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Table 3.5-6 - Calculation for Typical Roadside Ditch Design <br />u <br />This roadside ditch was designed for a maximum peak flow of 11.6 cfs. <br />The ditch was sized from "Hydrology and Sedimentology of Surface Hined Lands" <br />by C.T. Hann and B.J. Barfield, pages 130-132, for a non-vegetated channel <br />with an earth bottom and rubble sides. A trial and error solution was used to <br />find depth of flow and the velocity in the channel. <br />Manninq's Equation: Q 1"49 R2/J Siiz A <br />n <br />A = Cross Sectional Area of Flow in square feet. <br />S = Slope in ft/ft. <br />R = Hydraulic Radius in Feet <br />n Coefficient of Roughness for a triangular channel <br />T <br />• --- Ia ------ ,d <br />i <br />_ _ _ J <br />e <br />e <br />For Inflow Ditch: 2:1 Side Slopes <br />S = 0.033 ft/ft. <br />n = 0.032 (Earth Channel Rubble Sides) <br />For Design: A zdz = 2dz <br />d - Depth of Flow <br />z - E (Side Slopes) <br />d <br />T = Top Width <br />~zd 2d T2d- <br />R = 2 Vz+l = I2~rr\~ = 2V13 <br />Q = ~ 01032 ~ I (2 z ~ ) zi1J (0.0331iz) 2dz <br />• <br />3.5-Si May 14,1993 <br />