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STORMWATER MANAGEMENT MANUAL <br />TYPICAL ROUGHNESS COEFFICIENTS FOR OPEN CHANNELS <br />a. <br />b. <br />C. <br />d- <br />e. <br />TYPE OF CHANNEL AND DESCRIPTION <br />EXCAVATED OR DREDGED <br />Earth, straight and uniform <br />1. Clean, recently completed <br />2. Clean, after weathering <br />3. Gravel, uniform section, clean <br />4. With short grass, few weeds <br />Earth, winding and sluggish <br />1. No vegetation <br />2. Grass, some weeds <br />3. Dense weeds or aquatic plans in deep <br />channels <br />4. Earth bottom and rubble sides <br />5. Stony bottom and weedy banks <br />6. Cobble bottom and clean sides <br />Dragline- excavated or dredged <br />1. No vegetation <br />2. Light brush on banks <br />Rock cuts <br />1. Smooth and uniform <br />2. Jagged and irregular <br />Channels not maintained, weeds and brush <br />1. Dense weeds, high as flow depth <br />2. Clean bottom, brush on sides <br />3_ Same as above, but highest state of flow <br />4. Dense brush, high state <br />MINIMUM NORMAI. MAXJM M <br />0.016 <br />0.018 <br />0.022 <br />0.022 <br />0.023 <br />0.025 <br />0.030 <br />0.028 <br />0.025 <br />0.030 <br />0.025 <br />0.035 <br />0.025 <br />0.035 <br />0.050 <br />0.040 <br />0.045 <br />0.080 <br />0.018 <br />0.020 <br />0.022 <br />0.025 <br />0.025 <br />0.030 <br />0.027 <br />0.033 <br />0.025 <br />0.030 <br />0.030 <br />0.033 <br />0.035 <br />0.040 <br />0.030 <br />0.035 <br />0.035 <br />0.040 <br />0.040 <br />0.050 <br />0.028 0.033 <br />0.050 0.060 <br />0.035 0.040 <br />0.040 0.050 <br />0.080 <br />0.120 <br />0.050 <br />0.080 <br />0.070 <br />0.110 <br />0.100 <br />0.140 <br />REFERENCE ►u�c crow• vT.• OPEN Cl- t HYDRAwUCS TABLE 8028 <br />McGMW HILL BOOK COMPANY Isis <br />