1,559
edits
Changes
Jump to navigation
Jump to search
Line 54:
Line 54:
no edit summary
* Design storm intensity, i (mm/h)
* Design storm intensity, i (mm/h)
* 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 the infiltration volume deficit (pre-development minus post-development 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 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 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
* Proposed surface grade elevation at the practice location (metres above sea level, masl)
* 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
* 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)
* Effective porosity of any void-producing structure system (e.g. soil cells, chambers and associated aggregate) included in the storage reservoir, 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 storage reservoir)
==Decide if an underdrain will be included==
==Decide if an underdrain will be included==
* Step 1: Based on the median measured infiltration rate of the native soil at the estimated location and bottom elevation of the practice, or estimated from the median grain-size distribution results, decide if an underdrain will be included in the design.<br>
* Step 1: Based on the median measured infiltration rate of the native soil at the estimated location and bottom elevation of the practice, or estimated from the median grain-size distribution results, decide if an underdrain will be included in the design. See [[Design infiltration rate]] for guidance on field instruments, methods and number of measurements to be collected.<br>
If the median measured or field estimated infiltration rate of the underlying native soil (f<sub>f</sub>) is less than 15 mm/h, include an underdrain.
If the median measured or field estimated infiltration rate of the underlying native soil (f<sub>f</sub>) is less than 15 mm/h, include an underdrain.