The Manning Characteristic Roughness is used to characterise the surfaces over which water can flow in streams, channels, ditches and flumes. This article presents a reference of roughness values for many common materials of construction for channels and natural formations of streams.
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Usage of the Manning Characteristic Roughness
The Manning characteristic roughness can be used to calculate the velocity, flow rate, friction factor and head loss for water flowing in a channel or stream. It can also be used to calculate the Chezy coefficient. For a detailed description of these calculations see our article on flow in open channels and partially filled pipes.
If you are looking for the absolute roughness for flow through filled pipes, please see our article on absolute roughness of pipe material.
Typical Values of Manning Characteristic Roughness
The table below presents the manning characteristic roughness for many common materials of construction for channels and natural formations of streams.
|Characteristic Roughness||n (m1/6)|
|Pipes and Flumes|
|Concrete pipe, finished||0.012|
|Wood plank pipe or flume, planed||0.012|
|Wood plank pipe or flume, unplaned||0.013|
|Clay tile, smooth||0.013|
|Vitrified sewer pipe||0.013|
|Semicircular metal flumes, smooth||0.013|
|Concrete pipe, unfinished||0.015|
|Brick with cement mortar||0.015|
|Riveted steel pipe||0.017|
|Semicircular metal flumes, corrugated||0.028|
|Canals and ditches|
|Earth, straight, uniform||0.023|
|Winding sluggish canals||0.025|
|Dredged earth channels||0.028|
|Clean, straight bank, full stage||0.030|
|Winding, some pools and shoals||0.040|
|Same, but with stony sections||0.055|
|Sluggish reaches, very deep pools, rather weedy||0.070|