WSP05649 - Laserfiche WebLink

Home Browse Search

550 TOPPfNG ET AL: COLORADO RIVER SEDIMENT TRANSPORT, 2 1000 1900 S w 800 '" 0: <( J: 700 0 In Ci 0: 600 UI .... <( ;: 500 400 a) 1000 1900 S w 800 '" 0: <( J: 700 " In Ci 0: 800 ~ < ;: SOO 400 b) 2.S -+- LEes FERRY -o-lOWER MAR8lE CANYON ;:: ___ GIWIl CANYON --0-- ABOVE DIAMOND CREEK 2.0 !I)!!! Z!:; ~~ -40 ..'; 0-< 1.0 ';0 -<0 Z 00 O' z- 0 DAY 1 DAY 2 0.0 Figure 7. Hydrograph of the 1997 test flow (as measured at the Lees Ferry gage) and spatially averaged BUspended-sediment and bed-sediment data colleered at the four gages. The fine sediment on the bed was winnowed, and the suspended sand coarsened as the concentration of suspended sand decreased. The travel lime of the flood between the four gages has been removed in Figure 7 such that the beginning of day I at each site corresponds to the lime of the beginning of steady high discharge at each site. (a) Spatially averaged, mean-daily, nondimensional suspended-sand concentrations at the four gages. Mean-<laily concentrations at each gage were nondimensionalized by dividing the mean concentration on each day by the mean concen- tration over both days; error bars are I standard deviation. At the Lees Ferry gage the mean suspended-sand concentration over both days was 0.0010%; at the Lower Marble Canyon gage the mean suspended-sand concentration over both days was 0.046%; at the Grand Canyon gage the mean suspended-sand concentration over both days was 0.042%; and at the Above Diamond Creek gage the mean suspended-sand concentration over both days was 0.050%. (b) SpatiaUy averaged, mean-daily suspended-sill and clay concentrations non- dimensionalized using the. same approach as in Figure 7.. AI the Lees Ferry gage the mean suspended-silt and clay concentration over both days was 0.0015%; at the Lower Marble Canyon gage the mean suspended-silt and clay concentration over both days was 0.021 %; at the Grand Canyon gage the mean suspended-silt and clay concentration over both days Was 0.024%; and at the Above Diamond Creek gage the mean suspended- silt and clay concentration over both days was O.oJ8%. (c) SpatiaUy averaged, mean-<laily median size of suspended sand; error bars are I standard deviation. (d) Spatially averaged, mean-daily median size of the fine sediment (i.e., sand and finer material) on the bed at the Lower Marble Canyon and Above Diamond Creek gages; error bars are I standard deviation. On the basis of observations made during the 1996 flood experiment at the Grand Canyon gage, a minimum of 50 g of sample is required at three positions across tbe channel for data collected by a BM.54 sampler to be representative of the bed. Therefore days with fewer than three bed-sediment samples in excess of 50 g were excluded from this analysis. (e) Spatially averaged fraction of the fine sediment on the bed composed of 0.0625- to O.I25-mm sand at the Lower Marble Canyon and Above Diamond Creek gages. S. Coupled Cbanges in Suspended-Sand Concentration, Suspended-Sand Grain Size, and Bed Grain Size in tbe Colorado River Following Large Tributary Sand Inputs upstream supply of sand was depleted. Systematic coupled changes in sand grain size and concentration should also OCCUr in the Colorado River during periods when the upstream sup- ply of sand is enhanced during large tributary floods. To de. termine the style of coupled sand-transport and grain-size changes in the Colorado River during and following large tributary floods, we analyzed: (I) suspended- and bed- During both the 1996 flood experiment and the 1997 test flow, sand on the bed and in suspension coarsened as the