The formula to calculate the velocity is:

\[ V = \frac{1.00}{n} \cdot R^{2/3} \cdot S^{1/2} \]

Where:

• \(V\) is the velocity in meters per second (m/s).
• \(n\) is Manning’s coefficient, ranging from 0.010 to 0.035.
• \(R\) is the hydraulic radius in meters (m).
• \(S\) is the slope of the water surface.