# Retention swales

Revision as of 00:31, 29 September 2017 by Jenny Hill (talk | contribs)

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:

{Plainlist|1=Where:

- L = length of swale in m
- Q
_{p}= peak flow of the storm to be controlled, in m^{3}/s - m = swale side slope (dimensionless)
- S = the longitudinal slope (dimensionless)
- n = Manning's coefficeint (dimensionless)
- b = bottom width of trapezoidal swale, in m.}