Rapid Assessment of Hydrologic Performance of Low Impact Development Practices under Design Storms

Low impact development (LID) practices are often applied to compensate for surface imperviousness caused by urban development. These practices can mitigate flood risk by reducing runoff volume and peak flow and by delaying the time to peak flow. To select a suitable LID practice type and its surface area during the preliminary design process, it is necessary to rapidly estimate the hydrologic performance of various LID designs under design storms. This study provides a method and a toolbox for rapid assessment of the hydrologic performance of various LID practices, which can be useful to developers for establishment of preliminary LID designs. The hydrologic performance of three common types of LID practices (i.e., green roofs, bioretention cells, and infiltration trenches) under various design storms is first simulated using the Storm Water Management Model (SWMM). The results are then presented as performance curves on a unit storage basis. Look-up tables are further developed to assist the comparison and selection of the LID alternatives for various hydrologic performance targets. To facilitate SWMM modeling, a MATLAB toolbox is developed to automate the process of input modification, model simulation, result extraction, and postprocessing. Finally, the sensitivity of the look-up curves to design storm types and design specifications of bioretention cells is also analyzed, and the assumptions used in the development of these look-up curves are validated.