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The design storm event utilized to compare existing with approved <br />• channel stability was the 10-year, 24-hour precipitation event of 1.8 <br />inches. The methodology utilized to determine the peak flows is <br />described in the 1984 SCS publication entitled, Procedures for <br />Determining Peak Flows in Colorado. A curve number of 70 was selected <br />for this analysis. It is important to note that Section 4.05.3(2) of <br />the state regulations dictates that each reclaimed channel have the <br />capacity to convey the precipitation event with a 10-year recurrence <br />interval. To date, specific design stprms for assessing the <br />erodibility of reclaimed channels have not been determined by the <br />regulatory agencies. For the purposes of this analyses, however, the <br />10-year, 24-hour storm has been utilized to assess channel <br />erodibility. <br />The hydraulic parameters of each reclaimed channel were determined <br />following the completion of the peak flow calculations. The important <br />hydraulic parameters utilized in this analysis included the velocity, <br />hydraulic radius, slope, roughness coefficient, and boundary shear <br />stress. In performing the hydraulic calculations, a Manning's <br />roughness coefficient of 0.03 was utilized assuming good vegetation <br />growth on each channel. The calculations are also based on a <br />trapezoidal channel with a 12-foot bottom width and side-slopes of 3 <br />to 1. The normal depth procedure was utilized in estimating flow <br />depth, hydraulic radius, and velocity. Boundary shear stress (TO) was <br />estimated using the formula To = yRS where y is the specific weight of <br />water, R is the hydraulic radius and 5 is the channel slope. The <br />• <br />32 <br />