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• Tables 23-13, through 23-17, Outlet Morks Design, contain the primary <br />outlet discharge and design summary for each pond. The number of <br />orifices, their size and elevation is also summarized for each pond on <br />the Proposed Pond and Ditch Design Map, (Map 23-1). <br />Emergency Spillway Design <br />The SEDCAD+ computer model utilizes the combination of equations for a <br />drop inlet structure as presented in Applied Hydrology and Sedimentology <br />for Disturbed areas, pages 228-236. Discharge through the primary <br />outlet is considered to be negligible compared to discharge through the <br />riser. <br />At very low head, the riser crest acts as a weir and the flow is weir <br />controlled as follows: <br />• Q = CLH3/2 <br />Mhere: C = weir coefficient (3.1) <br />L circumference of inlet (ft) <br />H Height of water above inlet (ft) <br />As the reservoir depth increases. the inlet begins to act like an <br />orifice and the equation for orifice flow is utilized as follows: <br /> <br />Mhere: C' = orifice ccefflcient (0.60) <br />a -cross sectional area of Inlet (ftz) <br />g = gravitational constant (32.2 ft/sec=) <br />H = Height of water above inlet <br />As the head continues to increase and the outlet begins to flow full, <br />• flow is controlled by pipe flow and discharge 1s calculated as follows: <br />Q= a 2 H' 0.5 <br />(1+Ke+1(b+KcL) <br />23-144 <br />