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Manning's Roughness Coefficients

Manning's roughness coefficients for some common materials.

The Manning's roughness coefficient is used in the Manning's equation to calculate flow in open channels.

Coefficients for some commonly used surface materials:

Manning's Roughness Coefficients vs. Channel Type
Surface MaterialManning's Roughness
Coefficient
- n -
Asbestos cement 0.011
Asphalt 0.016
Brass 0.011
Brick and cement mortar sewers 0.015
Canvas 0.012
Cast or Ductile 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 - 0.022
Steel - Coal-tar enamel 0.010
Steel - smooth 0.012
Steel - New unlined 0.011
Steel - Riveted 0.019
Vitrified clay sewer pipe 0.013 - 0.015
Wood - planed 0.012
Wood - unplaned 0.013
Wood stave pipe, small diameter 0.011 - 0.012
Wood stave pipe, large diameter 0.012 - 0.013

Related Topics

  • Fluid Mechanics

    The study of fluids - liquids and gases. Involving velocity, pressure, density and temperature as functions of space and time.

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