Manning's Roughness Coefficients
Manning's roughness coefficients for some common materials.
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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:
| Surface Material | Manning'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 |
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