The GreenPlan-IT Modeling Tool is a spatially distributed hydrologic and water quality model that simulates watershed processes and LID performance. Built upon the publicly available EPA Storm Water Management Model (SWMM) version 5.0, the modeling tool can be used to establish baseline conditions as well as evaluate relative effectiveness of implementing LID across different areas within a watershed, based on the potential of each LID type for reducing contaminant loads and runoff volume. Within the GreenPlan-IT toolkit, the Modeling Tool serves as a bridge between the LID Site Locator Tool and the Optimization Tool - it takes potential LID sites identified through the LID Site Locator Tool as constraints and simulates the performance of various LID combinations created by the Optimization Tool.
The Modeling Tool can simulate the generation, fate and transport of stormwater runoff and associated pollutants from landscape, as well as resulting flow and pollutant loading reduction as they pass through various LIDs. Municipalities can use the tool to 1) establish the baseline conditions through the characterization of the modeled watershed before any new management activities are implemented; 2) identify high-yield runoff and pollution areas; and 3) more importantly, quantify any reduction made from LID implementation by performing before and after LID simulation. SWMM 5 is currently capable of simulating the hydrologic performance of seven types of LIDs. As with most modeling exercises, the model is calibrated using local data before it can be used by municipalities to simulate LID scenarios for their local watersheds.
The Modeling Tool is intended for use by city engineers and planners to develop and evaluate various management scenarios at the watershed scale, alone or within the Toolkit. The model outputs provide quantitative information on flow, pollutant loading, and reductions from management actions for studied watersheds, and can assist in developing watershed master plans or city and county general plans for stormwater runoff or pollutant control.