Optimizing Impervious Surface Distribution and Rainwater Harvesting for Urban Flood Resilience in Semi-Arid Regions

Flooding poses significant risks to urban areas, especially in regions vulnerable to climate change, where developing countries are disproportionately affected. Compared to rural areas, urban zones are more severely impacted by natural disasters, particularly flooding. This study explores the influence of surface cover types on runoff and flood risk, focusing on Italian city-2 and the Rizgary neighborhood in Erbil, Kurdistan Region of Iraq. Newly developed areas are compared to older quarters to assess how different surface compositions impervious versus permeable affect hydrological responses and flood generation. The Soil Conservation Service Curve Number (SCS-CN) method was employed to model runoff under varying rainfall scenarios. The results reveal that increasing the proportion of permeable surfaces significantly reduces runoff volumes and mitigates flood risks. The study also highlights the potential of household-level rainwater harvesting and the redevelopment of low-density neighborhoods with multi-story buildings as effective strategies to reduce runoff and enhance urban resilience. These findings underscore the importance of integrating permeable materials, green infrastructure, and water harvesting measures into urban planning. The research offers valuable insights for urban planners, policymakers, and developers aiming to reduce flood risks in rapidly urbanizing areas, particularly in cities like Erbil that face the dual challenges of urban expansion and climate change.