Comprehensive characterization and evaluation of coupled LID system responses to extreme rainfall events

With more extreme rainfall events driven by climate change, urban water management is becoming increasingly challenging. Low impact development (LID) practices provide effective and nature-based solutions and have been widely adopted globally. However, two critical questions must be addressed: (1) how do rainfall characteristics affect LID performance? (2) what LID drainage system design is most effective under extreme rainfall events? This study investigates how rainfall events, LID facility design, and LID spatial distribution influence the performance of a coupled LID system in a typical urban area under varying rainfall scenarios. In a typical densely populated residential area (3.24 ha residential community in Tianjin, China), we simulated 10,000 random rainfall events per scenario (30,000 in total) by using the Storm Water Management Model. Compared three scenarios, Scenario 3 with a comprehensive LID system, outperformed both the baseline configuration (Scenario 1) and the standardized setup (Scenario 2). Global sensitivity analysis results revealed that rainfall duration is the dominant factor influencing system performance, while bioretention layer thickness and vegetation coverage are critical LID design parameters. System performance evaluation used three proposed lumped indicators: Infiltration Coefficient (IC), Peak Arrival Coefficient (PAC), and Effectiveness Coefficient (EC). These findings demonstrate the coupling system's effectiveness against extreme rainstorms, provide a reference for optimizing LID parameters under climate change, and offer valuable guidance for planners and engineers to enhance climate resilience and evidence-based decision-making, thereby facilitating LID implementation in rapidly developing urban areas. • Rainfall duration is the key factor affecting LID stormwater control performance. • Bioretention thickness and vegetation fraction greatly improve LID efficiency. • A three-scenario comparison evaluates multi-LID system effectiveness. • The coupled LID system performs best under conditions of extreme rainfall. • LIDs spatial distribution has minor impact during tested extreme rainfall events.