Low Impact Development (LID) Representation in #InfoSWMM and Sustain

LID controls are represented by a combination of vertical layers whose properties are defined on a per-unit-area basis. This allows LIDs of the same design but differing areal coverage to easily be placed within different Subcatchments in a study area. During a simulation SWMM5 performs a moisture balance that keeps track of how much water moves between and is stored within each LID layer. As an example, the layers used to model a bio-retention cell and the flow pathways between them are shown below:

The following table indicates which combination of layers applies to each type of LID (required if listed and underdrain is optional for three types of LID’s):

When a user adds a specific type of LID control object to a SWMM5 project the LID Control Editor is used to set the design properties of each relevant layer (such as thickness, void volume, hydraulic conductivity, underdrain characteristics, etc.). These LID objects can then be placed within selected Subcatchments at any desired sizing (or areal coverage) by editing the Subcatchment's LID Controls property.