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Drainage Area D <br />There is a minor ephemeral channel that must be diverted around Sediment Pond C. <br />The 10 year peak flow for drainage area D is 836 cfs West Diversion Ditch #1 <br />ditch drains into this minor ephemeral channel. The maximum peak flow from this <br />channel is 9.19 cfs presented in Appendix B of Volume IX. The total design flow for this <br />channel is 17.55 cfs (8.36 + 9.19). <br />Drainage Ditch D -D1 <br />Manning's Equation <br />Flow In a Trapezoidal Channel <br />DEPTH <br />D <br />0.320 <br />FEET <br />WIDTH <br />W <br />10.000 <br />FEET <br />Slope <br />S <br />0.100 <br />EXPRESS AS DECIMAL <br />Mannings "N" <br />N <br />0.040 <br />EXPRESS AS DECIMAL <br />SIDE SLOPE <br />X <br />3.000 <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 - Drainage Ditch D -D1 <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 = 0.214 feet <br />None Required <br />Construct ditch D -D1 a minimum of 2 feet deep to provide for <br />freeboard and lessor ditch slopes. <br />2.562 inches <br />3.51 FEET ^2 <br />12.02 FEET <br />0.29 <br />5.18 FT /SEC <br />18.17 CFS <br />17.55 CFS <br />TR -76 EXH -8 -11 12 -12 <br />