Summary
The Manning Characteristic Roughness is used to characterise the surfaces over which water can flow in streams, channels, ditches and flumes. This article presents a reference of roughness values for many common materials of construction for channels and natural formations of streams.
Definitions
| : | Manning characteristic roughness |
Usage of the Manning Characteristic Roughness
The Manning characteristic roughness can be used to calculate the velocity, flow rate, friction factor and head loss for water flowing in a channel or stream. It can also be used to calculate the Chezy coefficient. For a detailed description of these calculations see our article on flow in open channels and partially filled pipes.
If you are looking for the absolute roughness for flow through filled pipes, please see our article on absolute roughness of pipe material.
Typical Values of Manning Characteristic Roughness
The table below presents the manning characteristic roughness for many common materials of construction for channels and natural formations of streams.
| Category | Characteristic Roughness | |
|---|---|---|
| Pipes and Flumes | Brass pipe | 0.010 |
| Pipes and Flumes | Plastic, smooth | 0.010 |
| Pipes and Flumes | Steel, smooth | 0.012 |
| Pipes and Flumes | Concrete pipe, finished | 0.012 |
| Pipes and Flumes | Wood plank pipe or flume, planed | 0.012 |
| Pipes and Flumes | Wood plank pipe or flume, unplaned | 0.013 |
| Pipes and Flumes | Asphalt, smooth | 0.013 |
| Pipes and Flumes | Clay tile, smooth | 0.013 |
| Pipes and Flumes | Vitrified sewer pipe | 0.013 |
| Pipes and Flumes | Semicircular metal flumes, smooth | 0.013 |
| Pipes and Flumes | Cast-iron pipe | 0.014 |
| Pipes and Flumes | Concrete pipe, unfinished | 0.015 |
| Pipes and Flumes | Brick with cement mortar | 0.015 |
| Pipes and Flumes | Riveted steel pipe | 0.017 |
| Pipes and Flumes | Semicircular metal flumes, corrugated | 0.028 |
| Canals and ditches | Earth, straight, uniform | 0.023 |
| Canals and ditches | Winding sluggish canals | 0.025 |
| Canals and ditches | Dredged earth channels | 0.028 |
| Canals and ditches | Gravel channels | 0.029 |
| Canals and ditches | Rubble | 0.025 |
| Natural-stream channel | Clean, straight bank, full stage | 0.030 |
| Natural-stream channel | Winding, some pools and shoals | 0.040 |
| Natural-stream channel | Same, but with stony sections | 0.055 |
| Natural-stream channel | Sluggish reaches, very deep pools, rather weedy | 0.070 |
| Natural-stream channel | Heavy brush | 0.100 |