Open Channel Calculator

Calculate normal depth and velocity using Manning's Equation.

Manning's Equation for Open Channels

Manning's equation is arguably the most widely used empirical formula for estimating flow velocity and discharge in open channels under uniform flow conditions.

Velocity Formula: V = (1/n) × R^(2/3) × S^(1/2)
Discharge Formula: Q = V × A

V: Average flow velocity (m/s)
n: Manning's roughness coefficient (dimensionless)
R: Hydraulic radius (m), Area (A) / Wetted Perimeter (P)
S: Longitudinal channel slope (m/m)

Understanding these parameters is critical for the design of storm sewers, irrigation channels, and natural river simulations (e.g. HEC-RAS analyses). This calculator utilizes the Newton-Raphson numerical method to directly solve for the normal water depth.

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Channel Shape

Design Discharge (Q) [m³/s]

Channel Slope (S) [m/m]

Roughness (n)

Bottom Width (b) [m]

Side Slope (z)

Channel Height (H) [m]

Water Height (y)

0.00 m

Flow Velocity (V)

0.00 m/s

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