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Ditch F21-2 <br />Manning's Equation <br />Flow In a Triangular Channel <br />Depth D 0.8 <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 2 <br />Slope = X:1 <br />AREA=(W*D)+(X*D^2)= <br />1.28 FEET ^2 <br />WETTED PERIMETER=(W)+2*[((X*D)^2+D^2)^0.5] 3.58 FEET <br />R=AREA/WETTED PERIMETER <br />0.36 <br />I V=(1.49/N)*(R^.667)*(S^.5)= <br />IQ=AXV= <br />IQ REQUIRED - Peak Discharge <br />lRiprap Sizing - Ditch F21-1 <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 = 1.22 feet <br />10.28 FT/SEC <br />13.16 CFS <br />11.59 CFS <br />15 inches Use 15" Rock <br />TR -81 App. B-55 09/13 <br />