Manning's n Coefficients |
Material |
Manning n |
Natural Streams |
Clean and Straight |
0.030 |
Major Rivers |
0.035 |
Sluggish with Deep Pools |
0.040 |
|
Excavated Earth Channels |
Clean |
0.022 |
Gravelly |
0.025 |
Weedy |
0.030 |
Stony, Cobbles |
0.035 |
|
Metals |
Brass |
0.011 |
Cast Iron |
0.013 |
Smooth Steel |
0.012 |
Corrugated Metal |
0.022 |
|
Floodplains |
Pasture, Farmland |
0.035 |
Light Brush |
0.050 |
Heavy Brush |
0.075 |
Trees |
0.15 |
|
Non-Metals |
Glass |
0.010 |
Clay Tile |
0.014 |
Brickwork |
0.015 |
Asphalt |
0.016 |
Masonry |
0.025 |
Finished Concrete |
0.012 |
Unfinished Concrete |
0.014 |
Gravel |
0.029 |
Earth |
0.025 |
Planed Wood |
0.012 |
Unplaned Wood |
0.013 |
Corrugated Polyethylene (PE) with smooth inner walls |
0.009–0.015 |
Corrugated Polyethylene (PE) with corrugated inner walls |
0.018–0.025 |
Polyvinyl Chloride (PVC) with smooth inner walls |
0.009–0.011 |