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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]]. <br>
In many cases the length of swale required will exceed the available space, so that an underground [[infiltration trenches|infiltration trench]] or a [[Dry ponds| dry pond]] will be a preferred solution.
===Triangular channel===
===Triangular channel===
Sizing a triangular channel for complete volume retention:
Sizing a triangular channel for complete volume retention:
<math>L=\frac{151,400Q_{p}^{\frac{5}{8}}m^{\frac{5}{8}}S^{\frac{3}{16}}}{n^{\frac{3}{8}}\left (\sqrt{1+m^{2}} \right )^{\frac{5}{8}}f}</math>
<math>L=\frac{151,400Q_{p}^{\frac{5}{8}}m^{\frac{5}{8}}S^{\frac{3}{16}}}{n^{\frac{3}{8}}\left (\sqrt{1+m^{2}} \right )^{\frac{5}{8}}q}</math>
===Trapezoidal channel===
===Trapezoidal channel===
:<math>L=\frac{360,000Q_{p}}{\left\{ b+2.388\left[\frac{Q_{p}n}{\left(2\sqrt{1+m^{2}-m}\right)S^{\frac{1}{2}}}\right ]^{\frac{3}{8}}\sqrt{1+m^{2}} \right \}f}</math>
Sizing a trapezoidal channel for complete volume retention:
<math>L=\frac{360,000Q_{p}}{\left\{ b+2.388\left[\frac{Q_{p}n}{\left(2\sqrt{1+m^{2}-m}\right)S^{\frac{1}{2}}}\right ]^{\frac{3}{8}}\sqrt{1+m^{2}} \right \}q}</math>
[[category:modeling]]
{{Plainlist|1=Where:
*''L'' = length of swale in m
*''Q<sub>p</sub>'' = peak flow of the storm to be controlled, in m<sup>3</sup>/s
*''m'' = swale side slope (m/m)
*''S'' = the longitudinal slope (m/m)
*''n'' = Manning's coefficient (dimensionless)
*''b'' = bottom width of trapezoidal swale, in m.
* ''q'' = flow per unit width (m<sup>2</sup>/s)}}
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[[Category:Infiltration]]
[[Category:Green infrastructure]]
[[Category:Modeling]]