Material | Manning's n |
---|---|
PIPES | |
Reinforced concrete | 0.013 |
Vitrified clay pipe | 0.013 |
Corrugated metal pipe | 0.023 |
Polyvinyl chloride (PVC) | 0.010 |
Smooth welded pipe | 0.011 |
NATURAL CHANNELS | |
Gravel beds, Straight | 0.025 |
Gravel beds, large boulders | 0.040 |
Earth, straight, some grass | 0.026 |
Earth, winding, no vegetation | 0.030 |
Earth, winding | 0.050 |
EXCAVATED CHANNELS | |
Clean, recently completed | 0.018 |
With short grass and weeds | 0.027 |
Earth bottom, rubble banks | 0.030 |
Stony bottom, weedy banks | 0.035 |
Not maintained, weeds high as flow depth | 0.080 |
LINED, CONSTRUCTED CHANNELS | |
Concrete, trowel finish | 0.013 |
Concrete, unfinished | 0.017 |
Gravel bottom, riprap banks | 0.033 |
OVERLAND "SHEET" FLOW | |
Smooth surfaces, Concrete, asphalt, bare Soil | 0.011 |
Short grass | 0.15 |
Dense grass | 0.24 |
Bermuda grass | 0.41 |
Light underbrush woods | 0.40 |
Dense underbrush woods | 0.80 |