Manning's Roughness Coefficient

Manning's roughness coefficient values for some common materials

Manning's roughness coefficient values are used in the Manning's formula for flow calculation in open flow channels. Coefficients for some common used surface materials can be found in the table below:

Surface Material Manning's Roughness
Coefficient
- n -
Asbestos cement 0.011
Asphalt 0.016
Brass 0.011
Brick 0.015
Canvas 0.012
Cast-iron, new 0.012
Clay tile 0.014
Concrete - steel forms 0.011
Concrete (Cement) - finished 0.012
Concrete - wooden forms 0.015
Concrete - centrifugally spun 0.013
Copper 0.011
Corrugated metal 0.022
Earth, smooth 0.018
Earth channel - clean 0.022
Earth channel - gravelly 0.025
Earth channel - weedy 0.030
Earth channel - stony, cobbles 0.035
Floodplains - pasture, farmland 0.035
Floodplains - light brush 0.050
Floodplains - heavy brush 0.075
Floodplains - trees 0.15
Galvanized iron 0.016
Glass 0.010
Gravel, firm 0.023
Lead 0.011
Masonry 0.025
Metal - corrugated 0.022
Natural streams - clean and straight 0.030
Natural streams - major rivers 0.035
Natural streams - sluggish with deep pools 0.040
Natural channels, very poor condition 0.060
Plastic 0.009
Polyethylene PE - Corrugated with smooth inner walls 0.009 - 0.015
Polyethylene PE - Corrugated with corrugated inner walls 0.018 - 0.025
Polyvinyl Chloride PVC - with smooth inner walls 0.009 - 0.011
Rubble Masonry 0.017
Steel - Coal-tar enamel 0.010
Steel - smooth 0.012
Steel - New unlined 0.011
Steel - Riveted 0.019
Vitrified Sewer 0.013 - 0.015
Wood - planed 0.012
Wood - unplaned 0.013
Wood stove pipe, small diameter 0.011 - 0.012
Wood stove pipe, large diameter 0.012 - 0.013

Related Topics

  • Fluid Mechanics - The study of fluids - liquids and gases. Involves various properties of the fluid, such as velocity, pressure, density and temperature, as functions of space and time.

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