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478 Topographic Response of a Bar are based upon 13 verticals computed for each cross section, compared to the 20-30 measured verticals per cross section. Therefore, the computed lateral distribution of unit discharge is somewhat smoother than the measured distribution. Computed Transport Rate of Bed-Material through Ouray Reach Similarly, the computed and measured rates of bed material transport through the Ouray reach are in good agreement. The rate of bed-material transport through each of the 41 cross sections in the Ouray reach was determined at a given discharge by integrating the computed local values in a cross section. Except for discharges around 275 m3/s, the cross-sectionally averaged sediment transport rates varied significantly through the reach. An estimate of the amount of bed-material larger than 0.0625 nun in diameter being transported through the Ouray reach at a given discharge can be determined by averaging over the 41 cross sections. Then, the relation between reach averaged bed-material transport and water discharge was determined for 6 discharges between 100 m3/s and 475 m3/s. An estimate of the mean annual bed-material load transported through the Ouray reach during the period from 1982-86 was computed using the recorded water discharges at the Jensen gage, and the locally determined bed-material transport relation. During the period of relatively large discharges, 1983-86, the mean annual bed-material load transported through the Ouray reach was computed to be approximately 3.1lC106 tons/yr. The mean annual load of bed-material sized sediment determined by sampling at the Jensen. gage and regression analysis was 2.7lC106 tons/yr _during the same period. One would expect the mean annual load of sand-sized material transported by the Green River through the Ouray reach to be somewhat larger than the quantity transported at the Jensen gage because the concentration of suspended sediment in the bottom 7.6 em of the flow is not sampled by the equipment used at the Jensen gage. Hence, the actual concentration of suspended sand at the Jensen gage is slightly greater than the measured. This discrepancy is greatest at small discharges and least at large discharges. Evolution of Bar Topography in Response to Various Discharges Adjustment of channel topography with time at a constant discharge was investigated at 3 discharges, 50 m3/s, 275 m3/s, and 475 m3/s. Each calculation begait with the same bed topography, that which existed on July 15 and 16, 1986 at a discharge of approximately 275 m3/s. The techniques used to determine the location of the banks and to compute erosion and deposition have been described above. Each calculatio'l covered 100 increments of 1728 seconds, or a total of 2 days. Evolution of channel topography in the Ouray reach at a constant discharge of 275 m3/s is shown in figure 7 at 5 cross sections, numbers 16, 18, 20, 22, and 24. These cross sections were selected to illustrate in detail changes in tbe bar topography. During the spring of 1986, discharge through the Ouray reach peaked at ov620 m3/s on June 8 and 9, and decreased - gradually .to..280 m3/s .on July.15 when the channel topography was surveyed. .-.-./ As one would expect, the channel topography was nearly in equilibrium with a discharge of 275 m3/s and computed changes in the bed elevation were everywhere quite small. The model calculations indicate that sediment is deposited very slowly on the bar surface and in the upstream portion of the primary channel. Conversely, sediment is eroded very slowly from the downstream portion of the primary channel. Predicted evolution of channel topography in the Ouray reach at a constant discharge of 475 m3/s is shown in figure 8 at 5 cross sections, numbers 16, 18, 20, 22, and 24. Near the head of the bar (cross section 16), there is no significant