Below is a table of n-values for a variety of open channel situations. Note that single values are offered for entire overbanks and channels (Overbanks, Floodplains) with unique bottom and sides. This can alleviate a need for using a multitude of n-values across a section.
| Material | Manning's n |
|---|---|
| CULVERTS | |
| Reinforced Concrete | 0.012 |
| HDPE pipe | 0.012 |
| Corrugated aluminum pipe | 0.031 |
| Corrugated steel pipe | 0.024 |
| Polyvinyl chloride (PVC) | .011 |
| Corrugated Poly | 0.024 |
| MAIN 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, stones and weeds | 0.050 |
| Sluggish reaches, weedy, deep pools | 0.070 |
| Weedy reaches, heavy underbrush | 0.100 |
| MOUNTAIN STREAMS | |
| Steep banks, no vegetation, cobbles | 0.040 |
| Steep banks, no vegetation, boulders | 0.050 |
| OVERBANKS, FLOODPLAINS | |
| Pasture, no brush, short grass | 0.030 |
| Pasture, no brush, tall grass | 0.035 |
| Cultivated, no crop | 0.030 |
| Cultivated, mature row crop | 0.040 |
| Heavy stand of timber, little undergrowth | 0.100 |
| Light brush | 0.050 |
| Dense brush | 0.100 |
| 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 or CONSTRUCTED CHANNELS | |
| Concrete, trowel finish | 0.013 |
| Concrete, unfinished | 0.017 |
| Gravel bottom, riprap banks | 0.033 |
| Source: Ven Te Chow (1959) |