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Ditch 7a <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 />0.33 <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 = A X V = <br />Q REQUIRED - Peak Discharge <br />Riprap Sizing - Ditch 7a <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 />1.69 FEET ^2 <br />4.11 FEET <br />0.41 <br />11.84 FT/SEC <br />20.04 CFS <br />19.08 CFS <br />D50 = 1.67 feet 20 inches Use 24" Rock <br />TR -98 App. B-36 01/15 <br />