A.6 Manning's N - Overland Flow
| Surface | n |
| Smooth asphalt | 0.011 |
| Smooth concrete | 0.012 |
| Ordinary concrete lining | 0.013 |
| Good wood | 0.014 |
| Brick with cement mortar | 0.014 |
| Vitrified clay | 0.015 |
| Cast iron | 0.015 |
| Corrugated metal pipes | 0.024 |
| Cement rubble surface | 0.024 |
| Fallow soils (no residue) | 0.05 |
| Cultivated soils Residue cover < 20% Residue cover > 20% | 0.06 0.17 |
| Range (natural) | 0.13 |
| Grass Short, Prairie Dense Bermuda grass | 0.15 0.24 0.41 |
| Woods Light underbrush Dense underbrush | 0.40 0.80 |
Source: McCuen, R. et al. (1996), Hydrology, FHWA-SA-96-067, Federal Highway Administration, Washington, DC