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STORMWATER MANAGEMENT MANUAL <br />TYPICAL ROUGHNESS COEFFICIENTS FOR OPEN CHANNELS <br />TYPE; O,E CHANNEL AND DESCRIPTION <br />EXCAVATED OR DREDGED <br />a. Earth, straight and uniform <br />1. <br />Clean, recently completed <br />2. <br />Clean, after weathering <br />3. <br />Gravel, uniform section, clean <br />4. <br />With short grass, few weeds <br />b. Earth, winding and sluggish <br />1. <br />No vegetation <br />2. <br />Grass, some weeds <br />3. <br />Dense weeds or aquatic plans in deep <br />channels <br />4. <br />Earth bottom and rubble sides <br />5. <br />Stony bottom and weedy banks <br />6. <br />Cobble bottom and clean sides <br />c. Dragline- excavated or dredged <br />1. <br />No vegetation <br />2. <br />Light brush on banks <br />d_ Rock cuLG <br />1. <br />Smooth and uniform <br />2. <br />Jagged and irregular <br />e. Channels not maintained, weeds and brush <br />1. <br />Dense weeds, high as flow depth <br />2. <br />Clean bottom, brush on sides <br />3. <br />Same as above, but highest state of flow <br />4. <br />Dense brush, high state <br />MINIMUM NORMAI. MAXIMUM <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 0.030 <br />0.030 0.033 <br />0.035 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 />i DW* I <br />aenraovrc nsur 13f27/%' <br />REFERENCE: <br />PC I CHOW. urt.. OPEN CHANNEL HYDRAULICS TABLE 802A <br />McGRAW HILL BOOK COMPANY 1%9 <br />