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. The influence of surface cover types on runoff and flood risk is examined in two different neighborhoods of Erbil, Kurdistan Region of Iraq, one representing a newly developed area and the other an older established neighborhood. A newly developed area is compared with an older quarter 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 estimate runoff under varying rainfall scenarios. The findings demonstrate that the implementation of impervious surfaces results in an approximately twofold increase in runoff generation during rainfall events, primarily due to the substantial reduction in infiltration and surface storage capacity. 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.