Optimizing Impervious Surface Distribution for Enhanced Urban Flood Resilience

Abstract: As urban populations grow and cities expand and develop, the likelihood of natural disasters, such as floods, increases accordingly. Urban centers and residential areas are highly susceptible to flooding. Flooding poses significant risks to urban areas, especially in regions vulnerable to climate change, where developing countries are disproportionately affected. In Erbil, the rapid expansion and urban development, particularly following the 2004 liberation by coalition forces, have resulted in the extensive conversion of agricultural and undeveloped lands both within and beyond the city's municipal boundaries into built-up areas. Compared to rural areas, urban areas are more significantly impacted by natural disasters, particularly flooding. This study explores the influence of surface cover types on runoff and flood risk, focusing on the Italian City-2 and Rizgary neighborhood in Erbil, Kurdistan Region of Iraq. The challenges associated with surface water management are not limited to new neighborhoods but are also prevalent in many older neighborhoods of the city. The Soil Conservation Service Curve Number (SCS-CN) method was employed to model runoff under varying rainfall scenarios. This study aimed to: (1) evaluate the impact of impervious surfaces in residential areas on runoff generation, emphasizing the role of urban design; (2) analyze how varying housing densities influence runoff under different rainfall scenarios, comparing Italian City 2 and Rizgary Neighborhood in Erbil to represent distinct urban typologies; and (3) explore the potential of the SCS-CN method for sustainable hydrological planning. The findings provide insights for optimizing urban planning, mitigating flood risks, and enhancing water resource management in semi-arid regions like Erbil. The results reveal that increasing the proportion of permeable surfaces significantly reduces runoff volumes and mitigates flood risks, as compared to areas dominated by impervious surfaces. These findings underscore the critical importance of integrating permeable materials and green infrastructure into urban design to enhance flood resilience. The study offers valuable insights for urban planners, policymakers, and developers by identifying optimal surface compositions for reducing flood risks in rapidly urbanizing areas. Additionally, the research emphasizes the urgent need for sustainable urban development policies, particularly in regions like Erbil, which face the dual challenges of rapid urbanization and climate change-induced risks.