# Free Online Manning Formula Trapezoidal Channel Calculator

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## Manning Formula Uniform Trapezoidal Channel Flow at Given Slope and Depth

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Inputs
 Bottom width m mm ft in X Side slope 1 (horiz./vert.) X Side slope 2 (horiz./vert.) X Manning roughness, n ? X Channel slope rise/run % rise/run X Flow depth m mm ft in X Bend Angle? (for riprap sizing) X Rock specific gravity (2.65) X Median rock size m mm ft in X
Results
 Flow area Flow area m^2 mm^2 ft^2 sq. in. X Wetted perimeter Wetted perimeter m mm ft in X Hydraulic radius Hydraulic radius m mm ft in X Velocity, v Velocity, v m/s ft/sec X Flow, Q (See notes) Flow, Q (See notes) m^3/s l/s Ml/d cfs gpm MGD X Velocity head, hv Velocity head, hv m mm ft in X Top width, T Top width, T m mm ft in X Froude number, F Froude number, F X Shear stress (tractive force), tau Shear stress (tractive force), tau N/m^2 psf X n for rock size per Strickler n for rock size per Strickler X n for rock size per Blodgett n for rock size per Blodgett X n for rock size per Bathurst n for rock size per Bathurst X Blodgett vs. Bathurst Blodgett vs. Bathurst X Required bottom angular rock size, D50 (Isbash & MC) ? Required bottom angular rock size, D50 (Isbash & MC) ? m mm ft in X Required side slope 1 angular rock size, D50 (Isbash & MC) ? Required side slope 1 angular rock size, D50 (Isbash & MC) ? m mm ft in X Required side slope 2 angular rock size, D50 (Isbash & MC) ? Required side slope 2 angular rock size, D50 (Isbash & MC) ? m mm ft in X Required angular rock size, D50 (Maynord, Ruff, and Abt 1989) Required angular rock size, D50 (Maynord, Ruff, and Abt 1989) m mm ft in X Required angular rock size, D50 (Searcy 1967) Required angular rock size, D50 (Searcy 1967) m mm ft in X