Site Evaluations
Lowe Creek
Site Information
Site Location:
Mt Hood NF, Forest Road 4671
Year Installed:
Pre-1987
Lat/Long:
121°53’55.08”W
44°56’55.13”N
Watershed Area (mi2): 6.0
Stream Slope (ft/ft)1: 0.0445
Channel Type: Step-pool
Bankfull Width (ft): 23.6
Survey Date:
1
April 5, 2007
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:
Hybrid projecting/mitered
Culvert Length:
70 ft
Inlet Type:
Hybrid projecting/mitered
Pipe Slope (structure slope): 0.05
Culvert Bed Slope: 0.035
(First hydraulic control upstream of inlet to first hydraulic control downstream of outlet.)
Culvert width as a percentage of bankfull width: 0.81
Alignment Conditions: Appears inline with natural channel.
Bed Conditions: Scoured at upstream end of pipe. Large cobbles to large boulders are creating steps
in culvert.
Pipe Condition: Left footing severely undermined at upstream end. May be some piping around sides
of pipe where erosion has occurred.
Hydrology
Discharge (cfs) for indicated recurrence interval
25% 2-yr
Qbf2
2-year
5-year
10-year
50-year
100-year
35
115
141
227
292
448
520
2
Bankfull flow estimated by matching modeled water surface elevations to field-identified bankfull elevations.
Lowe Creek
A—327
Culvert Scour Assessment
Points represent survey points
Figure 1—Plan view map.
A—328
Lowe Creek
Site Evaluations
History
The exact installation date is unknown, but
the culvert was included in the 1987 Western
Federal Lands Highway Division (WFLHD)
“Oregon Culvert Fish Passage Survey.” The field
survey for the WFLHD study was conducted on
November 27, 1987. The study describes the
culvert as an “open bottom arch with boulders
placed inside the barrel.” With respect to fish
passage, Oregon Department of Fish and
Wildlife (ODFW) staff described the culvert as
an “excellent open bottom arch installation;”
whereas WFLHD staff noted that the culvert
was in “fair” condition, the foundation was in
“poor” condition, and there was “moderate” outlet
scour. The culvert hydraulics were considered
“compatible” with the natural stream hydraulics.
They go on to note that open-bottom arches with
shallow foundations are susceptible to scour
and recommend that if foundation requirements
cannot be met (i.e., embedment depth), then
closed-bottom pipes should be installed.
The following are photos from the WFLHD study:
Culvert inlet.
Typical stream channel.
Site Description
The Lowe Creek culvert is an open-bottom arch
that projects from the roadfill. The culvert is
characterized by a deep scour pool at the inlet,
primarily concentrated along the left side of
the culvert where significant footing scour and
undermining has occurred. Downstream of the
scour pool, the bed is aggraded and levels off
forming a consistent riffle. The channel is against
the left side of the culvert for most of its length.
There has been deposition of material along the
right footing at the inlet. There is a large (greater
than 2-foot diameter) log just upstream and inside
of the culvert. There is significant erosion at the
sides of the culvert at the inlet and outlet.
The upstream representative reach consists
of a moderate gradient step-pool channel. The
upstream segment sits in a fairly confined and
narrow valley. Channel banks are steep with
high adjacent terraces that may only be active at
infrequent floods. Large boulders and fallen trees
line both banks. The reach consists of a series of
steps and pools.
The downstream representative reach consists of
a series of steep riffles interspersed with pools. A
relatively extensive low (active) flood plain exists
through this reach. Bed material was finer and
there were small log jams.
Lowe Creek
A—329
Culvert Scour Assessment
Survey Summary
Fourteen cross sections and a longitudinal
profile were surveyed at the Lowe Creek
crossing in April 2007 to characterize the culvert,
an upstream representative reach, and a
downstream representative reach. Representative
cross sections in the culvert were taken through
the downstream end of the pool and the riffle.
One additional cross section was surveyed
upstream to characterize the inlet as well as the
contraction of flow. Another two cross sections
were surveyed downstream of the culvert to
characterize the outlet and the expansion of flow.
Four cross sections were surveyed to
characterize the upstream representative reach;
one at the upstream boundary, one at the
downstream boundary, one through a step, and
one through a pool. Four cross sections were
also surveyed to characterize the downstream
representative reach; one at the upstream
boundary, one at the downstream boundary, one
through a pool, and one through a riffle.
Profile Analysis Segment Summary
The profile analysis resulted in a total of eight
profile segments. The two consecutive segments
downstream of the outlet, though similar in
gradient, were not combined in order to separate
out the transition area from the downstream
representative channel. The culvert consisted
of two profile segments, the upstream one
extending into the upstream transition area. The
upstream culvert segment was compared to
two representative profile segments, one in the
upstream channel and one in the downstream
channel. There was no suitable comparison for
the downstream segment in the culvert. The
upstream transition segment was compared to a
representative profile segment in the downstream
channel. The downstream transition segment was
compared to two representative profile segments,
one in the upstream channel and one in the
downstream channel. See figure 2 and table 1.
A—330
Scour Conditions
Observed conditions
Footing scour – The greatest amount of footing
scour is at the upstream end on the left bank
where the footing is undermined. The base of the
footing is suspended above the bed 2.5 feet at
the maximum depth of the scour pool. The lateral
extent of scour under the footing reaches 4 feet
at one location. Some of this scour may be the
result of a large log (greater than 2-foot diameter)
located at the inlet. Approximately 40 percent of
the footing on the left bank is undermined and all
of it is exposed. There is also scour around the
sides of the pipe at the inlet and outlet and there
may be some piping of flow around the culvert in
these areas. The “poor” foundation rating from
the WFLHD study and the suggestion regarding
foundation requirements suggest that some
foundation undermining may have been present
in 1987, but likely less than in 2007 or there
would have been more mention of it.
Culvert-bed adjustment – The culvert bed has
reduced its slope since installation (assuming the
culvert bed was constructed at the same gradient
as the structure). This flattening appears to be
mostly due to scour in the upstream portion of the
pipe. There is still streambed material throughout
the pipe and no bedrock is present on the bed.
Profile characteristics – The profile has a concave
shape through the crossing (figure 2). This shape
reflects scour at the inlet region. There is a
natural valley transition in this area. Upstream is
more confined with higher and less active floodplain terraces than the downstream reach.
Residual depths – The single culvert residual
depth is within the range of residual depths in
corresponding profile segments in the natural
channel (B and H) (figure 21). The single residual
depth in the downstream transition is also within
the range of corresponding profile segments
in the natural channel (B and H). There was
no residual depth in the corresponding profile
segment for the upstream transition.
Lowe Creek
Site Evaluations
Substrate – Bed-material distributions are similar
between the culvert and channel sample sites.
The culvert has more coarse material than the
downstream channel but similar abundance of
coarse material as the upstream channel. The
downstream channel has the greatest abundance
of fine material. Sorting and skewness values in
the culvert are within the range of those in the
natural channel (table 7).
Predicted conditions
*Note: As estimated in the model, backwater from
the culvert affects portions of the upstream reach
(figure 3). The backwater affects the upstream
representative reach for the Q50 and Q100. For this
reason, hydraulic metrics for these flows are not
used in the comparisons with culvert values.
Cross-section characteristics – The culvert
appears to affect most of the cross-section
metrics at the Qbf and above (figures 5 through
9 and 12 through 19). There is a dramatic
reduction in top width and an increase in depth
as flows rise. The culvert exhibits characteristics
of outlet control, with culvert characteristics (i.e.,
barrel roughness, slope, and area) creating
deep subcritical flow throughout most of the
barrel length. The flow passes through critical
depth near the downstream end. Cross-section
characteristics at the upstream transition (F) are
impacted by the culvert backwater at higher flows
(Q50 and Q100). At lower flows, the flow has lower
width and greater depth than the corresponding
profile segments (A), but this may be due partially
to changes in valley confinement. Cross-section
characteristics in the downstream transition (C)
are mostly within the range of corresponding
profile segments (B and H).
Shear stress – The modeling suggests that shear
stress is low in the culvert due to backwater
conditions that reduce the energy grade. Shear
stress near the downstream end of the culvert
is high where the flow passes through critical
depth (figure 10). Shear stress in the upstream
Lowe Creek
transition (F) is greater than the corresponding
profile segment (A) for flows up to the Q10 but is
less at the Q50 and Q100 because of backwater
effects (figures 10 and 19). Shear stress in the
downstream transition (C) is within the range of
corresponding profile segments (B and H).
Excess shear – The excess shear analysis shows
the culvert as having lower potential for bed
mobilization when compared to the upstream and
downstream channels (figure 20). This is due to
the backwater effect of the culvert that lowers the
energy grade and therefore lowers the applied
shear available to move material.
Velocity – The modeling suggests that velocity
is low in the culvert due to backwater conditions
that reduce the energy grade. Velocity near the
downstream end of the culvert is high where the
flow passes through critical depth (figure 11).
Velocity in the upstream transition (F) is similar
to the corresponding channel segment (A) at the
Q10 and below but is lower than the channel at the
Q50 and Q100 (figure 18) due to backwater effects.
Velocity in the downstream transition (C) is within
the range of corresponding channel segments (B
and H) at all modeled flows.
Scour summary
There is severe scour of the left bank footing
at the inlet and extending downstream
approximately 30 feet. This is a serious
maintenance issue that needs to be addressed
to ensure that the structural integrity of the
crossing is not compromised. This scour may be
partially related to culvert capacity, deposition of
coarse material upstream of the inlet, and a large
(greater than 2-foot diameter) midchannel log just
upstream and inside of the culvert. The drop into
the scour pool is larger than any drops observed
in the reference reaches. This has also resulted in
the deposition of material along the right footing
at the inlet and the shifting of the channel towards
the left. Downstream of the scour pool, the bed is
aggraded and levels off forming a consistent riffle.
A—331
Culvert Scour Assessment
Bed material at the inlet has likely eroded out
and redeposited at the downstream portion of the
culvert, contributing to bed flattening.
Modeling suggests that flow geometry and
hydraulics are highly impacted by the culvert,
especially at high flows that cause backwater
within and upstream of the culvert. The culvert
appears to be under outlet control at high flows,
with the length, roughness, and downstream
conditions raising the elevation of the flow
through much of the culvert. This condition serves
to reduce channel velocity and shear stress
through most of the culvert at very high flows
(Q50 and above). At these flows, the modeling
shows flow passing through critical depth near the
downstream end of the culvert, with associated
high shear stress and velocity that could cause
scour at this location. Prior to the inlet scour,
which widened the inlet area, the culvert may
have exhibited inlet control conditions that
contributed to the scour observed in the inlet
area. At more frequent flood events, inlet control
conditions may still be a concern, especially with
respect to the potential for increased scour of the
footing at the inlet
There is also significant erosion at the sides
of the culvert at the inlet and outlet, possibly a
result of flow contraction and expansion. Erosion
at the left bank upstream of the inlet is further
exacerbated by the coarse material and logs
that have deposited upstream of the inlet, thus
initiating lateral boundary adjustment.
AOP Conditions
Cross-section complexity – The sum of squared
height differences in the culvert cross sections
are both within the range of those in the channel
cross sections (table 3).
A—332
Profile complexity – Vertical sinuosity in the
upstream culvert segment (E) is slightly greater
than the values in the corresponding channel
segments (B and H) (table 4). Vertical sinuosity
in the upstream transition segment (F) is slightly
greater than the value in the corresponding
channel segment (A). Vertical sinuosity in the
downstream transition segment (C) is within the
range of values in the corresponding channel
segments (B and H).
Depth distribution – The upstream culvert cross
section has less channel margin habitat than the
natural channel but the downstream culvert cross
section is within the range of the natural channel
(table 5).
Habitat units – Habitat-unit distribution in the
culvert is within the range of that found in the
natural channel upstream and downstream of the
crossing (table 6).
Residual depths – The single culvert residual
depth is within the range of residual depths in
corresponding profile segments in the natural
channel (B and H) (figure 21). The single residual
depth in the downstream transition is also within
the range of corresponding profile segments
in the natural channel (B and H). There was
no residual depth in the corresponding profile
segment for the upstream transition.
Substrate – Bed-material distributions are similar
between the culvert and channel sample sites.
The culvert has more coarse material than the
downstream channel but similar abundance of
coarse material as the upstream channel. The
downstream channel has the greatest abundance
of fine material. Sorting and skewness values in
the culvert are within the range of those in the
natural channel (table 7).
Lowe Creek
Site Evaluations
Large woody debris – There was one 2- to 3-footdiameter piece of LWD present at the inlet to the
culvert. The piece may have been a contributor to
the scour present at the inlet. The representative
channel had high LWD abundance (table 8). LWD
formed steps and scour pools in the channel
outside the crossing and played a primary role in
habitat-unit creation and complexity. Features in
the culvert did not mimic the role of wood in the
natural channel.
AOP summary
Complexity measures and site observations
suggest that this is a good installation with
respect to AOP. There is good flow concentration
in the culvert that would support fish passage at
low flows. The hydraulics at the Qbf and below are
unaffected by the backwater effects described
earlier and are assumed to be amenable to fish
passage. There is also a dry bank along the right
side suitable for passage of terrestrial organisms.
There is also erosion on the sides of the culvert
at the inlet and outlet. These areas should be
stabilized with rock or concrete (e.g., wing-walls)
to prevent erosion around the edges of the pipe.
Regular maintenance of the site is needed to
remove woody debris, such as the large log that
is located at the inlet and may be contributing to
the inlet scour. Based on the presence of log jams
in the natural channel, wood transport is common
through this portion of Lowe Creek. Maintenance
needs to be conducted to manage for this wood
or the crossing needs to be made wide enough to
convey wood.
Design Considerations
This site is a poor installation with respect
to scour but appears to be suitable for AOP.
There are serious concerns with the structural
integrity of the structure that are primarily related
to the undermining of the left-bank footing at
the upstream end of the culvert. Additionally,
modeling suggests a severe effect on flow
geometry and hydraulics at the Q50 and above
that may create future scour problems within the
pipe. This design could be improved by use of a
wider culvert with greater capacity to convey high
flood flows. It is also clear that the footing depth
needs to be increased to extend below the depth
of maximum potential scour.
Lowe Creek
A—333
A—334
71
H
500
450
47
400
Table 1—Segment comparisons
250
XS 7:
Pebble count
(riffle)
A
B
H
D o w n s trea m T ra n s itio n
C
C
D is ta nc e a long be d (fe e t)
XS 6
U ps trea m T ra n s itio n
F
300
XS 5
D
R epres en ta tiv e
C h a n n el S eg men t
B
H
XS 4
C
C ulvert
C u lv ert S eg men t
E
E
350
B
0 .0 5 8
0 .0 7 8
0 .0 4 3
XS 3:
Pebble count
(pool)
Representative Channel
XS 2:
Pebble count
(riffle)
61
F
G
XS 1
0 .0 3 2
55
47
D
E
A
0 .0 1 7
0 .0 5 5
34
C
0 .0 4 9
45
B
0 .0 2 9
S e g m e n t G r a d ie n t
67
Figure 2—Lowe Creek longitudinal profile.
80
85
S egm ent
L e n g th ( f t)
A
Relative
90 elevation (feet)
95
100
105
110
115
S egm ent
13.4%
26.3%
9.7%
% D ifferen c e in
G ra d ien t
10.7%
4.9%
200
XS 10
Large log in inlet
XS 9
XS 8:
Pebble count
(pool)
E
150
F
XS 11
G
100
50
Representative Channel
XS 12:
Pebble count
(step)
XS 14
XS 13:
Pebble count
(pool)
H
0
Culvert Scour Assessment
Lowe Creek
n
o
i
t
a
v
e
l
E
)
t
f
(
Lowe Creek
0.1126 – 0.1187
0.1131 – 0.1197
0.1115 – 0.1217
0.0875 – 0.1298
0.1298 – 0.1328
0.1228 – 0.1336
A
B
C
E
F
H
SegmentRange of Manning's n values1
2
2
2
2
2
2
# of measured XSs
6
5
6
5
5
7
# of interpolated XSs
1
*
5
2
.
2
3
5
.
3
*
5
1 3
. .
4 4 4
100
6
.
4
*
3
3
3
3
3
.
5
*
6
6
6
6
6
5
.
.
5 6 6
7
.
6
8
.
6
5
2 5
. .
8 8 8
200
9
6
. 0
9 1
Main Channel Dis tance (ft)
3 6
. .
7 7 7
Culvert
3
.
0
1
*
5
6
.
0
1
*
2
.
1 1
1 1
4
.
1
1
*
5
7
5
.
1
1
5
7 7
2
. .
.
1 1 2 2
1 1 1 1
300
3
.
2
1
*
3
3
3
5
2
.
.
2 3 3
1 1 1
Stations with decimal values are interpolated cross sections placed along the surveyed profile.
5
.
2
Figure 3—HEC-RAS profile.
Elevation (ft)
90 *
5
.
85 1 2
0
95
100
105
110
115
*
6
6
6
4
.
3
1
7
.
3
1
4
1
400
Ground
W S 35 c fs
W S Qbf
W S Q10
W S Q50
W S Q100
L e ge nd
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.
Table 2—Summary of segments used for comparisons
Site Evaluations
A—335
)
t
f
(
A—336
Elevation (ft)
n
o
i
t
a
v
e
l
E
)
t
f
(
n
o
i
t
a
v
e
l
E
Station (ft)
60
80
104
n
o
i
t
a
v
e
l
E
n
o
i
t
a
v
e
l
E
)
t
f
(
Elevation (ft)
100
102
104
108
106
110
112
116
114
104
-20
106
108
112
110
114
116
120
118
0
0
20
Station (ft)
RS = 11
60
40
.1228
RS = 13
Station (ft)
40
20
.1313
.1228
.
1
2
2
8
80
.1313
60
.
1
3
1
3
100
80
L e ge nd
Bank St a
Ground
WS 35 c fs
WS Qbf
WS Q10
WS Q50
WS Q100
L e ge nd
Bank St a
Gr ound
WS 35 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 surveyed in as the bankfull channel boundary. Only those points called out in the field and supported by further hydraulic and topographic
analyses are marked below.
Elevation (ft)
-20
Gr ound
Bank St a
106
WS Q50
WS Q100
L e ge nd
WS 35 c fs
40
80
108
.
1
3
3
2
60
WS Qbf
20
.1332
RS = 12
Station (ft)
40
Bank St a
Gr ound
WS 35 c fs
WS Qbf
WS Q10
WS Q50
WS Q100
L e ge nd
110
.1332
20
.1336
WS Q10
0
0
RS = 14
.1336
Elevation (ft)
112
114
116
118
106
-20
108
110
114
112
116
118
122
120
.1336
)
t
f
(
Culvert Scour Assessment
Lowe Creek
n
o
i
t
a
v
e
l
E
)
t
f
(
Elevation (ft)
n
o
i
t
a
v
e
l
E
)
t
f
(
Lowe Creek
96
-40
-20
0
20
..
00
12
34
0
Station (ft)
.0934
RS = 8
Station (ft)
..
00
21
43
-20
40
20
.1305
.
1
3
0
5
60
40
Bank St a
Ground
WS 35 c fs
WS Qbf
WS Q10
WS Q50
WS Q100
L e ge nd
Bank St a
Gr ound
WS 35 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
96
-40
98
100
104
102
106
108
112
110
96
98
100
104
102
106
108
112
110
-20
20
.075
0
..
00
21
43
Station (ft)
.1
20
..
00
12
34
Station (ft)
RS = 7
40
60
.1287
RS = 9
40
.
0
7
5
80
60
L e ge n d
Bank St a
Ground
WS 35 c fs
WS Qbf
WS Q10
WS Q50
WS Q100
L e ge nd
100
B a n k S ta
In e ff
L e ve e
G ro u n d
W S 3 5 c fs
W S Qb f
W S Q1 0
W S Q5 0
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 surveyed in as the bankfull channel boundary. Only those points called out in the field and supported by further hydraulic and topographic
analyses are marked below. (continued)
Elevation (ft)
98
100
-40
.1305
n
o
i
t
a
v
e
l
E
Elevation (ft)
104
102
106
108
112
110
98
-60
100
102
106
104
108
110
114
112
RS = 10
)
t
f
(
Site Evaluations
A—337
)
t
f
(
A—338
Elevation (ft)
n
o
i
t
a
v
e
l
E
)
t
f
(
n
o
i
t
a
v
e
l
E
92
94
0
20
.1131
40
RS = 4
.1131
40
60
Station (ft)
Station (ft)
20
.1115
80
.1131
60
100
)
t
f
(
.1197
40
Station (ft)
60
80
L e ge n d
W S Q1 0 0
60
94
92
Bank St a
Station (ft)
80
100
98
40
WS Qbf
100
20
WS Q10
102
96
WS Q50
104
Bank St a
Ground
WS 35 c fs
L e ge nd
.1197
100
B a n k S ta
In e ff
G ro u n d
WS Q100
.1197
RS = 3
W S Qb f
W S 3 5 c fs
106
0
94
96
98
102
100
W S Q1 0
.1145
W S Q5 0
20
.1145
104
0
.1145
RS = 5
106
110
108
Ground
WS 35 c fs
n
o
i
L e ge nd
t
WS Q100
a
v
WS Q50
e
WS Q10
l
WS Qbf
E
80
B a n k S ta
In e ff
G ro u n d
W S 3 5 c fs
Elevation (ft)
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 surveyed in as the bankfull channel boundary. Only those points called out in the field and supported by further hydraulic and topographic
analyses are marked below. (continued)
Elevation (ft)
96
100
98
0
.1115
n
o
i
L e ge n d
t
W S Q1 0 0a
W S Q5 0v
e
W S Q1 0
l
W S Qb f
E
Elevation (ft)
102
104
108
106
-20
96
98
100
102
104
106
108
110
.1115
RS = 6
)
t
f
(
Culvert Scour Assessment
Lowe Creek
w
o
l
F
a
e
r
A
q
s
(
90
92
0
.1126
20
40
.1126
Station (ft)
60
.1126
80
100
B a n k S ta
L e ve e
G ro u n d
W S 3 5 c fs
n
o
L e gie n d
t
W S Q1 0 0
a
W S Q5 0
v
WS e
Q1 0
l
W S Qb f
E
90
0
20
40
Station (ft)
60
80
100
Bank St a
Ground
94
92
WS Qbf
WS 35 c fs
WS Q10
96
98
WS Q50
102
100
L e ge nd
.1187
WS Q100
.1187
104
.1187
RS = 1
Lowe Creek
0
0
A
50
B
100
Figure 5—Flow area (total) profile plot.
Flow area (sq ft)
100
200
300
400
500
600
C
150
200
Culvert
E
Main Channel Distance (ft)
D
250
F
300
G
350
Flow
H
400
Flow Area 35 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 surveyed in as the bankfull channel boundary. Only those points called out in the field and supported by further hydraulic and topographic
analyses are marked below. (continued)
Elevation (ft)
94
98
96
100
102
106
104
RS = 2
)
t
f
(
Elevation (ft)
)
t
f
n
o
i
t
a
v
e
l
E
)
t
f
(
Site Evaluations
A—339
r
d
y
H
s
u
i
d
a
R
.
P
.
W
0
20
40
60
80
100
120
0
A
50
0
0
A
50
Figure 7—Hydraulic radius.
Hydraulic radius (ft)
2
4
6
8
10
12
Figure 6—Wetted perimeter.
W.P. total (ft)
)
t
f
(
A—340
l
a
t
o
T
)
t
f
(
B
B
100
100
C
C
150
150
200
Culvert
E
200
Culvert
E
Main Channel Distance (ft)
D
Main Channel Distance (ft)
D
250
F
250
F
300
G
300
G
350
Flow
H
350
Flow
H
400
Legend
Hydr Radius 35 cfs
Hydr Radius Qbf
Hydr Radius Q10
Hydr Radius Q50
Hydr Radius Q100
400
W.P. Total 35 cfs
W.P. Total Qbf
W.P. Total Q10
W.P. Total Q50
W.P. Total Q100
Legend
Culvert Scour Assessment
Lowe Creek
x
a
M
l
h
C
h
t
p
D
p
o
T
0
20
40
60
80
100
0
A
50
0
50
100
150
D
200
Culvert
E
F
F
250
250
Main Channel Distance (ft)
200
Culvert
E
300
G
300
G
350
Flow
H
350
Flow
H
400
Legend
Max Chl Dpth Q100
400
Top Width 35 cfs
Top Width Qbf
Top Width Q10
Top Width Q50
Top Width Q100
Legend
0
Figure 9—Maximum depth.
Maximum channel depth (ft)
2
4
6
8
Main Channel Distance (ft)
Max Chl Dpth 35 cfs
Max Chl Dpth Qbf
Max Chl Dpth Q10
C
150
D
10
B
100
C
Max Chl Dpth Q50
A
B
12
14
16
Figure 8—Top width.
Top width (ft)
)
t
f
(
Lowe Creek
h
t
d
i
W
)
t
f
(
Site Evaluations
A—341
r
a
e
h
S
n
a
h
C
q
s
/
b
l
(
f
l
e
V
0
10
0
A
50
B
100
C
150
200
Culvert
E
Main Channel Distance (ft)
D
250
F
300
G
350
Flow
H
400
0
0
A
50
B
100
C
Figure 11—Velocity (channel) profile plot.
Velocity channel (ft/sec)
5
10
15
20
25
30
Figure 10—Shear stress (channel) profile.
150
200
Culvert
E
Main Channel Distance (ft)
D
250
F
300
G
350
Flow
H
400
Vel Chnl 35 cfs
Vel Chnl Qbf
Vel Chnl Q10
Vel Chnl Q50
Vel Chnl Q100
Legend
Shear Chan 35 cfs
Shear Chan Qbf
Shear Chan Q10
Shear Chan Q50
Shear Chan Q100
Legend
*Note: Shear at station 6.5 for the Q50 and Q100 are greater than 50 pounds per square foot and are therefore not shown.
Shear channel (lbs/sq ft)
l
n
h
C
)
s
/
t
f
(
A—342
20
30
40
50
Culvert Scour Assessment
Lowe Creek
Flow area (ft2)
A
B
E (culv)
H
E (Culvert)
C (DS Trans)
25%Q2
A
A
H
C (ds trans)F (us trans)
F (US Trans)
B
Figure 12—Flow area (total).
0
A
Flow
50Area (ft2)
100
150
200
B
E (culv)
A
A
H
F (US Trans)
E (Culvert)
C (DS Trans)
Qbf
C (ds trans)F (us trans)
H
100%
of the
values
B
B
50%
of the
values
E (culv)
E (Culvert)
C (DS Trans)
H
10
A
B
H
A
A
E (Culvert)
C (DS Trans)
50
C (ds trans)F (us trans)
E (culv)
Minimum value
25th percentile
F (US Trans)
Median (aka 50th percentile)
75th percentile
A
C (ds trans)F (us trans)
F (US Trans)
Maximum value
H
B
Lowe Creek
H
Box Plot Explanation
B
E (culv)
H
F (US Trans)
E (Culvert)
C (DS Trans)
100
C (ds trans)F (us trans)
H
Site Evaluations
A—343
B
B
C (DS Trans)
E (Culvert)
F (US Trans)
Hydraulic radius (ft)
A
A
B
E (culv)
H
25%Q2
C (ds trans)F (us trans)
E (Culvert)
A
Figure 14—Hydraulic radius.
0
A
B
B
B
B
B
Hydraulic Radius (ft)
2
4
6
F (US Trans)
Figure 13—Wetted perimeter.
25%Q2
C (DS Trans)
H
H
E (culv)
H
A
H
Qbf
C (ds trans)F (us trans)
E (culv)
Qbf
A
C (ds trans)F (us trans)
E (Culvert)
E (Culvert)
C (ds trans)F (us trans)
B
F (US Trans)
F (US Trans)
A
A
H
H
E (culv)
A
C (DS Trans)
C (DS Trans)
A
A
H
B
B
B
B
B
E (culv)
H
10
E (culv)
10
C (ds trans)F (us trans)
H
A
A
C (ds trans)F (us trans)
C (DS Trans)
C (DS Trans)
E (Culvert)
E (Culvert)
A
F (US Trans)
F (US Trans)
0
B
B
B
B
30
Wetted Perimeter (ft)
E (culv)
H
A
50
E (culv)
50
C (ds trans)F (us trans)
H
A
C (ds trans)F (us trans)
C (DS Trans)
C (DS Trans)
H
H
E (Culvert)
E (Culvert)
60
B
B
B
B
90
F (US Trans)
F (US Trans)
A
A
H
H
E (culv)
H
H
F (US Trans)
100
E (culv)
100
C (ds trans)F (us trans)
H
C (ds trans)F (us trans)
C (DS Trans)
C (DS Trans)
A
A
E (Culvert)
E (Culvert)
A—344
F (US Trans)
Wetted perimeter (ft)
H
120
Culvert Scour Assessment
Lowe Creek
C (DS Trans)
A
B
H
25%Q2
C (ds trans)F (us trans)
E (culv)
Figure 16—Maximum depth.
0
2
Maximum Depth (ft)
4
6
E (Culvert)
25%Q2
Figure 15—Top width.
8
E (Culvert)
A
C (ds trans)F (us trans)
A
B
B
B
B
A
A
E (culv)
F (US Trans)
F (US Trans)
H
A
Qbf
E (culv)
Qbf
C (ds trans)F (us trans)
H
A
C (ds trans)F (us trans)
E (culv)
E (Culvert)
E (Culvert)
H
F (US Trans)
F (US Trans)
H
H
H
H
A
A
C (DS Trans)
C (DS Trans)
A
A
B
B
B
B
B
A
H
10
E (culv)
10
C (ds trans)F (us trans)
H
A
A
C (ds trans)F (us trans)
E (culv)
E (Culvert)
E (Culvert)
0
F (US Trans)
F (US Trans)
40
C (DS Trans)
C (DS Trans)
H
H
Top Width (ft)
20
B
B
B
B
B
B
Maximum depth (ft)
C (DS Trans)
H
A
8. 4-11
50
E (culv)
50
C (ds trans)F (us trans)
H
A
C (ds trans)F (us trans)
E (culv)
E (Culvert)
E (Culvert)
60
B
B
B
B
80
F (US Trans)
F (US Trans)
A
A
C (DS Trans)
C (DS Trans)
H
H
E (culv)
H
H
F (US Trans)
100
E (culv)
100
C (ds trans)F (us trans)
H
C (ds trans)F (us trans)
C (DS Trans)
C (DS Trans)
A
A
E (Culvert)
E (Culvert)
Lowe Creek
F (US Trans)
Top width (ft)
H
100
Site Evaluations
A—345
F (US Trans)
E (Culvert)
C (DS Trans)
A
B
25%Q2
C (ds trans)F (us trans)
E (culv)
H
A
B
B
B
B
Figure 18—Velocity (channel).
0
C (DS Trans)
E (culv)
Qbf
E (culv)
Qbf
C (ds trans)F (us trans)
H
A
A
C (ds trans)F (us trans)
H
B
B
B
B
A
A
Velocity (ft/sec)
B
Velocity
(ft/sec)
2
4
6
8
E (Culvert)
Figure 17—Width-to-depth ratio.
25%Q2
F (US Trans)
E (Culvert)
E (Culvert)
E (culv)
B
F (US Trans)
F (US Trans)
H
H
H
H
A
A
C (DS Trans)
C (DS Trans)
A
A
C (ds trans)F (us trans)
A
E (culv)
H
10
E (culv)
10
C (ds trans)F (us trans)
H
A
A
C (ds trans)F (us trans)
E (Culvert)
E (Culvert)
H
F (US Trans)
F (US Trans)
B
B
B
B
B
A
C (DS Trans)
C (DS Trans)
H
H
E (culv)
H
A
50
50
C (ds trans)F (us trans)
E (culv)
H
A
C (ds trans)F (us trans)
E (Culvert)
E (Culvert)
0
F (US Trans)
F (US Trans)
A
A
H
H
20
Width-to-depth Ratio
B
B
B
B
40
C (DS Trans)
C (DS Trans)
A
A
E (culv)
H
H
F (US Trans)
100
E (culv)
100
C (ds trans)F (us trans)
H
C (ds trans)F (us trans)
C (DS Trans)
C (DS Trans)
60
E (Culvert)
E (Culvert)
A—346
F (US Trans)
Width-to-depth ratio
H
80
Culvert Scour Assessment
Lowe Creek
A
B
H
F (US Trans)
E (Culvert)
C (DS Trans)
25%Q2
C (ds trans)F (us trans)
E (culv)
H
0
100
200
H
C (DS Trans)
Qbf
H
400
A
A
F (US Trans)
C (ds trans)F (us trans)
E (culv)
E (Culvert)
B
300
Dis charge (cfs )
B
E (culv)
H
10
F (US Trans)
600
B
F (US Trans)
E (Culvert)
C (DS Trans)
A
50
C (ds trans)F (us trans)
E (culv)
H
H
B
DS Channel (DS pebble count) - riffle
Culvert (DS pebble count) - riffle
US Channel (DS pebble count) - step
A
A
H
E (Culvert)
C (ds trans)F (us trans)
C (DS Trans)
500
B
A
B
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
Figure 20—Excess shear stress.
Excess shear (Applied/tcrit)
Excess Shear (Applied / tcrit)
1
2
3
4
A
A
Figure 19—Shear stress (channel).
0
A
5
Shear Stress (lbs/ft2)
Shear stress (lbs/ft2)
B
Lowe Creek
10
15
20
B
H
F (US Trans)
E (Culvert)
C (DS Trans)
100
C (ds trans)F (us trans)
E (culv)
H
Site Evaluations
A—347
B
Culvert Scour Assessment
Table 3—Sum of squared height difference
Reach
XSUnit
Location
type
Culvert
Sum of squared
height difference
Within range of
channel conditions?
US
Pool
0.06
Yes
DS
Riffle
0.03
Yes
US
Pool
0.05
DS
Step
0.10
US
Pool
0.04
DS
Riffle
0.03
Upstream
Downstream
Table 4—Vertical sinuosity
Segment
LocationVertical Sinuosity (ft/ft)
A
DS channel
1.001
B
DS channel
1.009
C
DS transition
1.007
D
Culvert
1.000
E
Culvert
1.010
F
US transition
1.002
G
US channel
1.016
H
US channel
1.007
Table 5—Depth distribution
Reach
Culvert
XS
25% Q2
Location
Within range of
channel conditions?
US
1
No
DS
2
Yes
US
2
DS
2
US
3
DS
18
Upstream
Downstream
A—348
Lowe Creek
Site Evaluations
Table 6—Habitat unit composition
Percent of surface area
Reach
Pool Glide
Riffle
Step
Culvert
21%
0%
64%
3%
Upstream Channel
48%
0%
41%
11%
Downstream Channel
16%
0%
75%
2%
1.4

Residual Depth (ft)
1.2
1.0

0.8


0.6

Residual depth (ft)
0.4


0.2


Segment H
Segment G
Segment F
US Transition
Segment E
Culvert
Segment B
Segment D
Culvert
Segment A
Segment C
DS Transition
Segment B
Segment A
0.0
Culvert
Culvert
Segment G Segment H
Transition Segment D: Segment E:
Transition
Segment
F:
US
Segment C: DS
Figure 21—Residual depths.
Table 7—Bed material sorting and skewness
Reach
XSUnit Sorting
Location Type
Culvert
Within range Skewness Within range
of channel
of channel
conditions?
conditions?
US
Pool
1.50
Yes
0.13
Yes
DS
Riffle
1.47
Yes
0.26
Yes
US
Pool
1.59
0.12
DS
Step
1.25
0.14
US
Pool
1.55
0.31
DS
Riffle
2.34
0.37
Upstream
Downstream
Lowe Creek
A—349
Culvert Scour Assessment
Table 8—Large woody debris
Reach
Pieces/Channel Width
Culvert
0.34
`
Upstream
3.43
Downstream
4.22
Terminology:
US = Upstream
DS = Downstream
RR = Reference reach
XS = Cross section
A—350
Lowe Creek
Site Evaluations
View upstream through culvert.
View downstream through culvert.
View downstream of culvert inlet.
View of undercut left bank footing at upstream
end of culvert.
Downstream reference reach.
Upstream reference reach.
Lowe Creek
A—351
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 C las s (mm)
C ount
Item %
C umulative %
0
1
1
1
1
3
1
3
8
9
8
11
7
11
14
9
4
0
0
0
0%
1%
1%
1%
1%
3%
1%
3%
9%
10%
9%
12%
8%
12%
15%
10%
4%
0%
0%
0%
0%
1%
2%
3%
4%
8%
9%
12%
21%
30%
39%
51%
59%
71%
86%
96%
100%
100%
100%
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
Bedrock
100%
14
90%
80%
Frequency
12
70%
10
60%
8
50%
40%
Frequency
6
30%
4
20%
2
Cumulative Frequency
10%
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
11.3-16
5.7-8
<2
4-5.7
<2
0%
2-4
0
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
13
40
120
349
500
900
A—352
Cumulative Frequency
16
Material
P erc ent C ompos ition
Sand
Gravel
Cobble
Boulder
Bedrock
0%
30%
40%
29%
0%
Sorting Coefficient:
1.59
Skewness Coefficient: 0.12
Lowe 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)
C ount
Item %
C umulative %
0
0
1
0
0
0
0
0
4
5
9
6
12
14
12
13
11
0
0
0%
0%
1%
0%
0%
0%
0%
0%
5%
6%
10%
7%
14%
16%
14%
15%
13%
0%
0%
0%
0%
0%
1%
1%
1%
1%
1%
1%
6%
11%
22%
29%
43%
59%
72%
87%
100%
100%
100%
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
Bedrock
100%
16
14
Frequency
60%
10
40%
8
Frequency
6
20%
4
Cumulative Frequency
0%
2
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
-20%
2-4
0
2-4
4 - 5.7
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
43
78
210
500
600
700
Lowe Creek
Cumulative Frequency
80%
12
Material
P erc ent C ompos ition
Sand
Gravel
Cobble
Boulder
Bedrock
0%
11%
47%
41%
0%
Sorting Coefficient:
1.25
Skewness Coefficient: 0.14
A—353
Culvert Scour Assessment
Material
Frequency
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
1
1
1
1
3
2
5
7
7
19
9
17
9
3
9
2
0
0
0
1%
1%
1%
1%
1%
3%
2%
5%
7%
7%
20%
9%
18%
9%
3%
9%
2%
0%
0%
0%
1%
2%
3%
4%
5%
8%
10%
15%
23%
30%
49%
59%
76%
86%
89%
98%
100%
100%
100%
100%
20
100%
18
90%
16
80%
14
70%
12
60%
10
50%
8
Frequency
40%
Cumulative Frequency
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
<2
11.3-16
0%
16-22.6
0
5.7-8
10%
8-11.3
2
2-4
20%
4-5.7
30%
4
<2
6
Cumulative Frequency
Cross Section: Culvert – Upstream Pebble Count
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
35
100
236
470
600
A—354
Material
P erc ent C ompos ition
Sand
Gravel
Cobble
Boulder
Bedrock
1%
29%
56%
14%
0%
Sorting Coefficient:
1.50
Skewness Coefficient: 0.13
Lowe Creek
Site Evaluations
Material
S ize C las s (mm)
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
C ount
Item %
C umulative %
1
1
0
0
1
2
3
2
5
7
7
4
16
13
14
14
4
0
0
0
1%
1%
0%
0%
1%
2%
3%
2%
5%
7%
7%
4%
17%
14%
15%
15%
4%
0%
0%
0%
1%
2%
2%
2%
3%
5%
9%
11%
16%
23%
31%
35%
52%
66%
81%
96%
100%
100%
100%
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
Bedrock
18
100%
16
90%
14
80%
70%
Frequency
12
60%
10
50%
8
Frequency
6
40%
30%
Cumulative Frequency
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
<2
8-11.3
0%
11.3-16
0
5.7-8
10%
4-5.7
2
<2
20%
2-4
4
Cumulative Frequency
Cross Section: Culvert – Downstream Pebble Count
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
18
49
165
382
504
950
Lowe Creek
Material
P erc ent C ompos ition
Sand
Gravel
Cobble
Boulder
Bedrock
1%
22%
43%
34%
0%
Sorting Coefficient:
1.47
Skewness Coefficient: 0.26
A—355
Culvert Scour Assessment
Material
Frequency
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 %
0
1
0
1
4
4
3
10
5
10
8
14
19
11
6
3
0
0
0
0
0%
1%
0%
1%
4%
4%
3%
10%
5%
10%
8%
14%
19%
11%
6%
3%
0%
0%
0%
0%
0%
1%
1%
2%
6%
10%
13%
23%
28%
38%
46%
61%
80%
91%
97%
100%
100%
100%
100%
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
20
100%
18
90%
16
80%
14
70%
12
60%
10
50%
8
Frequency
6
40%
30%
4
20%
2
10%
Cumulative Frequency
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
11.3-16
16-22.6
5.7-8
8-11.3
2-4
<2
4-5.7
0%
<2
0
Cumulative Frequency
Cross Section: Downstream Reference Reach – Upstream Pebble Count
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
1024
2048
- 2048
- 4096
Particle Size Category (mm)
Particle Size Category (mm)
S ize C las s
S ize perc ent finer
than (mm)
D5
D16
D50
D84
D95
D100
11
23
100
210
340
420
A—356
Material
P erc ent C ompos ition
Sand
Gravel
Cobble
Boulder
Bedrock
0%
38%
53%
9%
0%
Sorting Coefficient:
1.55
Skewness Coefficient: 0.31
Lowe Creek
Site Evaluations
Cross Section: Downstream 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)
C ount
Item %
C umulative %
8
1
0
3
0
2
8
9
5
9
3
13
9
8
12
7
3
0
0
0
8%
1%
0%
3%
0%
2%
8%
9%
5%
9%
3%
13%
9%
8%
12%
7%
3%
0%
0%
0%
8%
9%
9%
12%
12%
14%
22%
31%
36%
45%
48%
61%
70%
78%
90%
97%
100%
100%
100%
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
Bedrock
100%
14
90%
12
70%
60%
Frequency
8
50%
6
Frequency
40%
30%
4
20%
2
Cumulative Frequency
80%
10
Cumulative Frequency
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
11.3-16
16-22.6
5.7-8
8-11.3
2-4
<2
4-5.7
0%
<2
0
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
1
18
100
300
430
750
Lowe Creek
Material
P erc ent C ompos ition
Sand
Gravel
Cobble
Boulder
Bedrock
8%
37%
33%
22%
0%
Sorting Coefficient:
2.34
Skewness Coefficient: 0.37
A—357