Low Impact Development (LID) is an increasingly popular alternative to "end of pipe" solutions. LIDs are designed to intercept, store and/or infiltrate precipitation before it reaches the conveyance system. LIDs are becoming an integral part of new development design and are also being retrofit into existing developments in order to promote infiltration, reduce storm water runoff and improve receiving water quality.

PCSWMM streamlines the modeling of LIDs on either a detailed, lot-level scale, or on a subwatershed or watershed scale for planning studies. The deterministic approach models physical processes within various LID control devices.

Supported LIDs include:

• permeable pavements,
• bio-retention areas and rain gardens,
• green roofs,
• rain barrels, cisterns with water reuse,
• vegetative swales and buffer strips,
• infiltration trenches, and more...

PCSWMM's capabilities for LID analysis include:

• detailed, physically-based, lot-level LID design and evaluation,
• master planning type studies, with quick assignment of multiple LIDs and treatment areas,
• evaluation of the long-term performance of LIDs with clogging (reduction of infiltration capacity),
• comparison of the continuous hydrologic and water quality benefits of various LID implementations with scenario comparison tools,
• use of Sensitivity-based Radio Tuning Calibration (SRTC) tool to determine sensitivity of different LID practices and parameters under different conditions,
• determination of effectiveness of LIDs for precipitation events of different types and timing using PCSWMM’s time series analysis/management tools (to evaluate reduction in peak runoff, total flow volume, pollutant load etc.),
• analyzation and comparison of results with flow-duration-exceedance curves, and more...