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• 25, 50, and 75 percent of watershed height <br />(Z). <br />S = 0.25(185 ft)(1220 ft + 2260 ft + 2480 ft) <br />4,124,800 ft <br />S = 0.067 moderate slope <br />Slope Adjustment Factor = 1.21 (Appendix E, <br />SCS, 1980) <br />Hydraulic Length = 3120 ft <br />Therefore, equivalent watershed area = 90.5 acres. (Appendix E, <br />SCS, 1980) <br />Actual q = equivalent q actual drainage area <br />• (equivalent drainage area <br />Peak flow = (actual q) (inches of runoff) (slope adjustment <br />factor) <br />For a CN of 69, <br />49 cfs/in,(95 acres l = 51 cfs/in. <br />190.5 acres/ <br />51 cfs/in. (0.07 in.)(1.21) 4.3 cfs <br />2. Watershed with collection ditches removed. <br />Area = 64 acres <br />• Average watershed slope <br />9 <br />