Manning’s Roughness Coefficients for Open Channel Flow
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:
| 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 |
