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• <br />n <br />the "Prospecting Pit" area. Here, the natural existing slope of the channel is <br />0.049 just upstream of the pit and increases to 0.056 below the pit. The channel <br />is designed to carry the peak discharge from the 10-year, 24-hour storm. The <br />floodplain will be such that the 100-year peak discharge is contained. The ehan- <br />nel shape transitions from a narrow channel with steep side slopes to a ride <br />• flat channel with flatter side slopes. The major portion of the restored channel <br />should be wide with flat side slopes. The upstream portion of the restored than- <br />, nel should be a transition from the narrower channel to the rider channel. Tha <br />transition should be approximately 75 feet long. The transition should be such <br />that the 10-year discharge is guided into the channel. A slight transition <br />may be required at the dovnstzeato end of the reclaimed area depending on the <br />C shape of the existing channel. The transitions should be gradual with no abrupt <br />changes in channel geometry. The length of the restored channel, excluding 75 <br />(' feet of transition, is approximately 600 feet. To maintain the natural gradient, <br />the channel is designed for a slope of 0.049. The channel shape is assumed <br />trapezoidal with side slopes of 4:1 and a base width of 50 feet. The design <br />• discharge is 2470 cfs, the peak discharge at the outlet of CH-4 just upstream <br />of the "Prospecting Fit". Assuming normal depth and applying Manning's equation, <br />the hydraulic characteristics can be determined. <br />Both upstream and downstream the Newlin Creek channel is armored with <br />alluvial cobbles and boulders. Also, within the channel some vegetative growth <br />exists which promotes resistance to the flow. Thus, to replace the protection _ <br />' provided by the armor layer and the vegetation, some type of channel lining is <br />required. The most applicable lining for the purpose is riprap. The riprap <br />is sized according to the method described in the orevious section. The required <br />rinra^ mean diameter is 1.5 feet for the channel. This should cover the channel <br />and extend five feet into the floodplain overbank (see Figure 8). Beyond the <br />overbank protected by riprap, the floodplain should be well vegetated. The <br />channel should be adequately lined with 12 to 18 inches of clay liner to prevent <br />seepage. The clay liner should be covered with 18 inches of gravel filter below <br />the riprap. <br />The remaining channels chat require restoration are located within the <br />Magpie Creek drainage. These are channel units PM-CH-13, PM-CH-11, PM-CH-6, <br />• and SW-11 drainage channel. The natural conditions of these drainages in the <br />area have boulders, shrubs, and trees giving high flow resistance which reduces <br />the erosive power of the runoff. It is impossible to place such growth and <br />