Culvert Scour Assessment
Transcript of Culvert Scour Assessment
A—480
Culvert Scour Assessment
Youngs Creek
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 Qbf
2 2-year 5-year 10-year 50-year 100-year
21 60 85 135 170 250 2862Bankfull flow estimated by matching modeled water surface elevations to field-identified bankfull elevations.
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Youngs Creek
Figure 1—Plan view map.
Points represent survey points
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Culvert Scour Assessment
Youngs Creek
HISTOrYThe 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 byKim 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 DeSCrIPTIOnThe 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.
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 SuMMArYFourteen 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
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Site evaluations
Youngs Creek
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 SuMMArYThe 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 COnDITIOnSObserved conditionsStructure 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.
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.
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Predicted conditionsCross-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 Q
10 (figures 5 through 9 and 12 through 17).
These results reflect the flow contraction created by the pipe. The upstream- and downstream-transition 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 Q
2, 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 Q
bf, 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 summaryOriginal material has scoured out of the pipe but has been replaced by material from upstream. This is an acceptable scenario for a stream-simulation 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
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 COnDITIOnSCross-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.
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Youngs Creek
Depth distribution – Depth distribution (at the 25-percent Q
2) 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 Q
2 (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.
AOP summaryScour 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 Q
2, 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 COnSIDerATIOnSInlet 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.
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Fig
ure
2—Y
oung
s C
reek
long
pro
filet
.
Tabl
e 1—
Seg
men
t Com
paris
ons
90
95
10
0
10
5
11
0
11
5
12
0
12
5
13
0
05
01
00
15
02
00
25
03
00
35
04
00
45
05
00
Dis
tan
ce
alo
ng
be
d (f
ee
t)
Rela
tive
elev
atio
n (f
eet)
A
C
D
E
F
G
H
I
XS 1
3:
Peb
ble
coun
t
(riffl
e/st
ep)
XS 2
:
Peb
ble
coun
t(ri
ffle)
XS 5
:
Peb
ble
coun
t
(riffl
e/st
ep)
XS 6
:
Peb
ble
coun
t
(poo
l)
XS 1
2:
Peb
ble
coun
t
(riffl
e/st
ep)
Cul
vert
Rep
rese
ntat
ive C
hann
el
Rep
rese
ntat
ive C
hann
el
BXS
1:
Peb
ble
coun
t
(riffl
e)
XS 1
4
XS 3
XS 1
1
XS 1
0
XS 9
XS 8
XS 7
XS 4
A
580.
058
B52
0.05
9C
900.
028
D24
0.13
1E
750.
101
F58
0.03
9G
340.
081
H22
0.03
4I
440.
088
Seg
men
t S
eg
me
nt
Len
gth
(ft
)S
eg
me
nt
Gra
die
nt
Relative elevation (ft)
CF
27
.4%
Up
str
ea
m T
ran
sit
ion
DI
32
.7%
EI
12
.3%
Do
wn
str
ea
m T
ran
sit
ion
BA
1.6
%B
G2
6.5
%
Cu
lve
rt S
eg
me
nt
Re
pre
se
nta
tiv
e
Ch
an
ne
l Se
gm
en
t
% D
iffe
ren
ce
in
Gra
die
nt
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Site evaluations
Youngs Creek
Tabl
e 2—
Sum
mar
y of
seg
men
ts u
sed
for
com
paris
ons
S
egm
ent
ran
ge
of
Man
nin
g's
n v
alu
es1
# o
f m
easu
red
XS
s #
of
inte
rpo
late
d X
Ss
A
0.
1417
– 0
.143
2 1
7
B
0.
1415
– 0
.151
7 2
7
C
0.
0929
– 0
.151
7 4
10
D
0.
1206
– 0
.136
2
4
E
0.
1358
– 0
.136
2
9
F
0.
1335
– 0
.136
9 1
9
G
0.
1245
– 0
.136
9 1
6
I
0.13
95 –
0.1
445
1 6
1 Obt
aine
d us
ing
equa
tion
from
Jar
rett
(198
4): n
= 0
.39S
0.38
R-0
.16,
whe
re S
=st
ream
slo
pe; R
=hy
drau
lic r
adiu
s.
Jarr
ett’s
equ
atio
n on
ly a
pplie
d w
ithin
the
follo
win
g ra
nges
: S =
0.0
02 to
0.0
8, R
= 0
.5 ft
to 7
ft. F
or c
ross
sec
tions
ou
tsid
e th
ese
rang
es, n
was
com
pute
d ei
ther
from
adj
acen
t sec
tions
that
fell
with
in th
e ra
nges
, usi
ng th
e gu
idan
ce
of A
rcem
ent a
nd S
chne
ider
(19
87),
or
from
the
HE
C-R
AS
rec
omm
enda
tions
for
culv
ert m
odel
ing.
Fig
ure
3—H
EC
-RA
S p
rofil
e.
01
00
20
03
00
40
05
00
90
10
0
11
0
12
0
13
0
Ma
in C
ha
nne
l Dis
tan
ce (
ft)
Elevation (ft)
Le
ge
nd
WS
Q
10
0
WS
Q
50
WS
Q
10
WS
Q
bf
WS
2
1 c
fs
Gro
un
d
1.8
1.9
33.2*
3.35*
3.5
4.5
4.75
4.9
5.3*
66.25
6.5
7.6
8.4
9.1*
9.2
9.4
9.6
9.73333*
9.86666*
1010.5
1111.3333*
11.6166*
11.9
12.05*
12.1
12.2
12.4
12.5
13.25*
13.55*
13.6
13.8
13.85*
13.9
1414.1
Elevation (ft)
Sta
tions
with
dec
imal
val
ues
are
inte
rpol
ated
cro
ss-s
ectio
ns p
lace
d al
ong
the
surv
eyed
pro
file.
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Culvert Scour Assessment
Youngs Creek
Fig
ure
4—C
ross
-sec
tion
plot
s. O
nly
mea
sure
d cr
oss
sect
ions
are
incl
uded
. Man
ning
’s n
val
ues
are
incl
uded
at t
he to
p of
the
cros
s se
ctio
n.
The
sta
tioni
ng (
RS
) co
rres
pond
s to
the
stat
ioni
ng o
n th
e H
EC
-RA
S p
rofil
e. G
reen
arr
ows
defin
e th
e in
effe
ctiv
e flo
w a
reas
. Bla
ck a
rrow
s re
pres
ent p
oint
s id
entifi
ed in
the
field
as
the
bank
full
chan
nel b
ound
ary.
Onl
y th
ose
poin
ts id
entifi
ed in
the
field
and
sup
port
ed b
y hy
drau
lic a
nd
topo
grap
hic
anal
yses
are
sho
wn
belo
w.
010
2030
4050
6012
012
112
212
312
412
512
612
712
812
913
0
R
S =
14
Sta
tion
(ft)
Elevation (ft)
Le
ge
nd
WS
Q10
0
WS
Q50
WS
Q10
WS
Qbf
WS
21
cfs
Gro
und
Ban
k S
ta
.144
5.1
445
.144
5
010
2030
4050
6011
511
611
711
811
912
012
112
212
312
412
5
R
S =
13
Sta
tion
(ft)
Elevation (ft)
Le
ge
nd
WS
Q10
0
WS
Q50
WS
Q10
WS
Qbf
WS
21
cfs
Gro
und
Ban
k S
ta
.124
5.1
245
.124
5
010
2030
4050
6011
311
411
511
611
711
811
912
012
112
212
3
R
S =
12
Sta
tion
(ft)
Elevation (ft)
Le
ge
nd
WS
Q1
00
WS
Q5
0
WS
Q1
0
WS
Qb
f
WS
21
cfs
Gro
un
d
Le
vee
Ba
nk
Sta
.136
9.1
369
.136
9
010
2030
4050
6011
111
211
311
411
511
611
711
811
912
012
1
R
S =
11
Sta
tion
(ft)
Elevation (ft)
Le
ge
nd
WS
Q10
0
WS
Q50
WS
Q10
WS
Qbf
WS
21
cfs
Gro
und
Ban
k S
ta
.136
.136
.136
Elevation (ft)Elevation (ft)
Elevation (ft)Elevation (ft)
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Site evaluations
Youngs Creek
Fig
ure
4—C
ross
-sec
tion
plot
s. O
nly
mea
sure
d cr
oss
sect
ions
are
incl
uded
. Man
ning
’s n
val
ues
are
incl
uded
at t
he to
p of
the
cros
s se
ctio
n.
The
sta
tioni
ng (
RS
) co
rres
pond
s to
the
stat
ioni
ng o
n th
e H
EC
-RA
S p
rofil
e. G
reen
arr
ows
defin
e th
e in
effe
ctiv
e flo
w a
reas
. Bla
ck a
rrow
s re
pres
ent p
oint
s id
entifi
ed in
the
field
as
the
bank
full
chan
nel b
ound
ary.
Onl
y th
ose
poin
ts id
entifi
ed in
the
field
and
sup
port
ed b
y hy
drau
lic a
nd
topo
grap
hic
anal
yses
are
sho
wn
belo
w. (
cont
inue
d)
010
2030
4050
6010
810
911
011
111
211
311
411
511
611
711
8
R
S =
10
Sta
tion
(ft)
Elevation (ft)
Le
ge
nd
WS
Q10
0
WS
Q50
WS
Q10
WS
Qbf
WS
21
cfs
Gro
und
Ban
k S
ta
.136
.136
.136
010
2030
4050
6010
310
410
510
610
710
810
911
011
111
211
3
R
S =
9
Sta
tion
(ft)
Elevation (ft)
Le
ge
nd
WS
Q10
0
WS
Q50
WS
Q10
WS
Qbf
WS
21
cfs
Gro
und
Ban
k S
ta
.136
.136
.136
010
2030
4050
6010
010
110
210
310
410
510
610
710
810
911
0
R
S =
8
Sta
tion
(ft)
Elevation (ft)
Le
ge
nd
WS
Q10
0
WS
Q50
WS
Q10
WS
Qbf
WS
21
cfs
Gro
und
Ban
k S
ta
.136
.136
.136
010
2030
4050
6010
010
110
210
310
410
510
610
710
810
911
0
R
S =
7
Sta
tion
(ft)
Elevation (ft)
Le
ge
nd
WS
Q1
00
WS
Q5
0
WS
Q1
0
WS
Qb
f
WS
21
cfs
Gro
un
d
Ine
ff
Ba
nk
Sta
.096
8.0
968
.096
8
Elevation (ft)Elevation (ft)
Elevation (ft)Elevation (ft)
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Culvert Scour Assessment
Youngs Creek
Fig
ure
4—C
ross
-sec
tion
plot
s. O
nly
mea
sure
d cr
oss
sect
ions
are
incl
uded
. Man
ning
’s n
val
ues
are
incl
uded
at t
he to
p of
the
cros
s se
ctio
n.
The
sta
tioni
ng (
RS
) co
rres
pond
s to
the
stat
ioni
ng o
n th
e H
EC
-RA
S p
rofil
e. G
reen
arr
ows
defin
e th
e in
effe
ctiv
e flo
w a
reas
. Bla
ck a
rrow
s re
pres
ent p
oint
s id
entifi
ed in
the
field
as
the
bank
full
chan
nel b
ound
ary.
Onl
y th
ose
poin
ts id
entifi
ed in
the
field
and
sup
port
ed b
y hy
drau
lic a
nd
topo
grap
hic
anal
yses
are
sho
wn
belo
w. (
cont
inue
d)
-20
-10
01
02
03
04
01
00
10
11
02
10
31
04
10
51
06
10
71
08
10
91
10
R
S =
6 N
ote
: n
valu
es
for
first
pro
file.
Sta
tion
(ft
)
Elevation (ft)
Le
ge
nd
WS
Q10
0
WS
Q50
WS
Q10
WS
Qbf
WS
21
cfs
Gro
und
Ban
k S
ta
.103
4
-20
-10
01
02
03
04
09
91
00
10
11
02
10
31
04
10
51
06
10
71
08
10
9
R
S =
5 N
ote
: n
valu
es
for
first
pro
file.
Sta
tion
(ft
)
Elevation (ft)
Le
ge
nd
WS
Q10
0
WS
Q50
WS
Q10
WS
Qbf
WS
21
cfs
Gro
und
Ban
k S
ta
.100
6
010
2030
4050
60989910
010
110
210
310
410
510
610
710
8
R
S =
4
Sta
tion
(ft)
Elevation (ft)
Le
ge
nd
WS
Q1
00
WS
Q5
0
WS
Q1
0
WS
Qb
f
WS
21
cfs
Gro
un
d
Ine
ff
Ba
nk
Sta
.136
2.1
362
.136
2
010
2030
4050
609697989910
010
110
210
310
410
510
6
R
S =
3
Sta
tion
(ft)
Elevation (ft)
Le
ge
nd
WS
Q10
0
WS
Q50
WS
Q10
WS
Qbf
WS
21
cfs
Gro
und
Ban
k S
ta
.144
9.1
449
.144
9
Elevation (ft)Elevation (ft)
Elevation (ft)Elevation (ft)
A—491
Site evaluations
Youngs Creek
Fig
ure
4—C
ross
-sec
tion
plot
s. O
nly
mea
sure
d cr
oss
sect
ions
are
incl
uded
. Man
ning
’s n
val
ues
are
incl
uded
at t
he to
p of
the
cros
s se
ctio
n.
The
sta
tioni
ng (
RS
) co
rres
pond
s to
the
stat
ioni
ng o
n th
e H
EC
-RA
S p
rofil
e. G
reen
arr
ows
defin
e th
e in
effe
ctiv
e flo
w a
reas
. Bla
ck a
rrow
s re
pres
ent p
oint
s id
entifi
ed in
the
field
as
the
bank
full
chan
nel b
ound
ary.
Onl
y th
ose
poin
ts id
entifi
ed in
the
field
and
sup
port
ed b
y hy
drau
lic a
nd
topo
grap
hic
anal
yses
are
sho
wn
belo
w. (
cont
inue
d)
1020
3040
5060
709697989910
010
110
210
310
410
510
6
R
S =
2
Sta
tion
(ft)
Elevation (ft)
Le
ge
nd
WS
Q10
0
WS
Q50
WS
Q10
WS
Qbf
WS
21
cfs
Gro
und
Ban
k S
ta
. 1 4 1 5
.141
5.1
415
2030
4050
6070
80929394959697989910
010
110
2
R
S =
1
Sta
tion
(ft)
Elevation (ft)
Le
ge
nd
WS
Q10
0
WS
Q50
WS
Q10
WS
Qbf
WS
21
cfs
Gro
und
Ban
k S
ta
.142
6.1
426
.142
6
Elevation (ft)
Elevation (ft)
A—492
Culvert Scour Assessment
Youngs Creek
Fig
ure
5—F
low
are
a (t
otal
) pr
ofile
plo
t.
Fig
ure
6—W
ette
d pe
rimet
er.
01
00
20
03
00
40
05
00
0
20
40
60
80
10
0
12
0
Ma
in C
ha
nne
l Dis
tanc
e (
ft)
Flow Area (sq ft)
Le
ge
nd
Flo
w A
rea
Q1
00
Flo
w A
rea
Q5
0
Flo
w A
rea
Q1
0
Flo
w A
rea
Qb
f
Flo
w A
rea
21
cfs
01
00
20
03
00
40
05
00
0
10
20
30
40
50
Ma
in C
ha
nne
l Dis
tanc
e (
ft)
W.P. Total (ft)
Le
ge
nd
W.P
. T
ota
l Q
10
0
W.P
. T
ota
l Q
50
W.P
. T
ota
l Q
10
W.P
. T
ota
l Q
bf
W.P
. T
ota
l 21
cfs
Cul
vert
A
B
C
D
E
F
G
H
I
Flow
Cul
vert
A
B
C
D
E
F
G
H
I
Flow
Flow area (sq ft) W.P. total (ft)
A—493
Site evaluations
Youngs Creek
01
00
20
03
00
40
05
00
5
10
15
20
25
30
35
40
45
Ma
in C
ha
nne
l Dis
tanc
e (
ft)
Top Width (ft)
Le
ge
nd
To
p W
idth
Q10
0
To
p W
idth
Q50
To
p W
idth
Q10
To
p W
idth
Qbf
To
p W
idth
21
cfs
01
00
20
03
00
40
05
00
012345
Ma
in C
ha
nne
l Dis
tanc
e (
ft)
Hydr Radius (ft)
Le
ge
nd
Hyd
r Ra
diu
s Q
10
0
Hyd
r Ra
diu
s Q
50
Hyd
r Ra
diu
s Q
10
Hyd
r Ra
diu
s Q
bf
Hyd
r Ra
diu
s 2
1 c
fs
Fig
ure
7—H
ydra
ulic
rad
ius.
Fig
ure
8—To
p w
idth
.
Hydraulic radius (ft) Top width (ft)
Cul
vert
A
B
C
D
E
F
G
H
I
Flow
Cul
vert
A
B
C
D
E
F
G
H
I
Flow
A—494
Culvert Scour Assessment
Youngs Creek
Fig
ure
9—M
axim
um d
epth
.
Fig
ure
10—
She
ar s
tres
s (c
hann
el)
profi
le.
01
00
20
03
00
40
05
00
0123456
Ma
in C
ha
nne
l Dis
tanc
e (
ft)
Max Chl Dpth (ft)
Le
ge
nd
Ma
x C
hl D
pth
Q1
00
Ma
x C
hl D
pth
Q5
0
Ma
x C
hl D
pth
Q1
0
Ma
x C
hl D
pth
Qb
f
Ma
x C
hl D
pth
21
cfs
01
00
20
03
00
40
05
00
05
10
15
20
25
Ma
in C
ha
nne
l Dis
tanc
e (
ft)
Shear Chan (lb/sq ft)
Le
ge
nd
Sh
ear
Ch
an Q
100
Sh
ear
Ch
an Q
50
Sh
ear
Ch
an Q
10
Sh
ear
Ch
an Q
bf
Sh
ear
Ch
an 2
1 c
fs
Cul
vert
A
B
C
D
E
F
G
H
I
Flow
Cul
vert
A
B
C
D
E
F
G
H
I
Flow
Maximum channel depth (ft) Shear channel (lb/sq ft)
A—495
Site evaluations
Youngs Creek
Fig
ure
11—
Vel
ocity
(ch
anne
l) pr
ofile
plo
t.
01
00
20
03
00
40
05
00
012345678
Ma
in C
ha
nne
l Dis
tanc
e (
ft)
Vel Chnl (ft/s)
Le
ge
nd
Ve
l Ch
nl Q
10
0
Ve
l Ch
nl Q
50
Ve
l Ch
nl Q
10
Ve
l Ch
nl Q
bf
Ve
l Ch
nl 2
1 c
fs
Cul
vert
A
B
C
D
E
F
G
H
I
Flow
Velocity channel (ft/s)
A—496
Culvert Scour Assessment
Youngs Creek
0
20406080100
120
A
B (
ds tr
ans)
C (
culv
)
D (
us tr
ans)
E (
us tr
ans)
FG
IA
B (
ds tr
ans)
C (
culv
)
D (
us tr
ans)
E (
us tr
ans)
FG
IA
B (
ds tr
ans)
C (
culv
)
D (
us tr
ans)
E (
us tr
ans)
FG
IA
B (
ds tr
ans)
C (
culv
)
D (
us tr
ans)
E (
us tr
ans)
FG
IA
B (
ds tr
ans)
C (
culv
)
D (
us tr
ans)
E (
us tr
ans)
FG
I
25%
Q2
Qbf
1050
100
Flow
Are
a (f
t2)
Bo
x P
lot
exp
lan
atio
n
Max
imum
val
ue
75th
per
cent
ile
Med
ian
(aka
50t
h pe
rcen
tile)
25th
per
cent
ile
Min
imum
val
ue
100%
of th
eva
lues
50%
of th
eva
lues
A
B (DS Trans)
C (Culvert)
D (US Trans)
E (US Trans)
F
G
I
Flow area (ft2)
Fig
ure
12—
Flo
w a
rea
(tot
al).
A
B (DS Trans)
C (Culvert)
D (US Trans)
E (US Trans)
F
G
I
A
B (DS Trans)
C (Culvert)
D (US Trans)
E (US Trans)
F
G
I
A
B (DS Trans)
C (Culvert)
D (US Trans)
E (US Trans)
F
G
I
A
B (DS Trans)
C (Culvert)
D (US Trans)
E (US Trans)
F
G
I
A—497
Site evaluations
Youngs Creek
Fig
ure
13—
Wet
ted
perim
eter
.
Fig
ure
14—
Hyd
raul
ic r
adiu
s.
01020304050
A
B (
ds tr
ans)
C (
culv
)
D (
us tr
ans)
E (
us tr
ans)
FG
IA
B (
ds tr
ans)
C (
culv
)
D (
us tr
ans)
E (
us tr
ans)
FG
IA
B (
ds tr
ans)
C (
culv
)
D (
us tr
ans)
E (
us tr
ans)
FG
IA
B (
ds tr
ans)
C (
culv
)
D (
us tr
ans)
E (
us tr
ans)
FG
IA
B (
ds tr
ans)
C (
culv
)
D (
us tr
ans)
E (
us tr
ans)
FG
I
25%
Q2
Qbf
1050
100
Wet
ted
Perim
eter
(ft)
012345
A
B (
ds tr
ans)
C (
culv
)
D (
us tr
ans)
E (
us tr
ans)
FG
IA
B (
ds tr
ans)
C (
culv
)
D (
us tr
ans)
E (
us tr
ans)
FG
IA
B (
ds tr
ans)
C (
culv
)
D (
us tr
ans)
E (
us tr
ans)
FG
IA
B (
ds tr
ans)
C (
culv
)
D (
us tr
ans)
E (
us tr
ans)
FG
IA
B (
ds tr
ans)
C (
culv
)
D (
us tr
ans)
E (
us tr
ans)
FG
I
25%
Q2
Qbf
1050
100
Hyd
raul
ic R
adiu
s (f
t)
A
B (DS Trans)
C (Culvert)
D (US Trans)
E (US Trans)
F
G
I
A
B (DS Trans)
C (Culvert)
D (US Trans)
E (US Trans)
F
G
I
A
B (DS Trans)
C (Culvert)
D (US Trans)
E (US Trans)
F
G
I
A
B (DS Trans)
C (Culvert)
D (US Trans)
E (US Trans)
F
G
I
A
B (DS Trans)
C (Culvert)
D (US Trans)
E (US Trans)
F
G
I
A
B (DS Trans)
C (Culvert)
D (US Trans)
E (US Trans)
F
G
I
A
B (DS Trans)
C (Culvert)
D (US Trans)
E (US Trans)
F
G
I
A
B (DS Trans)
C (Culvert)
D (US Trans)
E (US Trans)
F
G
I
A
B (DS Trans)
C (Culvert)
D (US Trans)
E (US Trans)
F
G
I
A
B (DS Trans)
C (Culvert)
D (US Trans)
E (US Trans)
F
G
I
Hydraulic radius (ft)Wetted perimeter (ft)
A—498
Culvert Scour Assessment
Youngs Creek
Fig
ure
15—
Top
wid
th.
Fig
ure
16—
Max
imum
dep
th.
01020304050
A
B (
ds tr
ans)
C (
culv
)
D (
us tr
ans)
E (
us tr
ans)
FG
IA
B (
ds tr
ans)
C (
culv
)
D (
us tr
ans)
E (
us tr
ans)
FG
IA
B (
ds tr
ans)
C (
culv
)
D (
us tr
ans)
E (
us tr
ans)
FG
IA
B (
ds tr
ans)
C (
culv
)
D (
us tr
ans)
E (
us tr
ans)
FG
IA
B (
ds tr
ans)
C (
culv
)
D (
us tr
ans)
E (
us tr
ans)
FG
I
25%
Q2
Qbf
1050
100
Top
Wid
th (f
t)
0123456
A
B (
ds tr
ans)
C (
culv
)
D (
us tr
ans)
E (
us tr
ans)
FG
IA
B (
ds tr
ans)
C (
culv
)
D (
us tr
ans)
E (
us tr
ans)
FG
IA
B (
ds tr
ans)
C (
culv
)
D (
us tr
ans)
E (
us tr
ans)
FG
IA
B (
ds tr
ans)
C (
culv
)
D (
us tr
ans)
E (
us tr
ans)
FG
IA
B (
ds tr
ans)
C (
culv
)
D (
us tr
ans)
E (
us tr
ans)
FG
I
25%
Q2
Qbf
1050
100
Max
Dep
th (f
t)A
B (DS Trans)
C (Culvert)
D (US Trans)
E (US Trans)
F
G
I
A
B (DS Trans)
C (Culvert)
D (US Trans)
E (US Trans)
F
G
I
A
B (DS Trans)
C (Culvert)
D (US Trans)
E (US Trans)
F
G
I
A
B (DS Trans)
C (Culvert)
D (US Trans)
E (US Trans)
F
G
I
A
B (DS Trans)
C (Culvert)
D (US Trans)
E (US Trans)
F
G
I
A
B (DS Trans)
C (Culvert)
D (US Trans)
E (US Trans)
F
G
I
A
B (DS Trans)
C (Culvert)
D (US Trans)
E (US Trans)
F
G
I
A
B (DS Trans)
C (Culvert)
D (US Trans)
E (US Trans)
F
G
I
A
B (DS Trans)
C (Culvert)
D (US Trans)
E (US Trans)
F
G
I
A
B (DS Trans)
C (Culvert)
D (US Trans)
E (US Trans)
F
G
I
Top width (ft) Maximum depth (ft)
A—499
Site evaluations
Youngs Creek
Fig
ure
17—
Wid
th-t
o-de
pth
ratio
.
Fig
ure
18—
Vel
ocity
(ch
anne
l).
0102030405060
A
B (
ds tr
ans)
C (
culv
)
D (
us tr
ans)
E (
us tr
ans)
FG
IA
B (
ds tr
ans)
C (
culv
)
D (
us tr
ans)
E (
us tr
ans)
FG
IA
B (
ds tr
ans)
C (
culv
)
D (
us tr
ans)
E (
us tr
ans)
FG
IA
B (
ds tr
ans)
C (
culv
)
D (
us tr
ans)
E (
us tr
ans)
FG
IA
B (
ds tr
ans)
C (
culv
)
D (
us tr
ans)
E (
us tr
ans)
FG
I
25%
Q2
Qbf
1050
100
W-D
Rat
io
02468
A
B (
ds tr
ans)
C (
culv
)
D (
us tr
ans)
E (
us tr
ans)
FG
IA
B (
ds tr
ans)
C (
culv
)
D (
us tr
ans)
E (
us tr
ans)
FG
IA
B (
ds tr
ans)
C (
culv
)
D (
us tr
ans)
E (
us tr
ans)
FG
IA
B (
ds tr
ans)
C (
culv
)
D (
us tr
ans)
E (
us tr
ans)
FG
IA
B (
ds tr
ans)
C (
culv
)
D (
us tr
ans)
E (
us tr
ans)
FG
I
25%
Q2
Qbf
1050
100
Velo
city
(ft/
sec)
A
B (DS Trans)
C (Culvert)
D (US Trans)
E (US Trans)
F
G
I
A
B (DS Trans)
C (Culvert)
D (US Trans)
E (US Trans)
F
G
I
A
B (DS Trans)
C (Culvert)
D (US Trans)
E (US Trans)
F
G
I
A
B (DS Trans)
C (Culvert)
D (US Trans)
E (US Trans)
F
G
I
A
B (DS Trans)
C (Culvert)
D (US Trans)
E (US Trans)
F
G
I
A
B (DS Trans)
C (Culvert)
D (US Trans)
E (US Trans)
F
G
I
A
B (DS Trans)
C (Culvert)
D (US Trans)
E (US Trans)
F
G
I
A
B (DS Trans)
C (Culvert)
D (US Trans)
E (US Trans)
F
G
I
A
B (DS Trans)
C (Culvert)
D (US Trans)
E (US Trans)
F
G
I
A
B (DS Trans)
C (Culvert)
D (US Trans)
E (US Trans)
F
G
I
Width-to-depth ratio Velocity (ft/sec)
A—500
Culvert Scour Assessment
Youngs Creek
0
0.51
1.52
2.53
3.54
4.55
050
100
150
200
250
300
350
Dis
char
ge
(cfs
)
Exce
ss S
hear
(Ap
plie
d / t
crit
)
US
Ch
an
ne
l (U
S p
eb
ble
co
un
t) -
riff
le/s
tep
US
Ch
an
ne
l (D
S p
eb
ble
co
un
t) -
riff
le/s
tep
Cu
lve
rt (
DS
pe
bb
le c
ou
nt)
- r
iffle
/ste
p
DS
Ch
an
ne
l (D
S p
eb
ble
co
un
t)
Fig
ure
19—
She
ar s
tres
s (c
hann
el).
Exc
ess
shea
r st
ress
is th
e ch
anne
l she
ar d
ivid
ed b
y th
e cr
itica
l she
ar fo
r be
d en
trai
nmen
t of t
he D
84 p
artic
le s
ize.
Val
ues
of e
xces
s sh
ear
grea
ter
than
1 in
dica
te b
ed m
ovem
ent f
or th
e D
84 p
artic
le s
ize.
Fig
ure
20—
Exc
ess
shea
r st
ress
.
051015202530
A
B (
ds tr
ans)
C (
culv
)
D (
us tr
ans)
E (
us tr
ans)
FG
IA
B (
ds tr
ans)
C (
culv
)
D (
us tr
ans)
E (
us tr
ans)
FG
IA
B (
ds tr
ans)
C (
culv
)
D (
us tr
ans)
E (
us tr
ans)
FG
IA
B (
ds tr
ans)
C (
culv
)
D (
us tr
ans)
E (
us tr
ans)
FG
IA
B (
ds tr
ans)
C (
culv
)
D (
us tr
ans)
E (
us tr
ans)
FG
I
25%
Q2
Qbf
1050
100
Shea
r Str
ess
(lbs/
ft2)
A
B (DS Trans)
C (Culvert)
D (US Trans)
E (US Trans)
F
G
I
A
B (DS Trans)
C (Culvert)
D (US Trans)
E (US Trans)
F
G
I
A
B (DS Trans)
C (Culvert)
D (US Trans)
E (US Trans)
F
G
I
A
B (DS Trans)
C (Culvert)
D (US Trans)
E (US Trans)
F
G
I
A
B (DS Trans)
C (Culvert)
D (US Trans)
E (US Trans)
F
G
I
Shear stress (lbs/ft2) Excess shear (Applied/tcrit)
A—501
Site evaluations
Youngs Creek
Table 3—Sum of squared height difference
reach XS unit Sum of squared Within range of Location type height difference channel conditions?
Culvert US Pool 0.03 No
DS Riffle/step 0.10 Yes
Upstream US Riffle/step 0.08
DS Riffle/step 0.12
Downstream Riffle 0.06
Table 4—Vertical Sinuosity
Segment Location vertical 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 XS 25% Q2 Within range of
Location channel conditions?
Culvert US 6 Yes
DS 10 No
Upstream US 2
DS 6
Downstream 7
A—502
Culvert Scour Assessment
Youngs Creek
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%
Figure 21—Residual depths.
Table 7—Bed material sorting and skewness
reach XS unit Sorting Within range Skewness Within range Location Type of channel of channel conditions? conditions?
Culvert US Pool 1.73 No 0.32 Yes
DS Riffle/step 1.67 No 0.42 Yes
Upstream US Riffle/step 2.10 0.36
DS Riffle/step 1.89 0.44
Downstream US Riffle 1.84 0.24
DS Riffle 2.23 0.51
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
Segment ASegment B:
DS TransitionSegment C:
Culvert
Segment D:US Transition
Segment E:US Transition
Segment F Segment G Segment HSegment I
Residual depth (ft)
Seg
men
t A
Seg
men
t B
DS
Tra
nsiti
on
Seg
men
t C
Cul
vert
Seg
men
t D
US
Tra
nsiti
on
Seg
men
t E
US
Tra
nsiti
on
Seg
men
t F
Seg
men
t G
Seg
men
t H
Seg
men
t I
Res
idua
l Dep
th (
ft)
A—503
Site evaluations
Youngs Creek
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.
A—504
Culvert Scour Assessment
Youngs Creek
Upstream reference reach. Upstream reference reach – upstream pebble count, between steps.
Upstream reference reach – downstream pebble Downstream reference reach – downstream pebblecount, step. count (step).
A—505
Site evaluations
Youngs Creek
Downstream reference reach – upstream pebble Downstream reference reach.count (riffle).
View downstream within culvert – pebble counts View upstream within culvert – pebble counts at flagged locations. at flagged locations.
A—506
Culvert Scour Assessment
Youngs Creek
Cross-Section: Upstream Reference Reach – Upstream Pebble Count
Sorting Coefficient: 2.10
Skewness Coefficient: 0.36
Material S ize C las s (mm) C ount Item % C umulative %
sand <2 3 3% 3%
very fine gravel 2 - 4 7 7% 10%
fine gravel 4 - 5.7 1 1% 11%
fine gravel 5.7 - 8 5 5% 16%
medium gravel 8 - 11.3 3 3% 19%
medium gravel 11.3 - 16 6 6% 26%
coarse gravel 16 - 22.6 1 1% 27%
coarse gravel 22.6 - 32 2 2% 29%
very coarse gravel 32 - 45 5 5% 34%
very coarse gravel 45 - 64 6 6% 40%
small cobble 64 - 90 17 17% 57%
medium cobble 90 - 128 9 9% 66%
large cobble 128 - 180 11 11% 78%
very large cobble 180 - 256 12 12% 90%
small boulder 256 - 362 7 7% 97%
small boulder 362 - 512 3 3% 100%
medium boulder 512 - 1024 0 0% 100%
large boulder 1024 - 2048 0 0% 100%
very large boulder 2048 - 4096 0 0% 100%
bedrock Bedrock 0 0% 100%
0
2
4
6
8
10
12
14
16
18
<22 - 4
4 - 5.75.7 - 88 - 11.3
11.3 - 1616 - 22.622.6 - 3232 - 4545 - 6464 - 90
90 - 128128 - 180180 - 256256 - 362362 - 512
512 - 10241024 - 20482048 - 4096
Bedrock
Partic le Size Category (mm)
Frequency
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
Cumulative Frequency
<2
2-4
4-5
.7
5.7
-8
8-1
1.3
11.3
-16
16-2
2.6
22.6
-32
32-4
5
45-6
4
64-9
0
90-1
28
128-1
80
180-2
56
256-3
62
362-5
12
512-1
024
1024-2
048
2048-4
096
Bed
rock
Fre
quen
cy
Cum
ulat
ive
Fre
quen
cy
Particle Size Category (mm)
S ize C las sS ize perc ent finer
than (mm)
D5 4
D16 9
D50 78
D84 205
D95 330
D100 420
Material P erc ent C ompos ition
Sand 3%
Gravel 37%
Cobble 50%
Boulder 10%
Bedrock 0%
A—507
Site evaluations
Youngs Creek
Cross-Section: Upstream Reference Reach – Downstream Pebble Count
Sorting Coefficient: 1.89
Skewness Coefficient: 0.44
Material S ize C las s (mm) C ount Item % C umulative %
sand <2 2 2% 2%
very fine gravel 2 - 4 2 2% 5%
fine gravel 4 - 5.7 1 1% 6%
fine gravel 5.7 - 8 2 2% 8%
medium gravel 8 - 11.3 0 0% 8%
medium gravel 11.3 - 16 0 0% 8%
coarse gravel 16 - 22.6 1 1% 9%
coarse gravel 22.6 - 32 2 2% 12%
very coarse gravel 32 - 45 3 4% 15%
very coarse gravel 45 - 64 2 2% 18%
small cobble 64 - 90 3 4% 21%
medium cobble 90 - 128 5 6% 27%
large cobble 128 - 180 9 11% 38%
very large cobble 180 - 256 12 14% 52%
small boulder 256 - 362 8 9% 61%
small boulder 362 - 512 18 21% 82%
medium boulder 512 - 1024 15 18% 100%
large boulder 1024 - 2048 0 0% 100%
very large boulder 2048 - 4096 0 0% 100%
bedrock Bedrock 0 0% 100%
0
2
4
6
8
10
12
14
16
18
20
<22 - 4
4 - 5.75.7 - 88 - 11.3
11.3 - 1616 - 22.622.6 - 3232 - 4545 - 6464 - 90
90 - 128128 - 180180 - 256256 - 362362 - 512
512 - 10241024 - 20482048 - 4096
Bedrock
Partic le Size Category (mm)
Frequency
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
Cumulative Frequency
<2
2-4
4-5
.7
5.7
-8
8-1
1.3
11.3
-16
16-2
2.6
22.6
-32
32
-45
45
-64
64
-90
90-1
28
128-1
80
180-2
56
256-3
62
362-5
12
512-1
024
1024-2
048
2048-4
096
Bedro
ck
Fre
quen
cy
Cum
ulat
ive
Fre
quen
cy
Particle Size Category (mm)
S ize C las sS ize perc ent finer
than (mm)
D5 5
D16 54
D50 240
D84 520
D95 700
D100 700
Material P erc ent C ompos ition
Sand 2%
Gravel 15%
Cobble 34%
Boulder 48%
Bedrock 0%
A—508
Culvert Scour Assessment
Youngs Creek
Cross-Section: Culvert – Upstream Pebble Count
Sorting Coefficient: 1.73
Skewness Coefficient: 0.32
Material S ize R ange (mm) C ount Item % C umulative %
sand <2 2 2% 2%
very fine gravel 2 - 4 3 3% 5%
fine gravel 4 - 5.7 0 0% 5%
fine gravel 5.7 - 8 5 5% 10%
medium gravel 8 - 11.3 5 5% 15%
medium gravel 11.3 - 16 7 7% 21%
coarse gravel 16 - 22.6 7 7% 28%
coarse gravel 22.6 - 32 3 3% 31%
very coarse gravel 32 - 45 11 11% 42%
very coarse gravel 45 - 64 6 6% 48%
small cobble 64 - 90 9 9% 56%
medium cobble 90 - 128 8 8% 64%
large cobble 128 - 180 22 21% 85%
very large cobble 180 - 256 11 11% 96%
small boulder 256 - 362 1 1% 97%
small boulder 362 - 512 3 3% 100%
medium boulder 512 - 1024 0 0% 100%
large boulder 1024 - 2048 0 0% 100%
very large boulder 2048 - 4096 0 0% 100%
bedrock > 4096 0 0% 100%
0
5
10
15
20
25
<22 - 4
4 - 5.75.7 - 88 - 11.3
11.3 - 1616 - 22.622.6 - 3232 - 4545 - 6464 - 90
90 - 128128 - 180180 - 256256 - 362362 - 512
512 - 10241024 - 20482048 - 4096
> 4096
Partic le Size Category (mm)
Frequency
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
Cumulative Frequency
<2
2-4
4-5
.7
5.7
-8
8-1
1.3
11.3
-16
16-2
2.6
22.6
-32
32-4
5
45-6
4
64-9
0
90-1
28
128-1
80
180-2
56
256-3
62
362-5
12
512-1
024
1024-2
048
2048-4
096
Bedro
ck
Fre
quen
cy
Cum
ulat
ive
Fre
quen
cy
Particle Size Category (mm)
S ize C las sS ize perc ent finer
than (mm)
D5 6
D16 14
D50 74
D84 180
D95 249
D100 420
Material P erc ent C ompos ition
Sand 2%
Gravel 46%
Cobble 49%
Boulder 4%
Bedrock 0%
A—509
Site evaluations
Youngs Creek
Cross-Section: Culvert – Downstream Pebble Count
Sorting Coefficient: 1.67
Skewness Coefficient: 0.42
<2
2-4
4-5
.7
5.7
-8
8-1
1.3
11.3
-16
16-2
2.6
22.6
-32
32-4
5
45-6
4
64-9
0
90-1
28
128-1
80
180-2
56
256-3
62
362-5
12
512-1
024
1024-2
048
2048-4
096
Bedro
ck
Fre
quen
cy
Cum
ulat
ive
Fre
quen
cy
Particle Size Category (mm)
Material S ize C las s (mm) C ount Item % C umulative %
sand <2 0 0% 0%
very fine gravel 2 - 4 1 1% 1%
fine gravel 4 - 5.7 1 1% 2%
fine gravel 5.7 - 8 2 2% 4%
medium gravel 8 - 11.3 1 1% 5%
medium gravel 11.3 - 16 8 7% 12%
coarse gravel 16 - 22.6 3 3% 15%
coarse gravel 22.6 - 32 7 6% 21%
very coarse gravel 32 - 45 4 4% 25%
very coarse gravel 45 - 64 8 7% 32%
small cobble 64 - 90 7 6% 39%
medium cobble 90 - 128 6 6% 44%
large cobble 128 - 180 15 14% 58%
very large cobble 180 - 256 15 14% 72%
small boulder 256 - 362 22 20% 93%
small boulder 362 - 512 6 6% 98%
medium boulder 512 - 1024 2 2% 100%
large boulder 1024 - 2048 0 0% 100%
very large boulder 2048 - 4096 0 0% 100%
bedrock Bedrock 0 0% 100%
0
5
10
15
20
25
<22 - 4
4 - 5.75.7 - 88 - 11.3
11.3 - 1616 - 22.622.6 - 3232 - 4545 - 6464 - 90
90 - 128128 - 180180 - 256256 - 362362 - 512
512 - 10241024 - 20482048 - 4096
Bedrock
Partic le Size Category (mm)
Frequency
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
Cumulative Frequency
S ize C las sS ize perc ent finer
than (mm)
D5 12
D16 25
D50 150
D84 309
D95 423
D100 550
Material P erc ent C ompos ition
Sand 0%
Gravel 32%
Cobble 40%
Boulder 28%
Bedrock 0%
A—510
Culvert Scour Assessment
Youngs Creek
Cross-Section: Downstream Reference Reach – Upstream Pebble Count
Sorting Coefficient: 1.84
Skewness Coefficient: 0.24
Material S ize C las s (mm) C ount Item % C umulative %
sand <2 3 3% 3%
very fine gravel 2 - 4 1 1% 4%
fine gravel 4 - 5.7 1 1% 5%
fine gravel 5.7 - 8 3 3% 8%
medium gravel 8 - 11.3 2 2% 10%
medium gravel 11.3 - 16 1 1% 11%
coarse gravel 16 - 22.6 4 4% 15%
coarse gravel 22.6 - 32 4 4% 19%
very coarse gravel 32 - 45 4 4% 23%
very coarse gravel 45 - 64 9 9% 31%
small cobble 64 - 90 12 12% 43%
medium cobble 90 - 128 12 12% 55%
large cobble 128 - 180 17 17% 72%
very large cobble 180 - 256 12 12% 83%
small boulder 256 - 362 8 8% 91%
small boulder 362 - 512 3 3% 94%
medium boulder 512 - 1024 6 6% 100%
large boulder 1024 - 2048 0 0% 100%
very large boulder 2048 - 4096 0 0% 100%
bedrock Bedrock 0 0% 100%
0
2
4
6
8
10
12
14
16
18
<22 - 4
4 - 5.75.7 - 88 - 11.3
11.3 - 1616 - 22.622.6 - 3232 - 4545 - 6464 - 90
90 - 128128 - 180180 - 256256 - 362362 - 512
512 - 10241024 - 20482048 - 4096
Bedrock
Partic le Size Category (mm)
Frequency
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
Cumulative Frequency
S ize C las sS ize perc ent finer
than (mm)
D5 6
D16 25
D50 105
D84 267
D95 535
D100 580
Material P erc ent C ompos ition
Sand 3%
Gravel 28%
Cobble 52%
Boulder 17%
Bedrock 0%
<2
2-4
4-5
.7
5.7
-8
8-1
1.3
11.3
-16
16-2
2.6
22.6
-32
32
-45
45
-64
64
-90
90-1
28
128-1
80
180-2
56
256-3
62
362-5
12
512-1
024
1024-2
048
2048-4
096
Bedro
ck
Fre
quen
cy
Cum
ulat
ive
Fre
quen
cy
Particle Size Category (mm)
A—511
Site evaluations
Youngs Creek
Cross-Section: Downstream Reference Reach – Downstream Pebble Count
Sorting Coefficient: 2.23
Skewness Coefficient: 0.51
Material S ize C las s (mm) C ount Item % C umulative %
sand <2 7 7% 7%
very fine gravel 2 - 4 1 1% 8%
fine gravel 4 - 5.7 2 2% 9%
fine gravel 5.7 - 8 1 1% 10%
medium gravel 8 - 11.3 1 1% 11%
medium gravel 11.3 - 16 7 7% 18%
coarse gravel 16 - 22.6 5 5% 23%
coarse gravel 22.6 - 32 8 8% 30%
very coarse gravel 32 - 45 1 1% 31%
very coarse gravel 45 - 64 9 8% 40%
small cobble 64 - 90 7 7% 46%
medium cobble 90 - 128 14 13% 59%
large cobble 128 - 180 18 17% 76%
very large cobble 180 - 256 10 9% 86%
small boulder 256 - 362 11 10% 96%
small boulder 362 - 512 4 4% 100%
medium boulder 512 - 1024 0 0% 100%
large boulder 1024 - 2048 0 0% 100%
very large boulder 2048 - 4096 0 0% 100%
bedrock Bedrock 0 0% 100%
0
2
4
6
8
10
12
14
16
18
20
<22 - 4
4 - 5.75.7 - 88 - 11.3
11.3 - 1616 - 22.622.6 - 3232 - 4545 - 6464 - 90
90 - 128128 - 180180 - 256256 - 362362 - 512
512 - 10241024 - 20482048 - 4096
Bedrock
Partic le Size Category (mm)
Frequency
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
Cumulative Frequency
<2
2-4
4-5
.7
5.7
-8
8-1
1.3
11.3
-16
16-2
2.6
22.6
-32
32-4
5
45-6
4
64-9
0
90-1
28
128-1
80
180-2
56
256-3
62
362-5
12
512-1
024
1024-2
048
2048-4
096
Bed
rock
Fre
quen
cy
Cum
ulat
ive
Fre
quen
cy
Particle Size Category (mm)
S ize C las sS ize perc ent finer
than (mm)
D5 1
D16 15
D50 100
D84 220
D95 318
D100 500
Material P erc ent C ompos ition
Sand 7%
Gravel 33%
Cobble 46%
Boulder 14%
Bedrock 0%