Flow in a swale

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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 swaleA shallow constructed channel, often grass-lined, which is used as an alternative to curb and channel, or as a pretreatment to other measures. Swales are generally characterized by a broad top width to depth ratio and gentle grades. (m3/s)
  • A = the cross sectional area of the swaleA shallow constructed channel, often grass-lined, which is used as an alternative to curb and channel, or as a pretreatment to other measures. Swales are generally characterized by a broad top width to depth ratio and gentle grades. (m2)
  • P = the wetted perimeter of the swaleA shallow constructed channel, often grass-lined, which is used as an alternative to curb and channel, or as a pretreatment to other measures. Swales are generally characterized by a broad top width to depth ratio and gentle grades. (m)
  • S = the longitudinal slope (m/m)
  • n = Manning's coefficient (dimensionless)