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| | 0.4 | | | 0.4 |
| |} | | |} |
− | | + | Before you begin you will need to know the following;<br> |
− | | + | * Catchment area (i.e. contributing drainage area), A<sub>c (m<sup>2) |
| + | * Catchment impervious area, A<sub>i (m<sup>2) |
| + | * Catchment runoff coefficient, C |
| + | * Design storm intensity, i (mm/h) |
| + | * Design storm duration, D (h) |
| + | * Infiltration target for design storm event, I<sub>d (mm) |
| + | * Drainage time target to fully drain the active storage, t (h), based on long-term average inter-event period for the location or local criteria |
| + | * Field infiltration rate of the underlying native soil f<sub>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 divided by a safety factor (z) |
| + | * Safety factor, z (dimensionless value between 2 and 3) chosen by designer |
| + | * Proposed surface grade elevation at the practice location (metres above sea level, masl) |
| + | * Elevation of the seasonally high water table or bedrock surface (metres above sea level, masl), below the practice location |
| + | * Effective porosity of any void-producing structure system (e.g. soil cells, chambers and associated aggregate) included, n' (if applicable) |
| + | * 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 filter bed surface; to storage reservoir; or both) |
| + | |
| ==Calculate the maximum overall depth== | | ==Calculate the maximum overall depth== |
| *Step 1: Determine what the planting needs are and assign appropriate depth of media, using the table above. | | *Step 1: Determine what the planting needs are and assign appropriate depth of media, using the table above. |