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<br />C <br />Diversion Ditches & CMPs <br />Ditch D-12 Across Site <br />MANNING'S EQUATION <br />FLOW IN A TRAPIZODIAL CHANNEL <br />• <br />DEPTH D 0.350 FEET <br />WIDTH W 8.000 FEET <br />SLOPE S 0.200 EXPRESS AS DECIMAL <br />Mannings "N" N 0.040 EXPRESS AS DECIMAL <br />SIDE SLOPE X 1.500 SLOPE = X:1 <br />AREA=(W*D)+(X*D^2)= 2.98 FEET^2 <br />WETTED PERIMETER=(W)+2((XD^ 2tD^2))^.5 9.26 FEET <br />R=AREA/WETTED PERMITER 0.32 <br />V=(1.49/N)*(R^.667)*(S^.5)= 7.83 FT/SEC <br />Q = A X V = 23.36 CFS <br />Q REQUIRED 20.11 CFS <br />The ditch will be a trapezoidal with an 8-foot bottom width <br />and a flow dept of 0.35 feet. The side slopes will be <br />1.5h:iv. With a freeboard of 0.3' the total required depth of <br />the ditch is 0.65 feet. Use a design depth of 1.5 feet. <br />Rip rap 6" or larger is required to protect the channel from <br />erosion. <br />RIPRAP SIZING <br />D50 <br />D50 <br />D50 <br />V <br />S <br />D50 <br />Size of Riprap <br />((V X S^.17)/7.58))^2 <br />Diameter in feet <br />Velocity <br />Slope <br />0.617 feet 7.405 inches <br />48" CMP C-6 <br />The capacity of the 48" CMPs is 65 CFS so they are sized <br />to handle the design flow of 20.11 CFS. <br />• <br />4-B:9 <br />October 1994 <br />