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• contribute streamflow at the point where the ephemeral stream <br />leaves the reclaimed surface. Given the present drainage area <br />and assuming reclaimed runoff conditions, the 10-year, 24-hour <br />precipitation event is calculated to produce a peak flow of 4.3 <br />cfs. (See Appendix). when the collection ditches are removed, <br />the watershed area will be reduced to approximately 65 acres, and <br />the projected peak flow would be reduced to 2.9 cfs. (See Appendix). <br />An ephemeral channel eight-feet wide, one-foot deep channel, <br />and with 3:1 side slopes (Figure 1) will be constructed across <br />the reclaimed surface. The constructed channel will begin at <br />approximately the 6305-foot contour line, and will end where the <br />reclaimed surface joins the undisturbed landscape at approxi- <br />mately 6150 feet. At the upper end, the reconstructed channel <br />• will feather into the uostream surface. At the downstream end, <br />the reconstructed channel will be blended into the geometry of <br />the natural drainage. <br />The longitudinal profile of the proposed channel, shown in <br />Figure 2, can be divided into two segments. The upper segment <br />has gentle gradient of 0.02, and the lower segment has steeper <br />gradient of 0.225. In the upper segment, the channel will be <br />topsoiled and re vegetated (See aoproved reclamation plan). The <br />topsoil available for reclamation in the upper reach includes a <br />sandy loam and gravelly loam. In the upper reach, the 10-year <br />peak flow would have an estimated flow velocity of 2.4 fps <br />(Figure 1). This value is within the limiting velocities <br />established by Lane (1955). The establishment of vegetation will <br />provide additional erosion protection. <br />2 <br />