Resilience Quantification of Low-Impact Development Systems Using SWMM and a Probabilistic Approach

Over the last few decades, there has been an increased demand for resilient low-impact development (LID) systems for stormwater management. During extreme uncertain events, a resilient LID system is expected not only to handle immediate stressors but also to rapidly adapt through changing and regulating itself to ensure continuous functionality. This study presents a new resilience quantification approach applicable to different LID systems. To demonstrate its utility, the developed approach was applied on a bioretention system. A set of equations for the LID system's functionality was developed, integrating an analytical probabilistic approach (APA) and the stormwater management model (SWMM) continuous simulation output. These equations were subsequently used to evaluate resilience indices such as robustness, rapidity, serviceability, and the LID system's reliability for different LID area ratios and surface depression storage depths. Both APA and SWMM exhibited similar resilience index values of 0.66-1.0 and 0.73-1.0, respectively. The overall reliability index values ranged from 60.50% to 100% when using SWMM and 56.67% to 100% when using APA, reflecting their consistency in predicting excellent system performance throughout the simulation period. However, the average rapidity index value prediction with APA was lower compared to SWMM. This slight variation was due to event-by-event hydrological simulation in APA, unlike the time step-by-time step continuous simulations in SWMM. The developed approach and findings of this study provide policy-makers with a consistent methodology to design resilient LID systems and empower decision-makers to strategize investment focused on optimized LID resilience-based designs. (C) 2022 American Society of Civil Engineers.