Manning's Roughness Coefficient Chart Table

Fluid Flow Table of Contents
Hydraulic and Pneumatic Knowledge

Manning's Roughness Coefficient Chart Table

The Gauckley – Manning coefficient, often denoted as n , is an empirically derived coefficient, which is dependent on many factors, including surface roughness and sinuosity . When field inspection is not possible, the best method to determine n is to use photographs of river channels where n has been determined using Gauckler – Manning's formula.

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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