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Ditch F -7a <br />Manning's Equation <br />Flow In a Triangular Channel <br />Depth <br />D <br />1.26 <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 =AXV= <br />Q REQUIRED - Peak Discharge <br />Riprap Sizing - Ditch F -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 />3.18 FEET ^2 <br />5.63 FEET <br />0.56 <br />14.60 FT /SEC <br />46.35 CFS <br />45.76 CFS <br />D50 = 1.24 feet 15 inches Use 15" Rock <br />Ditch F -7a was designed in Excel due to SedCad's inability to handle a <br />large peak flow and steep slope combination. The peak flow from Ditch <br />F -7 as shown on permit page App. 8 -18 was used as Ditch F -7 flows <br />directly in F -7a. <br />TR -72 App. B -18i 05/12 <br />