Manning Gravity Open Channel Flow Estimator

Open stormwater culvert and gravity sewer flow estimation based on hydraulic radius and slope.

Manning's Equation:

$ V = \frac{1.486}{n} \times R_h^{2/3} \times S^{1/2} \quad \text{and} \quad Q = V \times A $

Channel Parameters

Culvert Inner Diameter (Inches)

Channel Slope ($S$ in ft/ft) 0.01 = 1% Slope

Manning Roughness Coefficient ($n$)

Full Pipe Velocity 4.52 ft/s

Discharge Capacity 3.55 CFS

Flow Rate in GPM 1,593 GPM