Runoff Capture Methods Developed for Stormwater Low-Impact Development Designs

Efforts under stormwater best management practices have led to low-impact development (LID) concepts for innovative stormwater designs. The key issue involved in the revolution of stormwater management from quantity to quality control has been the selection of the design event. Among many innovative approaches, the concept of runoff capture has been widely accepted and evaluated with data analyses and mathematical models. In this paper, both runoff event and volume capture methods are derived using the exponential model and solved for a selected runoff capture rate. Both methods provide identical assessment of the runoff capture rate for a selected basin storage volume. Both methods provide the identical water quality capture volume (WQCV) when the runoff capture rate is set to be the 80th percentile of either rainfall or runoff population. Two design charts, one for the US continent and the other for mainland China, are produced, respectively, using the runoff capture methods. This paper provides examples using long-term continuous rainfall data recorded at the City of Denver, Colorado and the City of Beijing, China to illustrate how to apply the empirical approach, theoretical methods, design charts, and guidance on the selection of storage volumes for stormwater LID designs. (c) 2019 American Society of Civil Engineers.