Low Impact Development (LID)
Low impact development (LID) practises are represented in SWMM networks to capture surface runoff and typically provide a combination of retention, infiltration, and evapotranspiration functions using one of the following types of LID control:
- Bio-retention cells
- Rain gardens
- Green roofs
- Infiltration trenches
- Permeable pavements
- Rain barrels
- Rooftop disconnection
- Vegetative swales
Each type of LID control consists of a number of vertical layers whose properties are defined on a per-unit-area basis, which enables LIDs of the same type but which cover a different area, to be associated with the same subcatchment.
One or more LID controls can be associated with a subcatchment and during a simulation, ICM models their hydrological performance by determining how much water moves between, and is stored within, each LID layer. The performance of the LID controls is reflected in the runoff calculated for each subcatchment and reported in the subcatchment results.
The placement of LID controls within a subcatchment and the modelling of them in ICM follows the same methodology as SWMM5, which is described in detail in the SWMM5 User Guide and the SWMM Reference Manual, Volume III, Water Quality.
LID controls can be added to the database using the LID control tab on the Subcatchments Grid and are associated with a subcatchment via the LID controls field in the applicable Subcatchment's properties.
