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<br /> <br />DRAFT <br /> <br />The model riverbed was filled with sediment sized according to the gradation determined from the <br />scaling calculations. The bedform was shaped according to cross sections provided by WWE. <br />Templates were used in the model to form the sand according to the field data. Only the area from <br />the main dam to just upstream from the Union Avenue bridge contained sand. <br /> <br />Sediment discharge was estimated based on a bedload particle size distribution curve for the South <br />Platte River near Oxford Avenue and river characteristics, including top width, mean depth and <br />velocity, water discharge, water surface slope, and water temperature. These data were entered into <br />a computer program to determine bedload sediment discharge rates using several sediment <br />equations, including Schoklitsch, Kalinske, Meyer-Peter and Muller, and Rottmer (reference??). <br />Using the discharge scale ratio (L,1.5), the bedload discharge scaled to 70 pounds/hour or an <br />application rate of 17 pounds every 15 minutes in the physical model. <br /> <br />At a flow of 3,000 fi' /s (10-year flood), sediment tests were run with a low wall at radial gale <br />openings of 30 and 100 percent (2.5 and 8 feet). At the 3D-percent opening, a large deposit formed <br />in the Englewood intake area covering the first three water intakes. The sediment was shallower <br />near the upstream end of the intakes, where the flow enters. At the loo-percent radial gate <br />opening, some of the sediment deposit was reduced. However, the first few water intakes were still <br />covered. <br /> <br />The sediment test at a riverflow of 3,000 fi' /s was continued for 3 days with the raised solid wall <br />in place along the Englewood intake. Sediment was fed into the model upstream of the Union <br />Avenue bridge every 15 minutes. After 3 days, the deposition in the pool between the Union <br />Avenue dam and the fIrst rockfill dam appeared to be stable. Figures 44 and 45 are photographs <br />of the pool prior to the sediment test. Figures 46 and 47 show contours in the pool before and <br />after the test. <br /> <br />A large sand bar was deposited downstream of the main dam to the left of the boatchutes almost <br />to the end of the original stilling basin wall (fig. 48). Another deposit formed downstream of the <br />boatchute in an alluvial fan shape (fig. 49). Downstream from the sluice gate a deposit formed in <br />the submerged sluice area; however, there was no indication of any deposition in the area just <br />downstream of the radial gate. The high velocity under the gate keeps this area clear The <br />operation of the radial gate and the sluicing capacity are not affected by the downstream tailwater. <br />Figure 50 shows the dunes that formed upstream of the Union Avenue dam. <br /> <br />The deposits indicated by this test would probably take several years to occur, unless there is a <br />relatively large flood in 1 year. <br /> <br />Sediment deposits affect flow pallems in the pool. However, flow patterns are acceptable for <br />boating before or after deposition occurs. Before the sand deposits, the flow gradually turns toward <br />the second chute on the left bank. A back eddy forms downstream from the dam which will carry <br />boaters or sediment back towards the toe of the upstream dam. After the pool partially fills, the <br />back eddy is eliminated and the flow forms a channel turning gradually from boatchute 1 to <br />boatchute 2. <br /> <br />11 <br />