Modeling Low Impact Development at the Small-Watershed Scale: Implications for the Decision Making Process
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Negative effects of urban stormwater runoff on water environment have been a growing concern in the United States. Drastic change in land uses to urban communities with pavements from natural land uses can destroy the already established eco-hydrologic system prior to the land conversion. Low Impact Development practices (LIDs) have been used as an alternative stormwater management approach in urban areas. The effects of LIDs on hydrology and water quality have been widely accepted to be positive through research that generally indicates decrease in surface runoff volume and pollutant loads. However, LIDs can have varying effectiveness under different conditions. In this research, the effectiveness of LIDs was assessed under three urban development plans (compact high-density (UHD), conventional medium-density (UMD), and conservational medium-density (UMC)) and under various configurations of LIDs factors (types, locations, and percent allocations) for surface runoff, nitrate, and total phosphorus in order to identify their performance on improving stormwater runoff and water quality under such conditions. Rain gardens, rainwater harvesting systems, and permeable pavements, commonly used in urban areas, were selected. The Soil and Water Assessment Tool (SWAT) was modified to implement the LIDs simulations at a watershed scale. A manual optimization was attempted to identify the LIDs configurations that meet targeted reduction amounts in a cost-effective manner. Then the effectiveness of LIDs was evaluated for the three urban plans and for the optimized LIDs configurations. The research indicates that the effectiveness of LIDs varies under various conditions examined. Under urban development plans, the efficiency of LIDs was measured in the order of the following land uses for all variables: UMD > UMC > UHD. Among post-LIDs scenarios, the UHD scenario resulted in low amounts in surface runoff and nitrate while the UMD scenario predicted low TP yields. Under LIDs factors through the optimization, the various configurations of type, location, and percent allocation changed the effectiveness of LIDs and/or caused the same effectiveness of LIDs for each variable. This research is useful in that it can ultimately suggest proper strategies in urban watersheds to effectively control stormwater and help regulators establish effective LID policies based on the results.
Seo, Mijin (2014). Modeling Low Impact Development at the Small-Watershed Scale: Implications for the Decision Making Process. Doctoral dissertation, Texas A & M University. Available electronically from