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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 />