WSP05649

• File Number: 8220.101.10.D
• Description: Glen Canyon Dam/Lake Powell
• State: AZ
• Basin: Colorado Mainstem
• Date: 2/1/2000
• Author: Topping et al.
• Title: Colorado River Sediment Transport
• Water Supply Pro - Doc Type: Report/Study

554 TOPPING ET AL: COLORADO RIVER SEDIMENT TRANSPORT, 2

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-0- MEASURED SAND CONCENTRATION
_WATER DISCHARGE

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OCTOBER

NOVEMBER

DECEMBERO

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--0- MEAS\.R:D AT MCNE DIAMOND CREEK GAGE
...+... PREDIClED BY RANDlE AND PB.4BERTON (1987)

NOVEMBER

DECEMBER

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DECEMBER

Figure 10. Coupled changes in suspended-sand concentration and grain size in the Colorado River associ-
ated with the 1983 Little Colorado River ftood. (a) Suspended-sand concentration measured at the highway
89 bridge at Cameron during the September-October 1983 little Colorado River ftood and the computed
instantaneous discharge of water at the LCR near Cameron gage from mid-SepIember through mid.
December 1983. (b) Measured suspended-sand concentration at the three gages downstream from the mouth
of the little Colorado River and the suspended-sand concentration predicted by RiIndk and Pemberton (1987]
at the Grand Canyon gage. The measured concentration of suspended sand increased at all three downstream
gages on the Colorado River immediately following the tributary ftood peak. Because their approach was
based on a fixed grain-size distribution of bed sedimen~ RiIndk and Pemberton [1987] do not predict this
increase in concentration. (c) Measured median size of the suspended sand at the three gages downstream
from the mouth of the Little Colorado River. Input of sand from the Little Colorado River caused the grain
size to decrease. (d) Measured concentration of the finer (0.0625-0.125 nun) and coarser (0.25-2.0 mm)
suspended-sand at the Above Diamond Creek gage. Figure IOd shows the segregation of grain sizes that
occurred in the Colorado River following the tributary flood, with higher concentrations of finer sand
occurring in early October and higher concentrations of coarser sand occurring after mid-November. (e)
Spatially averaged median size of the fine sediment on the bed of the Colorado River at the three downstream
gages. Only at the Grand Canyon gage did the median size of the fine sediment on the bed decrease in
response to the Little Colorado River ftood. Data appearing in Figures We and Wf were first filtered using
the same approach as in Figure 7d. Also, because on some days more bed-sediment samples were collected
near the banks than in the central portion of the channel, samples from the near-bank regions (i.e., the right
and left 15% of the channel) were excluded from this analysis [Q avoid biasing the analysis toward the finer
near-bank sediment. (f) Spatially averaged fraction of the fine sediment on the bed composed of 0.0625- to
O.l25-mm sand. At all three downstream gages the amount of 0.0625- to 0.125-mm sand composing the fine
sediment on the bed increased from trace amounts to about 5% after the beginning of the Little Colorado
River flood. The bold vertical line in Figures lOb-IOf indicates the time of the beginning of the Little Colorado
River flood.