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STORMWATER- MANAGEMENT MANUAL <br />TYPICAL ROUGHNESS COEFFICIENTS FOR OPEN CHANNELS <br />TYPE OF CHANNEL AND DESCRIPTION MINIMUM NORMAL MAXIMUM <br />UNED OR BUILT -UP CHANNELS <br />a. CONCRETE <br />1. TROWEL FINISH <br />0.011 <br />0.013 <br />0.015 <br />2. FLOAT FINISH <br />0.013 <br />0.015 <br />0.016 <br />3. GUNITE, GOOD SECTION <br />0.016 <br />0.019 <br />0.023 <br />4. GUNITE, WAVY SECTION <br />0.018 <br />0.022 <br />0.023 <br />b. CONCRETE BOTTOM FLOAT FINISHED NTH SIDE OF <br />1. DRESSED STONE IN MORTAR 0.015 0.017 0.020 <br />2. RANSOM STONE IN MORTAR 0.017 0.020 0.024 <br />3. DRY RUBBLE OR RIPRAP 0.020 0.030 0.035 <br />c. GRAVEL BOTTOM WITH SIDES OF <br />1. FORMED CONCRETE 0.017 0.020 0.025 <br />2. RANDOM STONE IN MORTAR 0.020 0.023 0.026 <br />3. DRY RUBBLE OR RIPRAP 0.023 0.033 0.036 <br />d. ASPHALT <br />1. SMOOTH 0.013 0.013 -- <br />2. ROUGH 0.016 0.016 -- <br />e. GRASSED 0.030 0.040 0.0503.1 <br />REFERENCE: <br />CHOUP, V.T., OPEN CHANNEL HYDRAULICS TABLE 802C <br />McCPAW HILL BOOK c AW sass <br />