smokechaser coverage has been put
into effect, twice the allowable travel time will be required to reach many
small areas which in t o t a l make up the uncovered 40 percent of area. With
So percent of a large area covered, a 10 percent increase over allowable
t r a v e l times will reach almost every spot. Limits based on overtime
required were found easy to apply and were used as guides to desirable
completeness of coverage.
A limit used in deciding whether or not an additional fireman s t a tion was j u s t i f i e d in any l o c a l i t y was based on the quantity of danger
(integration of fuel danger, frequency of f i r e occurrence, and probable
damage) existing in the new coverage under consideration. Unless in the
area added to detection coverage plus that added to smokechasing coverage
a t o t a l of 16,000 or more danger points were found, the station was d i s carded. After applying t h i s l i m i t a t i o n , i t was found that the detection
and smokechaser coverages for whole forests ranged from 40 to 90 percent.
Following an administrative decision in 1935 to* increase efforts everywhere to control every f i r e in the f i r s t work period, a considerable
increase over the number of s t a t i o n s thus limited was made for occupancy
durina the prevalence of most severe burning conditions. These additional
8H
FIRE CONTROL PLANNING—NORTHERN ROCKY MOUNTAIN REGION
fireman s t a t i o n s were selected t o cover the l a r g e s t areas (particularly
those containing dangerous fuels) shown uncovered on detection and smokechaser composites. Road and man-power plans that had been worked out for
light reinforcement action were put into effect to a much greater extent
than previously.
In table 14 the coverage planned for each forest in each of the
four services of f i r e control, detection, smokechasing ( i n i t i a l a t t a c k ) ,
light reinforcements, and heavy reinforcements i s shown. In order to
make comparisons between forests these four coverage percentages were
averaged, equal weight being given to the importance of each service.
The standards used in obtaining these percentages are those applicable
to a burning severity corresponding to c l a s s 5 of the Danger Meter, which
represents the l e a s t severity in the class of burning conditions called
"Maximum." This table i s presented primarily as an example of what was
done. The percentages have been changed somewhat and they will continue
to fluctuate with additions of roads, changes in planned road locations,
and with annual and intra-seasonal decisions whether or not to man
certain fireman and crew s t a t i o n s . I t should be pointed out that the
percentages of coverage shown apply to fuels worse than average. Larger
percentages would be found for areas as a whole, disregarding fuels.
PROTECTION THAT CORRESPONDS WITH DANGER
A statement believed to be axiomatic i s that no danger e x i s t s
except where values e x i s t , and the greater the values threatened the
greater i s the danger.
The fact must be recognized that a conflagration i s l i k e l y to
o r i g i n a t e almost anywhere and any conflagration threatens a very large
area. Hence, if probable damage i s recognized in degree of preparedness, such recognition must be on a large area b a s i s . With t h i s in mind,
the r e l a t i v e average danger r a t i n g s of whole national forests are shown
in the l a s t column of t a b l e 14 where they can be compared with the average percentages of coverage worked out in planning. I t will be observed
that the average percentage of area covered (as planned) in different
forests i s somewhat proportional to the average danger. The coverage
percentages shown do not include the s t a t i o n s added in 1935 to meet most
severe burning conditions, but include only those that passed the t e s t
of covering 16,000 or more danger p o i n t s .
Since probable damage can be recognized only on a large area
b a s i s , the inclusion of values in rating the r e l a t i v e l y small area
covered by a p a r t i c u l a r station leaves the problem of t h r e a t s in lowvalue areas containing dangerous fuels p a r t i a l l y unanswered. Such
ratings also tend to leave large areas of uniformly low-danger fuels
without any coverage whatever. In final analysis i t was found necessary to make judgment decisions as to the addition or rejection of
more s t a t i o n s for fireman and reinforcement crews and more roads.
DEGREE OF COVERAGE PLANNED
85
Table 14.—Percentage of fuels worse than average in each western
national
forest
of Region One covered by each
service
of fire
control
as planned for "Maximum" ij
burning
conditions.
Forest and extent ofj
Reinforcements
\
development of
roads, trails, and 5
! Initial 1
Detection , attack : Light : Heavy •
landing fields
, Percent j> percent • Percent : Percent j
WITH 1934 TRANSPOR- s
,
TATION ROUTES
j
Nezperce
5
42
53
ji
76
\
1
47 ::
Selway
;5
28
:
75
:1
:
38
!i
41
Clearwater
1
5
73 j\
65
;
40
!
81
St. Joe
iI
79
:
81
l
79
;
l
72
Coeur d'Alene
98
j:
:
7 2 i;
76 j5
98
j:
Pend Oreille
j1
79
:
98
:
84
!;
6 6 s;
!
85
77
91
j
94
Kaniksu
Kootenai
{I
54 ;t
42
::
5 7 j5
96
!;
70
l
44
!
Blackfeet
::
52
::
:
91
I
I
66
j
57
:
64
Flathead
J
19
i
75
I
5
98
;
85
l
71
Cabinet
Lolo
!i
;
86
{
82
I
55
5
61
WITH PLANNED TRANSPORTATION ROUTES
Nezperce
Selway
Clearwater
St. Joe
Coeur d*Alene
Pend Oreille
Kaniksu
Kootenai
Blackfeet
Flathead
Cabinet
Lolo
!
t
J
j
:1
:
j;
5
:
;;
:j
{
49
79
83
79
74
76
85
61
52
69
71
55
j5
i
s;
I
:;
J
j:
l
:
:
!5
j1
65
49
81
83
80
88
84
59
73
57
75
62
I
I
:
!5
jI
j
i
:
I
I
:
94
96
100
99
98
99
98
99
99
88
99
99
:
i\
i
:
j1
]
:
;
I
iI
!\
:
55
51
86
91
100
94
97
84
51
27
96
96
!;
j•
\
j5
:j
jt
j1
jI
j;
it
::
:;
Average
percent- : Relative
age
i danger
covered
rating
Percent >
if
55
46
65
78
86
82
87
62
64
52
82
71
66
69
88
88
88
89
91
76
69
60
85
78
:
j:
t
:
:
;:
:
5
:
:
\
:
1.2
2.1
2.4
2.3
3.1
2.4
3.1
2.1
1.3
0.9
1.3
1.6
:
:
j\
:
:
:
:
:
:
l
I
I
1.2
2.1
2.4
2.3
3.1
2.4
3.1
2.1
1.3
0.9
1.3
1.6
1/
Corresponding with a Danger Meter rating of class 5.
2/
Relative danger ratings are for entire areas included within protection
boundaries regardless of ownership.
86
FIRE CONTROL PLANNING—NORTHERN
ROCKY MOUNTAIN REGION
A possible method of evaluating the relative average danger in
different large areas is to determine for a long period of years the
expense and damage caused by the average fire and multiply this by the
number of fires. If available or proposed funds were distributed on
this basis, planners could disregard values and build up coverages in
each service of control to best advantage according to fuels and frequencies of fire occurrence within different areas, until the limit
placed on funds stopped further additions. This method of rating danger
was the first one tried and, while it may be applicable in some regions,
it failed here because of the necessity for making allowances in some
areas for the strong influence of errors in action on costs of suppression and damage.
Considering the intangibility of fire damages, it would probably
be easiest to reach agreement on relative danger in different areas by
obtaining judgment decisions of three experienced men assigned to study
the best information available on fuel conditions, long-period frequency
of fire occurrence, and probable damage. From the planning experience
gained in this project, and from the danger ratings worked out and shown
in table iq., it appears that all large areas of the northern Rocky
Mountain region, disregarding national forest boundaries, could be grouped
into three danger classes. For each danger class of area it would be
logical and desirable to specify the degree of coverage considered necessary in each service of fire control. Each of the three classes of area
thus recognized in this region probably is similar in danger to large
areas in other regions, and through correlations the relative position of
this region's three classes in a total range of perhaps 10 classes could
be determined.
It should be recalled here that the present objective of fire control is the same for every part of every national forest, to control
every fire within the first work period. The unavoidable question must be
faced. Why have some areas been left with less fire-control strength
than others? The answer is that over a period of 30 years through analyses and group opinions, strength of fire control preparedness in different large areas was adjusted to estimated danger. Although preparedness
has been strengthened everywhere, the relative strength in different
areas is still governed to a large extent by probable danger.
It should be realized that what is purchased by investments and
annual expenditures for fire control is coverage of areas. In attempting to be efficient it appears logical to plan and establish the degree
of protection desired, which means no more or less than specifying the
degree of coverage needed in different large areas in each of the services of fire control, detection, initial attack, light reinforcements,
and heavy reinforcements. In final analysis such a statement constitutes a definite objective which in time can be adjusted to conform to
tolerable burned area and to the least total of cost and loss.
DEGREE OF COVERAGE PLANNED
87
In order to be prepared with any degree of coverage desired, plans
for roads and man power were worked out by steps of completeness.
After a l a r g e coverage has been put into effect, an increase even
as small as o.1 percent i s very expensive. Since s a t i s f a c t i o n of the
o b j e c t i v e n e c e s s i t a t e s recognition of r a t e of spread, r a t e of work ( f u e l s ) ,
and burning conditions, expenditures for determining these influences might
e a s i l y yield g r e a t e r returns than expenditures for increased coverages.
Until the desired degree of coverage i s s t a t e d , i t w i l l be imposs i b l e to s t a t e the planned cost of f i r e c o n t r o l . The form used in summar i z i n g c o s t s i s shown as figure 15.
SUMMARY
Standards of action necessary to control almost every fire in the
first work period were set up. These standards were based on evidence of
success and failure obtained in an exhaustive analysis of fire records.
Fuels, the materials in which fire control engineers operate, were
classified and mapped. Probable damage was appraised. Frequency of fire
occurrence was determined. Assuming danger to be a composite of these
three influences, an integration of them was made in order to evaluate
relative danger per acre.
By studying many possible combinations of existing and proposed
roads in relation to man-power stations, a combination believed most
satisfactorily to cover the danger was determined. Such a combination
was planned for use under each of four degrees of burning severity.
By changing detection and smokechaser stations, from those previously occupied to those selected in planning, the areas of national forests covered were increased in amounts ranging from 12 to 22 percent of
the whole areas.
It was found to be economically impossible to cover 100 percent of
any large area with detection and with the speed and strength of attack
specified by the standards adopted. Extremely high costs are involved in
the decisions, which have not yet been made, as to degree of coverage to
be provided when burning conditions are most critical. Since experience
and investigations are insufficient to indicate the relation between
degree of coverage and degree to which the objective is satisfied, an
interesting and highly important field is open for research.
In reporting progress to date a great deal of satisfaction is
derived from the facts that in recent years expenditures and preparedness for fire control have been increased greatly under every degree of
burning severity and, through planning, the entire structure has been
strengthened systematically.
88
FIFE CONTROL PLANNING—NORTHERN ROCKY MOUNTAIN REGION
•
Table 15.—Form used in summarizing
costs
of fire
control.
National Forest
ACREAGE
Total acreage presumed to be afforded adequate protection by the fire control organization recommended:
Acres,
Average annual
cost
Total
Per acre
Item of cost
&
Direct:
Average Condition (Regular) Protection Organiza*
tion - Temporary force only
$
4p
Minimum Condition Organization
Class 5,1 to 6 Emergency Overload Organization V
rt
M
"
6.1 to 7
,"
A
Indirect:
Maintenance Plus Amortization Costs - F,C, tran sportation equipment, paokstock, tools, K & H, and a!
Ll
forms of protection organization equipment cos ts
Salary and Expense of Year-long Forest Personne.
L
Chargeable to Prevention and Presuppression
Regional Office Indirect (Average from activity
cost
accounting summaries)
F•C, Impro vement s:
Structures of all types. Annual Amortization
Plus Maintenance Cost Existing
Proposed
Trails - All Classes - Annual Amortization
Plus Maintenance Cost Existing
Proposed
Roads:
Amortization Plus Maintenance
Existing
Proposed
I
$
3$
*
Total:
Cost of Maximum F.C. Organization Contemplated
Recommended for approval:
j
Date
1 9 3
_-
Forest Supervisor
0
89
PART
DETAILED
I I
PROCEDURES
I N PLAN
WORK
INSTRUCTIONS FOR FUEL-TYPE MAPPING
For efficient forest f i r e control, i t i s necessary that i n t e n s i t y of
attack on f i r e s vary with probable r a t e s of spread and with probable r e s i s tance to control. These are determined p r i n c i p a l l y by weather conditions
and fuel conditions. Methods of measuring fire-weather conditions over
large areas have been worked out for the northern Rocky Mountain region,
and r a t i n g s of local f i r e danger are being made daily during the f i r e season for many l o c a l i t i e s of the region. The next step in providing f i r e control planners and dispatchers with the information they need i s to p r e pare maps indicating what speed and strength of attack will be required to
suppress f i r e s occurring on given areas under a given degree of weather
danger.
In t h i s and other regions, many very detailed inventories showing
the quantity and character of green and dead fuels and t h e i r exposures
have been taken, and attempts have been made to base fire-control plans on
l a t e r i n t e r p r e t a t i o n s of these i n v e n t o r i e s . Thus far, t h i s method has not
been s a t i s f a c t o r i l y applied. In the method described here, no d e t a i l e d
inventory of physical conditions i s recorded; instead the man on the
ground, at the time of observing fuel conditions on an area, makes and
records an estimate of probable r a t e of f i r e spread and probable r e s i s t ance of f i r e to control. The p r i n c i p a l factors observed are kind, quant i t y , arrangement, and continuity of fine fuels and the exposure of such
fuels to sun and wind. These are the factors t h a t , together with weather
conditions, determine a f i r e ' s r a t e of spread, that i s , the number of
chains of perimeter i t produces per hour, and i t s resistance to control,
that i s , the number of man hours of suppression work i t requires per chain
of perimeter. Obviously, the number of man hours required per chain mult i p l i e d by the number of chains to be worked gives the firefighting job to
be done.
SELECTION AND TRAINING OF MAPPERS
Fuel mapping i s to be done by men having wide experience in the cont r o l of small f i r e s , or by others who have been thoroughly trained by such
men. An observant man can quickly learn to classify fuel conditions corr e c t l y , even if inexperienced in fighting f i r e , through supervised field
study of typical conditions described and c l a s s i f i e d in these instructions
(p. 100). Experience has shown that for best r e s u l t s a t r a i n e r should
i n s t r u c t mappers in groups of not more than 6. He should guide the men in
p r a c t i c e mapping u n t i l individually they can give consistent and accurate
r a t i n g s to the different fuel conditions observed. Trainees should be
encouraged to argue r a t i n g s . In t h i s way comparisons with other fuel cond i t i o n s are brought out.
90
FIRE CONTROL PLANNING—NORTHERN
ROCKY MOUNTAIN REGION
It has been said that the best possible fuel mapper would be a man
who had suppressed many small fires under many conditions but had never
seen a large fire. The idea behind this statement is that anyone who has
been strongly impressed by some experience with a large fire is likely to
overestimate the probable rate of spread represented by certain fuels,
unless he remembers clearly the conditions of drought and wind in which
this fire took place and its initial rate of spread. Men who have previously given efficient service as lookouts and smokechasers and who have
an inquiring turn of mind usually learn most rapidly and do the best
work.
Because of the value of the resources at stake in fire suppression
and the expense of fire-control operations, fuel mapping is highly responsible work. The mapper assumes part of the responsibility for correct
suppression action. Integrity and a high degree of consistency in drawing conclusions are essential qualifications.
FUELS AND CONDITIONS CONSIDERED
The fuels considered by fuel-type mappers are fine materials such
as tree branches less than 1 inch in diameter; shrubs and herbaceous
plants; loose, rotten wood and bark; frayed, broken trunks; checks, moss,
dead needles, and loose, rotten bark and wood on windfalls and on standing trees, living or dead; and needles, leaves, duff, weeds, grass, and
moss on the ground.
The travel time allowed a fireman is determined by conditions of
fuels. On areas newly logged or recently burned, fuel conditions become
worse rapidly, and consequently it is necessary to shorten travel times
and relocate stations. If fuel mapping is being done for the purpose of
planning location of man power and roads, it is necessary to predict the
condition of changing fuels so that correct coordination will exist
several years later. Maps made for the purpose of dispatching men to
fires should show the present condition of fuels and should be revised
annually for any areas on which conditions have changed conspicuously.
Ratings represent fuel conditions existing after a month of continuous midsummer drought.
The influence of frost-killed vegetation is disregarded.
Ratings refer to small fires only; after fires have attained
speed their spread is not appreciably influenced by small differences in
factors such as fuel moisture or protection from wind. Attention is
focused on what a fire is likely to do in the first two or three hours
after it becomes large enough to be discovered by & lookout, that is,
during the time required for travel and control by smokechasers.
INSTRUCTIONS FOR FUEL MAPPING
91
RATE OF SPREAD
The fuel-type mapper is expected to consider all the different
initial rates of fire spread that commonly occur in the northern Rocky
Mountain region after a month of drought, divide them roughly into three
equal classes called low, medium, and high, and assign each area he
encounters to one of these classes. A fourth classification, extreme,
is reserved for areas on which spread would be exceptionally rapid.
"Extreme" rating applies primarily to the worst parts of blow-down,
slash, and snag areas. It must be given where a dense stand completely
wind thrown is fully exposed to sun and wind. This classification is
applicable to exposed slopes densely covered with cheat grass, but not
to any other pure grassland condition.
The more difficult of the generally distributed fuels on an area
determine its rate-of-spread classification. If an area is approximately
uniform in fuel conditions with the exception of spots containing worse
fuels, the spots should be classified separately. If spots contain fuels
of high or extreme rate of spread, these spots should be shown even if
the map scale necessitates exaggeration of their true size.
Where a large fire has stopped naturally the mapper should not
assume that this is accounted for by the quantity and kind of fuel present, under drought conditions. Very often a fire's dying out has resulted
from precipitation, high humidity, change of wind direction, night cooling,
or a combination of these factors, rather than from fuel conditions.
Evidence as to causes of differences in rate of spread has been
obtained through forest research in widely separated regions of the
United States. This evidence is in the form of statistics based on
measurements of fuel moisture content, solar radiation, and wind movement
as influenced by shade, by obstructions to air movement, and by direction
and degree of slope.
INFLUENCE OF TREE OR BRUSH COVER
At the Priest River Experimental Forest, in northern Idaho,
Gisborne has established three fire-weather stations about 500 feet apart
in a line approximately parallel to the prevailing wind direction, southwest to northeast. All are on a flat originally covered by a dense overmature stand of the white pine-hemlock type. The station farthest south
is on an area that has been clear cut and is now fully exposed to wind
and sun. The next is at about the center of a 500-foot strip where cutting has reduced the density of the forest canopy to half. The third is
300 feet within a portion of the old-growth stand immediately northeast
of the half-cut area. It is evident that after a month of continuous
midsummer drought most of the differences in daily weather records at the
three stations must be attributed to differences in density of stand.
Records taken at these stations in the week August 10-16, 1931, were
sz
FIRE CONTROL PLANNING—NORTHERN ROCKY MOUNTAIN REGION
selected for study, because that week was in the worst part of a disastrous fire season and was without precipitation.
For that week, figure 22 shows the average hourly readings of temperature just under the surface of the duff and of relative humidity in
the instrument shelter, 4.5 feet above the ground, on the clear-cut, halfcut, and full-timbered plots, respectively. Readings varied very little
from day to day. During the daily period from 7:00 a.m. to 4:30 p.m. temperature was high and humidity low according to density of stand; in other
words, inflammability of fuels varied according to density of stand.
Although afternoon relative humidities of the air 4.5 feet above
the ground were much alike for the three plots, considerable differences
existed in afternoon moisture content of fine fuels at or near the ground
surface. The daily trends of moisture content of half-inch wood cylinders
10 inches above the ground are shown in table 17. Finest fuels, such as
grass, moss, and duff, can be ignited with a lighted match at times when
adjacent half-inch wood cylinders contain less than 8 percent moisture,
and are distinctly more inflammable when the cylinder moisture content
drops below 6 percent. In full timber, the moisture content of cylinders
10 inches above the ground sank to 8 percent shortly after 9:00 a.m. and
was a little more than 6 percent at 4:30 p.m. On the half-cut area it was
down to 6 percent even at 9:00 a.m., and on the clear-cut area it was
still lower. Thus, regardless of wind influence, the rate at which a fire
consumes fine fuels is definitely related to openness of stand.
Table 17.—Moisture content
of wood cylinders
and rate of wind
movement according
to density
of timber stand, at
Priest River Experimental
Forest
ij
Average moisture content
of i-inch wood cylinders
10 inches above ground
Plot
Clear cut
Half cut
Full timbered
2/
Average wind velocity
4.5 feet above ground
5:00 p.m» to
:9:00 a.m. to
9:00 a.m.
:5:00 p#m»
Miles per hour :Miles per hour
1.2
0.8
0.1
3,8
2.3
0.2
Data are for the week August xo-i6» 1931*
The relative-humidity data shown in figure 22 represent average daily
conditions in the northern Rocky Mountain region during periods when severe
burning conditions prevail. Previous to the week studied conflagrations
had occurred within 20 miles on one side of the Priest River forest and within 5 miles on the opposite side, and no rain had occurred to improve conditions. Relative humidities lower than those shown occur in the region frequently.
3v3
140
130
/
120
_
no
/
/
/
100
/'
80
•t
70
•
60
.
/
'
50
*>
40
^
/
/
—._
\
\
>'
\
- ^ • ^
•
^ ^
/
-^
JO.
•*•
'
/
90
A
\
/
/^-_
*"-
•Jf 30
a
20
iO
MidNight
Fig.
IA.M.
2
10
II
IP.M.
2
10
"
as.—Average
h o u r l y w e a t h e r r e a d i n g s d a r i n g week August 1 0 - 1 6 ,
i 9 3 i » a c c o r d i n g t o d e n s i t y of t i m b e r s t a n d , on P r i e s t R i v e r
Experimental F o r e s t :
A, T e m p e r a t u r e j u s t b e l o w duff s u r f a c e ;
B, R e l a t i v e h u m i d i t y 4 , 5 f e e t above g r o u n d .
Full—timbered p l o t
Half-cut plot
Clear—cut p l o t
MidNight
INSTRUCTIONS FOR FUEL MAPPING
9L
Findings agreeing with those presented here were arrived at by
Stickel (so) in the Northeast.
A dry prevailing wind d r i e s fuels and prepares them for more rapid
spread of f i r e , and wind movement at the time of a f i r e increases r a t e of
spread by supplying oxygen for combustion and by carrying hot a i r to u n u nited fuels. Evidence of the effects of wind movement appears in figure
22. On the full-timbered p l o t , where a i r that became heated could not
move freely, temperature continued to r i s e in l a t e afternoon, while on the
clear-cut p l o t , where a i r was free to c i r c u l a t e , i t was f a l l i n g . Records
of wind movement according to openness of stand are shown in t a b l e 17.
Although the wooded s t r i p s protecting two of the weather s t a t i o n s were not
wide, the average midday velocity of wind in the open was cut to 60 percenl
on the half-timbered area and to l e s s than 6 percent in the full-timbered.
Undoubtedly, on both these areas the a i r above the t r e e tops was moving as
fast as i t was at the height of the instrument s h e l t e r on the c l e a r - c u t
area.
Because of the fact l a s t mentioned, fuel mappers should be careful
to observe the condition of any fine and continuous fuels in the tops of
dead or green crowns. Moss, dead needles, or loose rotten bark and wood
on stag-topped t r e e s or on snags at the general canopy l e v e l of a stand
have the same effect on a f i r e ' s r a t e of spread as such material on the
ground in the open, except that humidity i s usually greater in the canopy.
INFLUENCE OF SLOPE AND TOPOGRAPHIC SHELTER
The influence of wind on spread of f i r e varies not only with chara c t e r of cover but with slope and topographic s h e l t e r . In the northern
Rocky Mountain region the prevailing wind direction i s from southwest to
northeast, and only rarely are f i r e s or fuels affected by general winds
of any other d i r e c t i o n . Local topography may change the direction of
prevailing wind, however. Fuel-type mappers must endeavor to detect any
local wind influences on inflammability and f i r e spread.
In some s i t u a t i o n s , for example at valley i n t e r s e c t i o n s , north
slopes are not always protected from drying winds.
Species and condition of vegetation frequently indicate the e x i s t ence or nonexistence of dry prevailing winds.
Air temperature at and near the ground and moisture content of
fuels, likewise, vary with slope and with topographic s h e l t e r . Obviously,
south slopes that are bombarded by the sun's rays a l l day and are perpendicular to them about noon receive the greatest possible quantity of
solar radiation per day. North slopes, if extremely steep, receive l i t t l e
or no direct sunlight. Kimball (11) has calculated and tabulated the
quantities of solar radiation received during different months in the
United States according to slope, l a t i t u d e , and a l t i t u d e . The sun's greatest a l t i t u d e on July 15 at the l a t i t u d e of Missoula may be considered representative for the northern Rocky Mountain region. This a l t i t u d e i s 64 0 ;
95
F I R E CONTROL PLANNING—NORTHERN ROCKY MOUNTAIN REGION
thus the exposure receiving the greatest radiation at Missoula i s a southfacing h i l l s i d e with slope of 26 , or 52 percent. Shade cast during a
portion of the day by mountains reduces the radiation received in many
places, Allowance for t h i s condition must be made by fuel mappers.
A simple and p r a c t i c a l way to judge the i n t e n s i t y of solar radiation on any surface i s to imagine a long s t r a i g h t tube reaching from the
e a r t h ' s surface toward the noon position of the sun. The sun's rays coming through t h i s tube w i l l spread over a greater area according as slope
d i f f e r s from the perpendicular to the tube. The greater the concentration of rays per square inch (or per acre), of course, the greater will be
the heating effect of solar radiation on fuels.
INFLUENCE OF FOREST TYPE
Figure 18 on page 69 of Part I shows for cut-over areas and for
green, uncut p o l e - s i z e or l a r g e r forests of each timber type in the northern Rocky Mountain region what percentages of f i r e s in the 10-year period
1921-30 spread at given i n i t i a l r a t e s . The r a t e s shown are averages for
the period between hour of discovery and beginning of attack, jy/
I t w i l l be observed that r a t e s of spread within the range shown
varied according to natural openness of timber stand. The greater the
openness of the stand, the greater was the proportion of f i r e s spreading
at r a t e s bordering on the dangerous. The brush-grass type i s the most
open and occurs in the most exposed s i t u a t i o n s . Spruce, white fir-cedar,
and cedar-hemlock grow in the most protected s i t u a t i o n s and are most
dense. Intermediate between these are the ponderosa pine, larch-Douglas
f i r , Douglas f i r , lodgepole pine and western white pine types. The subalpine type i s affected by too many variables to be included in general
comparisons. In the two most open types, brush-grass and ponderosa pine,
10 percent of the f i r e s spread at an average r a t e of 15 chains or more
per hour; in the two most dense types, white f i r - c e d a r and spruce, l e s s
than 2 percent spread at such a r a t e .
A study of factors important to fuel mappers was made by Bates (2)
on a "transect of a mountain valley" in the c e n t r a l Rocky Mountain region.
Fuel mappers in the northern Rocky Mountains can make many legitimate
inferences regarding probable r a t e of f i r e spread in different forest
types and s i t u a t i o n s from the following portions of Bates's conclusions:
"A transect of t h i s valley (700 feet wide, with axis in an e a s t west direction) was made, running as nearly as possible normal to the
contours of both slopes, in a s t r a i g h t line and on t h i s l i n e s t a t i o n s
were located a r b i t r a r i l y at i n t e r v a l s of exactly 50 feet. The valley
walls on e i t h e r side a t t a i n a gradient of about 45 percent, or 25°* the
steepest portion, as usual, being near the middle of e i t h e r slope.
11/
Usually an aggressive fire spreads not uniformly but at an irregularly
increasing rate. If the perimeter is 10 chains at the end of the first hour tnd
increases with an acceleration of 10 chains per hour, per hour, the perimeter is
30 chains at the end of the second hour. The average rate of spread for the a
hours is then 15 chains per honr, but the actual rate at the end of the second
hour is so chains per hour.
INSTRUCTIONS FOR FUEL MAPPING
96
"All of the south exposure is subjected to direct insolation at
some time during the day and during the entire year. As a result of this
insolation, high maximum temperatures are recorded at the surface of the
soil, the highest during 1921 being nearly 1500 P., and being fully 6o°
above that of the coolest neighboring site.
"We incline to the belief that this temperature of 1490 F. would
kill outright any yellow pine seedlings less than 2 months of age, and
certainly any seedling of other species at any time during the first
growing season.
"The extreme top portion of the south exposure, which Douglas fir
is capable of invading, shows almost as thorough drying of the surface
soil as any other portion, but appreciably lower temperatures.
"From the bottom of the valley to almost the top of the north
exposure relatively moderate temperatures are experienced, both on
account of the angle of incidence of the sun's rays and the completeness of the cover. On the lowest and also steepest portion of the north
exposure, the evaporation rate is lowest, the soil temperatures are lowest, the accumulation of moisture is greatest, and the drying of the
soil is most gradual. So far as these are the results of steep slope,
the conditions would probably exist in a degree if all cover were
removed.
"The upper portion of the north exposure becomes progressively
warmer and drier. Here, evidently are encountered about the mean temperature conditions which are favorable to Douglas fir. But it should be
noted on all similar exposures, once the Douglas fir forest is established,
there is a marked tendency for Englemann spruce to invade and supersede
fir."
It should be noted particularly that Bates found the naturally open
stands in situations where weather influences promote rapid spread of
fire. According to the evidence from other studies presented in the foregoing, openness of stand, whatever its cause, itself conduces to rapid
spread of fire. The inference is justified that natural openness of stand
is a stronger indication of high potential rate of fire spread than openness caused by thinning a naturally dense stand. In the latter case, however, failure to remove fine fuels that were parts of the trees taken out
may increase the potential rate of spread greatly. In making comparative
ratings of fire spread according to forest type and exposure, mappers are
cautioned to consider similar conditions of volume, continuity, and fineness of fuels.
Bates found that at the foot of the south exposure described in
the foregoing quotation ponderosa pine is struggling for existence on
the almost unforested area, that farther up the slope Douglas fir is
invading the ponderosa pine area, and that on the north exposure spruce
97
FIRE CONTROL PLANNING—NORTHERN ROCKY MOUNTAIN REGION
i s invading the Douglas f i r area. I t seems evident that the shade and
protection from wind afforded by t r e e s not only effect a direct l i m i t a tion of inflammability but make possible a s t i l l more dense and l e s s
inflammable stand.
Comparisons of timber types should be confined to normal green
stands of pole size and l a r g e r , free of such abnormalities as those
caused by insect epidemics, burns, logging, and blow-down.
I t must be remembered that timber type alone does not determine
probable r a t e of f i r e spread on a specific area. Type simply indicates
the local s t a t u s of some of the factors influencing r a t e of spread. Age
of stand in combination with quantity and condition of older, intermixed
dead and green t r e e s means much. Usually conditions that exist within a
stand of any age are complex. Many a stand that contains l e s s than 200
t r e e s per acre when 200 years old o r i g i n a l l y contained more than 2,000
t r e e s per acre. The fuel mapper cannot know without careful examination
whether or not the c a s u a l t i e s and other dead material from p a r t i a l cuttings or from s t i l l older stands are present. He should refrain from
classifying fuels on and near the ground unless he can see them at l e a s t
with f i e l d g l a s s e s . Even if a crown i s rather open, he cannot see through
i t from outside.
INFLUENCE OF PREVIOUS BURNING, CUTTING, AND BLOW-DOWN
Since f i r e s of any size in t h i s region usually k i l l the e n t i r e
stand, i t might be expected that f i r e would always spread much f a s t e r in
stands previously burned than in green stands of the same type. Such a
tendency was exhibited only by the fastest-spreading 15 percent of the
1,536 f i r e s recorded as originating on single burns during the 10-year
period 1921-30. In other words, if weather and fuel conditions were
c r i t i c a l i n i t i a l spread was faster on single burns than on unburned areas
of the same forest type, but under average burning conditions no differences were observed. The term "burn" was applied to large areas having a
more or l e s s dense cover of brush and reproduction not more than 30 years
old. The s t a t i s t i c s seem to prove that such growth shades fine fuels and
prevents a i r movement around them, although not so completely as mature
timber stands.
Decision as to probable influence of snags on r a t e of spread i s
very d i f f i c u l t . In order to estimate the p r o b a b i l i t y that f i r e w i l l run
between snags i t i s necessary to examine the fuel on the ground at t h e i r
feet and between them. The kinds of fine fuel present on snags determine t h e i r inflammability and the likelihood that f i r e will be spread by
sparks flying from them. The distance between snags and t h e i r exposure
to wind determine the probability that f i r e will spread from snag to snag
when cinder material i s present. Under ordinary conditions of wind and
snags on gentle slopes, f i r e i s not l i k e l y to spread between snags that
are more than 50 feet apart.
INSTRUCTIONS FOR FUEL MAPPING
98
Between burned areas and unburned clear-cut areas, both fully
exposed, there i s usually a great difference as to quantity and continui t y of fine fuels near and on the ground. Bare spots are frequent on the
former and rare on the l a t t e r . Past cutting operations have usually produced a high degree of openness in stands. When a complete set of curves
was made, by timber types, for i n i t i a l rates of spread of the 1,125 fires
of 1921-30 that originated on cut-over areas, i t was found that the rates
of spread, throughout their range, for every forest type, greatly exceeded
those of green forest and single burn. It was found also that the relative order was the opposite of what i t was for uncut stands; that i s ,
rates were lowest for the most open types bearing the smallest quantities
of foliage per acre and were highest for the most dense types. The differences in rate of spread according to timber type were small. On cutover areas rates were found to correspond more nearly to method and degree
of slash disposal than to timber type. On cut-over areas mappers should
observe carefully the volume and continuity of slash as well as the degree
of openness caused by removal of trees.
RESISTANCE TO CONTROL
Resistance to control, as stated previously, i s an expression of
the quantity of suppression work required per chain (or other unit) oi
fire perimeter. Resistance i s rated according to the same classification
as rate of spread — low, medium, high, and extreme. An outline of the
important factors in resistance follows:
Fine fuels present in
Quantity
Arrangement
'"standing green timber
snags
-< windfalls and slash
brush, reproduction, and grass
duff and roots
Size
Species
Decay
Trenching and dirt-smothering chance as affected b£
Roots
Soil
Rocks
Slope
99
FIRE CONTROL PLANNING—NORTHERN
ROCKY MOUNTAIN REGION
In estimating probable resistance the ftiel mapper will assume the
method of attack to be ordinary handiwork with the most suitable tools.
He should endeavor to visualize an efficient fireman doing whatever work
would be needed at the spot under consideration.
The rating will represent only the work required to corral a fire
and hold it through the midday burning period. In situations such as
under dense old stands, particularly on north slopes and protected flats,
much work is required to extinguish a small fire burning in deep duff and
rotten logs but relatively little work suffices to prevent its escape.
Under such conditions escape cannot take place except by way of fine fuel
connecting fuel on the ground with fuel in the tree tops. A connection
may be afforded by dead, moss-covered limbs hanging nearly to the ground,
mossy green foliage, or green hanging branches that bear considerable
quantities of dead needles and buds. During drought periods, a little
heat suffices to dry green coniferous foliage to the point at which it
will ignite.
It is frequently easier to prevent escape of a fire burning in a
tangle of large logs, by clearing fuels away from them and smothering fire
with dirt, than it is to prevent escape from a tangle of small logs.
In places, the mapper will recognize that the potential firesuppression job consists principally in felling a single burning snag. In
such a case the resistance should be thought of as the quantity of felling
work per snag plus the work caused by transmission of sparks to the
material in which the snag would fall and by possible new fires spreading
from burning cones and chunks rolling down steep slopes. In yew brush,
particularly, such new fires are difficult to control.
STANDARD RATINGS OF 43 TYPICAL CONDITIONS
At five training camps for fuel mappers 90 men, representing 10
national forests, agreed on ratings to be assigned to 43 sets of conditions typical for the northern Rocky Mountain region. The conditions and
ratings are listed in table 18. These examples have proved adequate as
a basis for training fuel mappers to rate correctly and consistently all
the fuel conditions encountered in the northern Rocky Mountain region.
INSTRUCTIONS FOR FUEL MAPPING
100
Table 18.—Classification 1} of 43 fuel conditions,
typical
for
the northern Rocky Mountain region, as to probable
rate of fire spread and probable resistance
of
fire
to
control.
Example
number :
1
2
3
4
:
:
:
:
:
:
i
: Rate of : R e s i s t a n c e
: spread ; t o c o n t r o l
Fuel c o n d i t i o n
Mature l a r c h - f i r , w h i t e p i n e , o r lodgepole
on p r o t e c t e d f l a t s or n o r t h e a s t s l o p e s ,
where w i n d f a l l i s l i g h t and not c o n t i n u o u s ; :
s t a n d dense enough t o s h e l t e r f a e l s on
ground. Ground v e g e t a t i o n c o n s p i c u o u s l y
low s h r u b s t h r o u g h o u t . Trees c l e a n and
snags few. Tree moss may be moderate • • • • • • *1
L
:1
L
M
5
L
:
:
t
M
:
M
I f w i n d f a l l and snags a r e moderate t o heavy,
continuous and i n t e r m i x e d w i t h only s c a t '•
t e r e d t r e e s of t h e old s t a n d , and r e p r o d u c t i o n does not f u l l y shade w i n d f a l l s
:
On p r o t e c t e d NE s l o p e s . . . . *
M
1:
H
H
5t
H
: I f stand i s exposed t o almost f u l l sun and
;
: I f w i n d f a l l and snags a r e moderate but con: spicuous and mixed w i t h t h i n but continuous
: g r a s s c a r p e t and s t a n d i s exposed t o wind
:
:
1
:
:
5
6
7
:
•
:
:
;
:
,
I f t h e s e same mature s t a n d s were burned
over by l i g h t f i r e , or were h e a v i l y bugk i l l e d , r e s u l t i n g i n dense r e p r o d u c t i o n
20-30 y e a r s o l d , not completely shading
w i n d f a l l s and mixed w i t h very heavy a c c u m u l a t i o n of limby w i n d f a l l s and continuous
r o t t e n , broom-topped, o r o t h e r w i s e i n f l a m mable snags 50-75 f e e t a p a r t
!
On p r o t e c t e d NE s l o p e s . . . .
j
1/ E = Extreme,
H - High,
M = Medium,
;
;
:
:
:
;
:
:
:
:
H
!
E
E
:
E
L = Low.
101
FIRE CONTROL PLANNING—NORTHERN ROCKY MOUNTAIN REGION
Example
number :
8
9
10
!:
:
:
!
:
:
:
:
; R a t e of : R e s i s t a n c e
: spread : t o c o n t r o l
Fuel c o n d i t i o n
S i n g l e burn i n v e r y heavy overmature s t a n d
of hemlock and c e d a r , on exposed f l a t and
g e n t l e s o u t h s l o p e . Windfall very heavy,
and c l u t t e r e d w i t h limby t o p s broken from
s n a g s . Grass conspicuous in p a t c h e s .
Snags t o t h e e x t e n t o f o n e - t h i r d of o r i g i n a l t r e e s remaining, mostly with broken
t o p s and f u l l of l i m b s . A e r i a l spread by
:
E
: I f small limbs of above stand had been
: consumed by a h o t t e r f i r e , o r i f s t a n d
t were on n o r t h s l o p e o r p r o t e c t e d from wind :
H
t
:
i
j
i
E
!
i
:
:
!
!
:
Hemlock and w h i t e p i n e , overmature, with
mixture of l a r c h - f i r . A l l s p e c i e s very
d e f e c t i v e . S c a t t e r e d snags and w i n d f a l l .
Moss c o n s p i c u o u s . Many t r e e s bushy t o
ground
On S s l o p e s , w i t h
mossy, bushy t r e e s
H
:
J
:
:
:
M
:
H
mossy, bushy t r e e s «
L
:
H
13
:
On N s l o p e s , with
14
i
On N or S s l o p e s , without mossy,
j
L
15
16
17
E
: I f p a r t i a l l y p r o t e c t e d from sun and wind,
H
12
E
Hemlock: o l d s a l e a r e a s where heavy
s t a n d s were g i r d l e d and t r e e s have now
:
broken off i n s e v e r a l s e c t i o n s , mixed w i t h
wind-thrown t r e e s . Much f i n e fuel on
:
ground. Snags numerous and broom-topped.
E
11
jl
: Hemlock: extremely dense s t a g n a t e d
. r e p r o d u c t i o n of hemlock, c e d a r , and w h i t e
pine 30-40 y e a r s o l d , on r o l l i n g S s l o p e .
Windfall heavy and l i m b y . Recent windf a l l s have crushed r e p r o d u c t i o n . Snags of
l a r c h and cedar remain, mostly more t h a n
M
:
*
:
:
:
H
:
E
M
:
E
: I f stand i s on a s l o p e somewhat p r o t e c t e d
j White pine 80 y e a r s t o m a t u r e , 30$
of t r e e s b u g - k i l l e d w i t h i n past 10
y e a r s . I n t e r m i x t u r e of s p r u c e and
f i r . On exposed, g e n t l e t o s t e e p S
t o 50%
to 15
larchslopes.
:
:
:
:
H
H
INSTRUCTIONS FOR FUEL MAPPING
102
Rate of
spread
Resistance
to control
H
H
. S i n g l e b u r n 20 y e a r s o l d i n white p i n e or
, l a r c h - f i r t y p e , on exposed SW s l o p e s ,
g e n t l e t o s t e e p . Old stand a l l dead and
most of i t remaining as w i n d f a l l , not yet
; shaded c o m p l e t e l y by w e l l - s t o c k e d s t a n d
! of r e p r o d u c t i o n
•
H
H
20
: I f on p r o t e c t e d NE s l o p e
M
H
21
! Lodgepole, f u l l mature stand 60$ bug. k i l l e d and windthrown, on exposed f l a t s
H
H
E
H
Example
number
18
Fuel c o n d i t i o n
:. White f i r , about 50$ dead, 80-200 y e a r s
o l d , c o n s t i t u t i n g 60$ of dense s t a n d of
: mixed ages and s p e c i e s . Trees bushy t o
ground. Fine limbs and dead n e e d l e s a l ready appearing on ground. Moss not
conspicuous on t r e e s . Exposed f l a t s
:
19
22
: Lodgepole, 1910 burn, w i n d f a l l heavy but
. shaded by dense r e p r o d u c t i o n 15 f e e t h i g h .
. On most exposed SW s t e e p s l o p e s
H
24
: I f on g e n t l e and somewhat p r o t e c t e d slopes
M
25
. S u b a l p i n e : d e n s e , mossy f i r ; s p r u c e , e t c .
with limbs t h i c k t o ground. Dead t r e e s
, i n t e r m i x e d . Where f u l l y exposed t o wind
23
H
26
27
28
29
30
; On p r o t e c t e d NE s l o p e s , and f u e l s s a f e
:
H
H
:
H
:
L
L
L
L
H
H
On f u l l y exposed r i d g e t o p s , but free
, from moss and bushy g r e e n or dead t r e e s .
.
;
,
:
Mixed b r u s h , w i t h l a r g e volume of windfall*J
and s n a g s . Dense t o medium c e a n o t h u s , w i l low or maple on SW s l o p e s with dead brush
and w i n d f a l l c o n s p i c u o u s . Grass s c a t t e r e d
i n p a t c h e s . Reproduction inconspicuous
: I f w i n d f a l l and snags a r e only moderate
:
H
J
M
I f dead b r u s h , w i n d f a l l , s n a g s , and g r a s s
M
M
03
FIRE CONTROL PLANNING—NORTHERN
Example
number :
31
ROCKY MOUNTAIN REGION
Fuel c o n d i t i o n
: Mature ponderosa p i n e , l a r c h - f i r , Douglas
: f i r , or s u b a l p i n e , open and conspicuously
: g r a s s y , on f u l l y exposed SW s l o p e s . Wind-
32
33
: I f i n t e r m i x e d r e p r o d u c t i o n i s dense
34
: I f stand was heavy and was cut or k i l l e d
: l e a v i n g l a r g e amount of broadcast s l a s h
: intermixed with much g r a s s , n e e d l e s , and
35
36
37
38
39
40
41
: Rate o f : R e s i s t a n c e
: spread : t o c o n t r o l
•
••
5
:
H
:
L
:
M
:
L
:
H
:
M
:
E
:
H
:
L
:
M
:
M
;
M
:
:
:
:
:
;
:
T h r i f t y young s t a n d s 40-80 y e a r s old of
w h i t e p i n e , l a r c h - f i r , o r mixed s t a n d s ,
i n c l u d i n g hemlock, cedar, and l o d g e p o l e ,
f u l l y stocked o r n e a r l y s o . Old w i n d f a l l s
and snags few and evenly s c a t t e r e d . Normal c a s u a l t i e s due t o crowding-out p r o c e s s
and snow breakage, e x i s t i n g f r e q u e n t l y as
t a n g l e s up t o 5 f e e t above ground. Stands
i dense enough t o shut off wind and sun from
:1 Stand open enough t o p e r m i t wind and sun
t o reach ground. On SW s l o p e s , r i d g e
! Same open s t a n d on p r o t e c t e d f l a t s o r
, Spruce: mature dense s t a n d s on p r o t e c t e d
stream bottoms and f l a t s . I f many snags
a r e p r e s e n t and t r e e s a r e bushy t o t h e
ground and c a r r y an accumulation of
: I f stand i s normally exposed t o c o n s i d : I f snags and bushy t r e e s a r e so s c a t t e r e d
': I f t r e e s a r e c l e a n , snags a r e almost
e n t i r e l y a b s e n t , w i n d f a l l o f f e r s no
problem, and f i n e f u e l s a r e almost absent
:
L
M
L
H
:
;
;
:
•
M
:
H
L
:
M
L
|
L
«
:
:
INSTRUCTIONS
Example
number :
42
43
FOR FUEL MAPPING
Fuel condition
: White fir: old decadent stand on gentle
; S slope. Considerable moss, scattered
• dead trees. Fire likely to start only
: Cheat grass, densely covering exposed
|Q4
: Rate of
j spread
Resistance
to control
j
:
;
L
11
S
L
:
LEGEND AND ILLUSTRATIONS
The legend used i s shown on page 106. A sample of field work i s
shown on page 50 of Part I, and illustrations of fuels are shown by the
frontispiece and on pages 52 and 55.
SCALE
Field work of satisfactory refinement cannot be done on maps of
scale smaller than 1 inch to the mile, and no smaller scale is to be used.
Fuel-type maps on a scale of 2 inches to the mile are needed by dispatchers, and this scale is consistent with the degree of accuracy to which
locations of fires can be determined with lookout instruments. Since all
plan work is done on maps having a scale of one-half inch to the mile, it
is necessary that the field maps be reduced in the office to this scale.
In making the office map, fine lines should be drawn with colored inks.
FIELD SUGGESTIONS
Fuel mappers should be required to use good-quality field glasses.
It is best always to decide on and record rate of spread first,
since rate of spread has an influence on resistance to control.
Pending decision as to a final rating, a tentative rating may be
recorded by writing on the map, with ordinary pencil, the initial letters
of the class designations. Thus "HM" may be written for high rate of
spread and medium resistance to control.
Where boundary lines between different fuels are conspicuous at
the borders of burns, frequently they can be observed and mapped at a
considerable distance more quickly than at close range.
The best place to observe the top of a dense crown canopy is from
across a valley.
105
FIRE CONTROL PLANNING—NORTHERN ROCKY MOUNTAIN REGION
•
CURRENT POSTING
Mappers are expected to keep office copies of f i e l d maps posted currently, usually daily, with good protection from every possible agency of
destruction. Protection i s required because crayon rubs off and smears
easily, and because there i s always a p o s s i b i l i t y of getting the field map
wet or losing i t .
RATE AND COST OF MAPPING
In fuel-type mapping of 15 million acres of land in the northern
Rocky Mountain region, the area covered per day by a man working alone
ranged from 3 to 7 sections, averaging between 4 and 5 sections. Within
the area accessible from roads the maximum per man day was found to be
about 5,000 acres; where t r a i l s were the only routes of t r a v e l , i t was not
more than 2,500 acres. Mapping was f a c i l i t a t e d by the high percentage of
burned area in the region, which permits mappers to see over long d i s tances. In dense stands of mixed species and age c l a s s e s , slow progress
must be expected.
The average cost of fuel type mapping on a scale of 1 inch to the
mile ranged, among different large u n i t s , from $1.50 to $2.00 per 1,000
acres. If field work had not been pushed, in recognition of urgent need
for the data in making fire-control plans, more d e t a i l could have been
shown and the cost would probably have averaged about $2.00 per 1,000
acres.
If a map scale of 2 inches to the mile were used, as i s desirable
for obtaining the d e t a i l needed by dispatchers, the progress of mapping
would be greatly retarded.
INSPECTION
A specimen inspection report on the form used in fuel-type mapping
follows:
INSTRUCTIONS FOR FURL MAPPING
106
Mapping Procedure
Symbols Used
Colors
Extreme rate of spread.
Green
Highest third of rates
of spread, except
extreme rates.
Medium third of
rates of spread
Lowest third of
rates of spread,
Line Directions
Extreme resistance to
control.
Medium third of
resistance range.
Highest third of resistance range, except
extreme resistance
Lowest third of
resistance range.
Sample Combinations
High rate of spread
and low resistance.
Low rate of spread
and high resistance.
Orange lines
Red lines
High rate of spread
and extreme resistanc
Medium rate of spread
and medium resistance.
Green lines
Red, solid
INSTRUCTIONS FOR FUEL MAPPING
Field Form
107
St.
Forest
Joe
INSPECTION MEMORANDUM - FUEL MAPPING
Check Inspected by
Papoose
Location of Area
Area checked
2370
8-2
Date
Date
Date
John Doe
Richard
Roe
Mapped by
Inspected by
Pk.
to Bearskull,
west
193JT
8-1$
193
and south
of
divide.
Acres.
SUMMARY FROM REVERSE SIDE OF THIS SHEET
(Percentages are based on inspector's figures.)
:
Total
: Total
\
shown
Total
i Total
Group : Rate of : Resistance : shown by : acceptably: overratedj underrated
: spread : to control : inspectorr by mapper : by mapper: by mapper
Fuel class
:
: Extreme • Extreme
High
j, Extreme
: Medium : Extreme
Extreme • High
: High
I : High
, Medium
High
Low
: High
Extreme
Medium
Medium
High
Subtotal
Medium
Medium
; High
: Low
Low
:
Medium
II !
Low
Medium
Low
• Low
Barrier
Subtotal
Total
Acres
:
Acres
i
150
: Acres
:
Acres
:
50
:
:
:
t
:
150
60
:
110
320
100
110
260
;:
:
j
540
:
:j
1410
;:
:
;
:
2050
2370
j
% of Inspector's Group I aresi
% of Inspector's Group II are*a
$ of Inspector's Group I and II area
Satisfactoriness of base map: Good
:
:
20
530
1360
0
s
:
10
:
:
40
:
1910
:
2170
;
Percent
81.2
;
93.2
91.5
50
50
Percent
0
2.5
2.1
50
100
:
100
:
150
j Percent
:
15.6
:
4.9
:
6.3
^
Fair
Poor
(Check one)
Kind of map used: Scale 2
Topographic
v/ Planimetric
Accuracy of locating boundaries of fuels; Satisfactory.
Type lines
this
area
follow
closely
topographic
on
features.
Posting of office copy. Frequency of posting and satisfactorinessj
Posted
to date
and
satisfactory.
Rate of mapping progress and comments thereon: Average
work day.
Satisfactory
under conditions
on areas
General remarks: Work very good: carefully
done:
about 4 sections
mapped.
neat.
per
FIRE CONTROL PLANNING—NORTHERN
ROCKY MOUNTAIN REGION
The summary shown on the preceding page is based on the following
data. This tabulation form is to be printed on the reverse side of summary sheets and inspectors are to be provided with an ample supply of
blank forms.
CHECK RECORD OF INDIVIDUAL AREAS
Mappers*
ratings
Rate : Acres
20
HH :
30
HH :
HM :
10
30
mi !
EL : 400
HM
ML
:
:
20
1400
EM
:
HH :
50
HL
100
80
MM
60
HL !
ML ;
m
100
60
10
:
:
:
:
:
:
:
:
:
:
:
:
:
:
:
:
:
!
Inspectors'
ratings
Rate : Acres
20
HH :
:
30
HH
10
HM :
30
HM !
360
HL :
40
ML !
20
HM
ML : 1300
MM
100
50
HM
100
HH s
70
HL !
10
MH :
MM s
0
50
MH :
HL :
10
! HL : 100
: ML :
60
: MM :
10
:
:
::
:
:
:
:
:
:
:
:
:
:
:
:
:
:
:
:
Mappers• acres
Acceptable
:
:
20
:
30
:
10
!
30
High :
Low
360
:
40
20
1300
; 100
50 :
100
70
10
50
10
10 :
100 :
60 •
10 ;
The inspector will take off on tracing paper, in pencil, type areas and
ratings shown by the mapper, and will orient this overlay over his map.
For each area rated by the mapper the inspector will indicate his rating
in the above spaces.
INSTRUCTIONS FOR SEEN-AREA MAPPING
The term "seen a r e a , " as used in the northern Rocky Mountain region
and in these i n s t r u c t i o n s , means the area that topography permits a f i r e man to see from a given detection s t a t i o n when the a i r i s c l e a r . The term
" v i s i b i l i t y " means the degree to which the atmospheric conditions existing
at a given time, together with the contrast between objects, permit the
human eye to identify the objects.
Existence of unseen spots i s dangerous according as f i r e s are l i k e l y
to occur on these spots, the fuel conditions are dangerous, and the values
at stake are high. The long discovery times of some f i r e s occurring in
unseen spots have caused f a i l u r e s in f i r e control. Obviously, f a i l u r e to
map seen areas correctly may r e s u l t in serious f i r e s .
A fire-detection station cannot be evaluated individually; i t must
be considered as one of a group. After a set of detection s t a t i o n s has
been selected that s a t i s f a c t o r i l y covers the more i r r e g u l a r portion of a
l o c a l i t y , i t has often been found that t h i s same set of s t a t i o n s s a t i s f a c t o r i l y covers a l l the remainder of the l o c a l i t y . Thus i t may be e n t i r e l y
superfluous to occupy some prominent peak that an inexperienced man might
have selected f i r s t .
Reliable seen-area maps must be made for many p o t e n t i a l detection
s t a t i o n s in order to sort out the smallest number of s t a t i o n s t h a t , in combination, will give the desired coverage. To f a c i l i t a t e sorting, the areas
seen from potential s t a t i o n s are traced, with black lacquer, onto sheets of
a transparent material. Over a glass-topped table lighted from beneath,
different combinations of seen areas are considered with reference to data
on frequency of f i r e , character of fuels, and values at stake.
POTENTIAL DETECTION STATIONS FROM WHICH TO MAP
DEFINITION OF "DETECTION STATION"
Conditions at the top of a mountain occupied by a lookout are
usually such that seen area may be somewhat enlarged by walking a short
distance from the observatory. I t would be impractical to require that a
separate seen-area map be made for each of the detection points on a 100foot p a t r o l route. On the other hand, separate maps are necessary for
points 1 mile apart. In general a detection station will be considered to
include, together with the observation point considered at the time of
mapping to be the most important, a l l the other points that l i e within 5
minutes' walking distance from i t . Usually the main point i s the one that
has the largest seen area, and the one at which living quarters would be
b u i l t if the point were manned. The group of points forming a detection
station i s regarded as one point.
110
FIRE CONTROL PLANNING—NORTHERN
ROCKY MOUNTAIN REGION
NUMBER OF STATIONS
Experience indicates that seen-area maps should be made for at
least twice as many detection s t a t i o n s as will f i n a l l y be selected for
occupancy, and that where decisions as to the r e l a t i v e merits of points
are d i f f i c u l t , maps should be made for at l e a s t three times that number.
Decisions are p a r t i c u l a r l y d i f f i c u l t for large areas where the standard
as to percent of area burned annually has been almost or entirely met
and i t i s felt that the unseen portions are l a r g e r and more dangerous
than they should be. The l e s s the number of detectors allowed per unit
of area, the greater i s the difficulty of deciding what combination of
s t a t i o n s i s best.
For a representative area of approximately one million acres
largely within the western white pine type, seen-area maps were made from
288 points, of which 178 were fireman s t a t i o n s and 110 were p a t r o l points.
Stations selected to be occupied under severe burning conditions numbered
181, of which 112 were fireman s t a t i o n s and 69 were p a t r o l points; in
other words, i t was planned that 112 men should man 181 p o i n t s . One point
was studied for every 3,200 acres, or every 5 square miles. The plan provides one detector for every 8,320 acres, or every 13 square miles. With
a l l these stations manned, the overlap of seen area would amount to 56 percent of the t o t a l .
Influence o£ Forest Type
General standards for number of potential points to be used in seenarea mapping have been set up on the basis of forest type. I t i s expected
that departure from these standards will often be d e s i r a b l e . Within the
general l i m i t s of the western white pine type, p o t e n t i a l points should
average one for every 3,200 acres; within the larch-Douglas f i r type, one
for every 4,000 acres; and within the ponderosa pine type, one for every
5,000 acres. Existing forest type maps provide a basis for applying these
standards. Very l i t t l e consideration needs to be given to the subalpine
type, from either the smokechasing or the detection standpoint, because i t s
needs will usually be s a t i s f i e d as a byproduct of satisfying the needs of
other types.
Influences of Topography and V i s i b i l i t y
The area seen from a single station i s largely determined by the
shape, depth, and steepness of drainages and the r e l a t i v e scale on which
nature constructed them.
As summer drought continues, dust and the smoke of forest f i r e s
decrease v i s i b i l i t y , and probable r a t e s of spread increase. Detection s t a tions must then be placed closer together to retain the early-season safety
in vision distance and to insure quick discoveries. In f i r e - c o n t r o l planning, a set of s t a t i o n s i s f i r s t selected to be manned when v i s i b i l i t y i s
average and other s e t s of s t a t i o n s , spaced less or more widely, are
selected to be manned when v i s i b i l i t y i s l e s s or greater than average.
I N S T R U C T I O N S FOR SEEN
AREA
MAPPING
III
Allowable vision limits range from 6 to 15 miles.
lEll!i£H££ 9.1 Smokechaser Travel Time
It must be kept constantly in mind that each detector is also a
smokechaser and must be placed in accordance with fixed limits of travel
time to fuels of different kinds. If a distribution of stations that
meets detection needs fails to satisfy smokechaser travel-time standards,
other stations must be added. Furthermore, since allowable travel time
is less when burning conditions are more severe, firemen must be placed
closer together as drought conditions continue. Smokechaser travel time
requirements must be anticipated from the first, and the seen areas of
stations to be added because of them must be taken into account in consic
ering potential detection points.
Allowable travel times for initial attack according to severity of
burning conditions and fuel conditions are given in tables 11 and 12, on
page 66 of Part I.
IHil!i^H££ Ql Frequency of Fire, Fuels, and Values
Obviously, areas on which the probabilities of serious trouble are
high should be better covered than areas low in probable trouble. The
areas on which greatest trouble must be expected are those where fires are
likely to occur frequently, probable rates of fire spread and resistance
to control are high, and damageable values are great. In choosing potential detection stations from which to'map seen areas these factors must be
known and kept constantly in mind, singly and in combination. Maps indicating the relative status of each of these factors are essential to firecontrol planning, and since they will be needed later for that purpose, it
is desirable to have them completed and made available to each seen-area
mapper before he begins his field work.
Fuel mapping is discussed in Part I, page 49, and instructions for
it are given in Part II, pages 89 to 108.
ROAD PATROL
STATIONS
It was found in fire-control plan work that construction of a road
along a high divide frequently permitted speed of travel sufficient to justify combining into a one-man job the detection duties previously assigned
to two or more separately manned stations. Obviously, fewer stations can
safely be included in a one-man job when burning conditions are severe than
at other times. What combinations are safe under different degrees of burning severity constitutes a problem in planning. On the seen-area mapper
falls the responsibility for providing evidence as to coverage obtainable,
through use of an automobile as well as by walking, in point-to-point
travel and detection observations. Wherever roads seem to offer possibilities of efficient point-to-point detection, points within 5 minutes' walking
distance from the roads by trail should be examined. The standard minimum
observation time for any point is 15 minutes. Although it is frequently
possible to make some observations from a moving automobile, particularly if
the observer is not driving, no observations thus made are assumed in planning.
112
F I F E CONTROL PLANNING—NORTHERN ROCKY MOUNTAIN REGION
PREPARATIONS FOR FIELD WORK
POTENTIAL-POINTS MAP AND BASE MAPS
Before f i e l d work i s begun, a " p o t e n t i a l - p o i n t s map" w i l l be p r e p a r e d . On t h i s map w i l l be shown a l l p o i n t s t h a t have been occupied by
d e t e c t o r s and a l l o t h e r s t h a t are known to be worth examining. Locat i o n s for p e r diem guards should be shown according as such guards can
be depended upon and a r e needed. L a t e r , during f i e l d work and in c o n s u l t a t i o n with men well acquainted with d i f f e r e n t l o c a l i t i e s , s t i l l o t h e r
p o i n t s worth i n v e s t i g a t i o n w i l l be discovered and added on t h e map
The
proposed work of s e e n - a r e a mapping near t h e boundaries of adjacent f o r e s t s should be c o o r d i n a t e d with t h a t on t h e o t h e r s i d e of the b o u n d a r i e s ,
to e l i m i n a t e d u p l i c a t i o n and to prevent omission of mapping needed.
Also, before f i e l d work i s begun an i n d i v i d u a l base map w i l l be
prepared for u s e at each of t h e p o t e n t i a l d e t e c t i o n p o i n t s . A topographi
map w i l l be used i f a v a i l a b l e , o t h e r w i s e a p l a n i m e t r i c map. Around t h e
d e t e c t i o n p o i n t a c i r c l e of 15-mile r a d i u s w i l l be drawn on the map with
ink. Each s e e n - a r e a mapper w i l l be provided with such a map for e*ach
p o i n t assigned t o him, and with blank maps t h a t can be used for p o i n t s
added as f i e l d work p r o g r e s s e s .
WRITTEN INSTRUCTIONS TO MAPPERS
When t h e p o t e n t i a l - p o i n t s map has been t e n t a t i v e l y completed,
b r i e f i n s t r u c t i o n s w i l l be prepared for each mapper. These w i l l s p e c i f y ,
by name o r number, from what p o i n t s he i s to map seen a r e a , under what
c o n d i t i o n s he i s expected t o work, and what o r d e r of procedure he i s t o
follow. Mappers should c a r r y both t h e g e n e r a l and s p e c i f i c i n s t r u c t i o n s
in t h e i r f i e l d mapping k i t s , and should thoroughly f a m i l i a r i z e themselves
with b o t h .
EQUIPMENT
For s a t i s f a c t o r y mapping i t i s e s s e n t i a l t h a t equipment be l i g h t
and c o n v e n i e n t . The items needed a r e as f o l l o w s :
Plywood map board, 16" x 16".
Knock-down t r i p o d (Army sketching c a s e ) .
Open-sight a l i d a d e ( i o " - i 6 n b a s e ) .
Abney level, percent
Compass (Forest Service standard or equal).
Timber scribe.
Belt ax.
Tree b r a c k e t for f a s t e n i n g map board to t r e e t o p .
Tree c l i m b e r s complete with s a f e t y b e l t .
Scale (in chains) .
Small p r o t r a c t o r .
INSTRUCTIONS FOR SEEN AREA MAPPING
113
Stiff-back folder 16" x 16" (for maps and tracing paper).
Profile sheet made on coordinate paper or cellophane.
Tracing cloth or paper.
Notebooks and paper.
Pencils, crayons, e r a s e r s , keel, c l i p s , e t c .
Heavy l e t t e r - s i z e envelopes.
Good-quality field g l a s s e s .
The o u t f i t should be packed in a canvas carrying case f i t t e d with
pockets and shoulder s t r a p s , to be carried on the back.
ORGANIZATION, PERSONNEL, AND TRAINING
For each forest a foreman of seen-area mappers should be selected.
This foreman must be qualified to inspect seen-area mapping; that i s to say,
he must be well qualified to map seen areas with a high degree of accuracy.
He should be held responsible for the quality and quantity of work done,
and for compliance with whatever instructions apply to the work. He should
be relieved of other work to the extent needed for efficiency.
Obviously, a man charged with the r e s p o n s i b i l i t y of providing seenarea maps to be used in deciding what combination of fire-detection s t a t i o n s
i s best should be one familiar with plan work and s u f f i c i e n t l y v e r s a t i l e and
observing to collect data on local conditions differing from the ordinary.
Before beginning field work mappers who have not previously received
special training will be trained in groups not exceeding six men to one
i n s t r u c t o r . Training conditions will approximate those of regular field
work as nearly as p o s s i b l e . Each man will be required to do a l l the mapping work necessary at one detection point, and to collect the prescribed
information as to improvements necessary for occupancy of the point. I t
i s expected that men not adapted to the job will be eliminated in the
course of the training period.
FIELD WORK
METHODS OF MAPPING SEEN AREAS
Several methods have been developed for determining the seen area
of a detection station. The profile method, which utilizes the data of a
contour map, cannot be depended upon unless the map is above average in
accuracy, but is useful as a rough guide. Tracings of the outlines of
shadows cast by a tiny light placed on' different peaks of a relief model
have value corresponding to the accuracy of the relief model. The photographic method, utilizing a specially constructed panoramic camera, is
adapted to use on a tower or on a point the view from which is not
obstructed by trees, where roundness of mountaintop is not a factor.
Obviously, it is not suited to mapping from a large number of forest-
IIH
FIRE CONTROL PLANNING—NORTHERN
ROCKY MOUNTAIN REGION
covered points many of which will never be improved. The plane-table survey method, used by the Forest Service in the northern Rocky iMountain
region, has a higher ratio of accuracy to cost than any other.
Under this method, interference of trees on mountaintops is overcome by climbing the trees and mapping from their tops. Roundness of mountaintop is overcome by setting the plane table at as many places as necessary around the break of the top. The following example illustrates the
method of procedure; A distant ridge partially in view over a nearer
ridge is identified on the leveled and oriented base map. An alidade is
used to locate on the map the points where the distant ridge disappears
behind the nearer ridge, and the distant ridge top between these points is
indicated on the map, by color, as seen. If a planimetric map is being
used, the horizontal distance across the area seen on the distant ridge is
estimated and on the map it is colored as seen. On planimetric maps of
this region recently made by the Forest Service from aerial photographs,
ridge tops are accurately shown by symbol.
If a contour map is being used, ihe vertical extent of the portion
of ridge seen is estimated, or measured, and this portion is identified on
the map and colored as seen. Measurement of the vertical distance seen
can be made with an Abney level. A device better adapted to constant use
with contour maps is a thin transparent profile sheet included in the
equipment list on page 112. The field profile method is identical with
the office profile method in principle. It should be used constantly during training periods and thereafter until the mapper is able to visualize
shapes, widths, and sizes of seen areas viewed from various distances and
in different kinds of terrain. The field profile sheet furnishes the mapper with a mechanical means of checking his work and should be used frequently even after he has become proficient in mapping. It is just as
important for the mapper to apply checks to his estimates as it is for a
timber cruiser occasionally to measure the diameter of a tree as a check
on his ocular estimate.
The position of the point from which mapping is done is determined
by the tracing-paper solution of the "3-point problem."
Profiles plotted from topographic maps will not be used except where
dense timber at round-topped points makes mapping uncertain even with a
great deal of tree climbing. They will not be used at any point as the
primary method of mapping in any directions except those in which the view
is seriously obstructed by trees, and will not be considered satisfactory
until checked by observation from, or through, trees.
Care should be taken to assume as the elevation of the observer the
observatory height advocated.
INSTRUCTIONS FOR SEEN AREA MAPPING
115
Mapping from Treetops
The mappers' most troublesome job will be encountered on heavily
timbered points where mapping will have to be done from the tops of
trees. To those unfamiliar with it the job looks impossible, yet a considerable amount of mapping by this method has been done with good results.
It is not expected that any man hanging in the top of a tree by a safety
belt is going to do as expert a job of mapping as if he were working on
the ground; but it has been demonstrated that mapping within the required
degree of accuracy can be done in this way, and in no other practical way
can the necessary information be obtained.
Obviously, a man must be a good climber to do this type of work
successfully.
Figure 23 shows a bracket used to attach a map board to a treetop
Use of the board and bracket instead of sketching by eye is required.
Mapping Scale and Symbols
Seen area will be shown to a distance of 15 miles from the mapping
point. All mapping will be done on base maps having a scale of one-half
inch to the mile. Exact location as determined by the 3-point method will
be shown by a fine-line cross with a circle around it. Area seen from the
mapping point will be shown in solid color, including all area seen from
points lying within 5 minutes* walking distance of the main point. Area
seen from points lying at greater distances will be shown by hachures, a
different color or line direction distinguishing what is added by each
point.
ACCURACY AMD REFINEMENT OF MAPPING
The quality of 'the base maps available varies considerably among
forests and even among different portions of the same forest. The range
of variation is from good topographic maps to poor planimetric maps. Any
map that falls below the present Forest Service standards for good planimetric maps is not acceptable as a base for seen-area mapping. If a forest is covered partly by a topographic map and partly by a good planimetric
map only, seen-area mappers will be given as much training as possible on
the topographically mapped portion.
At a distance of 7 miles from the mapper, it is permissible to
leave a 50-acre area undistinguished from the surrounding area as seen or
unseen if its boundaries cannot be distinguished definitely. The maximum
size allowable for unmapped spots increases with distance from the mapper.
At 10 miles it should not exceed 100 acres; at 15 miles such spots must
not be larger than 200 acres.
No attempt will be made to classify unseen areas as to whether
smoke rising from them would probably come into view of a detector. (The
factor of smoke rise was, however, considered in setting the maximum sizes
for unmapped spots. )
116
FIRE CONTROL PLANNING—NORTHERN ROCKY MOUNTAIN REGION
Although these i n s t r u c t i o n s require the mapping of seen areas to
a radius of 15 miles, i t has been found that in t h i s region the distance
to which vision i s r e l i a b l e averages only 8 to 11 miles. In order to
determine r e l i a b l e - v i s i o n l i m i t s , and to enable inspectors to allow for
them, the following graphic record will be made at half-hour i n t e r v a l s
by every mapper at every point from which seen-area mapping i s done. As
the mapping from any point progresses, the mapper will show, on a radial
l i n e j u s t outside the 15-mile l i m i t , the time of day he i s mapping each
sector. In the same radial direction he will estimate the distance at
which he finds i t d i f f i c u l t to distinguish unseen spots of 100-acre s i z e ,
and draw a dashed l i n e on the map at t h i s l i m i t . He will not draw such a
l i n e across sectors where vision to the r e l i a b l e limit i s obstructed by
topography.
So far as p o s s i b l e , seen area mapping will be scheduled in such a
way as to avoid working within 10 degrees of the s u n ' s d i r e c t i o n . A
desirable procedure i s to begin mapping 10 degrees ahead of the sun.
Small areas are invariably to be mapped as unseen if actual doubt
of seeing them e x i s t s in the mind of the mapper.
In determining differences between areas shown as seen by mappers
and areas so shown by inspectors, the locations as well as the acreages
of mapped spots must be recognized. I t has been found that even when
mapper and inspector show nearly the same t o t a l acreage of seen area,
often they differ greatly as to the location of many areas.
The mapper's "error" i s found by t o t a l l i n g the acreages of additions made by the inspector and the acreages of reductions made, and
expressing the average of these two sums as a percentage of the area
mapped by the inspector. Under most d i f f i c u l t conditions the error should
not exceed ,5 percent; under ordinary conditions i t should not exceed 3
percent.
A rapid and s a t i s f a c t o r i l y accurate method of measuring the many
small areas involved i s to scratch carefully a thin transparent sheet with
squares of small, known, equal s i z e , and through i t count the number of
squares lying within mapped areas.
PERPETUATION OF MAPPING STATIONS
I t i s highly important that f i r e - c o n t r o l managers be able to ident i f y for firemen the exact spots from which detection observations are
expected. Every spot from which mapping i s done will be perpetuated by a
blaze on a t r e e or, if no s u i t a b l e t r e e e x i s t s , on a stake not l e s s than q.
feet long and 2 inches in diameter, set securely in the ground or in a
mound of stones. The number of the station unit as shown by the p o t e n t i a l p o i n t s map will be scribed on the t r e e or stake of the unit considered to
be the main point. On each of the other t r e e s or stakes of the group will
be marked p l a i n l y , in crayon, the number of the unit and a l e t t e r identifying the spot. The r e l a t i v e locations of a l l observation points of the
group will be shown in a diagram on the back of the seen-area map of the
station u n i t .
li I
WZZZZZZZZBZZZZZZZZZZZZZkf'l6m SKETCHING
COUNTER SUNK WASHER
SET SCREW FOR
TOP
BOARD
7
/l6" HOLE
BOARD
VIEW
DETAIL
OF
ACTUAL
Pig. 23.—Bracket for fastening nap board to treetop.
HOOK
SIZE
INSTRUCTIONS FOR SEEN AREA MAPPING
118
RECORD OF CONDITIONS AT TIME OF MAPPING
Information corresponding to t h e following example w i l l be recorded
on t h e back of each s e e n - a r e a map a t t h e time when mapping i s completed.
No. 87, Eagle Point
(Number and name of point)
Date
August 16, 1932
Mapped by
John Doe
Weather
Cloudy and windy, threatening rain.
Visibility
Local smoke interference in N77 quadrant,
Actual mapping time (exclude interruptions)
5-3/4 hours
Remarks At spot A, I mapped from 30 feet up tree. From spot G, profile
used in direction S 20° W.
Any difficulties encountered in mapping will be described briefly.
In order to facilitate the transfer of information v en seen area
maps are used later over glass-topped tables, lighted from beneath, data
recorded on the backs of maps will not be placed over- any of the areas
colored on the face of the map.
PROGRESS MAPS
In order that the work of selecting potential detection points and
mapping from them may be systematically planned and scheduled, a progress
map will be kept up to date by the officer in charge and by each mapper
for the work for which he is responsible. On a tracing-cloth sheet the
size of the forest map, the area seen from each point will be entered in
solid color as it is mapped. A progress map kept up in this way will show
the sizes and locations of areas not yet covered. Seen-area maps prepared
in the office by the profile method will not be entered on the progress map
until checked by field mapping.
COLLECTION OF IMPROVEMENT-PLAN DATA
The form designed for
on page 120. This form will
paper. The coordinate paper
height of the observatory by
entry of improvement-plan information is shown
be reproduced on the blank side of coordinate
is to be used for working out the location find
methods described and illustrated in figure 24-
The time of a mapper on a mountaintop is too valuable to be used for
unnecessary purposes. The mapper will collect all the data called for by
the form only if he can do so without climbing the mountain a second time
for the purpose or causing material delay in mapping progress. Otherwise
he should omit the part indicated, which can then be collected at another
time by someone else.
119
F I R E CONTROL PLANNING —NORTHERN
ROCKY MOUNTAIN
REGION
FOLLOW-UP VORK AT SITES CHOSEN FOR OCCUPANCY
Check of Observatory Height and Location
After the seen area of each point i s transferred to a transparent
sheet, and composites showing a l l the seen area that can be obtained byoccupying different combinations of p o i n t s have been studied over a g l a s s topped t a b l e lighted from beneath, a set of s t a t i o n s w i l l be selected for
occupancy. I t may then become apparent that at some point under consideration no tower, or a lower tower than that determined by the preceding
method, may be satisfactory because one nearby lookout or perhaps two lookouts can see the lower slopes hidden if a tower i s not used. In other
cases single or duplicate coverage may be possible without a tower if short
p a t r o l s to secondary points are made. Distances to available p a t r o l points
together with frequency of f i r e occurrence, fuels, and values at stake in
the area under consideration have important bearings on the necessary
height of tower and the place on the mountaintop that i s determined to be
the main p o i n t , where the combination observatory and living quarters i s
to be constructed.
At the time of mapping from any p o t e n t i a l point, the adjacent
points that will be selected cannot be known. For t h i s reason a man
familiar with planning procedures a.nd with construction problems should,
before construction i s undertaken, re-examine conditions at each selected
point and make a final decision of tower height and location. In doing
t h i s he should carry with him for study a map showing the overlaps of
seen area from selected s t a t i o n s , and t h i s map should show which p o i n t s
have been selected for occupancy for the e n t i r e f i r e season and which are
to be short-season s t a t i o n s .
Scheduling P a t r o l s for Greatest Ef£icienc2
After the observatory i s constructed and t r e e s that i n t e r f e r e with
vision have been removed at each point selected for occupancy, the o r i g i n al seen area map of the point should be checked and corrected from the
actual location of the lookout map-board.
After t h i s has been done a study should be made to determine what
seen area i t i s desirable to add by the use of p a t r o l s (point-to-point
detection J to be required of the occupant of the s t a t i o n . Considering
the data discussed under the preceding subject, i t i s obvious that s e l e c tion of the most efficient set of p a t r o l s from any main point i s a complex problem involving the seen areas of main s t a t i o n s and p a t r o l s that
will be obtained from other points covering any p a r t i c u l a r area. I t i s
necessary not only to cover areas of greatest danger for the largest
possible number of hours, but to schedule times of observations so that a
dangerous area will not be l e f t uncovered by a l l detectors at the same
time.
Another problem in point-to-point detection, when burning condit i o n s are minimum and where roads have been constructed between s t a t i o n s ,
involves p a t r o l l i n g by one man to several s t a t i o n s , each of which will be
occupied by a detector when burning conditions become severe.
INSTRUCTIONS FOR SEEN AREA MAPPING
120
F i e l d Form
IMPROVIDENT-FLAN DATA
ENTRIES DOWN TO HEAVY LINE ARE IMPERATIVE AT EVERY POINT
Point no.
Name
Examined by_
Location
Date
, 19
.
A.
Improvements needed
1. Height of observation platform above ground
ft.
2. Sketch shape of hilltop and relative location of observer
on back of this sheet.
Z, Location of center of observation platform is to be marked
on ground by stake securely set, or by scribed tree. Has
this been done?
B.
Shape, etc., of hilltop
1. Is it sharp and rocky?
2.
" »
"
•• timbered?^
n
n
3.
rounded and open?
4.
" •
"
" timbered?
5 . P e c u l i a r d i f f i c u l t i e s of c o n s t r u c t i o n a t t h i s p o i n t
Timber
1 . a. How many t r e e s t o be cut to c l e a r f o r improvements?_
b . Green o r dead?
Average diameter
"
a.
b.
c.
d.
e.
f.
How f a r t o t i m b e r s u i t a b l e f o r c a b i n o r tower?_
Direction or location
Average l e n g t h
Av. diam.
Species
Green o r dead?
Standing o r down?
Straight
Sound
Can i t be skidded t o b u i l d i n g s i t e ?
Easy o r d i f f i c u l t chance?
^ ^
D.
Water
1. How far?
Direction_
2. Kind of water chance: Spring, how big?__
Stream, how wide?
Bog hole, swamp, or wet spot that can be developed?
E.
Horse feed
1 . How f a r ?
Direction
2 . Size of p a t c h
_ Kind of feed_
3 . How much fence needed t o hold stock?
4 . I s fence m a t e r i a l a v a i l a b l e ?
F.
Other remarks: S t a t e any important c o n s i d e r a t i o n s r e g a r d i n g t h e
use of t h i s point
Fig. 24.—Method for determining location and elevation of lookout.
First:
Sketch break of slope on scale of x"
Second:
Select by eye approximate building site, and with series of
Abney shots and pacings plat profile across it from steepest
point of break in slope (line A ) . From intersection of two
steepest slope lines on profile of line A, drop perpendicular
to ground line. This locates point X 28' horizontally from
steepest break in slope. At X, eye must be n « above'ground
to see over slope in both directions along line A.
Third:
Through X select line B in some direction in which it is important for the lookout to have continuous vision, and plat its
profile the same as above. This gives point Y as location from
which vision is possible in both directions along line B with
lowest possible elevation above ground (14').
Fourth:
Through Y select another line of sight, C, if necessary to
cover some other area which lookout should observe continuously.
Plat its profile. This gives point Z with a necessary height
of 16• for vision along line C. Proper location for center of
tower will be at center of triangle formed by points X, Y, Z.
Call this point T.
*
Fifth:
Insert location of T successively in profiles of lines A, B, and
C. This gives respective heights above ground of 13*, 17*, and
18 • • Therefore, when eye is 18• above ground at T it can see
over break of slope along all three lines of sight A, 3, and C.
If it is assumed that average lookout's eye is 5' from ground,
height of platfora in this case would have to be 13'.
to from 251 to 50'•
Heights of towers are multiples of 10'.
is indicated here.
Thus a 20-foot tower
INSTRUCTIONS FOR SEEN AREA MAPPING
122
A large amount of investigation remains to be done before the r e l a t i v e merits of stationary versus point-to-point detection are determined for
different conditions of danger. The question of whether i t i s b e t t e r with a
given amount of money available to see p a r t of an area a l l the time or a l l
the area part of the time i s being answered annually by many fire control
managers and in many different ways, any one of which may be best suited to
a given set of conditions.
Special i n s t r u c t i o n s are necessary for seen-area mapping that i s done
for the purpose of scheduling point-to-point detection. In formulating such
instructions i t i s necessary to recognize that much longer p a t r o l s are
desirable in certain l o c a l i t i e s than in o t h e r s , and special legends ? * necessary to d i f f e r e n t i a t e complete seen areas from additions obtained
p a t r o l s of different lengths.
ft
SUPERVISION AND INSPECTION
§
The officer in charge must give the job sufficient supervision to
insure that the work of different mappers i s being coordinated correctly and
that a l l information called for by i n s t r u c t i o n s i s being obtained and recorded in a s a t i s f a c t o r y manner. At l e a s t four inspections of each mapper's
work should be made during the season. The f i r s t inspection should be made
within 10 days after the mapper actually s t a r t s work. If inspection shows
clearly that the mapper i s not qualified to do the job, his services as a
mapper will be dispensed with immediately. If inspection shows only minor
weaknesses that can be corrected, the mapper w i l l be retained and a brief
opportunity given him to improve his work. A second inspection of each
doubtful man should be made within one week after the f i r s t , and a second
inspection of a l l men should be made within two weeks after the f i r s t .
There must be no hesitancy about dispensing with a mapper as soon as i t i s
definitely known that he i s incompetent or unwilling to do the work as
required.
Regional inspectors are responsible for checking the work done by
local inspectors in the same ways as the work of the f i e l d mappers i s checked. Inspectors are to record each inspection, and the records are to be
preserved. A copy of each record should be given to the man inspected. If
possible, inspection should be made in his presence and training of the mapper i s to be considered as important as determining the quality and quantity
of work performed. A typical inspection report on the standard form i s
shown on page 123.
RATE AND COST OF SEEN-AREA MAPPING
Other influences on speed than those discussed are time required for
travel, and l o s t time caused by rain and obscurity due to smoke, dust, and
clouds. The average time used for mapping from 2127 points was 2.5 days and
the cost $9.75 per p o i n t . Average costs on different national forests ranged
from $7.00 to $12.00.
INSTRUCTIONS FOR SEEN AREA MAPPING
123
Field Form
SEEN-AREA HAPPING
INSPECTION DATA REQUIRED
The following will constitute an adequate inspection of the work
done at one point:
(1) A check of all improvement information obtained against the
checker's judgment of that required,
(2) A check of the quantity of work done in a given time, due consideration being given to weather and travel conditions and to smoke, haze,
or other factors that may retard progress, (Under normal conditions,
average sketching time per point, for an experienced mapper should not
exceed 4 hours,
(3) A check of the quality of work done, made in the following
manner:
(a) Do the improvement job separately and compare results,
(b) Check seen-area mapping by an ocular check of entire
map; then select a sector of about 10$ of the seen
area mapped, containing the most difficult topography,
and remap it accurately. Remapping will be done on
original map. Boundary of inspector's seen areas will
be shown by ink or indelible-pencil lines,
(c)
Inspectors will date and initial each map inspected and
make suitable notes on it. Results will be considered
satisfactory if variation between mapper and inspector
is not more than 5% of entire seen area where good map
is available as base. Where it is necessary to use a
low-grade map as base, variation between mapper and
inspector must be less than 10%, Where most of the seen
area lies within 10 miles of the mapper, differences
between mapper and inspector should not exceed half
these percentages, under average conditions of mapping
difficulty.
Inspection data will be recorded on the form on the reverse side of
this page.
124
SEEN-AREA MAPPING - INSPECTION MEMORANDUM
Forest Coeur d 'Alene
gA
Point No.
None
Name
Mapped by
John Doe
Date
July
i
XV O o »
Inspected by
Richard
Roe
Date
July
12
193_^.
Check insp. by
H. R. Smith
Date
July
12
195 2.
I n s p e c t o r ' s check a g a i n s t mapper.
Area w i t h i n s e c t o r checked.
S e e n by i n s p .
10.600
Check i n s p e c t o r ' s c h e c k
a g a i n s t mapper
, inspector^
Area w i t h i n s e c t o r checked.
S e e n by c h k . i n s p .
Acres
Q.S^O
Acrea
46o
"
Added "
"
"
So
"
Deduct, by i n s p .
xto
"
Deduct." "
"
i7o
M
Av. of + and -
ql0
"
Av. o f + and -
12ft
"
$ of i n s p . ' s S . A .
2.0
%
% of chk. i n s p . ' s S.A.
lmg
%
Added "
"
RECORD OF MAPPER'S WORK.
Blank s p a c e s t o be f i l l e d out by
Reason f o r d i f f e r e n c e ;
Most of differences
blue Cr. igp acres of seen area not
shown.
I s accuracy s a t i s f a c t o r y ?
Yes
lie
beyond
appear s a t i s factory?
Comments of check i n s p e c t o r on accuracy
accuracy
very
10 miles.
Along
Choppy
hrs.
tocography
I f n o t , why n o t ?
Speed of m a p p e r : A c t u a l t i m e u s e d mapping s e e n a r e a
Y/as t i m e s a t i s f a c t o r y i n r e l a t i o n t o a c c u r a c y
Yes.
west is
difficult.
V i s i b l e l i m i t l i n e : Does i t
*<.apPing sectors
not shown.
inspector.
Except
strip
Yes.
Hour
of
along
Blue
Cr.,
good.
BUILDING-PLAIT DATA: C o m p l e t e ?
Yes
Remarks
Tower advocated
not essential
of bluff
necessary
anyway.
Satisfactory?
since
short
Patrol
GENERAL: I s p r o p o s e d - p o i n t s map k e p t p o s t e d c u r r e n t l y ?
I s c o m p o s i t e p r o g r e s s map p o s t e d c u r r e n t l y ?
Other remarks
Industrious
and plans his work
well.
CONCLUSIONS: Is employee OK for this job?
improvement
over
previous
inspect
ion.
Yes.
InexPerience
Bfry?
overcome
Yes
along
brink
Yes..
Yes.
Great
125
DETAILS OF TRANSPORTATION PLANNING
In topography such a s t h a t in much of t h e n o r t h e r n Rocky Mountains
read r o u t e s f r e q u e n t l y a r e most d i r e c t and c o n s t r u c t i o n c o s t s l e a s t in
brodd v a l l e y s and on o r near t h e t o p s of major and secondary d i v i d e s o r
long r i d g e s . Roads in t h e l a t t e r p l a c e s have t h e added advantage of p e r m i t t i n g down-hill walking from r o a d s t o f i r e s . These f a c t s a r e so obvious
one i s tempted to argue t h a t n a t u r e has a l r e a d y planned t h e l o g i c a l road
r o u t e s . However, t h e h i g h e s t c o s t s of c o n s t r u c t i o n a r e f r e q u e n t l y encount e r e d in g e t t i n g onto and off of d i v i d e s . Furthermore, t h e needs of f i r e
c o n t r o l a r e not s a t i s f i e d merely by c o n s t r u c t i n g roads in t h e l e a s t expens i v e p l a c e s . Apathy toward s y s t e m a t i c a l l y planning f i r e c o n t r o l roads i s
r a r e l y encountered among men who have gone onto t h e rugged and l a r g e
s l o p e s i n t e r m e d i a t e between r i d g e tops and v a l l e y bottoms and t r i e d to
answer t h e q u e s t i o n , how can we get men to t h i s p a r t i c u l a r spot of fuel
soon enough to give them a chance to e x t i n g u i s h a f i r e f a s t e r than i t w i l l
s p r e a d ? S t u d i e s of t h e very l i m i t e d degree to which t r a v e l - t i m e s t a n d a r d s
a r e s a t i s f i e d in l a r g e a r e a s , t h e r a p i d l y mounting annual expense of road
maintenance, and t h e d i f f i c u l t y of g e t t i n g i t done, g i v e s t r o n g evidence
of t h e need for very thorough p l a n n i n g .
T r a n s p o r t a t i o n p l a n n i n g i n v o l v e s p r i m a r i l y d e l i v e r i n g to any spot
t h e number of men needed. Under c e r t a i n c o n d i t i o n s , varying with i n t e n s i t y of burning s e v e r i t y , number of men ( r a t e of work) can compensate for
slowness of t r a v e l . The p r i n c i p a l c o n s i d e r a t i o n s involved a r e a l l o w a b l e
t r a v e l , time (dependent upon f u e l s and burning s e v e r i t y ) , r a t e of t r a v e l ,
l o c a t i o n of man power, and number of men p e r s t a t i o n . Since t h e roads
and man power needed when burning c o n d i t i o n s a r e worst a r e more than
enough a t o t h e r t i m e s , t h e work of p l a n n i n g for l e s s s e v e r e c o n d i t i o n s
i n v o l v e s p a r t i a l use of t h e maximum r e q u i r e d developments and man power.
In p l a n n i n g t h r e e s e r v i c e s of a c t i o n a r e i n v o l v e d , smokechasing ( i n i t i a l
a t t a c k ] , l i g h t r e i n f o r c e m e n t s (small crew a c t i o n ) , and heavy r e i n f o r c e ments ( l a r g e crew a c t i o n , o r heavy second l i n e d e f e n s e ) . Because d i r e c t
trunk r o u t e s a r e e s s e n t i a l t o heavy reinforcement a c t i o n , t h a t s e r v i c e i s
considered f i r s t .
HEAVY REINFORCEMENTS
(HEAVY SECOND LINE DEFENSE)
On pages 49 and 61 of P a r t I road p l a n n i n g f o r heavy reinforcement
a c t i o n i s d i s c u s s e d in d e t a i l s u f f i c i e n t t o g i v e a g e n e r a l knowledge of
t h e methods used. This work r e q u i r e s t h e s e r v i c e s of an e n g i n e e r e x p e r i enced in road c o n s t r u c t i o n and maintenance, and s i n c e s t a n d a r d c i v i l
e n g i n e e r i n g p r a c t i c e s a r e i n v o l v e d , d i s c u s s i o n of them i s o m i t t e d h e r e .
Heavy reinforcement a c t i o n means d e l i v e r i n g 100 o r more men t o any
spot by d a y l i g h t . The time a v a i l a b l e for a c t u a l t r a v e l i s s p e c i f i e d as
8.5 hours from t h e only c i t i e s t h a t can supply 100 men t o t h e western f o r e s t s of t h e region on s h o r t n o t i c e , Lewiston, Spokane, Missoula, B u t t e ,
and Great F a l l s .
FIRE CONTROL PLANNING—NORTHERN ROCKY MOUNTAIN REGION
The r a t e s of travel applied in planning to the movement of these
large crews during the night are; on roads, the rated speeds of p a r t i c u l a r
portions; on t r a i l s , 1.5 miles p e r hour; and off t r a i l s , 0.5 mile per
hour.
Studies of performance indicate that busses are s l i g h t l y f a s t e r
than trucks on main highways, but somewhat slower on forest roads. The
average speeds of these vehicles were applied to the use of either one.
The road speeds used were determined for main highways by commercial bus
schedules and experience with Forest Service trucks, and for forest roads
by t e s t s of several types of loaded trucks over 115 miles of representat i v e roads on the Coeur d'Alene and Clearwater f o r e s t s . Speeds on other
roads were based on comparisons. After excluding the poorest road (having
a speed of 6 miles per hour) the average speeds were found to vary from
8.2 to 18.6 miles per hour, the weighted average being 11.8. For similar
roads a speed of 10 miles per hour was used in plan work.
In determining coverage a sheet of tracing paper i s placed over the
forest map and an 8.5-hour time contour from each man power center i s
worked out, based on the existing road system. Another time contour q.
hours further i s worked out to show the limit reachable by approximately
10 o'clock, a.m. On another tracing similar contours are worked out showing the l i m i t s reached by use of the proposed road and t r a i l system. The
second tracing i s made after possible road routes have been investigated
and those roads proposed that extend the coverage into areas shown on the
f i r s t tracing as not reached. P a r t i a l tracings are used to show a l t e r n a tive p o s s i b i l i t i e s .
In determining the distances, in horizontal projection on the map,
reached by foot t r a v e l dividers are used, being set to allow for slope
and i n d i r e c t t r a v e l according to local conditions of topography and travel
obstructions.
LIGHT REINFORCEMENTS (SMALL CREW ACTION)
The necessity for providing a light reinforcement service i s d i s cussed on page 8 1 . Methods of planning to s a t i s f y t h i s need are discussed
in general on page 62. Knowledge of these data are assumed here.
Small crew action contemplates the use to the distance possible of
man power available in communities. Beyond the l i m i t s reachable by such
crews, the existence of hired crews located to best advantage in r e l a t i o n
to the road system i s assumed.
Airplane landing f i e l d s c o n s t i t u t e an important part of t h i s s e r vice. In planning for them and in determining coverage from them, the
time required for assembly of men and delivering them to each field from
Spokane and Missoula was determined and subtracted from the allowable
TRANSPORTATION PLANNING
127
travel time. It i s estimated that 20 men can be delivered to any landing
field west of the Continental Divide before dark.
The travel time l i m i t s are based on controlling a 50-acre fire
before 10 o'clock of the morning following spread of the f i r e . These
l i m i t s , according to crew size and resistance of the fuel to control, are
shown by table 9 on page 62.
METHOD OF WORKING OUT LIGBT REINFORCEMENT COVERAGE
On a forest map are shown the number of men available at different
points and the number of hours required for assembling them. The assembly
time i s subtracted from the t r a v e l time shown in t a b l e 9 for each fuel
resistance. The distance in terms of time to which each fuel can be covered i s thus determined.
Time contours in different symbols are used, one for each class of
fuel resistance. Using a sheet of tracing paper the s i z e of the one-half
inch to the mile forest map, and beginning at the point of assembly, the
f i r s t contour i s placed at the distance to which fuels of extreme r e s i s t ance can be reached by t r a v e l l i n g existing roads and t r a i l s , From t h i s
contour the additional distance to which fuels of high resistance can be
reached i s determined. The remaining contours for medium and low r e s i s t ance fuels are determined in the same way. This tracing i s then placed
over the fuel map. By inspection the fuels of extreme resistance that l i e
outside the f i r s t contour are identified and drawn in symbol on the t r a c ing. Similarly the fuels of high and medium r e s i s t a n c e lying outside t h e i r
respective contours are i d e n t i f i e d and shown in t h e i r respective symbols on
the tracing. Some of these uncovered fuels will be reached within contours
worked out from other s t a r t i n g p o i n t s , and when so covered they are erased
from the tracing. In t h i s manner the fuels covered and not covered from
a l l communities are determined.
Beyond the l i m i t s reachable from communities, sizes and locations
of crews are assumed that appear best according to s i z e of area to be
covered and the fuels l e f t uncovered are i d e n t i f i e d in the same manner as
j u s t described.
After determining coverages possible by t r a v e l l i n g the existing
road and t r a i l system, road and t r a i l extensions are made and proposed
landing fields are shown and the added coverages determined. After completing the composite coverage tracing, i t i s necessary to reconsider the
first decisions and for p a r t s of the forest to work out on p a r t i a l t r a c ings amended and a l t e r n a t i v e plans for completing coverage to the desired
degree.
Where the time contours of adjacent crews meet a division l i n e of
responsibility i s shown, and thus the area of each crew's responsibility
i s defined.
128
FIRE CONTROL PLANNING—NORTHERN ROCKY MOUNTAIN REGION
The speeds of travel assumed for small crews are somewhat f a s t e r than
those used for loo-man, heavy reinforcement crews. Small crews are moved by
passenger cars or light trucks about 5 miles per hour faster; foot t r a v e l on
t r a i l s i s about the same, 1.5 miles per hour, but walking off t r a i l s i s
assumed to be at the r a t e of 0.75 to 1.0 mile per hour, since local men
accustomed to such travel will usually be the type used.
METHOD OF DETERMINING ALLOWABLE TRAVEL TIMES (NIGHT
REINFORCEMENTS)
Although the s t a r t i n g time of action was assumed to be 5:00 p.m.,
studies of experience showed that about one hour must be allowed for l o s t
motion caused by delays in getting s t a r t e d and for f a i l u r e s to follow the
most direct routes. For t h i s reason 6*00 p.m. was used as the probable
time of s t a r t i n g action. From 6*00 p.m. to the next 10*00 a.m. i s 16 hours,
during which the jobs of travel and control are to be performed. By adding
the work that can be accomplished by a crew of p a r t i c u l a r size in the 16th
hour to that of the 15th, and e a r l i e r hours, one can determine the number
of hours before 10*00 a.m. required at a f i r e of p a r t i c u l a r size to control
i t , and the time remaining (out of 16 hours] can be u t i l i z e d for travel and
assembling men.
Based on the idea j u s t presented, figure 25 shows the graphical
method employed. Chart A shows the estimated influence of crew size on the
average r a t e of work per man per hour. The curve i s based on meager s t a t i s t i c a l data supplemented by a large number of estimates made by experienced men. The following influences were recognized;
1.
Size of f i r e , when l a r g e r than can be controlled by 5 men, prevents
the men from working back and forth across or around the f i r e and
a s s i s t i n g each other in removal of logs, attacking hot spots, and
prevents interchange of t o o l s .
2.
The best trained men are u t i l i z e d on the smallest sizes of f i r e ,
and the quality of personnel decreases with crew s i z e .
3.
The percentage of time necessarily subtracted from labor for
supervision increases with crew s i z e .
In charts B, C, D, and E the v e r t i c a l spacings of curves for different
of crews are determined by the values shown in chart A.
sizes
The influence of fatigue estimated by experienced men i s shown by
charts B, C, D, and E. Attention i s directed to the fact that night work i s
under consideration. I t i s assumed ( s a t i s f a c t o r i l y for the purpose) that
riding in trucks, walking, and working on a f i r e are equally fatiguing. It
will be observed that after reductions have been made through 10 hours of
time a f t e r 6°oo p.m., no reduction i s made from 4:00 a.m. to 7:00 a.m. This
i s due to the increase in daylight, permitting more effective work and offsetting increased fatigue.
129
tlI
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WORK
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NUMBER OF MEN IN CREW
G
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Fig. 25.—Method of determining
travel times for light reinforcement crews.
"T
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C.
In fuel of high resistance.
D.
In fuel of medium resistance.
E.
In fuel of Jow resistance.
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B, C, D, E. Rates of night work at
different lengths of time after 6^00 P««
as influenced by crew s i z e and f a t i g u e .
1
F. G. Travel times allowable according
to crew s i z e and fuel resistance.
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hourly outputs between the dashed l i n e s
and 10 oiclock are equal to go, 90, 130,
and 160 chains, respectively.
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Explanation of dashed l i n e s in charts B,
C, D, and E.
1
HOURS
G.
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To control 60 chains of perimeter.
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TRANSPORTATION PLANNING
130
The dashed l i n e s in charts B, C, D, and E crass each curve at a
point such that in the remaining hours 60, 90, 120, and 160 chains of
fire perimeter can be worked by the size of crew indicated, if the output of each man in each hour i s that indicated by the vertical scale.
The intersection points show on the horizontal scale the time that can be
used for travel plus that for assembling the crew. These times in relation to number of men per crew are plotted in chart F for control of 60
chains of perimeter and in chart G for control of 160 chains.
The probable perimeter of a 50-acre f i r e i s 120 chains; threefourths of i t i s 90 chains, and one-half i s 60 chains. For a very
irregular perimeter the length may be as much as one-third greater, or a
total of 160 chains. Another consideration necessary here i s that only
three-fourths of the perimeter of the average f i r e requires control work.
Since the f i r e may be very irregular in shape, the control of 160 chains
may be necessary with the unusual f i r e s that remain active throughout
the night. The curves of chart G show according to crew size the travel
times that can be used. Or, they can be used by dispatchers as guides
to the number of men that should be sent when a 50-acre fire i s at different distances (in time) from them, providing that the crew accomplishes
the rates of work assumed. In table 19 the number of men needed for any
size of f i r e i s shown. Attention i s directed to the fact that the smaller
crews were assumed, in working out these data, to be much more efficient
than the larger ones. The sharp bends (changes of slope) in the curves
of charts F and G show the combined influences of quality of man power and
fatigue.
Anyone experienced in fire suppression probably will be surprised
to observe in chart G and table 19 that 20 men are shown to be sufficient
(with short travel time) for control of 50-acre f i r e s in fuels of high
resistance to control. The essential consideration i s that rate of work,
and not merely number of men, must be estimated in dispatching. The
rate assumed here may be too high to include f e l l i n g enough snags to prevent escape of f i r e s during the next afternoon unless other crews are
sent.
In chart F are shown the travel times that could be used, according to crew s i z e , to control 60 chains of perimeter (half the average
perimeter of 50-acre f i r e s ) . These are the travel times used in planning the placement of small reinforcement crews. Obviously, one crew
working alone i s insufficient to do the job to be expected. The a s s i s t ance of neighboring crews was planned. The number of men involved in
action, then, i s that of several crews, and the travel time i s an average.
It was necessary to "try out" the standards in order to find out
how close together crews would be after the travel times of chart F are
satisfied. This study and later plan work shows that even these travel
times require a great many more men to be available per square mile than
have ever been contemplated in the past. In l o c a l i t i e s without roads,
or with few roads, i t i s extremely difficult to satisfy these specifications. The assumption that several small crews will be used for night
S3!
FIRE CONTROL PLANNING—NORTHERN ROCKY MOUNTAIN REGION
T a b l e 19.—Number of men needed in night
reinforcement
control
inactive
fires
of different
sizes
10 o'clock
of the next
forenoon.
action
before
to
Time 6:00 : Fuel
N u m b e r of men needed l/ 1iccording to size of fire
p.m.• to tresist- \
arrival : ance 5 5 ! 10 l 15 . 20 : 25 ! 30 : 35 ! 40 : 45 : 50
tacres :acres .acres acres .acres :acres :acres !acres jacres :acres
:Hrs,
! 14 : 30 t 5 4 : 90
7:00: 1 ;
E
: 5 ! 8 ; 10 ! 12 ! 13 ! 14 : 15 J 1 6 ; 17 j 19
p.nu:
;
H
: 5 I 6 ! 7 ! 7 ! 8 ! 8 : 9
:
M
L
. 5 ! 5 ! 5 : 5 . 6
8:00 : 2 ;
E
\ 16 : 40 ! 70
1 6 : 9 1! 11 3 13 : 14 ; 16 5 17 ! 19 . 21 j 23
:
H
;
M
. 6 : 7 I 8 \ 8 : 9 { 9 •. 10
! 5 : 5 : 6 ! 6 ! 7
L
! 18 ! 50 j
9:00 . 3
E
16 I 1 8 ! 21 !: 24 . 27 J 30
H
1 7 ! 10 : 12 : 14
5 : 7 ; 8 ! 9 1 9 ! 10 •; 10 : 11
:
M
! 5 : 6 ! 6 : 7 { 7 ! 7
!
L
E
23 * 60
10:00! 4
4, 14
: 16 : 18 ! 21 ! 26 •! 35 : 48 ! 60
H
:, 7 •
5 ! 6 : 8 : 9 ! 10 : 1 1 1 11 t 12 ! 13
:
M
:
5 ! 5 : 6 ; 7 ! 7 !: 8 : 8
L
! 35
70
11:00: 5
E
! 9 '! 13 :• 16 : 20 ! 24 . 30 ! 48 ! 70
H
:
6 ; 7 : 8 ; 10 : 1 1 ! 12 : 1 3 : 14 : 15
;
M
•
5 ', 6 : 6 : 7 ; 8 : 8 ! 9 : 9
5
L
*
!
12:00: 6 :
E
1
41 ! 57
10 ; 15 :,20 : 27
H
•
M
! 5 : 7 i1 8 : 10 ! 11 : 13 j 14 ! 15 . 16 : 18
•
5 ! 6 : 6 : 7 i 8 :! 8 t 9 :; 10 : 11
L
E
:
1:00: 7
12 : 18 .27 : 54 :
a,m.:
!:
H
:
;
M
; 6 ! 8 J 10 : 11 :. 13 ! 15 . 17 ! 19 . 21 ; 23
:
;:
7 : 8 . 8 :. 9 !. 10 : 11 s 12
! 5 ! 6
13
L
E
2:00s 8 ;
•
:
H
j 14 : 23 !. 60 :
M
! 8 i! 9 ! 11 j 13 : 16 ! 18 ; 21 •: 24 . 29 !. 35
L
, 10 :; 11 : 12 S 13 i 14 : 15
. 6 : 7 1. 8 : 9
9 !
E
3:00
*
H
! 19 ' 50
M
i 9 j 11 ! 14 : 17 : 21 : 25 !: 32 .! 55 ;
! 6 j 8 : 9 : 11 : 12 1! 13 . 15 ; 16 : 18 ; 20
L
:
4:00 10
E
H
J 22 : 60
•
1
M
i! 11 ; 14 : 18 t 23 ; 30 : 60
7 \ 9 \ 11 : 13 : 15 - 17 : 19 j 21 j 24 : 50
L
<
1
A.
•
iJ
JJ/
1
These d a t a a r e b a s e d on t h e r a t e s
s i v e f i r e s i n c r e a s e t h e number o f
f a t i g u e d are assuned.
Double t h e
expected.
Add h a l f i f t w o - t h i r d s
be n e c e s s a r y t o h o l d t h e f i r e .
E = E x t r e m e , H m H i g h , M = Medium,
of work shova i n f i g u r e 3 5 . For a g g r e s men shown.
T r a i n e d aen n o t s e r i o u s l y
n u n b e r shown i f o n l y h a l f t h e o u t p u t i s
i s expected.
F u r t h e r r e i n f o r c e m e n t s aay
L « Low.
CURRENT ACTION
132
attack on one f i r e , makes i t necessary for planners to study the crew man
power per unit of area as well as the locations of p a r t i c u l a r crews. The
chance e x i s t s that each of several f i r e s within a l o c a l i t y will require
crew action at the same time. However, as shown by figure 17, A, on page
64, t h i s p r o b a b i l i t y i s remote, since only 7 percent of a l l f i r e s become
larger than 50 acres.
In planning no travel times longer than 10 hours are used. This
specification i s made in recognition of the possible pick-up in burning
conditions that not infrequently occurs a*d increases during the forenoon.
INITIAL ATTACK (SMOKECHASEF ACTION)
Methods of working out individual s i l h o u e t t e s of coverage from
fireman s t a t i o n s and f i t t i n g them together into composites are discussed
on page 71. The t r a v e l times used in working out s i l h o u e t t e s are shown
by table 11 on page 66.
Roads needed for i n i t i a l attack are considered a f t e r those needed
for heavy and l i g h t reinforcement actions have been determined in the
order described. I t should be pointed out that the proposed roads planned for reinforcement action are assumed to exist before extensions are
made to s a t i s f y the travel-time standards of i n i t i a l attack. Existing
smokechaser coverage i s worked out, based on the roads and t r a i l s e x i s t ing on the date the study i s made. Unless extremely expensive construction i s involved, a connection to the road system i s planned for every
fireman (except in wilderness areas) and road and t r a i l extensions are
planned into areas of worst fuels.
CURRENT ACTION ACCORDING TO SIZE AND AGGRESSIVENESS OF FIRE
BSLAllQNS_BElWEEN.TSAVEL.il MEA.MAN_POjfES-ASB-EnEL
Dispatchers find i t necessary continually to estimate the number of
men that should be sent to f i r e s of various sizes and rates of spread,
located in different fuels, at different distances from man power s t a t i o n s ,
and occurring under different degrees of burning s e v e r i t y . Placement plans
provide only for meeting the conditions within certain steps of expansion
and contraction of preparedness, and within steps adjustments are l e f t for
current determination. However, before s e l e c t i n g the specifications to be
used in planning, analyses of speeds and strengths of attack believed to be
needed under every degree of burning severity were made. In addition to
t h e i r current application to dispatching these data are necessary to show
the number of men needed oer station under different degrees of burning
severity and as guides to the temporary placement of man power in lieu of
roads, pending completion of the planned road system.
133
FIRE CONTROL PLANNING—NORTHERN ROCKY MOUNTAIN REGION
In determining the number of men needed for control two very different conditions of f i r e aggressiveness are involved; night behavior, when
f i r e s usually do not spread appreciably; and behavior during midday burning periods, when i f control i s not established quickly while the f i r e i s
actively increasing in s i z e , i t probably will not be effected u n t i l many
hours l a t e r when night influences p r e v a i l .
NIGHT ATTACKS
The number of men needed in night attacks, according to s i z e of
f i r e and fuel r e s i s t a n c e , a f t e r different lengths of time have been used
for assembling men and t r a v e l l i n g after 6*.oo p.m. are shown by table 19.
The considerations to be recognized in application of these data are
discussed on pages 128-130. Until accurate data are collected on rates
of work involved in figure 25, no b e t t e r estimate of the number of men
needed can be made. The data used are the best available, and none of the
f a c t o r s can be l e f t out of consideration. These factors a r e ; fuel (the
material in which f i r e f i g h t e r s work), aggressiveness of f i r e , training of
men, influence of crew s i z e , and fatigue.
MIDDAY ATTACKS
I t i s necessary to focus attention on midday control of aggressive
f i r e s . They occur in every l o c a l i t y and measures of preparedness that
w i l l stop them at small size will be more than sufficient for a l l other
f i r e s . Efficient detection i s a necessity, that i s , such f i r e s must be
discovered almost as soon as they begin to spread. In the normal growth
of such f i r e s a stage i s reached when heat or speed of advance, or both,
make i t impossible for men to work d i r e c t l y in front of them. Although
attack from the rear may be the only feasible method, there can be no
assurance that the front will not be miles away before i t i s reached.
The elapsed time l i m i t between discovery and impossibility of work on the
front i s the outstanding consideration in control of such f i r e s . For the
sake of brevity in discussion, t h i s elapsed o v e r - a l l control time i s
c a l l e d "C" and the part of i t from discovery u n t i l attack i s begun i s
c a l l e d "a." The difference "f" i s used for f i r e f i g h t i n g .
Obviously, for a p a r t i c u l a r fuel the allowable "C" time varies
with severity of burning conditions, that i s , i t v a r i e s with r a t e of
spread. Under a p a r t i c u l a r degree of burning severity existing in a
l o c a l i t y , the allowable "C" time v a r i e s with the r a t e of spread in different fuels. No field studies of allowable MC" time have been made.
However, the correspondence between i t and Danger Meter ratings i s
i n d i r e c t l y available through correlations with r a t e s of spread in different fuels under different r a t i n g s of the Danger Meter,,
CURRENT ACTION
131
If each smokechaser could be imbued with the feeling of a race
between himself and the r a t e of spread, the goal being the "C" time l i m i t ,
more fires might be controlled within the f i r s t work period and without
reinforcement action. Enthusiasm for t h i s race i s dampened considerably
by the fact that the smokechaser always wins in about 75 percent of the
cases, but not when r a t e s of spread exceed 12 chains of perimeter increase
per hour. In such cases 83 percent of f i r e s in 1921-30 were attacked
within 1 hour after discovery if control within the f i r s t work period was
accomplished; 98 percent were attacked within 1 hour if r a t e of spread
exceeded 20 chains per hour. These data apply to any kind of fuel and are
amply supported by a thorough analysis of 8,789 f i r e s (all for which rates
of spread could be determined). Although TVIP average smokechaser of the
year 1937 may be b e t t e r equipped with "guts', asbestos hide, and training to
work on hot fronts than those of 1921-30, evidence does not point in that
d i r e c t i o n . However, more men are now being used in i n i t i a l attacks on
such f i r e s than formerly, thus speeding up the rate of work and shortening
the firefighting time, "f." These data must be regarded as good indications of necessary a r r i v a l time "a" a f t e r discovery of fast-spreading
f i r e s . These and other data indicate that the "C" time l i m i t under probable conditions of attack can be about 2.0 hours when r a t e of spread i s 20
chains per hour.
The allowable "C" time when rates of spread are only 3-5 chains per
hour appears from analyses to be about 6 hours. A high percentage of
f i r e s was s a t i s f a c t o r i l y controlled in 1921-30 when attack began in 4-5
hours after discovery. When prevailing burning conditions are at t h i s low
degree of severity, the c r i t i c a l midday burning period i s not longer than
4 hours during which attackers are threatened with the impossibility of
working directly on f i r e - f r o n t s . For t h i s reason MC" times longer than 7
hours are not worth consideration, since they involve work outside the
c r i t i c a l midday period.
In figure 26 the over-all control time after discovery, called "C",
believed to correspond with each r a t e of spread, i s shown by chart A.
Assuming the r a t e of spread to be that in the average of a l l fuels, the
correspondence believed to exist between average r a t e of spread and ratings given by Gisborne's Danger Meter i s shown in figure 2$.
Within the allowable "C" time the operations that must be included
are, in order of performance, report-get-away, t r a v e l , and f i r e f i g h t i n g .
Report-get-away time i s assumed to be constant and require 15 minutes.
Since firefighting time can be shortened by increasing the r a t e of work,
the t r a v e l time can be lengthened by sending more men, using a bulldozer,
a pump, or chemicals. Unless the efficiency of men i s known, numbers of
them do not indicate a p a r t i c u l a r r a t e of work. Rate of work by any
means i s the essential consideration.
Allowable travel time in relation to different r a t e s of work can be
determined for each of the multitude of combinations of factors involved.
In s e t t i n g out to do t h i s laborious job the work can be simplified and
systematized by f i r s t using l e t t e r s to represent each of the factors and
thereby determining t h e i r natural i n t e r r e l a t i o n and obtaining a correct
pattern for computations.
35
FIRE CONTROL PLANNING—NORTHERN ROCKY MOUNTAIN REGION
DERIVATION OF TRAVEL TIME FORMULA (MIDDAY ATTACKS)
Discovery of the f i r e at very small s i z e , when i t f i r s t begins to
spread, i s assumed regardless of time elapsed since i g n i t i o n . The
elapsed time from discovery to actual control, that i s safe to permit, i s
called "C."
Let C s time from discovery to control
Let a g time from discovery u n t i l attack i s Degun.
Let f = time spent in f i r e f i g h t i n g . Then f = C - a.
Until attack i s begun the length of perimeter, hence the job to be
done, increases.
Let p • average r a t e of perimeter increase during t h i s time, a.
Then ap • the perimeter when attack i s begun.
Even in active f i r e s not more than half of the perimeter requires
immediate action. Since the other half can be worked l a t e r , i t i s excluded
from the work that must be done within the control time, C.
The job to be done « o . s a p
Let W
r a t e of work, that i s , length of perimeter controlled per
unit of time that will accomplish control s a t i s f a c t o r i l y .
Then a r a t e of work, W, applied for f hours completes the job.
The job done « Wf, or since f » C - a.
"
" * V(C - a) m WC - Wa
s
Since the job
0.5 a p
Wa + o . s a p
a(W + 0 . 5 P )
a
to be done and the job done are the same,
• WC - Wa.
Add Wa to each member
« WC
» WC
= WC ~ (W + 0.5P ) This i s the required length of
a r r i v a l time after discovery.
Let 0,25 hour = allowance for report and get-away.
"
t « travel time, the desired and unknown quantity.
t • a -
0.25
Therefore t « WC + (W + 0.5P ) - 0.25 hour.
Computations of allowable travel time are most simply made by
neglecting the 0.25 hour report-get-away time and subtracting i t from each
a r r i v a l time, a, after the computations have been made.
For the sake of simplicity in deriving the formula i t was assumed
that one-half the perimeter existing at the time attack i s begun requires
action within the time limit MC." Actually the percentage varies with r a t e
of spread and an estimate of i t for any r a t e of spread i s shown in figure
26, B6
ENT
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F AR
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CHAINS PER HOUR
PERIMETER INCREASE
yz = 400 x
10 20 30 40 50
CHAINS PER HOUR
PERIMETER INCREASE
RATE OF SPREAD
CHAINS PER HOUR, VALUES O F ^ p "
32 25 18 14 12 10 8
65 4 3
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TRAVEL
5
CURVES DERIVED FROM EQUATION,
t=w^fp-a25H0UR
EXAMPLE:
WHENpr I0CH. PER HOUR
THEN%p = 62 (GRAPH B )
AND C = 3.5 (GRAPH A)
IF PERIMETER CAN BE
CONTROLLED AT THE RATE
OF 11 CHAINS PER HOUR
3.5X11
t .
?c
l
~ II +.62X10"*
t = 2.0 HOURS
IF 2 HOURS ELAPSES FROM
GET-AWAY TO ATTACK,
HELD LINE MUST BE
CONSTRUCTED AT THE RATE
OF I I CHAINS PER HOUR.
TIME
sj6.—Rate o f work and c o r r e s p o n d i n g t r a v e l t i m e l i a i t s
control f i r e s of i n d i c a t e d r a t e s of spread.
required
to
CURRENT ACTION
137
The general form of the travel time formula i s
1
CW
• r r i p - °- 2 s hour
In figure 26, B, a curve i s p l o t t e d which i s believed to approximate
the average percentage of the perimeter, at the time attack i s begun, that
must be fought within the "C" time l i m i t . I t should be noted that " p , "
used in the equation, i s r a t e of perimeter increase and not the perimeter
i t s e l f . However, the same result i s achieved by application of t h i s p e r centage to the r a t e of spread. Attention i s directed to percentages greater
than ioo shown by the curve. These mean that the f i r e by advancing during
the f i r e f i g h t i n g time produces a l a r g e r perimeter than that found on a r r i v a l .
Anyone experienced in making i n i t i a l a t t a c k s on f i r e s and familiar
with a n a l y t i c a l geometry will recognize that t h i s percentage i s 0 when r a t e
of spread i s 0 and that the curve must, be tangent to the v e r t i c a l axis at
the point 0, o« From the origin point the curve must r i s e at a continually
decreasing r a t e , but never stop r i s i n g . This description not only suggests
the p r o b a b i l i t y that a parabola i n t e r p r e t s the r e l a t i o n s h i p , but makes i t
almost obligatory to use one in the absence of contradictory evidence. I t
i s not presumed that the p a r t i c u l a r parabola used i s the one that field
investigations w i l l find to be correct. That i s too much to expect of an
estimate, even though i t i s based on the combined opinions of experienced
men. Another reason for using a mathematical curve, if one that i n t e r p r e t s
the data i s known, i s to prevent the error of placing some sections of the
curve at a l t i t u d e s that are inconsistent with the remainder of a l t i t u d e s .
APPLICATION OF TRAVEL TIME FORMULA
In making current plans and in taking action on f i r e s two very different methods of approaching the c r i t i c a l issue of midday control are
available. One i s the " t r i a l and error" method followed everywhere during
the past t h i r t y years. The other method i s to examine the requirements of
the c r i t i c a l issue and decide to what extent these requirements can be met
and to what extent i t i s economical to meet them. In other words, f i r s t ,
what speed and strength of attack i s required to control, at small s i z e ,
the percentage of a l l f i r e s that cause most of the burned area and damage?
Then, to what extent does i t appear to be physically possible with ordinary
man-power methods to do the job b u i l t up by fast-spreading fires? In r e l a tion to the time and energy that has been expended in conferences and
making elaborate judgment estimates, i t does not appear unreasonable to
examine c r i t i c a l l y and in d e t a i l the statement of the case presented in
summary by the t r a v e l time formula and the implications contained in i t .
In figure 26, C, curves corresponding to different r a t e s of f i r e
spread are shown. Each of these curves was worked out by the t r a v e l time
formula, using a p a r t i c u l a r r a t e of spread, different r a t e s of work, and
the applicable "C" and "p" values shown by graphs A and B. Each curve
138
FIRE CONTROL PLANNING—NORTHERN ROCKY MOUNTAIN REGION
shows the t r a v e l time that can be allowed if any p a r t i c u l a r r a t e of work i s
applied in attack. With the exception of 15 minutes allowed for r e p o r t - g e t away, the time i s that from efficient discovery u n t i l attack i s begun. The
rate of work that corresponds to any point on a curve i s that which r e s u l t s
from aggressiveness of the f i r e .
The required r a t e of extinguishment i s e n t i r e l y free from any consideration of how i t i s to be done. The set of curves simply c o n s t i t u t e s a
statement of what different degrees of f i r e aggressiveness require. After
studying them one might be able to decide whether or not he desires to p r o vide the r a t e of work required. For instance, for the 19 percent of a l l
f i r e s (shown by figure 17, B) that must be expected to have perimeter
increases of 18 chains per hour or more, i s i t more economical to provide
everywhere and within 1 hour after discovery, a midday work-rate of 20 chains
of held l i n e per hour, or after providing a smokechasing service that will
catch most of the f i r e s , to accept the probable burned area and make a strong
attack in the evening? One might decide that the highly expensive preparedness required to do the former i s j u s t i f i e d , where high danger (threat to
values) e x i s t s . Where resistance to control i s low, as with grass f i r e s , i t
i s not d i f f i c u l t in the v i c i n i t y of communities to provide a work-rate of 20
chains per hour. Bulldozers, horse-drawn plows, or water may be made a v a i l able within 1 hour to speed up an otherwise slow man-power r a t e of work. But
even for these l i g h t fuels in uninhabited l o c a l i t i e s with topography such as
that found on the 2,ooo-foot breaks of the Salmon River, providing anywhere
near t h i s r a t e of work everywhere i s not simply a problem of j u s t i f i c a t i o n ;
p r a c t i c a l l y , i t i s a physical impossibility.
If man power, using ordinary hand t o o l s , must be r e l i e d upon to accomplish the required work-rate, figure 27 shows the number of men required. In
t h i s figure the curves of figure 26 are reproduced, and a horizontal set of
curves i s superimposed on them, showing numbers of men estimated to be
required to accomplish the r a t e s of work indicated on the left-hand v e r t i c a l
scale. In the four right-hand v e r t i c a l columns, the numbers of men according to fuel r e s i s t a n c e are shown. The four classes of resistance are the same
as those used in the f i e l d in mapping fuels, extreme, high, medium, and low.
Figure 27 shows, by curves and interpolation between them, for any r a t e
of spread and any resistance to control the number of men that can be allowed
to use any p a r t i c u l a r length of travel time. For instance, if the men are
stationed 1 hour distant from a f i r e that spread at the r a t e of 10 chains per
hour, follow up the 1 hour v e r t i c a l l i n e to the dashed curve labelled 10 (at
the top of the s h e e t ) . At t h i s point a horizontal curve will be found, which
if followed to the r i g h t , shows that in fuels of low resistance 2 men are
required; in medium r e s i s t a n c e , 2 men; in high, 5 men; and in extreme r e s i s t ance, 35 men. For any other travel time the procedure i s the same.
If the r a t e of work that will be applied i s known, the horizontal
curves and the right-hand data on resistance should be disregarded e n t i r e l y
and the left-hand v e r t i c a l scale in relation to the r a t e of spread curves •
used. Since, in t h i s case, the data are the same as those shown by figure 26,
that figure, being more simple, should be used.
RATE
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a 7 . — Number of men and corresponding travel time limits require
control fires of indicated rates of spread and resistances
cont rol.
CURRENT ACTION
140
In determining the number of men according to fuel resistance i t was
necessary to use certain r a t e s of work believed to be applicable. The
rates used are shown by the v e r t i c a l scale of figure 28, B, where they are
labelled L, M, H, and E for low, medium, high, and extreme r e s i s t a n c e s , ,
respectively. The range of r a t e s shown i s based on 1,264 estimates obtained
from 25 experienced men covering small crew midday attacks on f i r e s in a
wide v a r i e t y of fuels. After discarding an additional 31 e r r a t i c estimates
on both ends of the range, the variation shown by the remainder of e s t i mates was found to have a range from 0.2 to 3.8 chains per man hour. This
range was divided into three equal p a r t s whose mid-points are; low r e s i s t ance, 3.2; medium, 2.0; and high, 0.8. The l e a s t r a t e of work, which
included a large number of cases, was 0.2 chains per man hour, and t h i s r a t e
was assigned to extreme resistance to control. The r a t e s of work thus
obtained are o p t i m i s t i c , that i s , support-for them cannot be found in f i r e
reports except by selecting the higher r a t e s accomplished.
The curves of figure 28, B, show the way in which r a t e of work i s
estimated to decrease as rate of spread increases. Stopping the front half
of f i r e s i s under consideration. When r a t e of spread i s as great as 50
chains per hour, i t i s doubtful that appreciable progress i s made against
the front half of any f i r e , except possibly in pure grass were resistance
to control i s very low. Whether the speed, at which the rate of work breaks
off abruptly to zero, i s 50 or 60 chains per hour i s unimportant; the l a t t e r
is used in figure 28, B. When r a t e of spread i s as low as 3 chains per hour,
i t has no influence on r a t e of work, but at progressively faster r a t e s , by
advancing here and there along the front and becoming hotter and h o t t e r , and
spotting ahead, the r a t e of work becomes l e s s and l e s s effective and finally
breaks off abruptly when the f i r e , personified, refuses to stay in one place
long enough to be fought by any number of men.
The description j u s t given, if t r u e , requires the use of a curve
closely approximating an e l l i p s e to i n t e r p r e t the r e l a t i o n s h i p . The curve
must be tangent to a horizontal l i n e at the v e r t i c a l axis, and i t must be
perpendicular to the horizontal axis at 60. I t must drop from i t s highest
position at an increasingly rapid r a t e . The curves of figure 28, B, are
e l l i p s e s and t h e i r general equation, i s given. For any set of e l l i p s e s ,
drawn as shown, the a l t i t u d e of points on each curve that are the same d i s tance from the v e r t i c a l axis i s the same percentage of the highest a l t i t u d e
in each curve. The percentage according to r a t e of spread i s shown at the
top of the figure. In determining the r a t e s of work possible against different r a t e s of spread, the uninfluenced r a t e was reduced by the applicable
percentage shown.
No allowance was made for fatigue, and i t i s believed not to be a
factor in work of such short duration as that represented in the usual
successful midday a t t a c k s . However, i t i s a factor in unsuccessful a t t a c k s ,
but for them overnight reinforcement action must be applied. The fatigue
curve applied to such attacks i s shown in figure 25.
mi
FIRE CONTROL PLANNING—NORTHERN ROCKY MOUNTAIN REGION
In figure 28, A, the estimated combined influences of crew s i z e on
rate of work are shown. These influences are discussed on page 128. More
evidence governing t h i s curve i s available than was at f i r s t recognized.
Data and estimates indicate that the work-rate of 50 men i s between 40 and
50 percent of that of 1-5 men. From the 45 percent p o i n t , the slope of the
curve must continue more slowly down to the right for s t i l l larger crews,
which are not shown. From t h i s point toward the l e f t , the curve must r i s e
at an increasingly f a s t e r r a t e . But no sudden change in slope can be made
without producing the result that l a r g e r crews w i l l be shown to do l e s s work
than smaller ones. In completing the curve from the l e f t side, the drop
must increase gradually and then f a s t e r . The most rapid decrease in quality
of personnel i s believed to be in crew sizes between 15 and 25 men.
If t h i s curve correctly approximates the f a c t s , i t i s conspicuous in
indicating the value of using trained men in u n i t s of 10 men or l e s s
assigned under a trained unit leader to separate sectors of f i r e perimeter.
Although the r a t e s of work assumed are o p t i m i s t i c , if the resulting increase
in work-rate should prove to be anywhere near that indicated as p o s s i b l e ,
the numbers of men greater than 15 shown as needed in the right-hand columns
of figure 27 could be reduced 10 to 30 percent. Even more important, f a s t e r
spreading f i r e s could be controlled with the increased work-rate. That many
such f i r e s will occur and require action i s evident in figure 28, C.
The data of t h i s figure are the same as those presented in figure 19
on page 70, except that r a t e of spread i s made the dependent variable;
dependent upon prevailing severity of burning conditions, as well as upon
character of fuel. The terms used in mapping fuels, extreme, high, medium,
and low are r e l a t i v e , and the whole range of variation in r a t e s of spread
increases with advance in severity of burning conditions. Each of the dots
at the 35 percent point indicates a c l a s s i f i e d f u e l ' s r a t e of spread
expected when burning severity i s in the middle of c l a s s 4, as rated by the
Danger Meter. When burning conditions are the average of c l a s s 5, the
c i r c l e s at the 16 percent point show the r a t e s of spread expected in each
indicated character of fuel. The p o s i t i o n s marked "x" at the 6.6 percent
point indicated the rates for average class 6 danger. Thus, the curve at
the top of the band called "Low" r a t e of spread indicates the way in which
i t i s believed the seasonal advance will affect the r a t e of spread at a
p a r t i c u l a r spot of fuel mapped in the r e l a t i v e c l a s s i f i c a t i o n "low."
I t should be pointed out that the r a t e s of spread and the percentages of them that correspond with different ratings of the Danger Meter
are not known with any degree of c e r t a i n t y . This uncertainty must continue
u n t i l severity of burning conditions at the spot where spread occurred, or
i s taking place, i s known. The r a t e s of spread shown as belonging to each
class of danger are believed to be those at the spots where the f i r e s .
occurred. The danger rating at a f i r e and not at some distant weather
station must be estimated by a dispatcher when satisfying control requirements.
142
15
20
25
30
NUMBER OF MEN
PER
PERCENT OF
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PESUMETER
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INDICATED RATE
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F i g . 3 8 . — F a c t o r s i n v o l v e d i n t"ae c o n s t r u c t i o n
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f
CLASSES
and u s e of f i g u r e a7«
A.
I n f l u e n c e o f crew s i z e on r a t e o f work.
B.
I n f l u e n c e of r a t e of spread on r a t e of work.
C.
P e r c e n t a g e of f i r e s t h a t o c c u r r e d i n f u e l s o f e x t r e m e ,
h i g h , s e d i u a , and l o w r a t e of spread c l a s s i f i c a t i o n s
i n w e s t e r n f o r e s t s of Region One 1 9 3 1 - 3 0 , i n c l u s i v e .
CURRENT ACTION
143
The three s e t s of p o i n t s marked on the curves of figure 28, C, represent the steps in degree of burning severity for which plans of preparedness were worked out. The f i r e control organization required for the least
severe of these degrees was called the "Average Season Organization." On
the horizontal scale i t . will be observed that t h i s degree of preparedness
s a t i s f i e s the requirements of 65 percent of a l l f i r e s . In table 20 the
t r a v e l time-man power requirements of t h i s degree of danger are shown, in
r e l a t i o n to fuel c l a s s i f i c a t i o n s .
The next higher degree of organization planned was called "First
Overload," meaning "over" the average requirements. The applicable c l a s s i fied r a t e s of spread are shown circled at 16 percent on the horizontal scale,
and in table 21 the t r a v e l time-man power requirements are shown according
to fuel c l a s s e s .
The next step for which plans were worked out was called "Second
Overload." The r a t e s of spread marked "x" at the 6.6 percent point indicate
the degree of danger, and in t a b l e 21 are shown the corresponding t r a v e l
time-man power requirements. The two "Overload" steps are included within
a degree of danger called "Maximum," in order to be consistent with the
danger called "Minimum" on the opposite side of that called "Average."
Plans were worked out for "Minimum" danger. They require organizat i o n s to cover only south and west slopes and f l a t s that carry fuels with
r a t e s of spread higher than average. I t i s probable that the severity of
burning conditions prevailing in such places i s that represented by class
4 and c l a s s 5 of the Danger Meter. These are the places that f i r s t show
the effects of advancing seasonal danger.
For dispatching purposes tables 20, 21, and 22 are applicable to more
steps in danger than those specified. In each of these t a b l e s i t will be
observed that the chains of perimeter increase per hour are shown. The r a t e
8 chains per hour appears under "Extreme" in t a b l e 20 and under "Medium" in
t a b l e 21, and i t will be found that the number of men according to fuel
c l a s s and travel time i s the same. If the dispatcher estimates that the
r a t e of spread i s or w i l l be any one of the r a t e s shown in any one of these
t a b l e s , he can use the t a b l e involved as a guide to action. Figures 26 and
27 are applicable to any r a t e of spread whenever and wherever i t occurs.
Danger ratings are not involved and whether fuel r e s i s t a n c e i s known from a
map or i s only o r a l l y described at the time, by one of the natural terms
extreme, high, medium, or low, the number of men required when any p a r t i c u l a r t r a v e l time i s necessary i s shown.
Another use of these data, p a r t i c u l a r l y tables 21 and 22, i s to show
the real obstacles confronting f i r e control managers and planners endeavoring to control every f i r e within the f i r s t work period. In table 21, i t
will be observed t h a t , when r a t e of spread in "high" c l a s s fuels i s >Q .... U?
per hour and fuel resistance i s high, 25 men cannot be allowed a travel time
longer than 2 hours. In t a b l e 22 when r a t e of spread in t h i s same c l a s s of
fuel i s 22 chains per hour, not more than 0.5 hour of time-distance between
man-power station and f i r e can be allowed. Under the i n t e n s i t i e s of road
system planned in inaccessible l o c a l i t i e s to date and under the degrees of
m
FIRE CONTROL PLANNING—NORTHERN ROCKY MOUNTAIN REGION
coverage worked out for smokechaser and l i g h t reinforcement action, a verylarge proportion of area l i e s beyond e i t h e r of these time-distances from
man power of even one man.
Unless dispatchers are told specifically what the r a t e of spread at
a p a r t i c u l a r f i r e will be and at what r a t e men can extinguish i t , i n s t r u c tions to control every f i r e in the f i r s t work period require that the
strongest action known to have been successful in similar fuels be taken
everywhere. And, back of action, planners apparently should determine the
man-power placement and road f a c i l i t i e s required to do t h i s . The facts
presented here show how d i f f i c u l t t h i s would be.
The gratifying trend toward being specific in f i r e control action i s
decidedly hampered by f a i l u r e for many years to collect the evidence on
influences that can show how to be specific. I t i s l e g i t i m a t e to doubt the
accuracy of requirements presented here, and in t h i s the author desires to
j o i n . However, i t can hardly be doubted that greater accuracy has resulted
from making the estimates than from avoiding them. If fatigue were
included, the requirements for midday action would be s t i l l more s t r i n g e n t .
If the requirements are found to be more stringent than required by the
degree of danger indicated, i t i s only necessary to move the action along
the scale of danger a few percent to where i t i s required, but for a smaller
percentage of f i r e s .
If the decision i s made not to be prepared to satisfy the requirements for successful midday a t t a c k s , attention i s necessarily focused on
the number of 5-10 nian u n i t s required per unit of area for night reinforcement action. After they are placed they become available for midday action
and to some extent they satisfy midday requirements.
Through plan work done to date the degree of coverage that corresponds with different numbers of men and mileages of road per unit of area
can be determined. But, since the percentage of fast-spreading f i r e s that
would be brought under control by completing different degrees of coverage
i s not known, definiteness would not be given to the f i r e control objective
by specifying a p a r t i c u l a r percentage of f i r e s to be controlled within the
f i r s t work period.
During the period of years required to determine such a correlation,
definiteness could be given to the objective by a r b i t r a r i l y deciding for
large areas of similar character the degree of coverage that will be completed in each of the services of f i r e control, detection and smokechasing
and l i g h t and heavy reinforcements. Obviously they are i n t e r r e l a t e d and
no one of these services can be planned independently of the o t h e r s . Until
f i r e control planners, who correspond with designing engineers of other
kinds, are told in d e f i n i t e terms what expenditures are permissible and
what specifications are desired in different p a r t s of the f i r e control
p l a n t , they cannot work out a s t r u c t u r e that will satisfy the board of
d i r e c t o r s . The function of t h i s progress report i s believed to be that of
identifying influences which cannot be avoided, determining approximately
t h e i r degree, and describing methods found s a t i s f a c t o r y for planning to
different degrees of completeness.
CURRENT ACTION
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148
CONTENTS OF PLANS; INDEXING, FILING
Maps, overlays, charts and other items belonging to the f i r e plan of
each forest are indexed according to the scheme shown below. All data p e r taining to each heading are given the key l e t t e r shown, In addition a
s e r i a l number i s given to each item. For example, under J , numbers J - i , J - 2 ,
and J~3 are given to the detection coverage maps made for minimum, average,
and maximum burning conditions, respectively, and further numbers are used
for a l l other items under detection coverage. The index completed with subheadings i s included in the written summary of plan work, and a copy i s kept
easily available for reference to f i l e s in which the plan maps and other
data are kept.
The o r i g i n a l method of f i l i n g plan data was in an imitation leather
folio the size of the l a r g e s t maps. A l a t e r and b e t t e r method, which p e r mits easy access to any two or more maps or tracings to be compared, i s to
label and r o l l each sheet separately and place a l l of them in a cupboard
constructed with shelves and compartments.
All data, including the o r i g i n a l seen-area map, r e l a t i n g to a p a r t i c u l a r fireman or crew s t a t i o n (either a p o t e n t i a l or occupied station) i s
placed in a l e t t e r - s i z e envelope, labelled with the number and name of the
point, and f i l e d in a regular correspondence f i l e drawer.
A copy of map "I", together with "plastacele" s i l h o u e t t e s , i s kept in an
especially constructed d i s p a t c h e r ' s t a b l e .
Attention i s called to the seen-area maps and s i l h o u e t t e s of the potent i a l detection s t a t i o n s that were not selected for occupancy. Since they
show what areas can be seen by going to any of the points studied, they can
be used to show dispatchers where to send special detectors after heavy concentrations of lightning s t r i k e s and at other times to cover areas not regul a r l y seen or in need of duplicate coverage.
Key
Letter
Item
A
Timber types.
B
Burned areas.
C
Occurrence maps, overlays, etc.
D
Fuel-type maps and overlays.
E
Valuation zone maps and data.
F
Total danger maps and data pertaining to them.
m
Item
Allowable smokechaser travel time tracings, etc.
Transportation system maps*
Index maps showing potential detection and smokechasing positions
considered.
Detection coverage maps and composites of all kinds.
Detection responsibility maps and composites.
Patrol coverage data.
(Open)
Smokechaser coverage maps and composites of all kinds,
Smokechaser responsibility maps and composites.
Plans for adding smokechasers at regularly occupied stations when
burning conditions are in maximum class. Since data included under
P and R are related, cross-referencing is necessary.
Man-power placement maps and tracings (locations of man powers).
Light reinforcement (small crew) coverage composites and maps.
Second-line defense coverage composites and maps.
Protection improvement maps and tracings.
Fire prevention plan maps, overlays, etc,
(Open)
Communication maps and tracings.
Organization and improvement summarization tables,
(Open)
Follow-up field work plan maps, overlays, etc.
PART 1 I I
S T A T I S T I C S FOR INDIVIDUAL N A T I O N A L FORESTS
AND OTHER S U P P O R T I N G DATA
Part I I I consists of analyses o r i g i n a l l y made for each national
forest. These were summarized l a t e r for the western f o r e s t s of the Region
and are shown in P a r t s I and I I .
The following i s a l i s t of items on which detailed work was done
for planning purposes, but which are not ready for p r e s e n t a t i o n .
1.
Number of f i r e s and area burned each year 1909-1933 in
each forest according to cause.
2.
Trend in average discovery time of lightning and mancaused f i r e s in each forest and year.
3.
Relation between increasing number of f i r e s and increasing number of detectors per unit of area. The number of
f i r e s was determined that occurred each year over a long
period of years in the same seen areas of 42 welldistributed lookouts that were occupied continuously
throughout the period. I t was found that the trend in
number of f i r e s , e i t h e r man-caused or l i g h t n i n g , was the
same there as elsewhere. In other words, more f i r e s were
not discovered simply because more detectors were placed.
4.
The success of each forest in preventing class C f i r e s
on days of heavy lightning f i r e concentrations was
investigated thoroughly. I t was found that the l a r g e s t
percentage of such f i r e s occurred neither at the highest a l t i t u d e s where the heaviest concentrations occurred
nor at the lowest a l t i t u d e s , but at intermediate ones.
5.
Change in 1910, and since then, in area of single burn
fuels.
6.
Details of working out and applying composite danger
r a t i n g s , i . e . , the integration of frequency of f i r e
occurrence, fuel danger, and values at stake.
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LITERATURE CITED
(1)
ADAMS, D. W.
1912.
METHODS AND APPARATUS FOR PREVENTION AND CONTROL OF FOREST
FIRES.
U. S. Dept. Agr. Bull. 113, 26 pp., iI I us. Washington,
D. C
(2)
BATES, C.
1923.
F.
THE TRANSECT OF A MOUNTAIN VALLEY.
Ecology 4 ( 1 ) : 54-62,
i I I us.
(3)
BUCK, C. C., AND FONS, W. L.
1935.
THE EFFECT OF DIRECTION OF ILLUMINATION UPON THE VISIBILITY
OF A SMOKE COLUMN. Jour. Agr. Res. 51: 907-918, Mlus.
Washington, D. C
(<0
(5)
BYRAM, G. M.
1935.
VISIBILITY PHOTOMETERS FOR MEASURING ATMOSPHERIC
ENCY.
Jour. Opt. Soc. Amer. 25: 388-395, iI tus.
DUBOIS, COERT
1914.
SYSTEMATIC FIRE PROTECTION IN CALIFORNIA FORESTS.
Dept. Agr. Unnumbered, 99 PP., Mlus.
(6)
FLINT,
1928.
(7)
TRANSPAR-
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U. S.
Washington, D. C.
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ADEQUATE F I R E
CONTROL.
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FOITZIK, L.
1932. SICHTWEITE BEI TAG UND TRAGWEITE BEI NACHT.
IMus.
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Zeits. 49: 134-139.
(8)
GISBORNE, H. T.
1928.
MEASURING FOREST FIRE DANGER IN NORTHERN IDAHO. U. S. Dept.
Agr. Misc. Pub. 29, 63 pp., H l u s .
Washington, D. C
(9)
1934.
MEASURING FOREST FIRE DANGER.
Quart. Nat. Fire Prot. Assn.
27: 323-328, I I I us.
(10)
1936.
THE PRINCIPLES OF MEASURING FOREST FIRE DANGER.
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(10A)
1936.
MEASURING FIRE WEATHER AND FOREST INFLAMMABILITY.
U. S.
Dept. Agr. Cire. 398, 58 pp., II I us. Washington, D. C.
in
(11)
KIMBALL, HERBERT
H.
1919. VARIATIONS IN THE TOTAL AND LUMINOUS RADIATION WITH
GEOGRAPHICAL POSITION IN THE UNITED STATES. U. S. MO. Weather
Rev. 47 (II): 769-793, TI I us.
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M C A R D L E , R.
E.
1935. A VISIBILITY METER FOR FOREST FIRE LOOKOUTS.
Forestry 33: 385-388, ilius.
JOUT.
(13)
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SOME V I S I B I L I T Y
FACTORS CONTROLLING THE E F F I C I E N T LOCATION
AND OPERATION OF FOREST F I R E LOOKOUT S T A T I O N S .
34: 802-81 I,
(14)
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NORCROSS, T . W . , AND GREFE, R. F .
1931.
TRANSPORTATION PLANNING TO MEET HOUR-CONTROL REQUIREMENTS.
Jour.
(15)
Jour.
I I I us.
PLUMMER.
F o r e s t r y 29: 1019-1033,
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(16)
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B.,
AND K O T O K , E.
I.
1923. FOREST FIRES IN CALIFORNIA 1911-20: AN ANALYTICAL STUDY.
U. S. Dept. Agr. Circ. 243, 80 pp., illus. Washington, D. C.
(17 )
1924. THE ROLE OF FIRE IN THE CALIFORNIA PINE FORESTS. U. S.
Dept. Agr. Bull. 1294, 80 pp., illus. Washington, D. C
(13)
1929. COVER TYPE AND FIRE CONTROL IN THE NATIONAL FORESTS OF
NORTHERN CALIFORNIA. U. S. Dept. Agr. Bull. 1495, 36 PP.,
illus. Washington, D. C
(19)
1930. THE DETERMINATION OF HOUR CONTROL FOR ADEQUATE FIRE
PROTECTION IN THE MAJOR COVER TYPES OF THE CALIFORNIA PINE
REGION. U. S. Dept. Agr. Tech. Bull. 209, 46 pp., illus.
Washington, D. C
(20)
STICKEL, P.
W.
1933. THE ROLE OF SILVICULTURE IN FOREST FIRE CONTROL.
Paper of Canada, Jan.: 20-24, illus.
(21)
U. S. W E A T H E R B U R E A U
1922. ATLAS OF AMERICAN AGRICULTURE.
illus. Washington, D. C.
(22)
Pu Ip and
PT. 2, CLIMATE.
WASHINGTON CONFERENCE OF REGIONAL FORESTERS
1930. C O M M I T T E E R E P O R T S . 10 1 pp., illus.
34 pp.,
Washington, D. C
,75
FIRE CONTROL PLANNING—NORTHERN ROCKY MOUNTAIN REGION
PERIMETER OF FIRE CORRESPONDING WITH AREA ENCLOSED
The data are placed on the l a s t pages of the report to make them most
easily available for reference.
Fire damage i s a consideration of the area enclosed within the f i r e
perimeter. But i t i s along the perimeter that a r a t e of work i s performed
and costs of control are incurred. For many purposes, including current
attacks on f i r e s , reported in terms of area, and making reports, i t i s
necessary to convert area to corresponding perimeter, and vice versa, to
convert perimeter to corresponding area. In order to do t h i s to a reasonable degree of accuracy, a thorough investigation of the relationship was
made, based on the following data;
66
48
32
1.0.2.
248
f i r e s smaller than 50 acres selected at random from f i r e reports
f i r e s of 50-400-acre size selected at random from f i r e reports
f i r e s of 0.1-1oo-acre size measured with instruments
hypothetical f i r e s of 3 shape classes drawn and measured on paper
fires, total
I t was found, for any size c l a s s , that the probable perimeter was 1.5
times that of the circumference of a c i r c l e corresponding to the area, and
that 92 percent of a l l the perimeters investigated were l e s s than 2.0 times
such a circumference.
For any area the smallest possible perimeter i s that of a c i r c l e .
From t a b l e s of circumferences for different areas, found in standard engineering handbooks, the relation of circumference to area can be p l o t t e d . Above
t h i s curve another can be p l o t t e d with ordinates twice that of the f i r s t
curve. Between these two curves 92 percent of perimeter-area r e l a t i o n s h i p s
can be expected to f a l l . If a t h i r d curve i s p l o t t e d half way between these
two, i t w i l l represent the probable perimeter for any area of f i r e or the
average for a l a r g e number of f i r e s .
In table 38 are shown the values that correspond to different points
along each of the curves of figure 36. Since each of these curves i s a
parabola, i t can be, and was, p l o t t e d d i r e c t l y from i t s equation. For t h i s
purpose the equations are given.
Let P = Perimeter, and A • Area
When the perimeter i s a circumference,
When the perimeter i s 1.5 times a circumference,
P
«,5 * 9 7t A
,
?us-
\l&.Z74-2>
I A
When the perimeter i s 2.0 times a circumference,
176
Table 38.—Perimeter of f i r e corresponding with area enclosed by i t .
Perimeter i s shoim in l i n e a r u n i t s of the same kind as the square u n i t s used for area.
If area i s in square chains, perimeter i 3 in c h a i n s .
Minimum
Probable
Maximum z/
Minimum 1/ Probable Z/
Maximum
perimeter
Area
perimeter
perimeter
perimeter
Area
perimeter
perimeter.
1.5 C
1 C
1.5 C
2 C
1 C
2 C
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20.0
22.5
25.0
27.5
30.0
32.5
35.0
37.5
40.0
42.5
45.0
47.5
50.0
52.5
55.0
57.5
60.0
65.0
70.0
75.0
80.0
85.0
90.0
95.0
100.0
110.0
120.0
130.0
140.0
150.0
160.0
170.0
180.0
190.0
200.0
l/
2/
3/
3.5
5.0
6.1
7.1
8.0
8.7
9.4
10.0
10.6
11.2
11.7
12.3
12.8
13.2
13.7
14.2
14.6
15.1
15.5
15.9
16.8
17.7
18.6
19.4
20.3
21.0
21.7
22.4
23.2
23.7
24.5
25.0
25.8
26.3
26.8
27.5
28.6
29.7
30.7
31.7
32.6
33.6
34.6
35.5
37.2
38.7
40.4
41.9
43.3
44.8
46.2
47.5
48.8
50.2
5.25
7.50
9.15
' 10.65
12.00
13.05
14.10
15.00
15.90
16.80
17,55
18.45
19.20
19.80
20.55
21.30
21.90
22.65
23.25
23.85
25.20
20.55
27.90
29.10
30.45
31.50
32.55
33.60
34.80
35.55
36.75
37.50
38.70
39.45
40.20
41.25
42.90
44.55
46.05
47.55
48.90
50.40
51.90
53.25
55.80
58.05
60.60
62.85
64.95
67.20
69.30
71.25
73.20
75.20
7.00
10. CO
12.20
14.20
16.00
17.40
18.80
20.00
21.20
22.40
23.40
24.60
25.60
26.40
27.40
28.40
29.20
30.20
31.00
31.80
33,60
35.40
37.20
38.80
40.60
42.00
43.40
44.80
46.40
47.40
49.00
50.00
51.60
52.60
53.60
55.00
57.20
59.40
61.40
63.40
65.20
67.20
59.20
71.00
74.40
77.40
80.80
83.80
86,60
89.60
92.40
95,00
97.60
100.40
210
220
230
240
250
260
270
280
290
300
320
340
360
380
400
425
450
475
500
550
600
650
700
750
800
850
900
950
1000
1050
1100
1150
1200
1250
1300
1350
1400
1450
1500
1550
1600
1650
1700
1750
1800
1850
1900
1950
2000
2050
2100
2150
2200
Perimeter i s t h a t of a c i r c l e corresponding with the a r e a .
Perimeter i s 1.5 times t h a t of a c i r c l e corresponding with the a r e a .
Perimeter i s 2.0 times t h a t of a c i r c l e corresponding with the a r e a .
51.4
52.5
53.7
54.8
56.0
57.1
58.3
59.4
60.4
61.5
63.4
65.4
67.2
69.1
70.9
73.1
75.2
77.2
79.3
83.2
86.8
90.4
93.7
97.0
100.2
103.4
106.3
109.3
112.1
114.8
117.5
120.2
122.8
125.4
127.8
130.3
132.6
134.9
137.3
139.6
141.8
144.0
146.1
148,3
150.4
152.5
154.6
156.5
158.6
160.5
162.5
164.4
166.3
77.10
78.75
80.55
82.20
84.00
85.65
87.45
89.10
90.60
92.25
95.10
98.10
100.80
103.65
106.35
109.65
112.80
115.80
118.95
124.80
130.20
135.60
140.55
145.50
150.30
155.10
159.45
163.95
168.15
172.20
176.25
180.30
184.20
188.10
191.70
195.45
198.90
202.35
205.95
209.40
212.70
216.00
219.15
222.45
225.60
228.75
231.90
234.75
237.90
240.75
243.75
246.60
249.45
102.80
105.00
107.40
109.60
112.00
114.20
116.60
118.80
120.80
123.00
126.80
130.80
134.40
138.20
141.80
146.20
150.40
154.40
158.60
166.40
173.60
180.80
187.40 <
194.00
200,40
206.80
212.60
218.60
224.20
229.60
235.00
240.40
245.60
250.80
255.60
260.60
265.20
269.80
274,60
279.20
283.60
288,00
292,20
296,60
300.80
305.00
309,20
313.00
317.20
321.00
325.00
328.80
332.60
177
Table 38 (Continued).—Perimeter of fire corresponding with area enclosed by it.
Area
Perimeter is shown in linear units of the same kind as the square units used for area.
If area is in square feet , perimeter is in feet.
Probable
Haximum 3/
llinimum
I.-inimum l/ Probable 2/
llaximum
perimeter
perimeter
perimeter
perimeter
perimeter
Area
perimeter
1.5 0
1.5 0
2 C
2 C
1 0
1 C
159
222
270
317
355
383
417
447
475
500
525
550
574
595
615
635
655
675
692
710
727
745
762
778
794
810
825
840
855
870
885
899
912
926
940
953
966
979
992
1004
1016
1028
1040
1052
1064
1075
1087
1099
1110
1121
2,000
4,000
6,000
8,000
10,000
12,000
14,000
16,000
18,000
20,000
22,000
24,000
26,000
28,000
30,000
32,000
34,000
36,000
38,000
40,000
42,000
44,000
46,000
48,000
50,000
52,000
54,000
56,000
58,000
60,000
62,000
64,000
66,000
68,000
70,000
72,000
74,000
76,000
78,000
80,000
82,000
84,000
86,000
83,000
90,000
92,000
94,000
96,000
98,000
100,000
.
238
334
405
476
532
581
626
670
712
750
737
825
861
892
922
952
982
1012
1039
1065
1091
1117
1144
1168
1191
1215
1237
1260
1232
1305
1327
1348
1369
1390
1410
1429
1450
1468
1488
1506
1524
1543
1560
1579
1596
1612
1631
1648
1665
1681
318
445
540
635
710
775
835
893
950
1000
1050
1100
1148
1190
1230
1270
1310
1350
1385
1420
1455
1490
1525
1557
1533
1620
1650
1630
1710
1740
1770
1798
1825
1853
1880
1905
1933
1958
1984
2008
2032
2057
2080
2105
2128
215.0
2175
2198
2220
2242
102,000
104,000
106,000
108,000
110,000
112,000
114,000
116,000
118,000
120,000
122,000
124,000
126,000
128,000
130,000
132,000
134,000
136,000
138,000
140,000
142,000
144,000
146,000
148,000
150,000
152,000
154,000
156,000
158,000
160,000
162,000
164,000
166,000
168,000
170,000
172,000
174,000
176,000
178,000
180,000
182,000
184,000
186,000
188,000
190,000
192,000
194,000
196,000
198,000
200,000
1132
1144
1154
1165
1175
1135
1196
1206
1216
1226
1236
1246
1257
1266
1275
1286
1295
1305
1315
1324
1334
1343
1351
1360
1370
1379
1387
1396
1405
1413
1422
1431
1440
1449
1456
1465
1474
1481
1490
1499
1508
1516
1525
1537
1541
1550
1559
1566
1575
1581
i
_l/ Perimeter is that of a circle corresponding wl/th the area.
Z/ Perimeter is 1.5 times that of a circle corresponding with the area.
3/ Perimeter is 2.0 times that of a circle corresponding with the area.
1698
1716
1731
1747
1762
1777
1794
1810
1624
1839
1854
1869
1885
1899
1912
1929
1942
1957
1972
1986
2001
2014
2026
2040
2055
2068
2081
2094
2107
2119
2134
2146
2160
2173
2184
2197
2211
2221
2235
2248
2262
2274
2287
2306
2311
2325
2338
2349
2362
2371
2264
2238
2308
2330
2350
2370
2392
2413
2432
2452
2472
2492
£514
2532
2550
2572
2590
2610
2630
2648
2668
2636
2702
2720
2740
2758
2775
2792
2810
2826
2845
2862
2880
2898
2912
2930
2948
2962
2980
2998
3016
3032
3050
3075
3082
3100
3118
3132
3150
3162
178
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Figure
36«—Perimeter
80
IN
of f i r e
90
100 110
120 130 140
SQ UARE
150 160 170 180
190 200
UNITS
c o r r e s p o n d i n g w i t h a r e a e n c l o s e d by i t .
i.o-C
The "i-C" curve shows the circumference of a c i r c l e . This i s the l e a s t
possible perimeter.
l.gr-C The " 1 . 5 - C curve shows the probable or average perimeter to be expected.
I t i s x.5 times the circumference of a c i r c l e .
3.o-C Very irregular perimeters w i l l f a l l between the "1.5-C" and H^-C" curves.
Not more than 8 percent of all cases will l i e above the "y-C« curve. I t
i » 2.0 times the circumference of a c i r c l e .
The perimeter shown by the vertical scale i s expressed in linear units of the same kind
as the square units of area shown by the horizontal scale. Thus, for areas in square
feet the perimeter in feet i s shown; for square chains, i t i s shown in chains. When
areas are expressed in acres, move the decimal point one place to the right to obtain
square chains; the corresponding perimeter in chains i s shown.
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2200
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2100
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1900
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1800
1700
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1600
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1500
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1200
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1000
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800
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600
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