Summary

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.

Definitions

:Manning characteristic roughness


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 Roughnessn (m1/6)
Pipes and Flumes
Brass pipe0.010
Plastic, smooth0.010
Steel, smooth0.012
Concrete pipe, finished0.012
Wood plank pipe or flume, planed0.012
Wood plank pipe or flume, unplaned0.013
Asphalt, smooth0.013
Clay tile, smooth0.013
Vitrified sewer pipe0.013
Semicircular metal flumes, smooth0.013
Cast-iron pipe0.014
Concrete pipe, unfinished0.015
Brick with cement mortar0.015
Riveted steel pipe0.017
Semicircular metal flumes, corrugated0.028
Canals and ditches
Earth, straight, uniform0.023
Winding sluggish canals0.025
Dredged earth channels0.028
Gravel channels0.029
Rubble0.025
Natural-stream channels
Clean, straight bank, full stage0.030
Winding, some pools and shoals0.040
Same, but with stony sections0.055
Sluggish reaches, very deep pools, rather weedy0.070
Heavy brush0.100


Further Reading

  1. Water Resources Engineering
  2. Hydraulic Engineering
  3. Perry's Chemical Engineers' Handbook, Eighth Edition
  4. Marks' Standard Handbook for Mechanical Engineers 11th Edition