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The channel is, designed using Mannings equation for a trapezoid <br />channel as described below: <br />Design Discharge = 1.35 cfs <br />Mannings n (riprapped channel) = 0.035 <br />Free Board = 1.0 ft <br />Slope = 20% <br />Channel Length = 175 ft <br />Slide Slope = 1.5:.1 <br />Bottom Width = 1 ft. <br />Normal Depth = 0.20 ft. <br />Channel Depth (with free board) = 1.3 ft. <br />Design Velocity = 5.0 ft/sec. <br />Hand placed riprap with a median diameter of 8 inches would pro- <br />vide adequate protection for velocities in excess of 10 feet per <br />second. Thus the riprap will provide protection for runoff <br />events larger than the 10 yr., 24 hr. precipitation event. <br />