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<br />Draft Fmal Completion Report to UDWR for Contract #93-1070, Amendment 3 <br /> <br />14 <br /> <br />sediment transport equations to model bed evolution. This combination of modeling strategies allows the simulation of <br /> <br />bed evolution and bar genesis in natural channels, and the sediment transport algorithm was formulated using Yalin's <br /> <br />(1963) sediment transport equation. Simulation results of the bed evolution model were compared with results from <br /> <br />Hooke's (1975) flume experiments. The topography predicted by the model was very similar to that produced in the <br /> <br />flume. although location of the deepest scour was predicted downstream rather than upstream of the bend apex. Overall, <br /> <br />the agreement between the sediment fluxes and bottom stresses were quite good. <br /> <br />The expanded model of Nelson and Smith (l989b) was applied to a river reach within the OurayNWR by <br /> <br />Andrews and Nelson (1989). Cross-section topography measured at 275 m3fs was used as model input, and response of <br /> <br />the channel was modeled for steady flow at 3 discharges (50, 275 and 475 m3fs) for 2-day periods. Validation of <br /> <br />modeled bed evolution was not possible. but calculated distribution of unit discharge and sediment transport compared <br /> <br />well to field measurements (Andrews ~ Nelson. 1989). Model results indicated that the river bed adjusted quickly to <br /> <br />changes in discharge. <br /> <br />Application of the And rews and Nelson (1989) <br />Model to the Green River <br /> <br />Channel form and geomorphology determine the availability of nursery habitat. Because channel form reflects <br /> <br />antecedent flows, nursery habitat availability is a product of antecedent flows. While it is not possible to experimentally <br /> <br />measure the response of the channel to all flow scenarios, it is desirable to predict channel response and, hence, habitat <br /> <br />availability for some scenarios. In the Green River basin. only one "experiment" (i.e., flood) occurs each year, and the <br /> <br />magnitude and timing of releases from Flaming Gorge Dam are regulated by many laws. Therefore, each experiment <br /> <br />bas different antecedent conditions. As an alternative, to physical experimentation. a flow and sediment transport model <br /> <br />that simulates bed evolution may be used to model bed and bar response to flood passage. The model used by Andrews <br /> <br />and Nelson (1989) is an example of such a flow and sediment transport model. and it is cited as an appropriate tool in <br /> <br />the Upper Colorado basin (Stanford. 1994) to model changes in channel topography in response to varied flow, <br /> <br />Geomorphology and Habitat Interactions <br /> <br />Instream Flow Philosophies <br /> <br />Historically, instream flow recommendations have been based on the flows necessary for maintaining a suitable <br />