Bioretention: Sizing and modeling

From LID SWM Planning and Design Guide
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  1. Gather input data:
    • The applicable infiltration coefficient (q) is calculated by applying the safety factor to the measured infiltration rate.
    • Determine the drainage catchment area (AD), and outline the location of the bioretention facility. To begin with, budget for at least 10% of the contributing impervious area to be required for the BMP.
    • Unless the biomedia fill material has been tested and certified otherwise, a porosity value (Vr) of 0.4 may be assumed (i.e. void ratio 40%).
    • Bioretention facilities are usually between 0.5 m and 1.25 m deep, owing to construction considerations. Determine the maximum available depth (cc max) from the site constraints. The Infiltration page lists these.
    • Identify the duration (D) and intensity (i) of design storm(s).
  2. Calculate the required area

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