Wet detention pond - Extreme flood (10-yr 24-hr) outlet configuration
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Design methodology
1-yr 24-hr Instantaneous volume 1-yr 24-hr routed (R124) 1/2 Pre-development 2-yr 24-hr peak Instantaneous volume) 1/2 Pre-development 2-yr 24-hr peak routed (R224)
Weir length (ft) 3.0 3.9 3.1 4.6
Weir elevation (ft) 114.72 110.2 114.7 110.1
Surface area at weir elevation (ac) 1.2 0.9 1.2 0.9
Peak discharge per design event (cfs)1 81.8 81.5 81.8 81.4
Peak water elevation per design event (ft) 118.4 112.0 118.4 111.8
Designed surface area at HWL (ac) 2.01 1.0 2.0 1.0

1Note that the Instantaneous volume method requires twice the surface area (4 percent vs 2 percent of drainage area) and about 6 more feet of storage depth than the routed method for this design event. This is the result of introducing the entire event volume at once versus the more realistic routing of inflow and outflow.

This page was last edited on 16 April 2020, at 18:18.

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