Manning n Values for Open Channel Flow
Manning roughness coefficients
Manning n values (roughness coefficients) compiled from the references listed under Discussion and References as well as the references at the bottom of this page. Manning n has no units.
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|Material||Manning n||Material||Manning n|
|Natural Streams||Excavated Earth Channels|
|Clean and Straight||0.030||Clean||0.022|
|Sluggish with Deep Pools||0.040||Weedy||0.030|
|Cast Iron||0.013||Light Brush||0.050|
|Smooth Steel||0.012||Heavy Brush||0.075|
|Clay Tile||0.014||Unfinished Concrete||0.014|
|Corrugated Polyethylene (PE) with smooth inner walls a,b||0.009-0.015|
|Corrugated Polyethylene (PE) with corrugated inner walls c||0.018-0.025|
|Polyvinyl Chloride (PVC) with smooth inner walls d,e||0.009-0.011|
Footnotes refer to Manning n table above. All other Manning n values (roughness coefficients) were obtained from the references listed in our Discussion and References page.
a Barfuss, Steven and J. Paul Tullis. Friction factor test on high density polyethylene pipe. Hydraulics Report No. 208. Utah Water Research Laboratory, Utah State University. Logan, Utah. 1988.
c Barfuss, Steven and J. Paul Tullis. Friction factor test on high density polyethylene pipe. Hydraulics Report No. 208. Utah Water Research Laboratory, Utah State University. Logan, Utah. 1994.
e Bishop, R.R. and R.W. Jeppson. Hydraulic characteristics of PVC sewer pipe in sanitary sewers. Utah State University. Logan, Utah. September 1975.
d Neale, L.C. and R.E. Price. Flow characteristics of PVC sewer pipe. Journal of the Sanitary Engineering Division, Div. Proc 90SA3, ASCE. pp. 109-129. 1964.
b Tullis, J. Paul, R.K. Watkins, and S. L. Barfuss. Innovative new drainage pipe. Proceedings of the International Conference on Pipeline Design and Installation, ASCE. March 25-27, 1990.
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