Manning's Roughness Coefficient

Manning's Roughness Coefficient

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Channel Material	Constant n
clean, uncoated cast iron	0.013-0.015
clean, coated cast iron	0.012-0.014
dirty, tuberculed cast iron	0.015-0.035
riveted steel	0.015-0.017
lock-bar and welded	0.012-0.013
galvanized iron	0.015-0.017
brass and glass	0.009-0.013
Wood Stove Pipe
small diameter	0.011-0.012
large diameter	0.012-0.013
Concrete
with rough joints	0.016-0.017
dry mix, rough forms	0.015-0.016
wet mix, steel forms	0.012-0.014
very smooth, finished	0.011-0.012
vitrified sewer	0.013-0.015
common-clay drainage tile	0.012-0.014
asbestos	0.011
planed timber	0.011
canvas	0.012
unplaned timber	0.014
brick	0.016
rubble masonry	0.017
smooth earth	0.018
firm gravel	0.023
corrugated metal pipe	0.022
natural channels, good condition	0.025
natural channels with stones and weeds	0.035
very poor natural channels	0.060

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