Free Online Manning Irregular Channel Calculator

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Irregular Channel Manning Uniform Flow Calculator

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Inputs

Water surface elevation		X
Channel slope, S		X

Results

Q ?	Q ?		X
Velocity check	Velocity check		X

Cross section points +/- (or copy/paste using the data area)
Point				Segment				Region
Sta	Elevation	R_h, Q region boundary (Bank)	Bottom shear τ	n	T	P_w	A	R_h	Comp. n	v	h_v	Fr	Q

Points data
(comma or tab separated)

Composite n: This calculator follows HEC-RAS Reference Manual in calculating region composite n using Chow 1959, page 136, equation 6-17 (not 6-18).
Rock lining: Use the Manning Trapezoidal Channel Calculator to design rock lining. This calculator is better suited to natural sections.
Velocity check: High velocity implies that there was a large elevation drop that created such high specific energy. That energy can be lost quickly at expansions, bends, or obstructions. Verify that this is reasonable for the site.