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Stormwater BMP Sizing

Size a bioretention cell or dry detention basin from drainage area and runoff coefficient — Water Quality Volume (WQV), required surface area, and infiltration time.

Input

bioretention only
detention only

Results

Water Quality Volume WQV (m³)
Required surface area (m²)
Storage volume at h
Estimated drain time (hr)
Drain time within target?
Method

WQV = P_wq · C · A_da / 1000 (m³). Bioretention: A_BMP = WQV / (h_pond + k·t/1000), where t is target drain time. Drain time = WQV / (k/1000 · A_BMP). Detention: A_BMP = A_factor · A_da typical; storage V = h · A_BMP.