The basic steps to implementing LID controls in a hydrologic model are:

1. Add generic LID controls to the model. This is done in the ”Low Impact Development Controls Manager’.
2. Add LID and catchment elements to the network drawing (see ”Low Impact Development Controls’).
3. Enter element-specific LID control and catchment data in the Properties pane. LID control attributes include designating a Parent Catchment and associating a generic LID (created in step 1). For additional details, see Low Impact Development Controls.
4. If the LID Control Type include an Underdrain Layer, then select a Underdrain Outflow Element to receive any underdrain flow from the LID.
5. Any excess surface flow from the LID will drain to the Parent Catchment. Option for the LID to send this surface outflow to the Impervious portion of the Parent Catchment or to the runoff collection point of the catchment.
6. Then continue with the modeling the remainder of the model as normal (e.g., enter remaining network and rainfall data, configure storm data, run the model, review results).

Implementation Notes

• Low-Impact Development (LID) controls as implemented in the software are based on the calculation methods used in EPA SWMM Version 5.1.012.
• LID elements can only be paired with catchments which use the EPA-SWMM or Time Area Runoff Methods.
• Only the hydrologic performance is modeled-pollutant removal impacts are not considered.
• A LID control element must be associated with a Parent Catchment. The Parent Catchment is the source of stormwater input to the LID control, and also receives discharge from the LID.
• The effect of a LID control on runoff is seen in the computed hydrograph for the LID control's Parent Catchment.