culvert scour assessment - us forest service€”332 culvert scour assessment lowe creek bed...

A—327

Site evaluations

Lowe Creek

Lowe Creek

Site Information

Site Location: Mt Hood NF, Forest Road 4671

Year Installed: Pre-1987

Lat/Long: 121°53’55.08”W Watershed Area (mi2): 6.0

44°56’55.13”N

Stream Slope (ft/ft)1: 0.0445 Channel Type: Step-pool

Bankfull Width (ft): 23.6 Survey Date: April 5, 20071Water 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 Qbf

2 2-year 5-year 10-year 50-year 100-year

35 115 141 227 292 448 5202Bankfull flow estimated by matching modeled water surface elevations to field-identified bankfull elevations.

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Culvert Scour Assessment

Lowe Creek

Figure 1—Plan view map.

Points represent survey points

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Site evaluations

Lowe Creek

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.

A—330


Lowe Creek

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.

SCOur COnDITIOnSObserved 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 flood-plain 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.

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Site evaluations

Lowe Creek

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 Q

50 and Q

100. 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 Q

bf 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 (Q

50 and Q

100). 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

transition (F) is greater than the corresponding profile segment (A) for flows up to the Q

10 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 Q

10 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.

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Lowe Creek

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 (Q

50 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).

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).

A—333

Site evaluations

Lowe Creek

Large woody debris – There was one 2- to 3-foot-diameter 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 Q

bf 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.

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 Q

50 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.

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.

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Lowe Creek

Fig

ure

2—Lo

we

Cre

ek lo

ngitu

dina

l pro

file.

Tabl

e 1—

Seg

men

t com

paris

ons

80

85

90

95

10

0

10

5

11

0

11

5

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

ele

vati

on (f

eet)

H

G

FE

DC

B

A

XS 1

3:

Peb

ble

coun

t

(poo

l)

XS 3

:

Peb

ble

coun

t(p

ool)

XS 1

2:

Peb

ble

coun

t(s

tep)

XS 8

:

Peb

ble

coun

t(p

ool)

XS 7

:

Peb

ble

coun

t(ri

ffle)

XS 2

:

Peb

ble

coun

t(ri

ffle)

Cul

vert

Rep

rese

ntat

ive C

hann

el

Rep

rese

ntat

ive C

hann

el

Larg

e lo

g in

inle

t

XS 1

XS 4

XS 5

XS 6

XS 9

XS 1

0XS

11

XS 1

4

A6

70

.02

9

B4

50

.04

9

C3

40

.04

3

D5

50

.01

7

E4

70

.05

5

F6

10

.03

2

G4

70

.07

8

H7

10

.05

8

Se

gm

en

t

Se

gm

en

t

Le

ng

th (

ft)

Se

gm

en

t G

rad

ien

t

EB

10

.7%

EH

4.9

%

Up

str

ea

m T

ran

sit

ion

FA

9.7

%

Do

wn

str

ea

m T

ran

sit

ion

CB

13

.4%

CH

26

.3%

Cu

lve

rt S

eg

me

nt

Re

pre

se

nta

tiv

e

Ch

an

ne

l Se

gm

en

t%

Dif

fere

nc

e in

G

rad

ien

t

A—335

Site evaluations

Lowe 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.

1126

– 0

.118

7 2

7

B

0.

1131

– 0

.119

7 2

5

C

0.

1115

– 0

.121

7 2

5

E

0.

0875

– 0

.129

8 2

6

F

0.

1298

– 0

.132

8 2

5

H

0.

1228

– 0

.133

6 2

61 O

btai

ned

usin

g eq

uatio

n fr

om J

arre

tt (1

984)

: n =

0.3

9S0.

38R

-0.1

6, w

here

S=

stre

am s

lope

; R=

hydr

aulic

rad

ius.

Jar

rett’

s eq

uatio

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

out

side

thes

e ra

nges

, n w

as c

ompu

ted

eith

er fr

om a

djac

ent

sect

ions

that

fell

with

in th

e ra

nges

, usi

ng th

e gu

idan

ce o

f Arc

emen

t and

Sch

neid

er (

1987

), o

r fr

om th

e H

EC

-RA

S r

ecom

men

datio

ns fo

r cu

lver

t m

odel

ing.

Fig

ure

3—H

EC

-RA

S p

rofil

e.

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.

01

00

20

03

00

40

08

5

90

95

10

0

10

5

11

0

11

5

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

3

5 c

fs

Gro

un

d

1.5*

22.25*

2.5

33.5

44.15*

4.3

4.6

5.33333*

5.66666*

66.5

6.7

6.8

77.3

7.6

88.25

8.5

99.6

1010.3

10.65*

1111.2*

11.4

11.575*

11.7

11.75

1212.2

12.3

12.5

1313.2333*

13.4666*

13.7

14

Cul

vert

Elevation (ft)

A—336


Lowe 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

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cros

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ctio

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stat

ioni

ng (

RS

) co

rres

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s to

the

stat

ioni

ng o

n th

e H

EC

-RA

S p

rofil

e. G

reen

arr

ows

defin

e th

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effe

ctiv

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w a

reas

. Bla

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pres

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ts s

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yed

in a

s th

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ll ch

anne

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nly

thos

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cal

led

out i

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ld a

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uppo

rted

by

furt

her

hydr

aulic

and

topo

grap

hic

anal

yses

are

mar

ked

belo

w.

-20

020

4060

8010

6

108

110

112

114

116

118

120

122

R

S =

14

Sta

tion

(ft)

Elevation (ft)

Le

ge

nd

WS

Q10

0

WS

Q50

WS

Q10

WS

Qbf

WS

35

cfs

Gro

und

Ban

k S

ta

.133

6.1

336

.133

6

-20

020

4060

8010

4

106

108

110

112

114

116

118

120

R

S =

13

Sta

tion

(ft)

Elevation (ft)

Le

ge

nd

WS

Q10

0

WS

Q50

WS

Q10

WS

Qbf

WS

35

cfs

Gro

und

Ban

k S

ta

.122

8.1

228

. 1 2 2 8

-20

020

4060

80

104

106

108

110

112

114

116

118

R

S =

12

Sta

tion

(ft)

Elevation (ft)

Le

ge

nd

WS

Q10

0

WS

Q50

WS

Q10

WS

Qbf

WS

35

cfs

Gro

und

Ban

k S

ta

.133

2.1

332

. 1 3 3 2

020

4060

8010

010

0

102

104

106

108

110

112

114

116

R

S =

11

Sta

tion

(ft)

Elevation (ft)

Le

ge

nd

WS

Q10

0

WS

Q50

WS

Q10

WS

Qbf

WS

35

cfs

Gro

und

Ban

k S

ta

.131

3.1

313

. 1 3 1 3

Elevation (ft)Elevation (ft)


A—337

Site evaluations

Lowe 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. T

he

stat

ioni

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

poin

ts s

urve

yed

in a

s th

e ba

nkfu

ll ch

anne

l bou

ndar

y. O

nly

thos

e po

ints

cal

led

out i

n th

e fie

ld a

nd s

uppo

rted

by

furt

her

hydr

aulic

and

topo

grap

hic

anal

yses

are

mar

ked

belo

w. (

cont

inue

d)

-60

-40

-20

020

409810

0

102

104

106

108

110

112

114

R

S =

10

Sta

tion

(ft)

Elevation (ft)

Le

ge

nd

WS

Q10

0

WS

Q50

WS

Q10

WS

Qbf

WS

35

cfs

Gro

und

Ban

k S

ta

.130

5.1

305

. 1 3 0 5

-40

-20

020

4060

9698100

102

104

106

108

110

112

R

S =

8

Sta

tion

(ft)

Elevation (ft)

Le

ge

nd

WS

Q10

0

WS

Q50

WS

Q10

WS

Qbf

WS

35

cfs

Gro

und

Ban

k S

ta

. 0 2 4. 0 1 3

.093

4. 0 1 3. 0 2 4

-40

-20

020

4060

9698100

102

104

106

108

110

112

R

S =

7

Sta

tion

(ft)

Elevation (ft)

Le

ge

nd

WS

Q10

0

WS

Q50

WS

Q10

WS

Qbf

WS

35

cfs

Gro

und

Ban

k S

ta

. 0 2 4. 0 1 3

.1. 0 1 3. 0 2 4


Elevation (ft)

020

4060

8010

0969810

0

102

104

106

108

110

112

R

S =

9

Sta

tion

(ft)

Elevation (ft)

Le

ge

nd

WS

Q1

00

WS

Q5

0

WS

Q1

0

WS

Qb

f

WS

35

cfs

Gro

un

d

Le

vee

Ine

ff

Ba

nk

Sta

.075

.128

7. 0 7 5

Elevation (ft)

A—338


Lowe 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. T

he

stat

ioni

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

poin

ts s

urve

yed

in a

s th

e ba

nkfu

ll ch

anne

l bou

ndar

y. O

nly

thos

e po

ints

cal

led

out i

n th

e fie

ld a

nd s

uppo

rted

by

furt

her

hydr

aulic

and

topo

grap

hic

anal

yses

are

mar

ked

belo

w. (

cont

inue

d)

020

4060

8010

09294969810

0

102

104

106

108

R

S =

4

Sta

tion

(ft)

Elevation (ft)

Le

ge

nd

WS

Q10

0

WS

Q50

WS

Q10

WS

Qbf

WS

35

cfs

Gro

und

Ban

k S

ta

.113

1.1

131

.113

1

020

4060

8010

0

92949698100

102

104

106

R

S =

3

Sta

tion

(ft)

Elevation (ft)

Le

ge

nd

WS

Q10

0

WS

Q50

WS

Q10

WS

Qbf

WS

35

cfs

Gro

und

Ban

k S

ta

.119

7.1

197

.119

7

Elevation (ft)

Elevation (ft)

020

4060

8010

094969810

0

102

104

106

108

110

R

S =

5

Sta

tion

(ft)

Elevation (ft)

Le

ge

nd

WS

Q1

00

WS

Q5

0

WS

Q1

0

WS

Qb

f

WS

35

cfs

Gro

un

d

Ine

ff

Ba

nk

Sta

.114

5.1

145

.114

5

Elevation (ft)

-20

020

4060

80

9698100

102

104

106

108

110

R

S =

6

Sta

tion

(ft)

Elevation (ft)

Le

ge

nd

WS

Q1

00

WS

Q5

0

WS

Q1

0

WS

Qb

f

WS

35

cfs

Gro

un

d

Ine

ff

Ba

nk

Sta

.111

5.1

115

.111

5

Elevation (ft)

A—339

Site evaluations

Lowe 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. T

he

stat

ioni

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

poin

ts s

urve

yed

in a

s th

e ba

nkfu

ll ch

anne

l bou

ndar

y. O

nly

thos

e po

ints

cal

led

out i

n th

e fie

ld a

nd s

uppo

rted

by

furt

her

hydr

aulic

and

topo

grap

hic

anal

yses

are

mar

ked

belo

w. (

cont

inue

d)

020

4060

8010

0909294969810

0

102

104

106

R

S =

2

Sta

tion

(ft)

Elevation (ft)

Le

ge

nd

WS

Q1

00

WS

Q5

0

WS

Q1

0

WS

Qb

f

WS

35

cfs

Gro

un

d

Le

vee

Ba

nk

Sta

.112

6.1

126

.112

6

020

4060

8010

0

9092949698100

102

104

R

S =

1

Sta

tion

(ft)

Elevation (ft)

Le

ge

nd

WS

Q10

0

WS

Q50

WS

Q10

WS

Qbf

WS

35

cfs

Gro

und

Ban

k S

ta

.118

7.1

187

.118

7

Elevation (ft)

Elevation (ft)

Fig

ure

5—F

low

are

a (t

otal

) pr

ofile

plo

t.

05

01

00

15

02

00

25

03

00

35

04

00

0

10

0

20

0

30

0

40

0

50

0

60

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

35

cfs

Cul

vert

A

B

C

D

E

F G

Flow

H

Flow area (sq ft)

A—340


Lowe Creek

Fig

ure

6—W

ette

d pe

rimet

er.

Fig

ure

7—H

ydra

ulic

rad

ius.

05

01

00

15

02

00

25

03

00

35

04

00

0

20

40

60

80

10

0

12

0

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 35

cfs

Cul

vert

A

B

C

D

E

F G

Flow

H

05

01

00

15

02

00

25

03

00

35

04

00

02468

10

12

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 3

5 c

fs

Cul

vert

A

B

C

D

E

F G

Flow

H

W.P. total (ft) Hydraulic radius (ft)

A—341

Site evaluations

Lowe Creek

Fig

ure

8—To

p w

idth

.

Fig

ure

9—M

axim

um d

epth

.

05

01

00

15

02

00

25

03

00

35

04

00

0

20

40

60

80

10

0

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

35

cfs

Cul

vert

A

B

C

D

E

F G

Flow

H

05

01

00

15

02

00

25

03

00

35

04

00

02468

10

12

14

16

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

35

cfs

Cul

vert

A

B

C

D

E

F G

Flow

H

Top width (ft) Maximum channel depth (ft)

A—342


Lowe Creek

Fig

ure

10—

She

ar s

tres

s (c

hann

el)

profi

le.

Fig

ure

11—

Vel

ocity

(ch

anne

l) pr

ofile

plo

t.

05

01

00

15

02

00

25

03

00

35

04

00

0

10

20

30

40

50

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 3

5 c

fs

Cul

vert

A

B

C

D

E

F G

Flow

H

*Not

e: S

hear

at s

tatio

n 6.

5 fo

r th

e Q

50 a

nd Q

100

are

grea

ter

than

50

poun

ds p

er s

quar

e fo

ot a

nd a

re th

eref

ore

not s

how

n.

05

01

00

15

02

00

25

03

00

35

04

00

05

10

15

20

25

30

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 3

5 c

fs

Cul

vert

A

B

C

D

E

F G

Flow

H

Shear channel (lbs/sq ft) Velocity channel (ft/sec)

A—343

Site evaluations

Lowe Creek

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

Fig

ure

12—

Flo

w a

rea

(tot

al).

0

50100

150

200

AB

C (

ds tr

ans)

E (

culv

) F (

us tr

ans)

HA

B

C (

ds tr

ans)

E (

culv

) F (

us tr

ans)

HA

B

C (

ds tr

ans)

E (

culv

) F (

us tr

ans)

HA

B

C (

ds tr

ans)

E (

culv

) F (

us tr

ans)

HA

B

C (

ds tr

ans)

E (

culv

) F (

us tr

ans)

H

25%

Q2

Qbf

1050

100

Flow

Are

a (f

t2) A

B

C (DS Trans)

E (Culvert)

F (US Trans)

H

A

B

C (DS Trans)

E (Culvert)

F (US Trans)

H

A

B

C (DS Trans)

E (Culvert)

F (US Trans)

H

A

B

C (DS Trans)

E (Culvert)

F (US Trans)

H

A

B

C (DS Trans)

E (Culvert)

F (US Trans)

H

Flow area (ft2)

A—344


Lowe Creek

Fig

ure

13—

Wet

ted

perim

eter

. F

igur

e 14

—H

ydra

ulic

rad

ius.

0

306090120

AB

C (

ds tr

ans)

E (

culv

) F (

us tr

ans)

HA

B

C (

ds tr

ans)

E (

culv

) F (

us tr

ans)

HA

B

C (

ds tr

ans)

E (

culv

) F (

us tr

ans)

HA

B

C (

ds tr

ans)

E (

culv

) F (

us tr

ans)

HA

B

C (

ds tr

ans)

E (

culv

) F (

us tr

ans)

H

25%

Q2

Qbf

1050

100

Wet

ted

Perim

eter

(ft)

0246

AB

C (

ds tr

ans)

E (

culv

) F (

us tr

ans)

HA

B

C (

ds tr

ans)

E (

culv

) F (

us tr

ans)

HA

B

C (

ds tr

ans)

E (

culv

) F (

us tr

ans)

HA

B

C (

ds tr

ans)

E (

culv

) F (

us tr

ans)

HA

B

C (

ds tr

ans)

E (

culv

) F (

us tr

ans)

H

25%

Q2

Qbf

1050

100

Hyd

raul

ic R

adiu

s (f

t)

A

B

C (DS Trans)

E (Culvert)

F (US Trans)

H

A

B

C (DS Trans)

E (Culvert)

F (US Trans)

H

A

B

C (DS Trans)

E (Culvert)

F (US Trans)

H

A

B

C (DS Trans)

E (Culvert)

F (US Trans)

H

A

B

C (DS Trans)

E (Culvert)

F (US Trans)

H

A

B

C (DS Trans)

E (Culvert)

F (US Trans)

H

A

B

C (DS Trans)

E (Culvert)

F (US Trans)

H

A

B

C (DS Trans)

E (Culvert)

F (US Trans)

H

A

B

C (DS Trans)

E (Culvert)

F (US Trans)

H

A

B

C (DS Trans)

E (Culvert)

F (US Trans)

H

Wetted perimeter (ft) Hydraulic radius (ft)

A—345

Site evaluations

Lowe Creek

Fig

ure

15—

Top

wid

th.

Fig

ure

16—

Max

imum

dep

th.

0

20406080100

AB

C (

ds tr

ans)

E (

culv

) F (

us tr

ans)

HA

B

C (

ds tr

ans)

E (

culv

) F (

us tr

ans)

HA

B

C (

ds tr

ans)

E (

culv

) F (

us tr

ans)

HA

B

C (

ds tr

ans)

E (

culv

) F (

us tr

ans)

HA

B

C (

ds tr

ans)

E (

culv

) F (

us tr

ans)

H

25%

Q2

Qbf

1050

100

Top

Wid

th (f

t) A

B

C (DS Trans)

E (Culvert)

F (US Trans)

H

A

B

C (DS Trans)

E (Culvert)

F (US Trans)

H

A

B

C (DS Trans)

E (Culvert)

F (US Trans)

H

A

B

C (DS Trans)

E (Culvert)

F (US Trans)

H

A

B

C (DS Trans)

E (Culvert)

F (US Trans)

H

Top width (ft)

02468

AB

C (

ds tr

ans)

E (

culv

) F (

us tr

ans)

HA

B

C (

ds tr

ans)

E (

culv

) F (

us tr

ans)

HA

B

C (

ds tr

ans)

E (

culv

) F (

us tr

ans)

HA

B

C (

ds tr

ans)

E (

culv

) F (

us tr

ans)

HA

B

C (

ds tr

ans)

E (

culv

) F (

us tr

ans)

H

25%

Q2

Qbf

1050

100

Max

imum

Dep

th (f

t)

8.4

-11

A

B

C (DS Trans)

E (Culvert)

F (US Trans)

H

A

B

C (DS Trans)

E (Culvert)

F (US Trans)

H

A

B

C (DS Trans)

E (Culvert)

F (US Trans)

H

A

B

C (DS Trans)

E (Culvert)

F (US Trans)

H

A

B

C (DS Trans)

E (Culvert)

F (US Trans)

H

Maximum depth (ft)

A—346


Lowe Creek

Fig

ure

17—

Wid

th-t

o-de

pth

ratio

.

Fig

ure

18—

Vel

ocity

(ch

anne

l).

020406080

AB

C (

ds tr

ans)

E (

culv

) F (

us tr

ans)

HA

B

C (

ds tr

ans)

E (

culv

) F (

us tr

ans)

HA

B

C (

ds tr

ans)

E (

culv

) F (

us tr

ans)

HA

B

C (

ds tr

ans)

E (

culv

) F (

us tr

ans)

HA

B

C (

ds tr

ans)

E (

culv

) F (

us tr

ans)

H

25%

Q2

Qbf

1050

100

Wid

th-t

o-de

pth

Rat

io

02468

AB

C (

ds tr

ans)

E (

culv

) F (

us tr

ans)

HA

B

C (

ds tr

ans)

E (

culv

) F (

us tr

ans)

HA

B

C (

ds tr

ans)

E (

culv

) F (

us tr

ans)

HA

B

C (

ds tr

ans)

E (

culv

) F (

us tr

ans)

HA

B

C (

ds tr

ans)

E (

culv

) F (

us tr

ans)

H

25%

Q2

Qbf

1050

100

Velo

city

(ft/

sec)

A

B

C (DS Trans)

E (Culvert)

F (US Trans)

H

A

B

C (DS Trans)

E (Culvert)

F (US Trans)

H

A

B

C (DS Trans)

E (Culvert)

F (US Trans)

H

A

B

C (DS Trans)

E (Culvert)

F (US Trans)

H

A

B

C (DS Trans)

E (Culvert)

F (US Trans)

H

Width-to-depth ratio

A

B

C (DS Trans)

E (Culvert)

F (US Trans)

H

A

B

C (DS Trans)

E (Culvert)

F (US Trans)

H

A

B

C (DS Trans)

E (Culvert)

F (US Trans)

H

A

B

C (DS Trans)

E (Culvert)

F (US Trans)

H

A

B

C (DS Trans)

E (Culvert)

F (US Trans)

H

Velocity (ft/sec)

A—347

Site evaluations

Lowe Creek

Fig

ure

19—

She

ar s

tres

s (c

hann

el).

Fig

ure

20—

Exc

ess

shea

r st

ress

.

05101520

AB

C (

ds tr

ans)

E (

culv

) F (

us tr

ans)

HA

B

C (

ds tr

ans)

E (

culv

) F (

us tr

ans)

HA

B

C (

ds tr

ans)

E (

culv

) F (

us tr

ans)

HA

B

C (

ds tr

ans)

E (

culv

) F (

us tr

ans)

HA

B

C (

ds tr

ans)

E (

culv

) F (

us tr

ans)

H

25%

Q2

Qbf

1050

100

Shea

r Str

ess

(lbs/

ft2)

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

size

. 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.

01234

010

020

030

040

050

060

0

Dis

char

ge

(cfs

)

Exce

ss S

hear

(Ap

plie

d /

tcrit

)

US

Ch

an

ne

l (D

S p

eb

ble

co

un

t) -

ste

p

Cu

lve

rt (

DS

pe

bb

le c

ou

nt)

- r

iffle

DS

Ch

an

ne

l (D

S p

eb

ble

co

un

t) -

riff

le

A

B

C (DS Trans)

E (Culvert)

F (US Trans)

H

A

B

C (DS Trans)

E (Culvert)

F (US Trans)

H

A

B

C (DS Trans)

E (Culvert)

F (US Trans)

H

A

B

C (DS Trans)

E (Culvert)

F (US Trans)

H

A

B

C (DS Trans)

E (Culvert)

F (US Trans)

H

Shear stress (lbs/ft2) Excess shear (Applied/tcrit)

A—348


Lowe 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 0.06 Yes

DS Riffle 0.03 Yes

Upstream US Pool 0.05

DS Step 0.10

Downstream US Pool 0.04

DS Riffle 0.03

Table 4—Vertical sinuosity

Segment Location vertical 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 XS 25% Q2 Within range of

Location channel conditions?

Culvert US 1 No

DS 2 Yes

Upstream US 2

DS 2

Downstream US 3

DS 18

A—349

Site evaluations

Lowe Creek

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%

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 1.50 Yes 0.13 Yes

DS Riffle 1.47 Yes 0.26 Yes

Upstream US Pool 1.59 0.12

DS Step 1.25 0.14

Downstream US Pool 1.55 0.31

DS Riffle 2.34 0.37

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

Segment A Segment B

Segment C: DSTransition Segment D:

CulvertSegment E:

Culvert

Segment F: USTransition

Segment G Segment H

Residual depth (ft)

Seg

men

t A

Seg

men

t B

Seg

men

t C

DS

Tra

nsiti

on

Seg

men

t D

Cul

vert

Seg

men

t E

Cul

vert

Seg

men

t F

US

Tra

nsiti

on

Seg

men

t G

Seg

men

t H

Res

idua

l Dep

th (

ft)

A—350


Lowe Creek

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—351

Site evaluations

Lowe Creek

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.

A—352


Lowe Creek

Cross Section: Upstream Reference Reach – Upstream Pebble Count

Sorting Coefficient: 1.59Skewness Coefficient: 0.12

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 1 1% 3%

medium gravel 8 - 11.3 1 1% 4%

medium gravel 11.3 - 16 3 3% 8%

coarse gravel 16 - 22.6 1 1% 9%

coarse gravel 22.6 - 32 3 3% 12%

very coarse gravel 32 - 45 8 9% 21%


small cobble 64 - 90 8 9% 39%

medium cobble 90 - 128 11 12% 51%

large cobble 128 - 180 7 8% 59%

very large cobble 180 - 256 11 12% 71%

small boulder 256 - 362 14 15% 86%

small boulder 362 - 512 9 10% 96%

medium boulder 512 - 1024 4 4% 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

<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

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 13

D16 40

D50 120

D84 349

D95 500

D100 900

Material P erc ent C ompos ition

Sand 0%

Gravel 30%

Cobble 40%

Boulder 29%

Bedrock 0%

A—353

Site evaluations

Lowe Creek

Cross Section: Upstream Reference Reach – Downstream Pebble Count



sand <2 0 0% 0%


fine gravel 4 - 5.7 1 1% 1%

fine gravel 5.7 - 8 0 0% 1%


medium gravel 11.3 - 16 0 0% 1%

coarse gravel 16 - 22.6 0 0% 1%

coarse gravel 22.6 - 32 0 0% 1%



small cobble 64 - 90 9 10% 22%

medium cobble 90 - 128 6 7% 29%

large cobble 128 - 180 12 14% 43%


small boulder 256 - 362 12 14% 72%

small boulder 362 - 512 13 15% 87%

medium boulder 512 - 1024 11 13% 100%

large boulder 1024 - 2048 0 0% 100%


bedrock Bedrock 0% 100%

0

2

4

6

8

10

12

14

16

<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


Frequency

-20%

0%

20%

40%

60%

80%

100%


<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



than (mm)

D5 43

D16 78

D50 210

D84 500

D95 600

D100 700


Sand 0%

Gravel 11%

Cobble 47%

Boulder 41%

Bedrock 0%

A—354


Lowe Creek

Cross Section: Culvert – Upstream Pebble Count


<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



sand <2 1 1% 1%


fine gravel 4 - 5.7 1 1% 3%

fine gravel 5.7 - 8 1 1% 4%


medium gravel 11.3 - 16 3 3% 8%

coarse gravel 16 - 22.6 2 2% 10%

coarse gravel 22.6 - 32 5 5% 15%



small cobble 64 - 90 19 20% 49%

medium cobble 90 - 128 9 9% 59%

large cobble 128 - 180 17 18% 76%


small boulder 256 - 362 3 3% 89%

small boulder 362 - 512 9 9% 98%

medium boulder 512 - 1024 2 2% 100%

large boulder 1024 - 2048 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


Frequency

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%



than (mm)

D5 12

D16 35

D50 100

D84 236

D95 470

D100 600


Sand 1%

Gravel 29%

Cobble 56%

Boulder 14%

Bedrock 0%

A—355

Site evaluations

Lowe Creek

Cross Section: Culvert – Downstream Pebble Count



sand <2 1 1% 1%


fine gravel 4 - 5.7 0 0% 2%

fine gravel 5.7 - 8 0 0% 2%


medium gravel 11.3 - 16 2 2% 5%

coarse gravel 16 - 22.6 3 3% 9%

coarse gravel 22.6 - 32 2 2% 11%



small cobble 64 - 90 7 7% 31%

medium cobble 90 - 128 4 4% 35%

large cobble 128 - 180 16 17% 52%


small boulder 256 - 362 14 15% 81%

small boulder 362 - 512 14 15% 96%

medium boulder 512 - 1024 4 4% 100%

large boulder 1024 - 2048 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


Frequency

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%


<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



than (mm)

D5 18

D16 49

D50 165

D84 382

D95 504

D100 950


Sand 1%

Gravel 22%

Cobble 43%

Boulder 34%

Bedrock 0%

A—356


Lowe Creek

Cross Section: Downstream Reference Reach – Upstream Pebble Count


Material S ize R ange (mm) C ount Item % C umulative %

sand <2 0 0% 0%


fine gravel 4 - 5.7 0 0% 1%

fine gravel 5.7 - 8 1 1% 2%


medium gravel 11.3 - 16 4 4% 10%

coarse gravel 16 - 22.6 3 3% 13%

coarse gravel 22.6 - 32 10 10% 23%



small cobble 64 - 90 8 8% 46%

medium cobble 90 - 128 14 14% 61%

large cobble 128 - 180 19 19% 80%


small boulder 256 - 362 6 6% 97%

small boulder 362 - 512 3 3% 100%

medium boulder 512 - 1024 0 0% 100%

large boulder 1024 - 2048 0 0% 100%


bedrock > 4096 0 0% 100%


than (mm)

D5 11

D16 23

D50 100

D84 210

D95 340

D100 420

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

> 4096


Frequency

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%


<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



Sand 0%

Gravel 38%

Cobble 53%

Boulder 9%

Bedrock 0%

A—357

Site evaluations

Lowe Creek

Cross Section: Downstream Reference Reach – Downstream Pebble Count



sand <2 8 8% 8%


fine gravel 4 - 5.7 0 0% 9%

fine gravel 5.7 - 8 3 3% 12%

medium gravel 8 - 11.3 0 0% 12%

medium gravel 11.3 - 16 2 2% 14%

coarse gravel 16 - 22.6 8 8% 22%

coarse gravel 22.6 - 32 9 9% 31%



small cobble 64 - 90 3 3% 48%

medium cobble 90 - 128 13 13% 61%

large cobble 128 - 180 9 9% 70%


small boulder 256 - 362 12 12% 90%

small boulder 362 - 512 7 7% 97%

medium boulder 512 - 1024 3 3% 100%

large boulder 1024 - 2048 0 0% 100%



0

2

4

6

8

10

12

14

<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


Frequency

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%


<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



than (mm)

D5 1

D16 18

D50 100

D84 300

D95 430

D100 750


Sand 8%

Gravel 37%

Cobble 33%

Boulder 22%

Bedrock 0%

culvert scour assessment - us forest service€”332 culvert scour assessment lowe creek bed...

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