Retention swales

From LID SWM Planning and Design Guide
Revision as of 00:31, 29 September 2017 by Jenny Hill (talk | contribs)
Jump to navigation Jump to search

These sizing equations are suggested for use in calculating the capacity of swales which have a larger proportion of surface flow. i.e. grass swales, rather than bioswales.

Triangular channel[edit]

Sizing a triangular channel for complete volume retention:

Trapezoidal channel[edit]

Sizing a trapezoidal channel for complete volume retention:


  • L = length of swale in m
  • Qp = peak flow of the storm to be controlled, in m3/s
  • m = swale side slope (dimensionless)
  • S = the longitudinal slope (dimensionless)
  • n = Manning's coefficeint (dimensionless)
  • b = bottom width of trapezoidal swale, in m.}