Site Evaluations
Fall Creek
Site Information
Site Location:
Willamette NF, S Willamette Valley, Fall Cr Rd west of Eugene
Year Installed:
Circa 1999
Lat/Long:
122°22”3.96”W
43°59”56.83”N
Watershed Area (mi2): 3.55
Stream Slope (ft/ft)1:0.0359
Channel Type:
Step-pool
Bankfull Width (ft): 21
Survey Date:
April 4, 2007
1
Water surface slope extending up to 20 channel widths up and downstream of crossing.
Culvert Information
Culvert Type:
Open-bottom arch
Culvert Material:
Annular CMP
Culvert Width:
19 ft
Outlet Type:
Mitered
Culvert Length:
80 ft
Inlet Type:
Mitered
Pipe Slope (structure slope): 0.03
Culvert Bed Slope: 0.037
(First hydraulic control upstream of inlet to first hydraulic control downstream of outlet.)
Culvert width as a percentage of bankfull width: 0.9
Alignment Conditions: Appears to be in good alignment with stream channel.
Bed Conditions: Large cobble to small boulder sized material forming very small steps and plane-bed
conditions.
Pipe Condition: Good condition. Minor rust in places.
Hydrology
Discharge (cfs) for indicated recurrence interval
25% 2-yr
Qbf2
2-year
5-year
10-year
50-year
100-year
67
180
269
401
491
689
774
Bankfull flow estimated by matching modeled water surface elevations to field-identified bankfull
elevations.
2
Fall Creek
A—215
Culvert Scour Assessment
Points represent survey points
Figure 1—Plan view map.
A—216
Fall Creek
Site Evaluations
History
There is no information available for site history.
Site Description
The Fall Creek culvert is a bottomless arch
mitered to conform to the slope of the road fill.
The bed is composed of sequences of small
steps (less than 1 foot in height), but can be
considered fairly uniform and plane-bed overall.
It is assumed that stable step structures were
not constructed within the culvert, although it is
possible that constructed bedforms have washed
out. Flow was wide and shallow and extended
from wall to wall in the culvert at the time of the
survey. There are no concentrations of flows
(e.g., pools and chutes) as there are in the
natural channel. Footings were not visible inside
the culvert. Large boulders lined the banks both
upstream and downstream of the culvert.
A series of boulder steps/cascades begin just
upstream of the culvert and continue through
the inlet. Just downstream of the inlet, the
gradient flattens. In the pipe, oversized angular
bed material creates a riffle interspersed by
backwatered pools during low flows. Grade
through the culvert is controlled by the
downstream aggradation of material. Downstream
of this deposition area is a drop in channel
elevation, which begins at the outlet.
Most likely as a result of its proximity to a
dispersed camping area, roughly 150 feet of
the channel upstream of the culvert is impacted
by engineered structures, including logs and a
riprapped bank. There are a total of approximately
eight pieces of large woody debris (LWD) that
have been cabled to boulders in this reach. The
upstream representative reach is located out of
the impact of both the culvert and these impacts.
The representative segment is characterized by
a bedrock wall along the left bank. The right bank
has a small flood plain surface which rises to an
active terrace. As a moderate gradient step-pool
Fall Creek
reach, the upstream reach mainly consists of a
bedrock-controlled step followed by a long deep
pool and then dropping off into a steep riffle.
There are signs of incision upstream of the
culvert inlet. This may be related to the elevation
of the culvert inlet or could also be related to
the previous installation. The presence of the
riprap bank suggests that bank erosion may
have been an issue on the right bank upstream
of the culvert. This could potentially have been
related to backwater-related material deposition
upstream of the outlet due to a previous culvert
that was undersized for the stream.
Survey Summary
Fourteen cross sections and a longitudinal profile
were surveyed along Fall Creek in April 2007
to characterize the culvert and an upstream
reference reach. No downstream reference
reach was established due to the proximity of
a tributary. In the culvert, representative cross
sections were taken through a riffle and a
backwatered pool. Two additional cross sections
were surveyed upstream to characterize the inlet
as well as the contraction of flow. Another cross
section was surveyed downstream of the culvert
to characterize the outlet. In order to capture
the full expansion of flow, cross sections were
surveyed along the tributary upstream of the
confluence, at the confluence, and below.
Representative cross sections in the upstream
reach were taken through a pool and steep
riffle. Two additional sections were taken to
characterize the upstream and downstream ends
of the reach.
Profile Analysis Segment Summary
The profile analysis resulted in a total of nine
profile segments. Segments upstream of the inlet
with similar gradients were not combined in order
to keep separate the upstream transition segment
(segment E) and to remove a segment influenced
by riprap (segment F) from the upstream
A—217
Culvert Scour Assessment
representative segments. The culvert consisted
of three profile segments. The downstream
and upstream segments in the culvert each
have comparable gradients to a representative
profile segment in the upstream channel. The
middle segment in the culvert is comparable
to two representative profile segments in the
upstream channel. The upstream transition
segment was comparable to one representative
profile segment in the upstream channel. The
downstream transition segment included a portion
of the channel downstream of the confluence of
the north fork tributary and so was not used for
comparative analysis.
Scour Conditions
Observed conditions
Footing scour – There was no observed scour
undermining footings or threatening structure
integrity.
Culvert-bed adjustment – The culvert bed shows
no obvious signs of adjustment Some gravel
and cobble material appears to have recently
aggraded in the pipe but it is unknown whether
the bulk of the streambed material observed
during the survey was placed in the pipe or
recruited from upstream. It is assumed that
the larger material found in the culvert (small
boulders) was placed there during construction.
Profile characteristics – The profile has a uniform
shape through the crossing (figure 2). There
is a valley transition in this area where the Fall
Creek valley widens as it approaches the tributary
junction located just downstream of the culvert.
Residual depths – Culvert-residual depths are at
the lower end of the range or lower than residual
depths in corresponding profile segments (figure
21).
A—218
Substrate – The culvert bed material distribution
is similar to the downstream sample site in the
upstream channel. The upstream sample in the
upstream channel exhibits a greater proportion
of sand and bedrock. These differences can be
attributed to the habitat unit (pool in the upstream
channel) and the location adjacent to a bedrock
wall along the left bank. Pebble count data is
presented at the end of this site summary.
Predicted conditions
Cross-section characteristics – Cross-section
flow characteristics are affected by the culvert,
particularly with respect to the width-related
measures top width and wetted perimeter (figures
5 through 9 and 12 through 17). This is true for
culvert segments (B, C, and D) and the upstream
transition segment (E).
Shear stress – Shear stress in the culvert is
mostly within the range of that found in the natural
channel except for at the downstream end of the
culvert where shear stress spikes sharply and the
maximum values exceed those in corresponding
profile segments (figures 10 and 19). Shear
stress in the upstream transition segment (E)
is within the range of the corresponding profile
segment (G).
Excess shear – The excess shear in the culvert
is greater than the excess shear in the natural
channel (figure 20). This is mainly attributable
to low applied shear values from the model at
the sample site in the upstream channel. Critical
shear-stress values are similar, and based on the
similar range of applied shear-stress values in
the culvert and the natural channel, excess shear
would be expected to be relatively similar as a
whole.
Fall Creek
Site Evaluations
Velocity – Model results suggest that velocity
in the culvert is mostly within the range of the
natural channel except for at the downstream
end of the culvert where velocity rises and values
exceed that of corresponding channel profile
segments (figures 11 and 18). Velocity in the
upstream transition segment (E) is within the
range of the corresponding profile segment (G).
Scour summary
There were no signs of scour within the pipe or at
inlet or outlet transition areas. Hydraulic modeling
suggests that hydraulics are relatively similar
between the culvert and the natural channel
except at the downstream end of the culvert
where velocity and shear stress increase to levels
above that found in the upstream channel. These
increases may result from expansion losses and
an increase in gradient as the channel drops to
meet the tributary junction. Scour at the inlet and
along the right bank at the upstream transition
area is protected by riprap.
AOP Conditions
Cross-section complexity – The sum of squared
height differences in the culvert cross sections
are smaller than those in the channel cross
sections (table 3).
Profile complexity – Vertical sinuosity in the
culvert segments are all lower than the values in
corresponding profile segments (table 4).
Depth distribution – Depth distribution results
indicate that the culvert is at the lower end of the
range (0) of the values in the upstream channel
(table 5).
Habitat units – The culvert is dominated by one
long riffle, whereas the upstream channel exhibits
more of a pool-riffle morphology (table 6). The
riffles in the upstream channel are steep riffles
that could also be characterized as small steps.
Fall Creek
Residual depths – Culvert residual depths are at
the lower end of the range or lower than residual
depths in corresponding profile segments (figure
21).
Substrate – The culvert bed-material distribution
is similar to the downstream sample site in the
upstream channel. The upstream sample in the
upstream channel exhibits a greater proportion
of sand and bedrock. These differences can be
attributed to the habitat unit (pool in the upstream
channel) and the location adjacent to a bedrock
wall along the left bank. Pebble count data is
presented at the end of this site summary.
Large woody debris – There was no LWD present
in the culvert (table 8). The natural channel had
low to moderate LWD abundance. LWD formed
occasional steps and scour pools in the channel
outside the crossing. Some wood was placed
and cabled in the stream upstream of the culvert
and helped to form steps and to provide habitat
complexity in this area. Features in the culvert did
not mimic the role of wood in the natural channel.
AOP summary
Complexity measures indicate low cross-section
and profile complexity in the culvert. This matches
well the site observations of a plane-bed uniform
channel through the culvert. The culvert bed
does not exhibit the same pool-riffle/step type
morphology of the upstream representative
channel. There are fewer protruding roughness
elements (i.e., boulders) and less pools that may
provide velocity refuge for passage of migrating
fish. There are also no concentrations of flows
(e.g., pools and chutes) as there are in the
natural channel. Flow was wide and shallow and
extended from wall to wall in the culvert at the
time of the survey. Passage may be a concern
at low flows because of the large width-to-depth
ratio. There are no exposed banks for terrestrial
organism passage.
A—219
Culvert Scour Assessment
Design Considerations
This installation appears to be a good design with respect to scour resistance. There is material
throughout the culvert and no signs of scour in the pipe or at inlet or outlet transition areas. The
installation is not as favorable for aquatic organism passage (AOP). The uniform channel and wallto-wall flow may create conditions in the pipe that are less suitable for AOP than what is found in the
upstream representative channel. Creating pool-riffle/step sequences, channel banks, and protruding
roughness elements (i.e., boulders) would enhance fish passage at low and high flows and would also
allow for passage of terrestrial organisms.
A—220
Fall Creek
Fall Creek
Relative elevation (ft)
600
XS 1
500
XS 2
A
ri g h t b a n k tri b
C o n fl u e n c e w i th
XS 3
B
XS 4
XS 5
XS 6 :
H
G
I
I
G
E
XS 7
400
(ri ffl e )
P ebble c ount
D
C u lv e rt
R e p re s e n ta tiv e C h a n n e l
S egment
C
B
C
C
D
U p s tre a m T ra n s itio n
C u lv e rt S e g m e n t
Table 1—Segment Comparisons
Figure 2—Fall Creek longitudinal profile.
70
75
8 0 elevation (feet)
Relative
85
90
95
100
E
300
R i p -ra p b a n k
29.2%
18.7%
20.8%
22.2%
32.1%
% D iffe re n c e in
G ra d ie n t
D is ta n c e a lo n g b e d (fe e t)
XS 8
XS 9
F
S egm ent
A
B
C
D
E
F
G
H
I
200
XS 1 0
G
XS 1 1 :
100
R e p re s e n ta ti ve C h a n n e l
(s te p )
P ebble c ount
XS 1 2 :
(p o o l )
P ebble c ount
S egm ent L ength (ft)
75
15
38
27
90
104
35
36
93
H
I
S egm ent
G ra dient
0.026
0.057
0.039
0.020
0.043
0.032
0.031
0.070
0.030
XS 1 3
0
Site Evaluations
A—221
n
o
i
t
a
v
e
l
E
)
t
f
(
A—222
C
D
E
G
H
I
0.1027-0.1120
0.1008-0.1049
0.1008-0.1016
0.1025-0.1078
0.0958-0.1064
0.0961-0.1057
0.0937-0.1057
2
1
1
2
2
1
1
# of measured XSs
12
5
6
6
8
5
2
# of interpolated XSs
3
.
75 4 4
0
80
85
90
95
100
105
5
7
.
4 5
*
5
3
.
5
7
.
5
5
2
.
6
7
*
5
4 7 8
. . .
7 7 7 8
100
*
2
.
8
*
4
.
8
*
6
.
8
*
8
.
8 9
*
5
0
.
9
*
1
.
9
*
5
1
.
9
*
* 5
2 2
. .
9 9
200
*
* 5
4 4
. .
9 9
5
.
9
9
.
9
*
1
.
0
1
Main Channel Dis tance (ft)
*
* 5
3 3
. .
9 9
*
2 3
8 1
3 5
3 5 6
. . .
0 0 0
1 1 1
300
8
.
0 1
1 1
*
5
2
3
.
1
1
*
5
5
.
1
1
*
5
7
7
1
.
.
1 2 2
1 1 1
2
.
2
1
3
.
2
1
Stations with decimal values are interpolated cross sections placed along the surveyed profile.
5
1
.
6
Figure 3—HEC-RAS profile.
1
5
5 7
. .
2 2
1 1
400
3
1
Obtained using equation from Jarrett (1984): n = 0.39S0.38R-0.16, where S=stream slope; R=hydraulic radius. Jarrett’s
equation only applied within the following ranges: S = 0.002 to 0.08, R = 0.5 ft to 7 ft. For cross sections outside these ranges,
n was computed either from adjacent sections that fell within the ranges, using the guidance of Arcement and Schneider
(1987), or from the HEC-RAS recommendations for culvert modeling.
B
SegmentRange of
Manning’s n values1
Table 2—Summary of segments used for comparisons
500
Ground
W S 67 c fs
W S Qbf
W S Q10
W S Q50
W S Q100
L e ge nd
Culvert Scour Assessment
Fall Creek
Fall Creek
Elevation (ft)
n
o
i
t
a
v
e
l
E
)
t
f
(
n
o
i
t
a
v
e
l
E
)
t
f
(
92
-20
-10
0
10
30
20
Station (ft)
10
.1049
RS = 11
Station (ft)
20
.1051
30
40
40
50
.1049
.1051
50
60
Bank St a
Ground
WS 67 c fs
WS Qbf
WS Q10
WS Q50
WS Q100
L e ge nd
Bank St a
Ground
WS 67 c fs
WS Qbf
WS Q10
WS Q50
WS Q100
L e ge nd
n
o
i
t
a
v
e
l
E
)
t
f
(
Elevation (ft)
88
-20
90
92
94
96
98
100
92
-10
94
96
98
100
102
104
-10
0
.
1
0
2
7
.
1
0
0
8
0
10
.1027
30
20
Station (ft)
10
.1008
RS = 10
Station (ft)
20
RS = 12
.1008
30
40
.1027
40
50
50
60
Bank St a
Gr ound
WS 67 c fs
WS Qbf
WS Q10
WS Q50
WS Q100
L e ge nd
Bank St a
Gr ound
WS 67 c fs
WS Qbf
WS Q10
WS Q50
WS Q100
L e ge nd
Figure 4—Cross-section plots. Only measured cross sections are included. Manning’s n values are included at the top of the cross section.
The stationing (RS) corresponds to the stationing on the HEC-RAS profile. Green arrows define the ineffective flow areas. Black arrows
represent points identified in the field as the bankfull channel boundary. Only those points identified in the field and supported by hydraulic and
topographic analyses are shown below.
Elevation (ft)
94
96
.1049
0
.1051
n
o
i
t
a
v
e
l
E
Elevation (ft)
98
100
102
104
94
-10
96
98
100
102
104
106
RS = 13
)
t
f
(
Site Evaluations
A—223
n
o
i
t
a
v
e
l
E
)
t
f
(
A—224
Elevation (ft)
n
o
i
t
a
v
e
l
E
)
t
f
(
80
-10
0
.0958
10
10
Station (ft)
20
.0958
RS = 7
30
30
Station (ft)
20
.1078
.0958
40
40
50
50
.1078
60
60
B a n k S ta
In e ff
G ro u n d
W S 6 7 c fs
W S Qb f
W S Q1 0
W S Q5 0
W S Q1 0 0
L e ge n d
Bank St a
Ground
WS 67 c fs
WS Qbf
WS Q10
WS Q50
WS Q100
L e ge nd
n
o
i
t
a
v
e
l
E
)
t
f
(
Elevation (ft)
0
80
-20
82
84
86
88
90
92
82
84
86
88
90
92
94
-10
10
.1037
0
40
Station (ft)
30
50
20
Station (ft)
10
.0968
30
RS = 6
Note: n values for first profile.
20
.1037
RS = 8
.1037
40
60
50
70
L e ge nd
Bank St a
Ground
WS 67 c fs
WS Qbf
WS Q10
WS Q50
WS Q100
L e ge nd
Bank St a
Ground
WS 67 c fs
WS Qbf
WS Q10
WS Q50
WS Q100
Figure 4—Cross-section plots. Only measured cross sections are included. Manning’s n values are included at the top of the cross section.
The stationing (RS) corresponds to the stationing on the HEC-RAS profile. Green arrows define the ineffective flow areas. Black arrows
represent points identified in the field as the bankfull channel boundary. Only those points identified in the field and supported by hydraulic and
topographic analyses are shown below. (continued)
Elevation (ft)
82
84
0
.1078
n
o
i
t
a
v
e
l
E
Elevation (ft)
86
88
90
92
108
106
104
102
100
98
96
94
92
90
88
86
-10
RS = 9
)
t
f
(
Culvert Scour Assessment
Fall Creek
Fall Creek
Elevation (ft)
n
o
i
t
a
v
e
l
E
)
t
f
(
n
o
i
t
a
v
e
l
E
)
t
f
(
76
-20
-10
0
0
Station (ft)
10
.04
RS = 2
20
20
Station (ft)
10
30
30
40
.07
40
50
50
B a n k S ta
In e ff
G ro u n d
W S 6 7 c fs
W S Qb f
W S Q1 0
W S Q5 0
W S Q1 0 0
L e ge n d
n
o
i
t
a
v
e
l
E
)
t
f
(
Elevation (ft)
76
-10
78
80
82
84
86
88
78
-10
80
82
84
86
88
90
.07
0
0
.
0
9
5
9
10
10
.042
30
RS = 1
Station (ft)
20
30
.0959
Station (ft)
20
.0959
RS = 4
40
.07
40
50
50
60
B a n k S ta
In e ff
G ro u n d
W S 6 7 c fs
W S Qb f
W S Q1 0
W S Q5 0
Bank St a
Ground
WS 67 c fs
WS Qbf
WS Q10
WS Q50
WS Q100
L e ge nd
60
L e ge n d
W S Q1 0 0
Figure 4—Cross-section plots. Only measured cross sections are included. Manning’s n values are included at the top of the cross section.
The stationing (RS) corresponds to the stationing on the HEC-RAS profile. Green arrows define the ineffective flow areas. Black arrows
represent points identified in the field as the bankfull channel boundary. Only those points identified in the field and supported by hydraulic and
topographic analyses are shown below. (continued)
Elevation (ft)
78
80
82
.07
-10
Bank St a
Ground
WS 67 c fs
WS Qbf
WS Q10
WS Q50
WS Q100
L e ge nd
n
o
i
t
a
v
e
l
E
Elevation (ft)
84
86
88
80
-20
82
84
86
88
90
92
.0961
RS = 5
Note: n values for first profile.
)
t
f
(
Site Evaluations
A—225
w
o
l
F
a
e
r
A
q
s
(
80
0
.06
10
40
Station (ft)
30
.07
50
60
70
Bank St a
Ground
WS 67 c fs
WS Qbf
WS Q10
WS Q50
WS Q100
L e ge nd
78
-20
80
82
84
86
88
90
-10
.06
0
.06
20
Station (ft)
10
RS = 14
*River Stations 15 and 14 represent the tributary which enters below the culvert between sections 3 and 2
20
.06
n
o
i
t
a
v
e
l
E
30
.07
40
50
L e ge n d
B a n k S ta
In e ff
G ro u n d
W S 6 7 c fs
W S Qb f
W S Q1 0
W S Q5 0
W S Q1 0 0
A—226
0
0
B
C
D
Culvert
100
E
Figure 5—Flow area (total) profile plot.
Flow area (sq ft)
50
100
150
200
Flow
300
G
Main Channel Distance (ft)
200
F
H
400
I
500
Flow Area 67 cfs
Flow Area Qbf
Flow Area Q10
Flow Area Q50
Flow Area Q100
Legend
Figure 4—Cross-section plots. Only measured cross sections are included. Manning’s n values are included at the top of the cross section.
The stationing (RS) corresponds to the stationing on the HEC-RAS profile. Green arrows define the ineffective flow areas. Black arrows
represent points identified in the field as the bankfull channel boundary. Only those points identified in the field and supported by hydraulic and
topographic analyses are shown below. (continued)
Elevation (ft)
82
84
86
88
90
92
RS = 15
)
t
f
(
Elevation (ft)
)
t
f
n
o
i
t
a
v
e
l
E
)
t
f
(
Culvert Scour Assessment
Fall Creek
r
d
y
H
s
u
i
d
a
R
.
P
.
W
100
E
200
F
Flow
300
G
H
H
400
I
500
W.P. Total Q100
Legend
15
20
25
30
35
Hydraulic radius (ft)
A—227
0
B
C
D
Culvert
Figure 7—Hydraulic radius.
0
1
2
3
4
5
6
100
Flow
300
G
Main Channel Distance (ft)
200
F
Main Channel Distance (ft)
400
I
500
Hydr Radius 67 cfs
Hydr Radius Qbf
Hydr Radius Q10
Hydr Radius Q50
Hydr Radius Q100
Legend
W.P. Total 67 cfs
W.P. Total Qbf
W.P. Total Q10
0
E
40
C
D
Culvert
W.P. Total Q50
B
45
50
55
Figure 6—Wetted perimeter.
W.P. total (ft)
)
t
f
(
Fall Creek
l
a
t
o
T
)
t
f
(
Site Evaluations
x
a
M
l
h
C
h
t
p
D
p
o
T
100
E
200
F
Flow
300
G
H
H
400
I
500
Top Width Q10
Legend
10
15
20
25
30
0
100
200
300
Flow
G
400
I
500
Max Chl Dpth Q100
Legend
1
Figure 9—Maximum depth.
Maximum channel depth (ft)
2
3
4
5
Main Channel Distance (ft)
Max Chl Dpth 67 cfs
Max Chl Dpth Qbf
Max Chl Dpth Q10
F
6
C
D
Culvert
Max Chl Dpth Q50
B
7
8
9
Main Channel Distance (ft)
Top Width 67 cfs
Top Width Qbf
Top Width Q100
0
E
35
C
D
Culvert
Top Width Q50
B
40
45
50
Figure 8—Top width.
Top width (ft)
)
t
f
(
A—228
h
t
d
i
W
)
t
f
(
Culvert Scour Assessment
Fall Creek
r
a
e
h
S
n
a
h
C
q
s
/
b
l
(
)
t
f
l
e
V
0
5
0
B
C
D
Culvert
100
E
Velocity channel (ft/sec)
A—229
0
B
C
D
Culvert
100
E
Figure 11—Velocity (channel) profile plot.
0
2
4
6
8
10
12
Figure 10—Shear stress (channel) profile.
Shear channel (lbs/sq ft)
l
n
h
C
)
s
/
t
f
(
Fall Creek
10
15
20
25
Flow
Flow
G
Main Channel Distance (ft)
200
F
300
300
G
Main Channel Distance (ft)
200
F
H
H
I
400
400
I
500
500
Vel Chnl 67 cfs
Vel Chnl Qbf
Vel Chnl Q10
Vel Chnl Q50
Vel Chnl Q100
Legend
Shear Chan 67 cfs
Shear Chan Qbf
Shear Chan Q10
Shear Chan Q50
Shear Chan Q100
Legend
Site Evaluations
100
150
200
E (US Trans)
D (Culvert)
C (Culvert)
H
H
25% Q2
E (us trans)
B (culv)
C (culv)
D (culv)
G
G
Figure 12—Flow area (total).
0
I
H
H
G
E (US Trans)
Qbf
E (us trans)
B (culv)
C (culv)
D (culv)
G
I
E (US Trans)
C (Culvert)
G
H
H
G
10
E (us trans)
B (culv)
C (culv)
D (culv)
50%
of the
values
D (Culvert)
I
B (Culvert)
I
G
G
E (US Trans)
H
50
E (us trans)
B (culv)
C (culv)
D (culv)
Minimum value
25th percentile
H
I
Median (aka 50th percentile)
75th percentile
Maximum value
I
D (Culvert)
C (Culvert)
B (Culvert)
A—230
Flow50
Area (ft2)
Flow area (sq ft)
B (Culvert)
100%
of the
values
I
D (Culvert)
C (Culvert)
B (Culvert)
I
Box Plot Explanation
H
H
G
E (US Trans)
100
E (us trans)
B (culv)
C (culv)
D (culv)
G
I
Culvert Scour Assessment
Fall Creek
I
D (Culvert)
C (Culvert)
B (Culvert)
H
D (Culvert)
C (Culvert)
E (US Trans)
E (US Trans)
H
25% Q2
E (us trans)
B (culv)
C (culv)
D (culv)
G
G
Figure 14—Hydraulic radius.
0
Hydraulic Radius (ft)
2
4
6
H
Figure 1­3—Wetted perimeter.
I
I
I
G
H
Qbf
E (us trans)
B (culv)
C (culv)
D (culv)
Qbf
E (us trans)
G
G
G
25% Q2
B (Culvert)
B (Culvert)
B (culv)
C (culv)
D (culv)
C (Culvert)
C (Culvert)
H
H
E (us trans)
D (Culvert)
D (Culvert)
E (US Trans)
E (US Trans)
H
I
I
G
H
10
H
10
E (us trans)
B (culv)
C (culv)
D (culv)
G
E (us trans)
B (culv)
C (culv)
D (culv)
C (Culvert)
C (Culvert)
G
D (Culvert)
D (Culvert)
B (culv)
C (culv)
D (culv)
I
I
G
G
H
I
B (Culvert)
B (Culvert)
E (US Trans)
E (US Trans)
H
H
G
I
I
I
I
0
G
H
50
H
50
E (us trans)
B (culv)
C (culv)
D (culv)
G
E (us trans)
B (culv)
C (culv)
D (culv)
B (Culvert)
B (Culvert)
15
C (Culvert)
C (Culvert)
30
D (Culvert)
D (Culvert)
E (US Trans)
E (US Trans)
G
G
45
I
I
I
I
60
G
H
100
H
100
E (us trans)
B (culv)
C (culv)
D (culv)
G
E (us trans)
B (culv)
C (culv)
D (culv)
C (Culvert)
C (Culvert)
H
H
E (US Trans)
E (US Trans)
B (Culvert)
B (Culvert)
B (Culvert)
B (Culvert)
G
G
Wetted Perimeter (ft)
Hydraulic radius (ft)
C (Culvert)
D (Culvert)
D (Culvert)
H
H
Fall Creek
I
I
I
I
Wetted perimeter (ft)
D (Culvert)
Site Evaluations
A—231
E (US Trans)
D (Culvert)
G
H
25% Q2
E (us trans)
B (culv)
C (culv)
D (culv)
G
G
Figure 16—Maximum depth.
0
Maximum Depth (ft)
2
4
6
8
Figure 15—Top width.
E (US Trans)
H
H
I
I
G
H
G
H
Qbf
E (us trans)
B (culv)
C (culv)
D (culv)
Qbf
E (us trans)
E (US Trans)
E (US Trans)
25% Q2
B (Culvert)
B (Culvert)
B (culv)
C (culv)
D (culv)
C (Culvert)
C (Culvert)
G
G
E (us trans)
D (Culvert)
D (Culvert)
H
H
B (culv)
C (culv)
D (culv)
I
I
I
I
G
H
G
H
10
E (us trans)
B (culv)
C (culv)
D (culv)
10
E (us trans)
B (culv)
C (culv)
D (culv)
B (Culvert)
B (Culvert)
E (US Trans)
E (US Trans)
H
C (Culvert)
C (Culvert)
G
G
G
D (Culvert)
D (Culvert)
H
H
I
I
0
I
I
I
I
10
G
H
G
H
50
E (us trans)
B (culv)
C (culv)
D (culv)
50
E (us trans)
B (culv)
C (culv)
D (culv)
B (Culvert)
B (Culvert)
E (US Trans)
E (US Trans)
20
C (Culvert)
C (Culvert)
G
G
30
I
I
I
I
40
D (Culvert)
D (Culvert)
H
H
B (Culvert)
B (Culvert)
G
H
H
G
H
100
E (us trans)
B (culv)
C (culv)
D (culv)
100
E (us trans)
B (culv)
C (culv)
D (culv)
B (Culvert)
B (Culvert)
C (Culvert)
C (Culvert)
C (Culvert)
C (Culvert)
E (US Trans)
E (US Trans)
Top Width (ft)
Maximum depth (ft)
D (Culvert)
D (Culvert)
D (Culvert)
G
G
A—232
H
Top width (ft)
I
I
I
I
50
Culvert Scour Assessment
Fall Creek
Velocity (ft/sec)
A—233
H
G
G
E (US Trans)
E (US Trans)
D (Culvert)
D (Culvert)
H
25% Q2
E (us trans)
B (culv)
C (culv)
D (culv)
G
H
Figure 18—Velocity (channel).
0
B (Culvert)
H
Qbf
E (us trans)
G
E (us trans)
Qbf
B (culv)
C (culv)
D (culv)
B (Culvert)
C (Culvert)
Velocity
3 (ft/sec)
6
9
12
I
I
I
Figure 17—Width-to-depth ratio.
C (Culvert)
C (Culvert)
G
G
E (us trans)
E (US Trans)
E (US Trans)
25% Q2
D (Culvert)
D (Culvert)
H
H
I
I
G
H
G
H
10
E (us trans)
B (culv)
C (culv)
D (culv)
10
E (us trans)
B (culv)
C (culv)
D (culv)
B (Culvert)
B (Culvert)
B (culv)
C (culv)
D (culv)
I
E (US Trans)
E (US Trans)
H
C (Culvert)
C (Culvert)
G
G
G
D (Culvert)
D (Culvert)
H
H
B (culv)
C (culv)
D (culv)
I
I
I
I
H
G
H
G
H
50
E (us trans)
B (culv)
C (culv)
D (culv)
50
E (us trans)
B (culv)
C (culv)
D (culv)
I
B (Culvert)
B (Culvert)
G
E (US Trans)
E (US Trans)
I
0
C (Culvert)
C (Culvert)
G
G
10
D (Culvert)
D (Culvert)
H
H
B (Culvert)
B (Culvert)
I
I
I
I
Width-to-depth Ratio
G
H
G
H
100
E (us trans)
B (culv)
C (culv)
D (culv)
100
E (us trans)
B (culv)
C (culv)
D (culv)
B (Culvert)
B (Culvert)
20
E (US Trans)
E (US Trans)
30
C (Culvert)
C (Culvert)
G
G
40
D (Culvert)
D (Culvert)
H
H
Fall Creek
I
I
I
I
Width-to-depth ratio
C (Culvert)
Site Evaluations
A—234
Shear stress (lbs/sq ft)
H
25% Q2
E (us trans)
B (culv)
C (culv)
D (culv)
G
I
600
Dis charge (cfs )
400
H
800
Qbf
E (us trans)
B (culv)
C (culv)
D (culv)
G
1000
I
H
I
Culvert - riffle
US Channel (DS pebble count) - step
10
E (us trans)
B (culv)
C (culv)
D (culv)
G
Figure 20—Excess shear stress.
Excess shear stress is the channel shear divided by the critical shear for bed
entrainment of the D84 particle size. Values of excess shear greater than 1 indicate
bed movement for the D84 particle size.
0.5
Excess Shear (Applied / tcrit)
0
0
200
1
1.5
2
2.5
3
3.5
4
Figure 19—Shear stress (channel).
0
5 Stress (lbs/ft2)
Shear
10
15
20
25
H
50
E (us trans)
B (culv)
C (culv)
D (culv)
G
I
H
100
E (us trans)
B (culv)
C (culv)
D (culv)
G
I
Culvert Scour Assessment
Fall Creek
Site Evaluations
Table 3—Sum of squared height difference
Reach
XS LocationUnit type
Culvert
Sum of squared height difference
Within range of
channel conditions?
US
Riffle
0.03
No
DS
Riffle
0.03
No
US
Pool
0.13
DS
Step
0.05
Upstream
Table 4—Vertical sinuosity
Segment
LocationVertical Sinuosity (ft/ft)
A
DS transition
1.002
B
Culvert
1.003
C
Culvert
1.001
D
Culvert
1.001
E
US transition
1.005
F
US channel
1.001
G
US channel
1.003
H
US channel
1.008
I
US channel
1.010
Table 5—Depth distribution
Reach
XS Location
25% Q2
Culvert
Within range of
channel conditions?
US
0
Yes
DS
0
Yes
US
2
DS
0
Upstream
Table 6—Habitat unit composition
Percent of surface area
Reach
Pool Glide
Riffle
Step
Culvert
10%
0%
86%
0%
Upstream Channel
41%
0%
50%
0%
Fall Creek
A—235
Culvert Scour Assessment
1.6
1.4
Residual Depth (ft)
1.2
1.0
0.8
0.6
Residual depth (ft)
0.4
0.2
Segment I
Segment H
Segment G
Segment F
Segment E
US Transition
Segment D
Culvert
Segment C
Culvert
Segment B
Culvert
Segment A
DS Transition
0.0
Culvert
Culvert
Culvert
Segment I
Segment
B:
Segment
C:
Segment
D: Segment E: Segment F Segment G Segment H
Segment
A:
DS Transition
US Transition
Figure 21—Residual depths.
Table 7—Bed material sorting and skewness
Reach
XSUnit
Sorting
Location Type
Within range Skewness
of channel
conditions?
Culvert
US
Riffle
1.59
Upstream
US
Pool
2.69
0.38
DS
Step
1.54
0.04
Yes
0.15
Within range
of channel
conditions?
Yes
Table 8—Large woody debris
Reach
Pieces/Channel Width
Culvert
0
Upstream
0.81
Terminology:
US = Upstream
DS = Downstream
RR = Reference reach
XS = Cross section
A—236
Fall Creek
Site Evaluations
View upstream through culvert.
View downstream through culvert.
Upstream reference reach – upstream pebble
count, pool. Upstream reference reach – downstream pebble
count, steep riffle/step.
View downstream from outlet at confluence with tributary on right.
Fall Creek
A—237
Culvert Scour Assessment
Cross section : Upstream Reference Reach – Upstream Pebble Count
Material
sand
very fine gravel
fine gravel
fine gravel
medium gravel
medium gravel
coarse gravel
coarse gravel
very coarse gravel
very coarse gravel
small cobble
medium cobble
large cobble
very large cobble
small boulder
small boulder
medium boulder
large boulder
very large boulder
bedrock
S ize R ange (mm)
C ount
Item %
C umulative %
12
2
2
1
4
2
1
7
7
10
11
4
7
5
8
2
1
12%
2%
2%
1%
4%
2%
1%
7%
7%
10%
11%
4%
7%
5%
8%
2%
1%
0%
0%
12%
12%
14%
16%
17%
21%
23%
24%
32%
39%
49%
60%
64%
71%
77%
85%
87%
88%
88%
88%
100%
<2
2-4
4 - 5.7
5.7 - 8
8 - 11.3
11.3 - 16
16 - 22.6
22.6 - 32
32 - 45
45 - 64
64 - 90
90 - 128
128 - 180
180 - 256
256 - 362
362 - 512
512 - 1024
1024 - 2048
2048 - 4096
> 4096
0
12
14
100%
90%
12
Frequency
70%
60%
8
50%
6
40%
Frequency
4
30%
Cumulative Frequency
80%
10
20%
2
10%
Bedrock
2048-4096
1024-2048
362-512
512-1024
256-362
180-256
128-180
64-90
90-128
45-64
32-45
22.6-32
16-22.6
11.3-16
5.7-8
8-11.3
<2
4-5.7
<2
0%
2-4
0
Cumulative Frequency
2-4
4 - 5.7
5.7 - 8
> 4096
32 -45
45-64
64- 90
8 - 11.3
90 - 128
11.316
- 16
-22.6
22.6- 32
128180
- 180
256
- 256
362
- 362
- 512
512 - 1024
Particle Size Category (mm)
1024
2048
- 2048
- 4096
Particle Size Category (mm)
S ize C las s
S ize perc ent finer
than (mm)
D5
D16
D50
D84
D95
D100
1
4
60
210
350
570
A—238
Material
P erc ent C ompos ition
Sand
Gravel
Cobble
Boulder
Bedrock
12%
37%
28%
11%
12%
Sorting Coefficient: 2.69
Skewness Coefficient:0.38
Fall Creek
Site Evaluations
Cross section : Upstream Reference Reach – Downstream Pebble Count
Material
sand
very fine gravel
fine gravel
fine gravel
medium gravel
medium gravel
coarse gravel
coarse gravel
very coarse gravel
very coarse gravel
small cobble
medium cobble
large cobble
very large cobble
small boulder
small boulder
medium boulder
large boulder
very large boulder
bedrock
S ize C las s (mm)
<2
2-4
4 - 5.7
5.7 - 8
8 - 11.3
11.3 - 16
16 - 22.6
22.6 - 32
32 - 45
45 - 64
64 - 90
90 - 128
128 - 180
180 - 256
256 - 362
362 - 512
512 - 1024
1024 - 2048
2048 - 4096
Bedrock
C ount
Item %
C umulative %
1
2
0
0
2
1
1
3
8
15
13
15
7
6
14
7
1
1%
2%
0%
0%
2%
1%
1%
3%
8%
15%
13%
15%
7%
6%
14%
7%
1%
0%
0%
6%
1%
3%
3%
3%
5%
6%
7%
10%
18%
32%
45%
60%
67%
73%
86%
93%
94%
94%
94%
100%
6
16
100%
14
90%
Frequency
70%
10
60%
8
50%
40%
Frequency
6
30%
4
20%
Bedrock
2048-4096
1024-2048
362-512
512-1024
256-362
180-256
90-128
128-180
64-90
45-64
32-45
22.6-32
11.3-16
16-22.6
Cumulative Frequency
2-4
4 - 5.7 - 8
32 -45
45-64
64- 90
8 - 11.3
90 - 128
Bedrock
11.316- 16
-22.6
22.6- 32
128180
- 180
256
- 256
362
- 362
- 512
512 - 1024
Particle Size Category (mm)
1024
2048
- 2048
- 4096
Particle Size Category (mm)
S ize C las s
S ize perc ent finer
than (mm)
D5
D16
D50
D84
D95
D100
12
40
100
308
450
520
Fall Creek
5.7-8
<2
8-11.3
0%
4-5.7
0
<2
10%
2-4
2
Cumulative Frequency
80%
12
Material
P erc ent C ompos ition
Sand
Gravel
Cobble
Boulder
Bedrock
1%
31%
40%
22%
6%
Sorting Coefficient:
1.54
Skewness Coefficient: 0.04
A—239
Culvert Scour Assessment
Cross section : Culvert – Upstream Pebble Count
Material
sand
very fine gravel
fine gravel
fine gravel
medium gravel
medium gravel
coarse gravel
coarse gravel
very coarse gravel
very coarse gravel
small cobble
medium cobble
large cobble
very large cobble
small boulder
small boulder
medium boulder
large boulder
very large boulder
bedrock
S ize C las s (mm)
<2
2-4
4 - 5.7
5.7 - 8
8 - 11.3
11.3 - 16
16 - 22.6
22.6 - 32
32 - 45
45 - 64
64 - 90
90 - 128
128 - 180
180 - 256
256 - 362
362 - 512
512 - 1024
1024 - 2048
2048 - 4096
Bedrock
C ount
Item %
C umulative %
2
1
1
0
2
5
4
5
9
10
14
9
13
10
11
3
1
0
0
0
2%
1%
1%
0%
2%
5%
4%
5%
9%
10%
14%
9%
13%
10%
11%
3%
1%
0%
0%
0%
2%
3%
4%
4%
6%
11%
15%
20%
29%
39%
53%
62%
75%
85%
96%
99%
100%
100%
100%
100%
16
100%
14
90%
Frequency
70%
10
60%
8
50%
40%
Frequency
6
30%
4
20%
Bedrock
2048-4096
512-1024
1024-2048
362-512
256-362
180-256
128-180
64-90
90-128
45-64
32-45
22.6-32
16-22.6
8-11.3
Cumulative Frequency
2-4
4 - 5.7 - 8
32 -45
45-64
64- 90
8 - 11.3
90 - 128
Bedrock
11.316- 16
-22.6
22.6- 32
128180
- 180
256
- 256
362
- 362
- 512
Particle Size Category (mm)
512 - 1024
1024
2048
- 2048
- 4096
Particle Size Category (mm)
S ize C las s
S ize perc ent finer
than (mm)
D5
D16
D50
D84
D95
D100
10
25
85
242
341
600
A—240
11.3-16
<2
5.7-8
0%
4-5.7
0
<2
10%
2-4
2
Cumulative Frequency
80%
12
Material
P erc ent C ompos ition
Sand
Gravel
Cobble
Boulder
Bedrock
2%
37%
46%
15%
0%
Sorting Coefficient:
1.59
Skewness Coefficient: 0.15
Fall Creek