Rapid assessment of hydrologic performance of low impact development practices at different implementation levels

Abstract

In recent years, low impact development (LID) practices have been widely used to manage stormwater and to restore natural hydrologic regimes. During preliminary design, it is often necessary to identify the required LID practice area that can meet the control target of peak flow and runoff volume. Currently, equation-based methods (e.g. the Rational and the Curve Number method) and hydrological models are often used. However, the coefficients required by the equation-based methods are often site-specific and inaccurate. On the other hand, the hydrological models may not provide direct and intuitive results due to model complexity. This study employed EPA SWMM, a dynamic hydrologic/hydraulic model, to investigate the surface peak flow and surface runoff volume reductions of various LID implementation levels. A MATLAB code was developed to automate the processes of input file modification, model execution, result extraction and post-processing. A few commonly used LID practices, e.g. porous pavement and bioretention cells, were examined. The results were summarized as performance curves which can be used to quickly assess the hydrologic performance of the preliminary designs. Furthermore, a few equations based on the concept of water balance were proposed, which can be used to quickly estimate the required LID practice area using hand calculations. Finally, sensitivity analysis was performed on design storm characteristics, catchment hydrological properties and LID design configurations, etc.