# Flow in a swale

Flow (Q) in an open channel, such as a swale, may be calculated using Manning's equation$Q=VA=\frac{R^{\frac{2}{3}}S^{\frac{1}{2}}}{n}$ Where$R=\frac{A}{P}$

Where:

• Q = the flow in the swale (m3/s)
• A = the cross sectional area of the swale (m2)
• P = the wetted perimeter of the swale (m)
• S = the longitudinal slope (m/m)
• n = Manning's coefficient (dimensionless)