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HORNBY'S
PRINCIPLES
OF FIRE
CONTROL
PLANNING
BY H. T. GISBORNE •
NorthernRockyMountainForestand RangeExperimentStation
On August 27, 1937, Lloyd G. Hornby died o.f heart failure on the Toboggan Creek forest fire
in the Clearwater National Forest. Few if any men in or out of the U.S. Forest Servicehave
made a greater contribution t• fire .control plannin,g than did he. In the following article,
H. T. Gisborneoutlines the principles of fire control planning developedby Mr. Hornby, emphasizingthe major features which have too often been obscuredby the detailed technical proce-
dures of the componentprocesses
of fuel type classification,
seen area mapping,smokechaser
coverage,transportationplanning, etc.
fire makesperimeter.
chargeof fire controlplanningresearch 2. Fuel type classificationis necessaryto
at the Northern Rocky Mountain For- showthe two basicfactors:rate of spreadand
est and RangeExperimentStation,he brought resistance to control.
to the taska background
of training,experience, 3. Plans must be made for first-attack conto spot or crown
and inherentability whichwasuniqueas it was trol before the fire commences
well suitedto the opportunities
of this work. exceptunderclass6 or class7 dangerin the
His training in both engineeringand forestry, extremefuel types.
of fires, and values
his fifteenyearsof field experience
from smoke- 4. Fuel type, occurrence
chaserand ranger to supervisorof three na- at stake must be coordinated for most economitional forests,and his exceptionalingenuity, cal yet adequatefire control.
5. Lookouts, firemen, and crews have the
practicallyassureda researchthat would make
a major contribution to forest fire control. dual responsibilityof detectionand smokeIt is universallyconcededthat his Fire Con.trol chasing.
Planr•ingin the Northern Rocky Mountain Re-'
6. Transportationand communicationplangion has revitalizedand very nearly revolution- ning shouldfollow and be basedupon fire conized fire control planning processes
through- trol planningand other forest-use
requirements
out the United States.
for multiple use.
It was Hornby'splan, beforehe died on the
7. Fire controlplanningfor the "worstfirst"
fire line in August 1937, to summarize automaticallysimplifiesthe process.
8. The conditionscreating a fire problem
the principlesbasicto his work, but exceptfor
a three-pagelong-handdraft of a memorandum are not static. Fire control planningis therefound in his files after his death, this sum- fore a continualprocessof revisionand refine-
'HEN
Lloyd
G.
Hornby
was
placed
in
mary was never written. On the basis of this
men t.
memorandum,his various reports, and six
years of almost daily contactand work with
him, the writer here attemptsto outline those
principlesas accuratelyas one personcan attempt to presentmaterial for another person.
The analogiesused in several casesto emphasizethe similaritybetween
fire controlplanning and engineeringpracticesare Hornby's
own,whichhe employedfrequently.
The eight major principleswhich,with one
exception,are apparent in his publishedreport can be briefly expressedas follows:
The first, and perhapsmost basic, principle
developedby this researchwas that successful
fire control requires"held line to be built
faster than the fire makes perimeter." This
principle had been subconsciously
and dimly
recognizedin the past, but it has been within
the past few years only that the old method
of estimatingthe job of line building on the
basisof acresof fire was replacedby estimates
basedon perimeter. This first principle recognizes the superiority of the perimeter basis,
1.
Held line must be built faster than the
and in
addition
considers the fact
that
fuel
type is the major determinantof the rate of
spread or rate of perimeter increase, which
•Acknowledgmentis ma.de to Clayton S. Crocker mustbe assumed
for eachareain planningnorand ClarenceB. Sutliff, who also ha,d worked closely mal controlmeasures
for it. Omitting proper
with Mr. Hornby, for reviewing this article and for
of fuel typesin fire control plantheir suggestions
for improvingit.saccuracyand scope. consideration
292
HORNBY'S
PRINCIPLES
OF FIRE
CONTROL
PLANNING
293
beingequal."
ning is analogousto an engineer planning to requiredit, otherconsiderations
construct a massivebuilding without examinOne impedimentto the understandingand
ing the rock or quicksandon whichit is to rest. properuseof fuel type mapsis the fact that
"Proper consideration"may vary, of course,
from broad generalizationsin regions of uniform fuel types to detailed measurements,
surveys, and maps in regions of great variation
in rate of spreadof fire.
The secondprinciple, which logically follows, is to measure and rate this basic factor,
individualfires often spreadat ratesdifferent
from that indicatedby the map. It is obvious,
however, that even the most carefully identified and mapped rate of spread,at a certain,
averagebad level of burningseverity,will not
be reached under favorable weather conditions
and will be exceeded when the weather is worse
fuel type. To do this Hornby originatedthe than averagebad. No single map could be
dual basis, physical classificationof fuel •nade,and kept simple, which would showall
types including rate of spread and resistance rates of spread for all weather conditions.
to control. His methodsof evaluating these The major purposeof this work is not to proare describedin "Fire Control Planningin the ducea fuel type map whichcanbe usedfor deNorthern Rocky Mountain Region," and "Fuel terminingthe manpowerto sendto individual
Type Mapping in Region One."•He assumed fires, under any combinationof weathercon"burningseverity,"classof fire danger,or fuel ditions. The chief purpose is to determine
condition,that shouldbe usedin fuel type map- the normal high-rate of perimeter increase
ping to be "averagebad," leavingits precisedefi- which can be expectedso often or so consistnition to be determinedlater by actualmeasure- ently that it should be planned for. This
ment. Here he followedthe practiceof an en- normal, high-ratevariessignificantlyaccording
gineer who would estimatehis costsof making to fuel type. This principle thereforeholds
excavations
in clay on the basisof the clay that it is better engineering,better forestry,
beingwet, and thereforemoredifficultto handle better science,to identify such a factor conthan if it were dry. The precisedefinition of sciously and accordingto certain standards
and without uni"wet" is of lessimportancethan would be the rather than subconsciously
complete failure to consider this condition. versal standards.
The measurement
rather than the approxima- This illustrates the researchquality of this
tion of eachfuel type is one phaseof this work work. The objective is the evolution of a
ß requiring much additionalresearch. Hornby methodwhichcan be usedsimilarlyby all men,
was engagedin suchwork the day he died.
in preferenceto "the judgmentof someperson
A brief statementof Hornby'sconceptionof or persons with or without going to the
fuel types and their basicuse was includedin trouble" of identifyingand evaluatingall the
his final memorandum:"When a particular factors. It has been consistentlyrealized that
level of burningseverityprevailsover a large the presentevaluationsof fuel type can be iraarea, the same speed and strengthof attack proved,with time and additionalresearch,but
is not requiredfor everykind of fuel" . ....
fire controlplanningwithoutfuel type classifi"One way to station manpowerover an area cation is, to use another analogy, like estiis to acceptthe judgmentof somepersonor mating the cost of road or railroad construcpersons,with or without going to the trouble tion from a topographicmap alone with no
of comparing fuels and mapping their loca- k•owledge of the soils, clay banks, or rock
tions. Anotherway is to map the fuels,set up ledgesthroughwhichthe cutsmustbe made.
•ninimumstandardsof speedand strengthof
The third principle is that control of a fire
attack accordingto severityof burning condi- (in Region One) by the first attackingforces
tions,and stationmanpowerto satisfythesere- shouldbe plannedfor "beforethe fire beginsto
quirements. Under the latter procedurethe spot or crown." Other criteria suchas "consame class of fuels would receive the same trol before 10 a.m. of the next burning petreatment (degree of fire control) wherever riod," and the "percentageof area burned,"
it existedand wheneverthe burningseverity by timber types as recommended
by the regional foresters, Washington conferenceof
altornby, L. G. Fuel type mapping in Region One.
Jour. Forestry 33:67-72.
1935.
1930, have been used, but for the reduction
and gradual elimination of those large fires
294
JOURNAL
OF FORESTRY
which are chieflyresponsiblefor overburn,a the need of attemptingto apply this fourth
more basically natural criterion is needed. principle, including values as well as fuel
Hornby insisted that "after the crown fire typesand the occurrence
rate.
The fact that valid inferences cannot be
stage is reached, no assuranceof control at
any particular size can be given," and under drawn unlessthe measurements
or ratings of
certain conditionsthis stage may be reached all the basicfactorsare integratedled Hornby
before 10 a.m. of the next burning period. to his searchfor a "total dangerrating" which
He also pointed out that the analysisof the would integrate fuel types, occurrence,and
recordsof 12,056 fires in Region One shows values. He was nevercompletelysatisfiedwith
that over a periodof yearssilviculturallyade- the formula that he originated. By this forquate protection,the basisof the Washington mula there is obtained from the fuel type
conference
standards,can be providedwithout maps an estimateof the acres per hour that
99.99 percent control of all fires in the first will probably burn during the first few hours
or even the secondwork period.
after origin on an average bad day. This,
The likelihood of spotting or crowning multipliedby the damage,in dollars,that would
varies,of course,both with fuel type and with be done, is called "damageper hour." Then
burningseverity. The presentprinciples,how- damageper hour plus expenseper hour (based
ever, do not include plans to meet the worst on the fuel type classificationof resistanceto
possibleconditions
of eitherfuel type or class control) gave total probable"cost per hour"
of fire dangerin the first attackany morethan for any unit of area. And costper hour mulan engineerbuildsto withstandthe worstpos- tiplied by the occurrenceindex for that area
sible earthquakeor the worst possibleflood. gives a figure approximating"total danger."
Engineers
knowthat the damagein suchcases Such numericalratingsfor differentareascan
is often less than the cost of completepro- be compared and the relative needs for fire
tection. This third principle of "control be- control facilities and manpowerthereby deterfore crowning"therefore excludesthose rare mined, with less than previous dependence
firesoriginating
in extremefuel typeson class upon the personaljudgment,knowledge,lack
6 or 7 days, when fuel moistures are under of knowledge,or bias of the individual.
5 percent,relativehumidityunder 15 percent, This attempt to obtain numerical ratings is
and winds19 m.p.h. or more. The damagesadditional evidenceof the scientificquality of
fromsuchexplosive
firescanmosteconomicallythis research. It is emphasizedby Lord Kelbe minimizedby large crew suppression
ac- vin's statement,"that when you can measure
tion, the same as for other fires which for other what you are speakingabout,and expressit in
reasonsescapecontrolby a reasonably
econom- numbers,you know somethingabout it. But
ical first attack.
when you cannotexpressit in numbersyour
The fourth principleis that fuel types,oc- knowledgeis of a meager and unsatisfactory
currence of fires, and values at stake must kind. It may be the beginningof knowledge,
be coordinatedby the processes
of planning but you have scarcelyin your thoughtsadif the resultantpermanent
facilities(buildings, vancedto the stageof a science."
roads,and telephonelines) and the temporary The impossibilityof immediatelyevaluating
manpower(contactmen, lookouts,smokechasers,all of the factorsof "total danger"with conand small crews), are to be held to an econom- sistent dependability is obvious. But here
ical minimum,yet adequate
protection
is to be again, as in fuel type mapping,it is evident
providedduringseasons
of criticaldanger.The that carefully prepared estimatescan now be
use of this principle is not as apparent in made, with a sufficientlylow error to give a
Hornby'smajor reportsas are the otherprin- better basisfor fire control planning,more
ciples. This is beca/lseit has not beenex- "independentof the idiosyncrasies
of the inpedientto date to attemptto place dollar dividual."
The fifth principle which is contrary to
values'on eachof the diversifiedusesor purposesof forestareasincludingstreamflowregu- l•racticesin some sectionsof the country is
lation, soil conservation,
wildlife production,the "dual responsibility"of lookouts,firemen,
recreation,live-stock,and timber products.Fire and crews. This had beenappliedwith graducontrolplannerscannotescape,however,from ally increasingintensityin Region One begin-
ttORNBY'S
PRINCIPLES
OF
FIRE
CONTROL
PLANNING
295
ning about 1920. As national inspector of large crewcoverage(providedmerelyby roads
fire control,Major E. W. Kelley gave marked from outsidesourcesof labor) is planned for
impetusto the practicein 1927 to 1929. By all areas of fuels in which fire could be exthis principle lookout men are not only to pected to escape any reasonablyeconomical
chase smoke when that can be done without
first attack, as mentioned in discussingthe
impairing the detectioncoverage,but look- third principle. Naturally, thesemost difficult
out station locations are to be selected, other fires are most likely and should be expected
things being equal, so that thesemen can serve most frequentlyin the worst fuel types. The
this dual purpose. It would appear to be de- actiondemanded,undersuchconditions,is supcidedly uneconomicalto build a lookout sys- pressionby large crews, and roads must be
tem capableof first discovering99.99 percent available reasonablynear such areas of worst
of all fires when firemen, trail crews, and fuels to expeditearrival of these large supseveralother units of the fire control organiza- pressioncrews. If these roads are planned
tion can be dependedupon for considerable first, later planningof roadsfor use by small
crews, smokechasers,
and firemen-lookouts,will
detectioncoverage.
Closely related to this fifth principle of automaticallybenefit. By the reverseprocess
"dual responsibility"
is the sixth, or "multiple roadsare first plannedfor the lookouts,smokeuse of roads." Althoughnot generallyrecog- chasers,and patrolmen,and are often found to
nized at the time Hornby was developing be unsatisfactoryfor expeditingthe arrival of
his principles, it is now standard practice large crews at the areas of worst fuels where
to plan for the lower cost, to each line of the catastrophicfires are most likely to origwork, and the greater efficiencyof a transpor- inate. As the reductionof the sizeof large fires
tation systemdesignedby correlatingthe re- is the presentmajor requisiteto satisfactory
quirements for (1) fire control, (2) utiliza- fire control, logical planning must be for the
tion or removal of forestproducts,(3) recrea- "worst first."
tion and (4) general administration. By this
The eighth, and final, principle applied
principle, transportationplanning is a distinct- throughoutall phasesof fire control planning
ly accessoryprocesswhich should follow and in Region One is that none of the basic facbe basedupon the previousdeterminationof tors of the fire problem--fueltype, occurrence,
manpowerplacementadequatefor fuel types or values at stake--is constant or static. Each
as well as for other forestrequirements.
Com- of theseis known to change,perhapsslowly,
municationplanning similarly becomesa sub. with time. The rating of the relative weight
sequentprocess;it is evendependentupon, or of each factor therefore undoubtedly will
at least affectedby, the resultsof transporta- change, slowly but steadily with increased
tion planning. Transportationor communi- knowledge,and perhaps radically for short
cationplanningwithoutcompleteconsiderationperiods accordingto the dominanceof some
of fuel typesand their manpowerrequirements, individual's philosophy. Preliminary plans
or without correlatingutilization, recreation, thereforeshould deal with averages,with ingrazing, and other needsis analogousto dam dicative trends, with combinations of factors,
construction without streamflow measurements.
always endeavoringto prevent single and exSuch dams have been built--and rebuilt, after ceptionalcasesfrom resultingin over-'building
the high-waterthat shouldhave been foreseen. or completelyneglecting
any essentialphaseof
The seventh of these principles for fire the fire control organization. Likewise, this
controlplanningis to plan first for the worst, principle shouldtemperall finality of concluor for the "worst first." By "worst" is meant sionand shouldpredicatecontinualrevisionand
the mostdangerous
fuel types. The plansfor refinementof the plans.
10 national forests comprising 17 million
Hornby's contention,supported by ample
acresof land in RegionOne have repeatedly evidencein RegionOne, that a strongand apdemonstrated
that if provisionsare made first parentlycostly first attack is usually the most
for the worstfuel typesa large proportionof economicalin the most dangerousfuel types,
the easier types is automaticallygiven satis- can hardly be called a principle. It is, howfactory, or even superlativedetection,smoke- ever, a generalitysupportinghis worst first
chaser,and crewcoverage.By this principle principle,and onewhichis basicto the proper
296
JOURNAL
OF FORESTRY
financingof adequatefire control in this re- forest fire control forces, and had seen the
deleterious
gion.
effects of the short-term
limitation
The personnelfactor was recognizedby on so many other forests,that he was occaHornby as vital. He stressedthe requirement sionally pessimisticconcerningthe successful
of both adequatenumbersof men and ade- applicationof his or anyone else's fire conquate training. His last memorandumstates: trol plans. He knew that the best of plans,
"Errors (on the fire line) are so numerous basedon specificidentification
of all significant
that their
elimination
constitutes an outstand-
factors, each well evaluated, and all consist-
ing problem,"and, "Ratesof fire suppressionently integrated,could not function most efta.
work, per man per hour, are so slow that ciently unless applied by a competentperunwieldynumbersof men are required even sonnel. He knew that any lack of policy or
on firesof moderate
size." Thesephases
of fire financial limitation, which interfered with the
controlplanning,and the preventionof fires, retention,year after year, of a trained and
were recognizedby Hornby as calling for competentpersonnelcould prevent the full
such distinctly different action as to be out- improvementof fire control efficiencythat
sidethe scopeof his particularresearch.
might be expectablefrom planningmethods
The little pessimismthat Hornby felt con- that he or anyoneelse might devise. He concerningthe possibleprogressof fire control finedhis work,however,to developingmethods
planningarosefrom the indeterminacy
of the and a planning procedurewhich would propersonnel
factor. He had had so muchper- vide any personnelwith facilitiesimpersonally
sonal experiencein the loss of trained and suitedto local conditionsof fuel type, occurcompetentshort-termmembersof his national rence of fires, and values at stake.
A DESIGN
FOR EXPERIMENTS
IN THINNING
FOREST
STANDS
BY J. G. OSBORNE
SouthernForest ExperimentStation•
Thinning experime•nts
have taken up _aconsistentlylarge shareof forest-research
programs,and
can be expectedto continueto do so. This paper presentsan experimentaldesign which is
intendedto aid iu increasingthe amountof informationobtainedfrom such experiments.
of thinning employed,and the kind of final
ANY
ofthe
early
e:•periments
infor-
estry were madeto determinethe effects of various methodsof thinning
on tree growthand on the yield per acre in
variousforestproducts.
Sincethesestudies
have
continuedto occupya prominentposition in
forest-research
programs,and since, as stated
by Yates (3), it is profita'bleto expendconsiderablework in developinga techniquein a
field in whichmuchexperimental
work is likely
stahdsought
varywidely,but certainprinciples
of experimentation
are common
to all thinning
research.Effortstowardsdeveloping
an ade-
quate experimentaldesign,therefore,must be
madein accordwith at leastfour basicrequirements,whichbriefly statedare:
(1) That adequateprovision be made to
assurethe reliability of the resultsobtained;
(2) That the experiment
be efficient,which
to be undertaken,it has been consideredworth
meansthat early and accurateinformationbe
while to devote at least some research to imobtained,
andthatthenumberof plotsandtotal
provingthe techniqueof thinningexperiments.area necessary
to providea givenbody of inOBJECTIVESOF A SATISFACTORY
TECHNIQUE formation be at a minimum;
(3) That the experiment
shouldpermitthe
The typeof standto be thinned,the method inductionof generalprinciplesof response,
•The author gratefully acknowledgesthe assistance from which the probableresultsof thinning
and ,helpful suggestionsgiven by R. A. Chapman, It.
underotherconditions
may be deduced;
Bull, and A. L. MacKinney of the Southern Forest
Experiment Station, and by F. X. Schumacherformerly
of the U.S. Forest Service, Washington, D.C.
(4) That, in order to obtain assuredreliabil-
ity of the results,the limitationsas to original