Culvert Scour Assessment
Youngs Creek
Site Information
Site Location:
Willamette NF, Forest Rd 21
Year Installed:
Circa 2002
Lat/Long:
122°26’10.61”W
43°30’40.77”N
Watershed Area (mi2): 2.92
Stream Slope (ft/ft)1: 0.0635
Channel Type: Step-pool
Bankfull Width (ft): 13.5
Survey Date:
March 21 2007
1Water surface slope extending up to 20 channel widths up and downstream of crossing.
Culvert Information
Culvert Type:
Pipe arch
Culvert Material:Annular CMP
Culvert Width:
14 ft
Outlet Type:
Mitered
Culvert Length:
62 ft
Inlet Type:
Mitered
Pipe Slope (structure slope): 0.067
Culvert Bed Slope: 0.028
(First hydraulic control upstream of inlet to first hydraulic control downstream of outlet.)
Culvert width as a percentage of bankfull width: 1.02
Alignment Conditions: May have been constructed in alignment with previous channel location but
channel adjustment upstream has resulted in the culvert being off-alignment. Scour of culvert bed on
left side at inlet may be partially due to alignment.
Bed Conditions: Well-graded bed material distribution in culvert. Large cobbles/boulders forming
steps.
Pipe Condition: Some structure joints open but not leaking. Little to no rust.
Hydrology
Discharge (cfs) for indicated recurrence interval
25% 2-yr
Qbf2
2-year
5-year
10-year
50-year
100-year
21
60
85
135
170
250
286
2
Bankfull flow estimated by matching modeled water surface elevations to field-identified bankfull elevations.
A—480
Youngs Creek
Site Evaluations
Points represent survey points
Figure 1—Plan view map.
Youngs Creek
A—481
Culvert Scour Assessment
History
The Youngs Creek culvert was installed in 2002
and replaced a smaller, closed-bottom pipe.
Bed material was placed into the culvert during
construction, and is assumed to have been
sourced from the channel bed beneath the
previous culvert. There was no sorting or grading
of material during placement and no bedforms or
banks were constructed in the culvert. The culvert
was placed on the existing horizontal alignment
of the old structure and was placed on a vertical
alignment between the lower and upper channel
slopes. It is possible that the outlet scour pool
was filled during construction.
The culvert lost most of the placed material at
some point after construction. Since then, in the
last year or two, stream headcutting and channel
edge adjustment sediments have been deposited
in the culvert. The culvert has not experienced
overtopping. There has been no significant
maintenance or management of the site since
construction.
The above information was furnished by
Kim Johansen, USFS.
An assessment of nearby stream gauges
suggests that nothing more than a 5-year
recurrence interval event has occurred in the
region since construction.
Site Description
The Youngs Creek culvert is a large pipe arch
mitered to conform to the roadfill. There are a
series of cascades and steps just upstream of the
inlet to the culvert. This steep channel transitions
to a flatter slope through a scour pool exposing
the bottom of the pipe through the inlet. Below
the inlet, material from upstream has deposited
on top of the original fill, altering the grade.
Grade through the culvert is controlled by the
downstream aggradation of material, evident by
the drop in channel elevation at the outlet.
A—482
The upstream representative reach was located
above a long cascade. The representative
segment consisted of a series of log and rock
steps interspersed by plunge pools, backwater
pools, and riffles. Small boulders and large
cobble comprised the majority of the bed, with
the deposition of small gravels and even some
fines in the backwater pools. With the exception
of a narrow active terrace along the right bank,
the channel abutted the valley walls. Downed
trees were prevalent through this reach, adding
structure to the channel and providing cover.
Downstream of the culvert, the channel flows
through oversized angular rocks which appear to
be sourced from either the culvert or the adjacent
banks which were lined with riprap. Riprap lines
both banks upstream and downstream of the
culvert. Debris from roadside clearing covered
the section of channel downstream of the outlet.
Below this, the channel consisted of a series
of steep riffles interspersed by pools. A tall
terrace along the left bank confines flows to the
channel. Below the downstream boundary of the
downstream reach, the channel opens up to a
wide flood plain before joining the Middle Fork
Willamette. While some wood was present in the
channel, it did not serve a structural role as it did
in the upstream reach.
The crossing is located in an area of gradual
valley transition from the Youngs Creek stream
valley into the broad flood-plain valley of the
Middle Fork Willamette. The greatest transition
occurs a couple hundred feet downstream of the
culvert.
Survey Summary
Fourteen cross sections and a longitudinal profile
were surveyed along Youngs Creek in March
2007 to characterize the culvert, an upstream
reference reach, and a downstream reference
reach. Representative cross sections were
taken in the culvert through a pool/glide and at
a steep riffle/step. One additional cross section
Youngs Creek
Site Evaluations
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.
Representative cross sections in the upstream
channel were taken through a step and between
steps. An additional two sections were taken
to characterize the upstream and downstream
boundaries of the representative reach.
Representative cross sections in the downstream
channel were taken through two riffles. An
additional two sections were taken to characterize
the upstream and downstream boundaries of the
reach.
Profile Analysis Segment Summary
The profile analysis resulted in a total of nine
profile segments. The two segments downstream
of the outlet, which had similar gradient, were
not combined in order to separate out the outlet
transition segment for analysis. The culvert
consisted of one profile segment. The culvert
segment had gradient comparable to one
representative profile segment in the upstream
channel. Two upstream transition segments
were each comparable to one representative
profile segment in the upstream channel. The
downstream transition segment was comparable
to two representative profile segments, one in the
upstream channel and one in the downstream
channel. See figure 2 and table 1.
Scour Conditions
Observed conditions
Structure scour – This closed-bottom culvert has
been scoured to the base at the upstream end
(on right bank for 2 feet and on left bank for 20
feet). The main flow is along the side/base of the
culvert on the left side at the upstream end and
along the right side at the downstream end.
Youngs Creek
Culvert-bed adjustment – According to the
structure designer, originally placed material
scoured out of the pipe and it subsequently
refilled. Slope measurements indicate there
has been a flattening of the culvert bed
profile (assuming the original culvert bed
was constructed at the same gradient as
the structure). The pipe slope is 6.7 percent
compared to a bed slope of 2.8 percent.
Profile characteristics – The profile has a concave
shape through the crossing, with the maximum
concavity occurring at the inlet and just upstream.
The profile shape may be partly due to the
natural valley transition occurring in this area as
the Youngs Creek valley meets the broad valley
of the Middle Fork Willamette. However, site
observations suggest that much of the shape is
also due to crossing-related channel incision at
the inlet and upstream. The culvert may have
been placed lower in the profile than the original
stream. This could relate to channel adjustments
from the previous culvert or may also be a result
of restrictions in height imposed by the height of
the road prism.
Residual depths – Culvert residual depths have
a similar and slightly greater range than those in
the representative profile segment (F) (figure 21).
The upstream transition segments (D and E) have
greater residual depths than the corresponding
profile segment (I), but there was only one
residual depth in segment I. The downstream
transition segment had lower residual depths than
corresponding profile segments.
Substrate – Culvert bed material distributions are
similar to the natural channel, with generally more
boulder-sized material in the natural channel.
Pebble counts are provided at the end of this
summary. Bed-material sorting in the culvert
was lower than the range found in the natural
channel but values did not diverge from the range
significantly. Culvert-skewness values were within
the range of the natural channel.
A—483
Culvert Scour Assessment
Predicted conditions
Cross-section characteristics – Cross-section
characteristics vary between the culvert and the
corresponding profile segment (F) for most of
the cross-section metrics beginning at or above
the Q10 (figures 5 through 9 and 12 through 17).
These results reflect the flow contraction created
by the pipe. The upstream- and downstreamtransition segments have values that are mostly
within the range of their corresponding profile
segments, except the upstream transitions have
lower widths and greater depths than the natural
channel at high flows.
Shear stress – The range of shear stress in the
culvert becomes less than that of the natural
channel segment (F) as flows increase above the
25-percent Q2, but maximum shear stress values
remain similar (figures 10 and 19). Shear stress
in the upstream transition segment E becomes
greater than the corresponding profile segment
(I) above the Qbf, but the other transition segment
(D downstream) is within the range of segment
I. Shear stress in the downstream transition
remains within the range of the corresponding
profile segments for all modeled flows.
Excess shear – The excess shear analysis
suggests that the culvert excess shear may be
at the lower end of the range of that found in the
natural channel (figure 20).
Velocity – Velocity in the culvert has a broader
range of that found in the natural channel but the
median values remain similar for all flows (figures
11 and 18).
Scour summary
Original material has scoured out of the pipe but
has been replaced by material from upstream.
This is an acceptable scenario for a streamsimulation type design; except that the new
culvert bed has adjusted to a flatter slope than
the originally constructed bed (assuming the
original culvert bed was constructed at the same
gradient as the structure). There is now scour to
A—484
the culvert base at the upstream end of the pipe
and aggraded material at the downstream end.
The reduced slope of the bed reduces shear
stress and may prevent the efficient transport
of material through the pipe. Slope adjustments
may be related to the culvert being placed at a
low elevation in the profile, possibly due to height
limitations imposed by the height of the road
prism.
Site observations suggest that the low elevation
of the inlet may have initiated scour at the inlet
area, which triggered upstream incision. Material
sourced from the bed and banks as a result
of this incision then collected upstream of the
inlet (visible as cobbles and small boulders just
upstream of the inlet), possibly during a large
event when the culvert was backwatered (debris
plugging?). The aggraded material upstream of
the inlet resulted in lateral boundary adjustment,
resulting in the sinuous planform upstream of the
inlet.
The historical occurrence of material scouring
out of the culvert indicates a risk of loss of bed
material; however, the excess shear analysis and
the fact that the culvert re-filled suggest that any
scour will likely be replaced by material moving in
from upstream.
AOP Conditions
Cross-section complexity – The sum of squared
height difference in the downstream culvert cross
section is within the range of those in the channel
(table 3). The sum of squared height difference in
the upstream culvert cross section is lower than
the range in the natural channel, but the habitat
units differ (pool in culvert versus riffle/step in
channel), making comparisons difficult.
Profile complexity – Vertical sinuosity in the
culvert is lower than that found in the natural
channel (table 4). The abundance of wood in the
natural channel may account for greater profile
complexity.
Youngs Creek
Site Evaluations
Depth distribution – Depth distribution (at the
25-percent Q2) in the culvert is at the upper
range or above that which is found in the natural
channel (table 5). The high values in the culvert
are related to the aggraded bar material that is
just inundated at the 25-percent Q2 (see figure 4).
Habitat units – The culvert has a greater
abundance of pool habitat compared to the
natural channel (table 6), which is related to the
flatter profile that allows for a long pool in the
upstream portion of the culvert that is in contrast
to the short step-pools typically found in the
natural channel.
Residual depths – Culvert residual depths have
a similar and slightly greater range than those in
the representative profile segment (F) (figure 21).
The upstream transition segments (D and E) have
greater residual depths than the corresponding
profile segment (I), but there was only one
residual depth in segment I. The downstream
transition segment had lower residual depths than
corresponding profile segments.
Bed material – Culvert bed material distributions
are similar to the natural channel, with generally
more boulder-sized material in the natural
channel. Pebble counts are provided at the end of
this summary.
Large woody debris – There was no LWD present
in the culvert (Table 8). The representative
channel had moderate to high LWD abundance.
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.
Youngs Creek
AOP summary
Scour to the base in the upstream portion of
the culvert may create lack of bed roughness
elements for fish passage. The thalweg also
runs along the edge or base of the culvert for
much of the length, again indicating a lack of
roughness and velocity refuge for migrating
fish. And there are fewer boulders in the culvert
that are important for providing velocity refuge.
Profile complexity is less in the culvert; however,
depth distribution is good in the culvert at the 25
percent Q2, suggesting the availability of channel
margin habitat for passage at this flow. At the low
flow level during the survey, there was aggraded
material along the banks in the culvert that could
provide for passage of terrestrial organisms;
however, the banks were not continuous through
the culvert on either side.
Design Considerations
Inlet scour, upstream incision, and upstream
lateral boundary adjustment could likely have
been reduced by raising the invert elevation
of the culvert bed; however, this may have
required raising the elevation of the road prism at
considerable expense. Adding stable, embedded
boulders into the culvert bed would reduce risk
of scour to the culvert base, which is currently
occurring. Use of an open-bottom arch at this
location would allow for the construction of stable
bed elements while not significantly reducing
culvert capacity. Creation of continuous banks
along the culvert walls would reduce the smooth
wall-based flow currently occurring along much
of the length and would also benefit terrestrial
organism passage.
A—485
A—486
Relative elevation (ft)
500
XS 1:
Pebble count
(riffle)
450
A
400
XS 2:
Pebble count
(riffle)
Table 1—Segment Comparisons
XS 5:
Pebble count
(riffle/step)
XS 9
A
G
D o w n s trea m T ra n s itio n
B
B
E
200
XS 10
1.6%
26.5%
32.7%
12.3%
% D ifferen c e in
G ra d ien t
27.4%
D is ta nc e a long bed (feet)
250
XS 8
D
R epres en ta tiv e
C h a n n el S eg men t
F
300
XS 6:
Pebble count
(pool)
XS 7
I
I
C
C ulvert
D
E
U ps trea m T ra n s itio n
C u lv ert S eg men t
C
350
XS 4
S egment G radient
0.058
0.059
0.028
0.131
0.101
0.039
0.081
0.034
0.088
XS 3
B
Figure 2—Youngs Creek long profilet.
90
95
100
S egment
L ength (ft)
58
52
90
24
75
58
34
22
44
Representative Channel
S egment
A
B
C
D
E
F
G
H
I
105
Relative elevation (feet)
110
115
120
125
130
XS 11
150
F
XS 13:
Pebble count
(riffle/step)
100
Representative Channel
XS 12:
Pebble count
(riffle/step)
G
H
50
I
XS 14
0
Culvert Scour Assessment
Youngs Creek
n
o
i
t
a
v
e
l
E
)
t
f
(
Youngs Creek
0.1417 – 0.1432
0.1415 – 0.1517
0.0929 – 0.1517
0.1206 – 0.136
0.1358 – 0.136
0.1335 – 0.1369
0.1245 – 0.1369
0.1395 – 0.1445
A
B
C
D
E
F
G
I
SegmentRange of Manning's n values1
1
1
1
2
2
4
2
1
# of measured XSs
6
6
9
9
4
10
7
7
# of interpolated XSs
1
90
0
8
.
1
9
.
1
*
2
.
3 3
Figure 3—HEC-RAS profile.
Elevation (ft)
100
110
120
130
*
9 3
. .
4 5
6
5
2
.
6
5
.
6
6
.
7
4
.
8
200
4
.
9
5
.
0
1
Main Channel Dis tance (ft)
*
1 2
. .
9 9
*
6
6
6
6
8
. 0
9 1
*
3
3
3
3
.
1
1
1
1
300
*
6
6
1
6
.
1
1
9
.
1
1
*
5
0
.
2
1
1
.
2
1
2
.
2
1
4
.
2
1
5
.
2
1
*
5
2
.
3
1
*
5
5
.
3
1
Stations with decimal values are interpolated cross-sections placed along the surveyed profile.
*
5
5
3 5 5 7
. . . .
3 3 4 4
100
*
3
3
3
3
6 7
. .
9 9
6
.
3
1
400
8
.
3
1
*
5
8
.
3
1
9
.
3 4
1 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.
Table 2—Summary of segments used for comparisons
1
.
4
1
500
Ground
W S 21 c fs
W S Qbf
W S Q10
W S Q50
W S Q100
L e ge nd
Site Evaluations
A—487
n
o
i
t
a
v
e
l
E
)
t
f
(
A—488
Elevation (ft)
n
o
i
t
a
v
e
l
E
)
t
f
(
0
0
.1369
10
10
.1445
20
.1369
20
30
Elevation (ft)
Station (ft)
30
RS = 12
Station (ft)
.1445
40
.1369
40
50
50
.1445
60
60
B a n k S ta
L e ve e
G ro u n d
W S 2 1 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 21 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
(
n
o
i
t
a
v
e
l
E
Elevation (ft)
Elevation (ft)
121
120
119
118
117
116
115
114
113
112
111
125
124
123
122
121
120
119
118
117
116
115
0
0
.136
.1245
10
10
20
.136
20
.1245
Station (ft)
30
RS = 11
Station (ft)
30
RS = 13
40
40
.1245
.136
50
50
60
60
Bank St a
Ground
WS 21 c fs
WS Qbf
WS Q10
WS Q50
WS Q100
L e ge nd
Bank St a
Ground
WS 21 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.
123
122
121
120
119
118
117
116
115
114
113
130
129
128
127
126
125
124
123
122
121
120
RS = 14
)
t
f
(
Culvert Scour Assessment
Youngs Creek
)
t
f
(
Youngs Creek
Elevation (ft)
n
o
i
t
a
v
e
l
E
)
t
f
(
n
o
i
t
a
v
e
l
E
0
0
10
10
.136
.136
20
20
.136
Elevation (ft)
Station (ft)
30
.136
RS = 8
Station (ft)
30
40
40
.136
50
50
.136
60
60
Bank St a
Ground
WS 21 c fs
WS Qbf
WS Q10
WS Q50
WS Q100
L e ge nd
Bank St a
Ground
WS 21 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
(
n
o
i
t
a
v
e
l
E
Elevation (ft)
Elevation (ft)
110
109
108
107
106
105
104
103
102
101
100
0
0
113
112
111
110
109
108
107
106
105
104
103
10
.0968
10
.136
20
20
Station (ft)
30
.0968
RS = 7
Station (ft)
30
.136
RS = 9
40
40
.0968
50
50
.136
60
L e ge nd
60
B a n k S ta
In e ff
G ro u n d
W S 2 1 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 21 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)
110
109
108
107
106
105
104
103
102
101
100
118
117
116
115
114
113
112
111
110
109
108
RS = 10
)
t
f
(
Site Evaluations
A—489
)
t
f
(
A—490
Elevation (ft)
n
o
i
t
a
v
e
l
E
)
t
f
(
n
o
i
t
a
v
e
l
E
0
10
.1362
-10
20
0
Elevation (ft)
Station (ft)
30
.1362
RS = 4
Station (ft)
10
40
20
50
.1362
30
40
60
B a n k S ta
In e ff
G ro u n d
W S 2 1 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 21 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
(
n
o
i
t
a
v
e
l
E
Elevation (ft)
Elevation (ft)
106
105
104
103
102
101
100
99
98
97
96
0
109
108
107
106
105
104
103
102
101
100
99
-20
10
.1449
-10
20
0
Station (ft)
30
.1449
RS = 3
Station (ft)
10
.1006
40
20
RS = 5
Note: n values for first profile.
50
.1449
30
60
40
L e ge nd
Bank St a
Ground
WS 21 c fs
WS Qbf
WS Q10
WS Q50
WS Q100
L e ge nd
Bank St a
Ground
WS 21 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)
108
107
106
105
104
103
102
101
100
99
98
110
109
108
107
106
105
104
103
102
101
100
-20
.1034
RS = 6
Note: n values for first profile.
)
t
f
(
Culvert Scour Assessment
Youngs Creek
Youngs Creek
n
o
i
t
a
v
e
l
E
)
t
f
(
.
1
4
1
5
20
30
.1415
Elevation (ft)
Station (ft)
40
50
.1415
60
70
Bank St a
Ground
WS 21 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)
102
101
100
99
98
97
96
95
94
93
92
20
30
.1426
40
Station (ft)
50
.1426
RS = 1
60
70
.1426
80
Bank St a
Ground
WS 21 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. (continued)
106
105
104
103
102
101
100
99
98
97
96
10
RS = 2
)
t
f
(
Site Evaluations
A—491
w
o
l
F
a
e
r
A
q
s
(
)
t
f
A—492
.
P
.
W
l
a
t
o
T
)
t
f
(
0
0
A
B
100
0
0
A
B
Figure 6—Wetted perimeter.
W.P. total (ft)
10
20
30
40
50
100
C
Culvert
C
Culvert
Figure 5—Flow area (total) profile plot.
Flow area (sq ft)
20
40
60
80
100
120
E
300
E
300
Main Channel Distance (ft)
200
D
Main Channel Distance (ft)
200
D
F
F
Flow
G
Flow
G
400
H
400
H
I
I
500
500
W.P. Total 21 cfs
W.P. Total Qbf
W.P. Total Q10
W.P. Total Q50
W.P. Total Q100
Legend
Flow Area 21 cfs
Flow Area Qbf
Flow Area Q10
Flow Area Q50
Flow Area Q100
Legend
Culvert Scour Assessment
Youngs Creek
Youngs Creek
p
o
T
h
t
d
i
W
0
1
2
3
4
5
0
A
B
0
100
200
D
E
300
F
Flow
G
Flow
G
H
400
400
H
I
I
500
500
Top Width Q100
Legend
Hydr Radius 21 cfs
Hydr Radius Qbf
Hydr Radius Q10
Hydr Radius Q50
Hydr Radius Q100
Legend
5
10
Figure 8—Top width.
Top width (ft)
15
20
25
Main Channel Distance (ft)
Top Width 21 cfs
Top Width Qbf
Top Width Q10
Culvert
C
300
F
30
B
E
Main Channel Distance (ft)
200
D
Top Width Q50
A
100
Culvert
C
35
40
45
Figure 7—Hydraulic radius.
Hydraulic radius (ft)
)
t
f
(
r
d
y
H
s
u
i
d
a
R
)
t
f
(
Site Evaluations
A—493
r
a
e
h
S
n
a
h
C
q
s
/
b
l
(
0
1
2
3
4
5
6
0
A
B
A—494
0
A
B
100
100
Culvert
C
Culvert
C
Figure 10—Shear stress (channel) profile.
Shear channel (lb/sq ft)
0
5
10
15
20
25
Figure 9—Maximum depth.
Maximum channel depth (ft)
)
t
f
x
a
M
l
h
C
h
t
p
D
)
t
f
(
E
300
E
300
Main Channel Distance (ft)
200
D
Main Channel Distance (ft)
200
D
F
F
Flow
G
Flow
G
H
400
400
H
I
I
500
500
Shear Chan 21 cfs
Shear Chan Qbf
Shear Chan Q10
Shear Chan Q50
Shear Chan Q100
Legend
Max Chl Dpth 21 cfs
Max Chl Dpth Qbf
Max Chl Dpth Q10
Max Chl Dpth Q50
Max Chl Dpth Q100
Legend
Culvert Scour Assessment
Youngs Creek
Youngs Creek
l
e
V
l
n
h
C
)
s
/
t
f
(
0
0
A
B
100
Culvert
C
Figure 11—Velocity (channel) profile plot.
Velocity channel (ft/s)
1
2
3
4
5
6
7
8
E
300
Main Channel Distance (ft)
200
D
F
Flow
G
400
H
I
500
Vel Chnl 21 cfs
Vel Chnl Qbf
Vel Chnl Q10
Vel Chnl Q50
Vel Chnl Q100
Legend
Site Evaluations
A—495
Flow area (ft2)
A
F
G
G
D (US Trans)
25%Q2
I
I
F
B (DS Trans)
C (Culvert)
(us trans)
B (ds trans)
D (usE trans)
C (culv)
E (US Trans)
Figure 12—Flow area (total).
0
20
A
Flow Area (ft2)
40
60
80
A
G
G
E (US Trans)
D (US Trans)
Qbf
I
I
B (DS Trans)
C (Culvert)
(us trans)
B (ds trans)
D (usE trans)
C (culv)
F
F
A
50%
of the
values
A
C (culv)
F
G
D (US Trans)
10
I
A
Minimum value
25th percentile
C (culv)
G
D (US Trans)
50
I
I
G
C (Culvert)
B (DS Trans)
(us trans)
B (ds trans)
D (usE trans)
F
F
Median (aka 50th percentile)
75th percentile
I
G
F
C (Culvert)
(us trans)
B (ds trans)
D (usE trans)
B (DS Trans)
Maximum value
E (US Trans)
A
A—496
100
120
100%
of the
values
E (US Trans)
A
Box Plot Explanation
A
G
G
E (US Trans)
D (US Trans)
100
I
I
F
B (DS Trans)
C (Culvert)
(us trans)
B (ds trans)
D (usE trans)
C (culv)
F
Culvert Scour Assessment
Youngs Creek
A
G
E (US Trans)
D (US Trans)
F
B (DS Trans)
C (Culvert)
A
D (US Trans)
F
G
25%Q2
(us trans)
B (ds trans)
D (usE trans)
C (culv)
E (US Trans)
Figure 14—Hydraulic radius.
0
Hydraulic Radius (ft)
1
2
3
4
5
F
Figure 13—Wetted perimeter.
25%Q2
G
I
A
A
C (culv)
C (Culvert)
Qbf
F
G
F
G
Qbf
(us trans)
B (ds trans)
D (usEtrans)
C (culv)
C (Culvert)
I
(us trans)
B (ds trans)
D (usEtrans)
D (US Trans)
D (US Trans)
I
I
E (US Trans)
E (US Trans)
C (culv)
A
B (DS Trans)
B (DS Trans)
F
F
(us trans)
B (ds trans)
D (usE trans)
I
I
A
A
A
C (culv)
F
G
F
G
10
(us trans)
B (ds trans)
D (usEtrans)
C (culv)
10
I
(us trans)
B (ds trans)
D (usE trans)
C (Culvert)
C (Culvert)
G
D (US Trans)
D (US Trans)
G
G
E (US Trans)
E (US Trans)
I
I
F
F
F
B (DS Trans)
B (DS Trans)
G
G
A
A
A
I
A
A
A
A
0
C (culv)
F
G
F
G
50
(us trans)
B (ds trans)
D (usEtrans)
C (culv)
50
I
(us trans)
B (ds trans)
D (usE trans)
C (Culvert)
C (Culvert)
20
D (US Trans)
D (US Trans)
I
I
E (US Trans)
E (US Trans)
30
B (DS Trans)
B (DS Trans)
F
F
40
I
A
A
A
A
50
C (culv)
F
G
F
G
100
(us trans)
B (ds trans)
D (usE trans)
C (culv)
100
I
I
I
(us trans)
B (ds trans)
D (usE trans)
C (Culvert)
C (Culvert)
A
A
D (US Trans)
D (US Trans)
G
G
E (US Trans)
E (US Trans)
I
I
F
F
10 Perimeter (ft)
Wetted
Hydraulic radius (ft)
B (DS Trans)
B (DS Trans)
B (DS Trans)
G
G
Youngs Creek
I
Wetted perimeter (ft)
C (Culvert)
Site Evaluations
A—497
B (DS Trans)
C (culv)
Maximum depth (ft)
D (US Trans)
A
C (Culvert)
C (culv)
C (Culvert)
F
G
25%Q2
(us trans)
B (ds trans)
D (usE trans)
D (US Trans)
Figure 16—Maximum depth.
0
1
Max Depth (ft)
2
3
4
5
6
F
25%Q2
I
A
A
A
C (culv)
G
F
G
Qbf
(us trans)
B (ds trans)
D (usEtrans)
C (culv)
Qbf
I
(us trans)
B (ds trans)
D (usEtrans)
F
I
A
A
A
A
A
A
A
E (US Trans)
E (US Trans)
Figure 15—Top width.
B (DS Trans)
F
(us trans)
B (ds trans)
D (usE trans)
I
C (Culvert)
C (Culvert)
G
G
E (US Trans)
E (US Trans)
I
I
D (US Trans)
D (US Trans)
G
B (DS Trans)
B (DS Trans)
F
F
F
C (culv)
F
G
F
G
10
(us trans)
B (ds trans)
D (usEtrans)
C (culv)
10
I
(us trans)
B (ds trans)
D (usE trans)
C (Culvert)
C (Culvert)
G
G
E (US Trans)
E (US Trans)
I
I
D (US Trans)
D (US Trans)
A
B (DS Trans)
B (DS Trans)
F
F
0
I
A
A
A
A
10
C (culv)
F
G
F
G
50
(us trans)
B (ds trans)
D (usEtrans)
C (culv)
50
I
(us trans)
B (ds trans)
D (usE trans)
C (Culvert)
C (Culvert)
G
G
E (US Trans)
E (US Trans)
I
I
D (US Trans)
D (US Trans)
20
B (DS Trans)
B (DS Trans)
F
F
Top Width (ft)
I
A
A
A
A
30
C (culv)
F
G
G
F
G
100
(us trans)
B (ds trans)
D (usE trans)
C (culv)
100
I
I
I
(us trans)
B (ds trans)
D (usE trans)
C (Culvert)
C (Culvert)
G
G
D (US Trans)
D (US Trans)
I
I
E (US Trans)
E (US Trans)
40
B (DS Trans)
B (DS Trans)
F
F
A—498
G
Top width (ft)
I
50
Culvert Scour Assessment
Youngs Creek
D (US Trans)
F
B (DS Trans)
A
C (Culvert)
C (culv)
C (Culvert)
F
G
25%Q2
(us trans)
B (ds trans)
D (usE trans)
D (US Trans)
Figure 18—Velocity (channel).
0
E (US Trans)
I
A
A
F
G
F
G
Qbf
(us trans)
B (ds trans)
D (usEtrans)
C (culv)
Qbf
I
I
A
A
A
A
A
A
Velocity
2 (ft/sec)
4
6
8
F
Figure 17—Width-to-depth ratio.
C (Culvert)
C (Culvert)
E (US Trans)
25%Q2
D (US Trans)
D (US Trans)
G
G
C (culv)
E (US Trans)
I
I
E (US Trans)
(us trans)
B (ds trans)
D (usEtrans)
B (DS Trans)
B (DS Trans)
F
F
(us trans)
B (ds trans)
D (usE trans)
A
C (culv)
F
G
F
G
10
(us trans)
B (ds trans)
D (usEtrans)
C (culv)
10
I
(us trans)
B (ds trans)
D (usE trans)
B (DS Trans)
B (DS Trans)
C (culv)
I
C (Culvert)
C (Culvert)
G
E (US Trans)
E (US Trans)
F
D (US Trans)
D (US Trans)
G
G
F
F
I
I
G
G
A
I
A
A
A
A
0
F
G
F
G
50
(us trans)
B (ds trans)
D (usEtrans)
C (culv)
50
I
(us trans)
B (ds trans)
D (usE trans)
C (culv)
C (Culvert)
C (Culvert)
I
I
E (US Trans)
E (US Trans)
10
D (US Trans)
D (US Trans)
30
B (DS Trans)
B (DS Trans)
F
F
40
I
A
A
A
A
50
F
G
F
G
100
(us trans)
B (ds trans)
D (usE trans)
C (culv)
100
I
I
I
(us trans)
B (ds trans)
D (usE trans)
C (culv)
C (Culvert)
C (Culvert)
60
D (US Trans)
D (US Trans)
G
G
E (US Trans)
E (US Trans)
I
I
F
F
W-D
20Ratio
Velocity (ft/sec)
A
B (DS Trans)
B (DS Trans)
G
G
Youngs Creek
I
Width-to-depth ratio
B (DS Trans)
Site Evaluations
A—499
Shear stress (lbs/ft2)
A
C (culv)
G
G
D (US Trans)
E (US Trans)
25%Q2
I
I
F
(us trans)
B (ds trans)
D (usE trans)
F
Excess shear (Applied/tcrit)
A
G
E (US Trans)
D (US Trans)
B (DS Trans)
150
200
Dis charge (cfs )
250
Qbf
G
300
I
I
F
C (Culvert)
(us trans)
B (ds trans)
D (usEtrans)
C (culv)
F
C (culv)
F
G
G
E (US Trans)
D (US Trans)
A
C (Culvert)
A
C (Culvert)
A
F
Figure 20—Excess shear stress.
E (US Trans)
50
DS Channel (DS pebble count)
Culvert (DS pebble count) - riffle/step
US Channel (DS pebble count) - riffle/step
Values of excess shear greater than 1 indicate bed movement for the D84 particle size.
F
G
G
I
I
F
(us trans)
B (ds trans)
D (usE trans)
C (culv)
D (US Trans)
US Channel (US pebble count) - riffle/step
10
I
I
(us trans)
B (ds trans)
D (usE trans)
B (DS Trans)
350
A
B (DS Trans)
Excess shear stress is the channel shear divided by the critical shear for bed entrainment of the D84 particle size.
1
0.5
Excess Shear (Applied / tcrit)
0
0
50
100
1.5
2.5
2
3.5
3
4
5
4.5
A
A
Figure 19—Shear stress (channel).
0
B (DS Trans)
5 Stress (lbs/ft2)
Shear
10
15
C (Culvert)
A—500
20
25
30
A
G
G
D (US Trans)
E (US Trans)
100
I
I
F
C (Culvert)
B (DS Trans)
(us trans)
B (ds trans)
D (usE trans)
C (culv)
F
Culvert Scour Assessment
Youngs Creek
A
Site Evaluations
Table 3—Sum of squared height difference
Reach
XSUnit
Location
type
Culvert
Sum of squared
height difference
Within range of
channel conditions?
US
Pool
0.03
No
DS
Riffle/step
0.10
Yes
US
Riffle/step
0.08
DS
Riffle/step
0.12
Riffle
0.06
Upstream
Downstream
Table 4—Vertical Sinuosity
Segment
LocationVertical Sinuosity (ft/ft)
A
DS channel
1.007
B
DS transition
1.005
C
Culvert
1.005
D
US transition
1.033
E
US transition
1.018
F
US channel
1.008
G
US channel
1.016
H
US channel
1.028
I
US channel
1.006
Table 5—Depth distribution
Reach
Culvert
XS
25% Q2
Location
Within range of
channel conditions?
US
6
Yes
DS
10
No
US
2
DS
6
Upstream
Downstream
Youngs Creek
7
A—501
Culvert Scour Assessment
Table 6—Habitat unit composition
Percent of surface area
Reach
Pool Glide
Riffle
Step
Culvert
72%
0%
28%
0%
Upstream Channel
29%
0%
39%
2%
Downstream Channel
17%
0%
83%
0%
1. 6

1. 4
1. 0











Segment F
Segment D: Segment E:
US Transition US Transition
Segment G
Segment H
Culvert
Segment B: Segment C:
DS Transition
Segment G
Segment B
DS Transition
Segment A
Segment A




0. 0
Segment E
US Transition



Segment D
US Transition
0. 2



Segment H
Segment I
0. 6
Residual depth (ft)
0. 4
Segment F
0. 8
Segment C
Culvert
Residual Depth (ft)
1. 2
Segment I
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
1.73
No
0.32
Yes
DS
Riffle/step
1.67
No
0.42
Yes
US
Riffle/step
2.10
0.36
DS
Riffle/step
1.89
0.44
US
Riffle
1.84
0.24
DS
Riffle
2.23
0.51
Upstream
Downstream
A—502
Youngs Creek
Site Evaluations
Table 8—Large woody debris
Reach
Pieces/Channel Width
Culvert
0
Upstream
1.22
Downstream
2.06
Terminology:
US = Upstream
DS = Downstream
RR = Reference reach
XS = Cross-section
View upstream towards culvert outlet.
View downstream towards culvert inlet.
View upstream from roadway.
View downstream from roadway.
Youngs Creek
A—503
Culvert Scour Assessment
Upstream reference reach.
Upstream reference reach – upstream pebble count, between steps.
Upstream reference reach – downstream pebble count, step.
Downstream reference reach – downstream pebble
count (step).
A—504
Youngs Creek
Site Evaluations
Downstream reference reach – upstream pebble count (riffle).
Downstream reference reach.
View downstream within culvert – pebble counts at flagged locations.
View upstream within culvert – pebble counts
at flagged locations.
Youngs Creek
A—505
Culvert Scour Assessment
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 %
3
7
1
5
3
6
1
2
5
6
17
9
11
12
7
3
0
0
0
0
3%
7%
1%
5%
3%
6%
1%
2%
5%
6%
17%
9%
11%
12%
7%
3%
0%
0%
0%
0%
3%
10%
11%
16%
19%
26%
27%
29%
34%
40%
57%
66%
78%
90%
97%
100%
100%
100%
100%
100%
18
100%
16
90%
14
80%
70%
Frequency
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
16-22.6
11.3-16
5.7-8
8-11.3
<2
4-5.7
<2
0%
2-4
0
Cumulative Frequency
Cross-Section: Upstream Reference Reach – 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
4
9
78
205
330
420
A—506
Sorting Coefficient:
Material
P erc ent C ompos ition
Sand
Gravel
Cobble
Boulder
Bedrock
3%
37%
50%
10%
0%
2.10
Skewness Coefficient: 0.36
Youngs Creek
Site Evaluations
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 %
2
2
1
2
0
0
1
2
3
2
3
5
9
12
8
18
15
0
0
0
2%
2%
1%
2%
0%
0%
1%
2%
4%
2%
4%
6%
11%
14%
9%
21%
18%
0%
0%
0%
2%
5%
6%
8%
8%
8%
9%
12%
15%
18%
21%
27%
38%
52%
61%
82%
100%
100%
100%
100%
20
100%
18
90%
16
80%
14
70%
12
60%
10
50%
8
Frequency
40%
6
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: Upstream Reference Reach – Downstream Pebble Count
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
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
5
54
240
520
700
700
Youngs Creek
Sorting Coefficient:
Material
P erc ent C ompos ition
Sand
Gravel
Cobble
Boulder
Bedrock
2%
15%
34%
48%
0%
1.89
Skewness Coefficient: 0.44
A—507
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 R ange (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
> 4096
C ount
Item %
C umulative %
2
3
0
5
5
7
7
3
11
6
9
8
22
11
1
3
0
0
0
0
2%
3%
0%
5%
5%
7%
7%
3%
11%
6%
9%
8%
21%
11%
1%
3%
0%
0%
0%
0%
2%
5%
5%
10%
15%
21%
28%
31%
42%
48%
56%
64%
85%
96%
97%
100%
100%
100%
100%
100%
25
100%
90%
20
70%
Frequency
15
60%
50%
10
Frequency
40%
30%
5
20%
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
16-22.6
11.3-16
5.7-8
8-11.3
<2
4-5.7
<2
0%
2-4
0
Cumulative Frequency
80%
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
6
14
74
180
249
420
A—508
Sorting Coefficient:
Material
P erc ent C ompos ition
Sand
Gravel
Cobble
Boulder
Bedrock
2%
46%
49%
4%
0%
1.73
Skewness Coefficient: 0.32
Youngs Creek
Site Evaluations
Cross-Section: Culvert – 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
1
1
2
1
8
3
7
4
8
7
6
15
15
22
6
2
0
0
0
0%
1%
1%
2%
1%
7%
3%
6%
4%
7%
6%
6%
14%
14%
20%
6%
2%
0%
0%
0%
0%
1%
2%
4%
5%
12%
15%
21%
25%
32%
39%
44%
58%
72%
93%
98%
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
25
100%
90%
20
70%
15
60%
Frequency
50%
10
Frequency
40%
30%
5
20%
Cumulative Frequency
80%
Cumulative Frequency
10%
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
5.7-8
<2
2-4
<2
8-11.3
0%
4-5.7
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
12
25
150
309
423
550
Youngs Creek
Sorting Coefficient:
Material
P erc ent C ompos ition
Sand
Gravel
Cobble
Boulder
Bedrock
0%
32%
40%
28%
0%
1.67
Skewness Coefficient: 0.42
A—509
Culvert Scour Assessment
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 %
3
1
1
3
2
1
4
4
4
9
12
12
17
12
8
3
6
0
0
0
3%
1%
1%
3%
2%
1%
4%
4%
4%
9%
12%
12%
17%
12%
8%
3%
6%
0%
0%
0%
3%
4%
5%
8%
10%
11%
15%
19%
23%
31%
43%
55%
72%
83%
91%
94%
100%
100%
100%
100%
18
100%
16
90%
14
80%
70%
Frequency
12
60%
10
50%
8
Frequency
6
40%
30%
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
Cumulative Frequency
2-4
4 - 5.7 - 8
32 -45
45-64
64- 90
8 - 11.3
90 - 128
Bedrock
11.3
16- 16
-22.6
22.6- 32
128180
- 180
256
- 256
362
- 362
- 512
512 - 1024
Particle Size Category (mm)
1024
2048
- 2048
- 4096
Partic le Siz e Category (mm)
S ize C las s
S ize perc ent finer
than (mm)
D5
D16
D50
D84
D95
D100
6
25
105
267
535
580
A—510
11.3-16
<2
16-22.6
0%
5.7-8
0
8-11.3
10%
2-4
2
4-5.7
20%
<2
4
Cumulative Frequency
Cross-Section: Downstream Reference Reach – Upstream Pebble Count
Sorting Coefficient:
Material
P erc ent C ompos ition
Sand
Gravel
Cobble
Boulder
Bedrock
3%
28%
52%
17%
0%
1.84
Skewness Coefficient: 0.24
Youngs Creek
Site Evaluations
Material
S ize C las s (mm)
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
<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 %
7
1
2
1
1
7
5
8
1
9
7
14
18
10
11
4
0
0
0
0
7%
1%
2%
1%
1%
7%
5%
8%
1%
8%
7%
13%
17%
9%
10%
4%
0%
0%
0%
0%
7%
8%
9%
10%
11%
18%
23%
30%
31%
40%
46%
59%
76%
86%
96%
100%
100%
100%
100%
100%
20
100%
18
90%
16
80%
14
70%
12
60%
10
50%
8
Frequency
40%
6
30%
4
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
11.3-16
16-22.6
5.7-8
8-11.3
2-4
4-5.7
<2
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
15
100
220
318
500
Youngs Creek
Cumulative Frequency
0%
<2
0
Cumulative Frequency
Cross-Section: Downstream Reference Reach – Downstream Pebble Count
Sorting Coefficient:
Material
P erc ent C ompos ition
Sand
Gravel
Cobble
Boulder
Bedrock
7%
33%
46%
14%
0%
2.23
Skewness Coefficient: 0.51
A—511