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Ditch F21 -2 <br />Manning's Equation <br />Flow In a Triangular Channel <br />Depth <br />D <br />0.9 <br />Feet <br />Width <br />W <br />0 <br />Feet <br />Slope <br />S <br />0.3 <br />Express as Decimal <br />Mannings "N" <br />N <br />0.04 <br />Express as Decimal <br />Side Slope <br />X <br />2 <br />Slope = X:1 <br />AREA= (W *D) +(X *D ^2)= <br />WETTED PERIMETER= (W) +2 *[((X *D) "2 +D "2) ^0.5] <br />R= AREA/WETTED PERIMETER <br />V= (1.49/N) *(R ^.667) *(S ^.5) = <br />Q =AXV= <br />IQ REQUIRED - Peak Discharge <br />IRiprap 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 />1.62 FEET ^2 <br />4.02 FEET <br />0.40 <br />11.12 FT /SEC <br />18.02 CFS <br />17.89 CFS <br />D50 = 1.43 feet 17 inches Use 18" Rock <br />TR -76 App. B -40 12/12 <br />