Open Channel Calculator

Calculate normal depth and velocity using Manning's Equation.

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

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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