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→Determine the required surface area of the storage reservoir
For practices with no underdrain:
For practices with no underdrain:
<math>A_{r}=V_{i}/[d_{i}+(f'\times D)]</math>
<math>A_{r}=V_{i}/[d_{i}+(f'\times D)]</math>
{{Plainlist|1=Where:
*V<sub>i</sub> = Infiltration volume target for the design storm event (m<sup>3</sup>), based on average annual water budgets for pre- and post-development scenarios, and the target of maintaining pre-development infiltration volume.
*d<sub>i</sub> = Infiltration water storage depth of the practice (m), see equations above to calculate for with and without underdrain designs.
*f' = Design infiltration rate of the underlying native soil (m/h)
*D= Duration of design storm (h)<br>
If A<sub>r</sub> is greater than A<sub>p</sub>, calculate the design infiltration water storage depth, d<sub>i</sub>', required to capture the infiltration volume target for the design storm:
<math> d_{i}' = (V_{i}/A_{p})- (f'\times D)</math>
{{Plainlist|1=Where:
{{Plainlist|1=Where:
*V<sub>i</sub> = Infiltration volume target for the design storm event (m<sup>3</sup>)
*V<sub>i</sub> = Infiltration volume target for the design storm event (m<sup>3</sup>)
*d<sub>i</sub> = Infiltration water storage depth of the practice (m), see equations above to calculate for with and without underdrain designs.
*A<sub>p</sub> = Surface area of the practice (m<sup>2</sup>, see equations above to calculate for designs that deliver water to a surface ponding area vs. directly to storage reservoir.
*f' = Design infiltration rate of the underlying native soil (m/h)
*f' = Design infiltration rate of the underlying native soil (m/h)
*D= Duration of design storm (h)
*D= Duration of design storm (h)<br>
<br>
*Step 13: Calculate practice drainage time, t<sub>p</sub> (h), which is the time required to fully drain d<sub>i</sub> or d<sub>i</sub>' assuming one dimensional drainage from the storage reservoir bottom:
==Calculate peak flow rates==
==Calculate peak flow rates==