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| * 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 infiltration water storage 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 active water storage components of the practice (i.e surface ponding and infiltration water storage depths), 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 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 |
| * Safety factor, z (dimensionless value between 2 and 3) chosen by designer based on consideration of risk factors | | * Safety factor, z (dimensionless value between 2 and 3) chosen by designer based on consideration of risk factors |