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<br />TABLE IV-l <br /> <br />.....--.~-- <br /> <br />Normal <br /> <br />I <br />~J <br /> <br />~ <br />~ <br /> <br />MANNING ROUGHNESS COEFFICIENT - <br />CHANNELS <br /> <br />0.011 <br />0.014 <br />_ ___----O-:i)-n. <br />0.012 <br />0.013 <br />0.015 <br />0.014 <br />0.015 <br />0.015 <br />0.024 <br />0.018 <br />0.020 <br />0.026 <br /> <br />Nature of Surface <br /> <br />Neat cement surface <br />Vitrified sewer pipe <br />Metal flumes, smooth <br />Concrete, precast <br />Cement mortar surfaces <br />Common-clay drainage tile <br />Concrete, monolithic <br />Brick with cement mortar <br />Cast iron <br />Cement rubble surfaces <br />Riveted steel <br />Canals and ditches, smooth earth <br />Metal flumes, corrugated <br />Canals: <br />Dredged in earth, smooth <br />In rock cuts, smooth <br />Rough beds and weeds on sides <br />Rock cuts, jagged and irregular <br />Natural streams: <br />Smoothest <br />Roughest <br />Very weedy <br />Grass: <br />Longer than 24 inches <br />10 to 24 inches <br />6 to 10 inches <br />Shorter than 6 inches <br />Concrete Channels: <br />Trowel Finish <br />Float Finish <br />Unfinished <br />Shotcrete, troweled, not wavy <br />Shotcrete, trowelp.d, wavy <br />Shotcrete, unfinished <br />Street Sections, generalized composite section <br /> <br />--- ---~ <br /> <br />34 <br /> <br />0.027 <br />0.035 <br />0.030 <br />0.040 <br /> <br />~ <br />I <br />, <br />o <br />! <br />I <br /> <br />~- <br />." <br /> <br />! <br />~, <br />~I <br />"" <br /> <br />! <br />~ <br />~ <br />~; <br /> <br />0.030 <br />0.050 <br />0.100 <br /> <br />0.150 <br />0.100 <br />0.060 <br />0.045 <br /> <br />0.013 <br />0.015 <br />0.017 <br />0.018 <br />0.020 <br />0.022 <br />0.016 <br /> <br />