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* Design storm duration, D (h)
* Design storm duration, D (h)
* Infiltration volume target for the design storm event, V<sub>i</sub> (m<sup>3</sup>), based on average annual water budgets for the catchment for pre- and post-development scenarios and equal to the infiltration volume deficit (pre-development minus post-development annual infiltration)
* Infiltration volume target for the design storm event, V<sub>i</sub> (m<sup>3</sup>), based on average annual water budgets for the catchment for pre- and post-development scenarios and equal to the infiltration volume deficit (pre-development minus post-development annual infiltration)
* Drainage time, t (h), time required to fully drain the active water storage components of the practice (i.e surface ponding and active storage reservoir depths), based on local criteria or long term average inter-event period for the location
* Drainage time, t (h), time required to fully drain the internal water storage reservoir of the practice, based on local criteria or long term average inter-event period for the location
* Field measured infiltration rate of the underlying native soil, f (mm/h), median of field measurements or based on interpolation from median grain-size distribution results
* Field measured infiltration rate of the underlying native soil, f (mm/h), median of field measurements or based on interpolation from median grain-size distribution results
* Design infiltration rate of the underlying native soil, f' (mm/h), median field measured value, f divided by a safety factor, z
* Design infiltration rate of the underlying native soil, f' (mm/h), median field measured value, f divided by a safety factor, z
* Effective porosity of the storage reservoir fill material, including any void-forming structures (e.g. pipes, chambers, tanks, soil cells, etc.) and surrounding aggregate, n'
* Effective porosity of the storage reservoir fill material, including any void-forming structures (e.g. pipes, chambers, tanks, soil cells, etc.) and surrounding aggregate, n'
* Types of plants to be supported by the filter media bed (i.e. grasses vs. mix of grasses, plants and shrubs vs. trees)
* Types of plants to be supported by the filter media bed (i.e. grasses vs. mix of grasses, plants and shrubs vs. trees)
* How runoff will be delivered to the practice (i.e. to surface ponding area, or directly to storage reservoir)
* How runoff will be delivered to the practice (i.e. to surface ponding area, or directly to internal water storage reservoir)
This spreadsheet tool has been set up to perform all of the bioretention sizing calculations shown below and allows side-by-side comparison of equation outputs for each potential design approach or constraint scenario.<br>
This spreadsheet tool has been set up to perform all of the bioretention sizing calculations shown below and allows side-by-side comparison of equation outputs for each potential design approach or constraint scenario.<br>