Quantifying LID impact: A modified metric for enhanced flood mitigation and urban resilience

Climate change and rapid urbanization significantly increase urban flooding, overwhelming traditional drainage systems. Traditional stormwater infrastructure requires innovative solutions like Low Impact Development (LID). LID practices mimic natural hydrology, reducing runoff and mitigating flood risk. This study evaluates the effectiveness of various LID practices in urban drainage systems, and proposed a novel modified metric approach to quantify LID effectiveness, aiming to inform sustainable urban planning and flood risk management. Storm Water Management Model (SWMM) was used to simulate pre-development, post-development, and post-development with LID scenarios, incorporating bio-retention cells (BRC), permeable pavement (PP), and rain barrels (RB). A novel modified performance matrix, alongside traditional metrics, evaluated LID performance in restoring pre-development hydrological conditions. Results showed significant reductions in total outfall volume, peak runoff, and flood volume across all LID scenarios. The combined LID approach (BRC, PP, and RB) achieved the highest performance, with 85 % reduction in total outfall volume, 80 % in peak runoff, and 92 % in flood volume, closely approximating pre-development conditions. BRC consistently demonstrated high individual performance. The modified performance matrix highlighted the contribution of LIDs in restoring pre-development hydrology, emphasizing the importance of integrated LID approaches for sustainable urban design and flood risk management in rapidly urbanizing environments. This study highlights the value of modified metric for evaluating LID effectiveness and its role in building more resilient urban environments.