Valley Creek
General Information
Valley Creek is a tributary of the Salmon River at Stanley, Idaho. The study
reach is a 1,500 ft length of stream at the Geological Survey (USGS) gage 13295000
(Valley Creek at Stanley, Idaho) in the Sawtooth National Forest. The site is just
upstream of the confluence with the Salmon River at an elevation of about 6,222 ft. The
drainage area is 148.9 mi2 and the geology of the watershed is predominantly intrusive
igneous and valley deposits associated with glaciation.
In 1994 and 1995 personnel of Case Western Reserve University and personnel of
the US Geological Survey (USGS) both independently measured sediment transport at
this site. USGS personnel also measured sediment transport on two dates during the high
flows in 1997. Additional information collected at this site include a survey of the stream
reach, pebble counts of the substrate surface and core samples of the substrate subsurface
material. Figures 1 and 2 show photographs of looking upstream and downstream from a
foot bridge about 300 ft upstream of the USGS gage.
Figure 1. Valley Creek looking downstream from the foot bridge.
Figure 2. Valley Creek looking upstream from the foot bridge.
Daily mean discharge records are available for May 1911 to October 1913, May
1921 to December 1971, April 1972 to September 1972 and October 1992 to present.
Estimated average annual discharge (Qa) for the stream is 205 ft3/s and the estimated
bankfull discharge (Qb) is 850 ft3/s. The range of daily mean discharge for the period of
record is 34 ft3/s to 1,900 ft3/s. The largest discharge recorded was 2,000 ft3/s on May
24, 1956.
Channel Profile and Cross-Section
Figure 3 shows the longitudinal profile for the channel bed in the center of the
channel, the water surface elevations along each bank at the time of the survey and
bankfull flow elevations (floodplains). The average gradient for the study reach is 0.0040
ft/ft. Cross-sections of the channel were surveyed at seven location locations. Figure 3
shows the locations of the five cross-sections surveyed by CWRU personnel and the three
cross-sections surveyed by USFS personnel (underlined). Cross-section 4 (not
underlined) is the upstream side of the foot bridge and cross-section 2 (cross-section 5
underlined) is at the USGS gage.
168
Valley Creek
166
Elevation, ft
164
162
XS5
160
XS4
158
XS3
Center of Channel Bed Elevation
Water Surface Elevation Left Edge
Water Surface Elevation Right Edge
Bankfull Elevation Left Side
Bankfull Elevation Right Side
156
154
152
0
200
400
XS2
XS5
XS4
600
800
XS1
XS6
1000
1200
1400
1600
Distance, ft
Figure 3. Longitudinal profile of the study reach in Valley Creek.
40
Valley Creek
Elevation, ft
30
at USGS Staff Plate
20
10
Qa
0
1994 survey
1998 survey
-10
-100
-50
0
50
100
150
200
Distance, ft
Figure 4. Cross-section of Valley Creek at the USGS staff plate.
250
Channel Geometry
Figure 4 shows the cross-section at the USGS gage at Valley Creek. The channel
geometry relationships for this cross-section are shown in Figure 5. All data collected
from Sept. 1992 through Jan. 1998 were used to develop the displayed power
relationships with discharge. Sediment transport was measured during discharges
ranging from 139 to 1,420 ft3/s. Wading measurements of sediment transport within 150
ft of this cross-section were at discharges ranging from 166 to 680 ft3/s. For this range of
discharges, the estimated stream width, estimated average depth and estimated average
velocity varied from 72.0 to 79.6 ft, 1.32 to 2.35 ft, and 1.8 to 3.6 ft/s, respectively. The
average reach gradient is 0.0040 ft/ft.
1000
10
Valley Creek
Average Velocity
0.518
y = 0.124x
2
R = 0.95
Width
0.072
y = 49.874x
2
R = 0.74
10
1
Average Depth
0.412
y = 0.160x
2
R = 0.90
Average Velocity, ft/s
Width and Depth, ft
100
1
Note: Hydraulic geometry relationships developed from
discharge measurements taken within 20 feet (upstream
or downstream) of gage between Sept. 1992 and Jan.
1998.
0.1
10
100
1000
0.1
10000
Discharge, ft3/s
Figure 5. Width, average depth, and average velocity versus stream discharge at the
cross-section at the USGS gage on Valley Creek. (Open symbols represent
data collected prior to Sept. 1992 and were not used to develop the power
relationships.)
Channel Material
Surface pebble counts were made at three cross-sections (XS4, XS5, and XS6) by
USFS personnel and at one cross-section (XS1) by CWRU personnel in 1994. Surface
pebble counts were also made at four cross-sections and four cores of subsurface material
were collected, one at each cross-section, in 1995. The D50 and D90 for the combined
pebble counts (1995) in the reach were 40 mm and 132 mm, respectively (Figure 6).
About 16% of the surface material was sand (2 mm) size or smaller in the 1995 sampling.
The D50 and D90 for the combined subsurface cores (1995) were 21 mm and 81 mm,
respectively. The D50 for the surface of the floodplain material ranged between 0.16 and
0.22 mm.
100
Valley Creek
90
80
Percent Finer
70
Floodplain
Samples
60
50
40
30
20
Surface 1995
Subsurface 1995
Surface 1994 CWRU
Surface 1994 USFS
10
0
0.01
0.1
1
10
100
1000
Particle Size, mm
Figure 6. Particle size distribution for surface and subsurface substrate samples
in the Valley Creek reach.
Sediment Transport
The bedload and suspended load measurements in water years 1994 through 1997
were all made at various locations within the reach. All measurements by Case Western
Reserve University personnel were at the foot-bridge, about 300 ft upstream of the gage.
USGS personnel made measurements near the gage at discharges less than about 700
ft3/s. At higher flows they made measurements 500 ft and 1,000 ft downstream of the
gage and at highest discharges they made measurements from the highway bridge about
1,000 ft downstream of the gage. The sediment transport data includes 116 measurements
of bedload transport and 71 measurements of suspended sediment. Sediment transport
measurements spanned a range of stream discharges from 139 ft3/s (0.68Qa; 0.16Qb) to
1,420 ft3/s (6.96Qa; 1.67Qb). Bedload transport ranged from 0.0077 to 89.8 t/d and
suspended transport ranged from 1.08 to 223 t/d. At discharges less than about 500 ft3/s
suspended transport accounts for the majority of the material in transport and at higher
discharges bedload accounts for the majority of material in transport (Figure 7).
1000
Valley Creek
Sediment Transport, tons/day
100
10
1
0.1
Suspended
1.875
y = 8.645E-05x
2
R = 0.75
BCF=1.320
Total Bedload
2.808
y = 2.463E-07x
2
R = 0.59
BCF=1.823
Total Bedload-Bridge
Total Bedload-Foot Bridge
Total Bedload Wading (within 150 ft of gage)
Total Bedload Wading (500-1000 ft downstream)
Suspended - Bridge
Suspended - Foot Bridge
Suspended (Wading within 150 ft of gage)
0.01
Suspended (Wading 500-100 ft downstream)
Qa
Qb
0.001
10
100
1000
Discharge, ft3/s
Figure 7. Bedload and suspended load transport rate versus discharge.
10000
The bedload transport rates by size class (Figure 8) shows that the larger rates are
associated with material 0.5 to 2 mm diameter and 2 to 8 mm diameter. Only seven
bedload samples contained material larger than 32 mm diameter and these were at
discharges of 614 ft3/s and larger.
100
Valley Creek
Bedload Rate, tons/day
10
1
0.1
0.01
<0.5mm
2.643
y = 4.089E-08x
2
R = 0.59
0.5-2mm
2.591
y = 4.694E-07x
2
R = 0.56
2-8mm
3.054
y = 1.775E-08x
2
R = 0.54
8-32mm
2.506
y = 8.096E-08x
2
R = 0.49
>32mm
0.627
y = 5.874E-02x
2
R = 0.10
Qb
Qa
<0.5mm
0.5-2mm
2-8mm
8-32mm
>32mm
0.001
10
100
1000
3/
Discharge, ft s
Figure 8. Bedload transport rate versus discharge for selected size classes
10000
The largest particle in the bedload sample generally increased with discharge
(Figure 9). The largest particle measured in a bedload sample was 141 mm at a discharge
of 1,390 ft3/s. There is also a weak trend of increasing median size of the bedload sample
with increasing discharge. The largest median size of a bedload sample was 18.5 mm.
The relationship between discharge and the largest particle in the bedload sample and the
observations of painted rock movement suggest that discharges near bankfull discharge
are capable of moving the median diameter particles on the channel surface.
1000
Valley Creek
Largest Painted
Rock Moved
1995
Bedload Size, mm
100
D50 for four
surface pebble
counts
2
R = 0.59
D50 for four
subsurface cores
10
2
R = 0.12
1
Qa
Qb
Median Size
Largest Particle
0.1
10
100
1000
10000
Discharge, ft3/s
Figure 9. Largest particle in the bedload sample and median size of the sample
versus stream discharge for Valley Creek.
Painted Rock Transport
A total of forty painted rocks were placed across two transects (twenty per
transect) on April 12, 1995. Daily mean discharge on the day of rock placement was 219
ft3/s. The size of the rocks ranged from 69 to 190 mm diameter (b-axis) at transect 1,
which represents the D69 up to the D96 of the average surface particle size distribution
measured in the reach in 1995. The size of the rocks ranged from72 to 206 mm diameter
(b-axis) at transect 2, which represents the D71 up to the D97 of the average surface
particle size distribution measured in the reach in 1995. Transport of the rocks as of
August 11, 1995 are shown in Figures 10 and 11.
60
Valley Creek
Painted Rocks
Transect 1
Downstream Distance Moved, ft
50
40
30
20
10
Particle
B-axis, mm
140
87
150
104
178
85
190
75
170
100
165
88
185
83
130
85
165
M
69
160
81
77
80
M
0
23
26
29
32
36
38
41
44
47
50
53
56
59
62
65
68
71
74
Distance Across Stream, ft
Figure 10. Transport distance of painted rocks at transect 1.
60
Valley Creek
Painted Rocks
Transect 2
Downstream Distance Moved, ft
50
40
30
20
Particle
B-axis, mm
10
91
175
72
130
73
148
84
206
85
132
80
141
74
146
76
160
73
M
M
M
64
68
72
139
95
142
76
80
84
0
8
12
16
20
24
28
32
36
40
44
48
52
56
60
Distance Across Stream, ft
Figure 11. Transport distance of painted rocks at transect 2.
Thirty five of the forty rocks were found. Of those found, eight had moved more
than 1 ft. Most of the movement occurred for rocks in transect 1. The maximum
transport distance was 51.5 ft for a 75mm diameter rock and the average was transport
distance was 3.0 ft. The largest daily mean discharge during this period was 1,020 ft3/s
on June 6, 1995 and the largest instantaneous discharge was 1,070 ft3/s on the same date.