Manning's Roughness Coefficient Chart Table


Fluid Flow Table of Contents
Hydraulic and Pneumatic Knowledge
Fluid Power Equipment

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

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