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Ditch F4 <br />Manning's Equation <br />Flow In a Triangular Channel <br />Depth D 1.4 <br />Feet <br />Width W 0 <br />Feet <br />Slope S 0.3 <br />Express as Decimal <br />Mannings "N" N 0.04 <br />Express as Decimal <br />Side Slope X 1.5 <br />Slope = X:1 <br />AREA=(W*D)+(X*D^2)= <br />2.77 FEET ^2 <br />WETTED PERIMETER=(W)+2*[((X*D)^2+D^2)^0.5] 4.90 FEET <br />R=AREA/WETTED PERIMETER <br />0.57 <br />V=(1.49/N)*(R^.66 7)*(S".5)= <br />IQ=AXV= <br />IQ REQUIRED - Peak Discharge <br />Sizing - Ditch F-4 <br />D50 = Size of Riprap <br />D50 = ((V X S".17)/7.58))"2 <br />D50 = Diameter in feet <br />V =Velocity <br />S = Slope <br />D50 = 2.25 feet <br />13.96 FT/SEC <br />38.72 CFS <br />38.17 CFS <br />27 inches Use 24" Rock <br />TR -81 App. B-35 10/13 <br />