# mann

The table below lists values of Manning’s roughness coefficient for channel flow (Chow, 1959).

<table data-full-width="true"><thead><tr><th>Characteristics of Channel</th><th width="100">Minimum</th><th width="100">Normal</th><th width="100">Maximum</th></tr></thead><tbody><tr><td><strong>Main channels</strong></td><td></td><td></td><td></td></tr><tr><td>a. clean, straight, full stage, no rifts or deep pools</td><td>0.025</td><td>0.030</td><td>0.033</td></tr><tr><td>b. same as above, but more stones and weeds</td><td>0.030</td><td>0.035</td><td>0.040</td></tr><tr><td>c. clean, winding, some pools and shoals</td><td>0.033</td><td>0.040</td><td>0.045</td></tr><tr><td>d. same as above, but some weeds and stones</td><td>0.035</td><td>0.045</td><td>0.050</td></tr><tr><td>e. same as above, lower stages, more ineffective slopes and sections</td><td>0.040</td><td>0.048</td><td>0.055</td></tr><tr><td>f. same as "d" with more stones</td><td>0.045</td><td>0.050</td><td>0.060</td></tr><tr><td>g. sluggish reaches, weedy, deep pools</td><td>0.050</td><td>0.070</td><td>0.080</td></tr><tr><td>h. very weedy reaches, deep pools, or floodways with heavy stand of timber and underbrush</td><td>0.075</td><td>0.100</td><td>0.150</td></tr><tr><td><strong>Mountain streams, no vegetation in channel, banks usually steep, trees and brush along banks submerged at high stage</strong>s</td><td></td><td></td><td></td></tr><tr><td>  a. bottom: gravels, cobbles, and few boulders</td><td>0.030</td><td>0.040</td><td>0.050</td></tr><tr><td>  b. bottom: cobbles with large boulders</td><td>0.040</td><td>0.050</td><td>0.070</td></tr><tr><td><strong>Excavated or dredged channels</strong></td><td></td><td></td><td></td></tr><tr><td>a. Earth, straight, and uniform</td><td> </td><td> </td><td> </td></tr><tr><td>  1. clean, recently completed</td><td>0.016</td><td>0.018</td><td>0.020</td></tr><tr><td>  2. clean, after weathering</td><td>0.018</td><td>0.022</td><td>0.025</td></tr><tr><td>  3. gravel, uniform section, clean</td><td>0.022</td><td>0.025</td><td>0.030</td></tr><tr><td>  4. with short grass, few weeds</td><td>0.022</td><td>0.027</td><td>0.033</td></tr><tr><td>b. Earth winding and sluggish</td><td> </td><td> </td><td> </td></tr><tr><td>  1.  no vegetation</td><td>0.023</td><td>0.025</td><td>0.030</td></tr><tr><td>  2. grass, some weeds</td><td>0.025</td><td>0.030</td><td>0.033</td></tr><tr><td>  3. dense weeds or aquatic plants in deep channels</td><td>0.030</td><td>0.035</td><td>0.040</td></tr><tr><td>  4. earth bottom and rubble sides</td><td>0.028</td><td>0.030</td><td>0.035</td></tr><tr><td>  5. stony bottom and weedy banks</td><td>0.025</td><td>0.035</td><td>0.040</td></tr><tr><td>  6. cobble bottom and clean sides</td><td>0.030</td><td>0.040</td><td>0.050</td></tr><tr><td>c. Dragline-excavated or dredged</td><td> </td><td> </td><td> </td></tr><tr><td>  1.  no vegetation</td><td>0.025</td><td>0.028</td><td>0.033</td></tr><tr><td>  2. light brush on banks</td><td>0.035</td><td>0.050</td><td>0.060</td></tr><tr><td>d. Rock cuts</td><td> </td><td> </td><td> </td></tr><tr><td>  1. smooth and uniform</td><td>0.025</td><td>0.035</td><td>0.040</td></tr><tr><td>  2. jagged and irregular</td><td>0.035</td><td>0.040</td><td>0.050</td></tr><tr><td>e. Channels not maintained, weeds and brush uncut</td><td> </td><td> </td><td> </td></tr><tr><td>  1. dense weeds, high as flow depth</td><td>0.050</td><td>0.080</td><td>0.120</td></tr><tr><td>  2. clean bottom, brush on sides</td><td>0.040</td><td>0.050</td><td>0.080</td></tr><tr><td>  3. same as above, highest stage of flow</td><td>0.045</td><td>0.070</td><td>0.110</td></tr><tr><td>  4. dense brush, high stage</td><td>0.080</td><td>0.100</td><td>0.140</td></tr><tr><td><strong>Lined or constructed channels</strong></td><td> </td><td> </td><td> </td></tr><tr><td>a. Cement</td><td> </td><td> </td><td> </td></tr><tr><td>  1. neat surface</td><td>0.010</td><td>0.011</td><td>0.013</td></tr><tr><td>  2. mortar</td><td>0.011</td><td>0.013</td><td>0.015</td></tr><tr><td>b. Wood</td><td> </td><td> </td><td> </td></tr><tr><td>  1. planed, untreated</td><td>0.010</td><td>0.012</td><td>0.014</td></tr><tr><td>  2. planed, creosoted</td><td>0.011</td><td>0.012</td><td>0.015</td></tr><tr><td>  3. unplaned</td><td>0.011</td><td>0.013</td><td>0.015</td></tr><tr><td>  4. plank with battens</td><td>0.012</td><td>0.015</td><td>0.018</td></tr><tr><td>  5. lined with roofing paper</td><td>0.010</td><td>0.014</td><td>0.017</td></tr><tr><td>c. Concrete</td><td> </td><td> </td><td> </td></tr><tr><td>  1. trowel finish</td><td>0.011</td><td>0.013</td><td>0.015</td></tr><tr><td>  2. float finish</td><td>0.013</td><td>0.015</td><td>0.016</td></tr><tr><td>  3. finished, with gravel on bottom</td><td>0.015</td><td>0.017</td><td>0.020</td></tr><tr><td>  4. unfinished</td><td>0.014</td><td>0.017</td><td>0.020</td></tr><tr><td>  5. gunite, good section</td><td>0.016</td><td>0.019</td><td>0.023</td></tr><tr><td>  6. gunite, wavy section</td><td>0.018</td><td>0.022</td><td>0.025</td></tr><tr><td>  7. on good excavated rock</td><td>0.017</td><td>0.020</td><td> </td></tr><tr><td>  8. on irregular excavated rock</td><td>0.022</td><td>0.027</td><td> </td></tr><tr><td>d. Concrete bottom float finish with sides of</td><td> </td><td> </td><td> </td></tr><tr><td>  1. dressed stone in mortar</td><td>0.015</td><td>0.017</td><td>0.020</td></tr><tr><td>  2. random stone in mortar</td><td>0.017</td><td>0.020</td><td>0.024</td></tr><tr><td>  3. cement rubble masonry, plastered</td><td>0.016</td><td>0.020</td><td>0.024</td></tr><tr><td>  4. cement rubble masonry</td><td>0.020</td><td>0.025</td><td>0.030</td></tr><tr><td>  5. dry rubble or riprap</td><td>0.020</td><td>0.030</td><td>0.035</td></tr><tr><td>e. Gravel bottom with sides of</td><td> </td><td> </td><td> </td></tr><tr><td>  1. formed concrete</td><td>0.017</td><td>0.020</td><td>0.025</td></tr><tr><td>  2. random stone mortar</td><td>0.020</td><td>0.023</td><td>0.026</td></tr><tr><td>  3. dry rubble or riprap</td><td>0.023</td><td>0.033</td><td>0.036</td></tr><tr><td>f. Brick</td><td> </td><td> </td><td> </td></tr><tr><td>  1. glazed</td><td>0.011</td><td>0.013</td><td>0.015</td></tr><tr><td>  2. in cement mortar</td><td>0.012</td><td>0.015</td><td>0.018</td></tr><tr><td>g. Masonry</td><td> </td><td> </td><td> </td></tr><tr><td>  1. cemented rubble</td><td>0.017</td><td>0.025</td><td>0.030</td></tr><tr><td>  2. dry rubble</td><td>0.023</td><td>0.032</td><td>0.035</td></tr><tr><td>h. Dressed ashlar/stone paving</td><td>0.013</td><td>0.015</td><td>0.017</td></tr><tr><td>i. Asphalt</td><td> </td><td> </td><td> </td></tr><tr><td>  1. smooth</td><td>0.013</td><td>0.013</td><td> </td></tr><tr><td>  2. rough</td><td>0.016</td><td>0.016</td><td> </td></tr><tr><td>j. Vegetal lining</td><td>0.030</td><td> </td><td>0.500</td></tr></tbody></table>

#### References

> Chow, V.T., 1959, Open-channel hydraulics: New York, McGraw-Hill, 680 pp.


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