Assessing the Performance of Various Stormwater Control Measures in a Full-Scale Low Impact Development (LID) Testbed under Climate Change Scenarios Using SWMM

Abstract:

Low Impact Development (LID) or Green Infrastructure (GI) are the stormwater control measures (SCM) designed to mitigate the adverse impacts of urbanization by mimicking the pre-development hydrology, restoring the natural flow regime and enhancing the water quality. The performance of these systems is highly variable and dependent of the design parameters such as the filtration media, and local conditions such as climate. To conduct a comparative evaluation of three different LID designs under same conditions, a full-scale LID testbed was implemented at the university of Texas at San Antonio (UTSA). The LID testbed consists of a sand filter basin and two rain gardens with two different biofiltration media: (1) the regional standard biofiltration media and (2) an innovative custom blend with use of limestone sand in the mixture. The LID designs are tested in duplicates - with and without impermeable liner - to investigate the potential impacts of the direct infiltration on water quality and aquifer recharge. The performance of all cells is assessed in terms of quantity and quality control by monitoring the rainfall, inflow and outflow rates and volume, water level and moisture content in cells; and collecting flow-paced stormwater samples at the inlet and six outlets. Using the field measurement, a Storm water Management Model (SWMM) was developed, calibrated and validated to simulate the hydraulic and water quality performance of the LID testbed. The model was used to assess effectiveness and sensitivity of each LID control under changing environment. Specifically, this study evaluated the ability of each LID control to mitigate the alternations brought by climate change in hydrologic terms and the treatment of pollution, such as total suspended solids (TSS). The climate change projections were compared to the historic rainfall regime, along with the performance of the testbed under different regimes. Design recommendations were elaborated in order to better mitigate the impacts of urbanization and future climatic changes accordingly.