Evaluation of the Effectiveness of Low Impact Development Practices (LIDs) under Various Conditions

Stormwater problems from urban development have been occurring in recent years in the United States. 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 indicated to be positive through much of research, showing the decrease of surface runoff volumes and pollutant loadings. However, LIDs can cause different effectiveness under a variety of conditions. In this study, the effectiveness of LIDs was assessed under various urban planning (a compact high-density urban type (UHD), a conventional medium-density urban type (UMD), and a conservational medium-density urban type (UMC)) and under various LIDs conditions (types, locations, and percent allocations of LIDs) for surface runoff, nitrate, and total phosphorus to evaluate the effectiveness of LIDs for these conditions at a development scale.

Rain gardens, rainwater harvesting systems, and permeable pavements were considered for simulations. The Soil and Water Assessment Tool (SWAT) was used and model development was performed to simulate the LIDs considered. A manual optimization was used to identify the LIDs conditions that meet both targeted reduction amounts and minimal cost. The effectiveness of LIDs was evaluated for the three urban land uses and for the optimized LIDs conditions.

The study demonstrated different effectiveness of LIDs under various conditions considered. Under the condition of the urban land uses, the largest reduction by LIDs occurred in the order of following land uses for all variables: in UMD land use > in UMC land use > in UHD land use. Among post-LIDs scenarios, the UHD land use represented low values for surface runoff and nitrate and the UMD land use for TP. For the LIDs optimization, the various combinations of type, location, and percent allocation for each variable changed the effectiveness of LIDs and/or caused the same effectiveness of LIDs. This study can ultimately suggest proper strategies on a watershed scale to effectively control stormwater and help regulator establish effective LID policies based on the results.