| Boundary | Manning n (ft1/6) |
|---|---|
| Very smooth surfaces such as glass, plastic, or brass | 0.010 |
| Very smooth concrete and planed timber | 0.011 |
| Smooth concrete | 0.012 |
| Ordinary concrete lining | 0.013 |
| Good wood | 0.014 |
| Vitrified clay | 0.015 |
| Shot concrete, untroweled, and earth channels in best condition | 0.017 |
| Straight unlined earth canals in good condition | 0.020 |
| Rivers and earth canals in fair condition; some growth | 0.025 |
| Winding natural streams and canals in poor condition; considerable moss growth | 0.035 |
| Mountain streams with rocky beds and rivers with variable sections and some vegetation along banks | 0.041-0.050 |