Building resilient urban drainage systems by integrated flood risk index for evidence-based planning.

Urban flooding poses a significant risk to cities worldwide, exacerbated by increasing urbanization and climate change. Effective flood risk management requires comprehensive assessments considering the complex interaction of social, economic, and environmental factors. This study developed an innovative Urban Flood Risk Index (FRI) to quantify and assess flood risk at the sub-catchment level, providing a tool for evidence-based planning and resilient infrastructure development. This study integrates Geographic Information System (GIS), Storm Water Management Model (SWMM), Analytic Hierarchy Process (AHP), and the Pressure-State-Response (PSR) framework. The FRI incorporates seven pressure and state indicators and three response indicators weighted by expert judgment. The FRI was calculated by combining the weighted sub-indices, classifying flood risk into five levels. Results showed that 51% of the study area experienced high pressure, with 26% facing very-high pressure. The state index indicated that 55% of the area falls under a moderate state, while 21% exhibits a high state. Importantly, the response index highlighted the effectiveness of Low Impact Development (LID) practices, with 20% of the area showing high to very-high response levels. The integrated FRI demonstrated an overall moderate flood risk level for maximum sub-catchments, emphasizing the positive impact of LID practices in mitigating flood risk despite existing pressures and system limitations. This evidence-based assessment provides a valuable tool for sub-catchment level flood risk assessment. It empowers decision-makers to prioritize investments, target interventions, and develop adaptive strategies to enhance urban resilience in a changing climate.