Open Channel Flow Calculator

Find open-channel flow rate using Manning's equation.

Manning's roughness n

Flow area

Hydraulic radius

Channel slope (m/m)

Flow rate (m³/s) 3.065

Formula: Q = (1/n)·A·R^(2/3)·√S

Step-by-step with your numbers:

1. Values used:

2. Manning's roughness n = 0.013

3. Flow area = 2

4. Hydraulic radius = 0.5

5. Channel slope = 0.001 m/m

7. Flow rate = 3.065m³/s

Did we solve your problem today?

Manning's equation estimates flow in open channels like rivers, canals and gutters.

The math behind it

Q = (1/n)·A·R^(2/3)·√S, where n is roughness, R the hydraulic radius and S the slope.

n 0.013, A 2 m², R 0.5 m, S 0.001 → about 3.07 m³/s.

What is Manning's n?

A roughness coefficient — about 0.013 for concrete, higher for natural streams.