Hydraulic Modeling for Flood Hazard Monitoring In urbanized catchment, Addis Ababa, Ethiopia.

This study addresses the escalating flood risks in Addis Ababa, Ethiopia, driven by climate change, rapid urbanization, Deforestation and expanding impervious surfaces. It employs an integrated approach combining HEC-RAS version 6 hydraulic modeling with GIS-based multi-criteria analysis to produce detailed flood hazard and risk maps under various return periods. Using datasets from open topography, Earth Explorer, ESRI, climate archives, land use, soil information, and field surveys, the research identifies high-risk zones—particularly Kebena, Akaki, and Bole Bulbula—due to flat topography, dense settlements, and inadequate drainage infrastructure. The development of a 2D hydraulic model with diffusion wave and sub-grid capabilities simulated flood extents, depths (up to 1.8 meters), and velocities (up to 3 m/s), revealing critical vulnerabilities affecting roads, settlements, and municipal areas. Key drivers such as deforestation and urban expansion exacerbate flood susceptibility. The resulting flood risk maps highlight urgent needs for improved drainage systems, floodplain zoning, and early warning mechanisms, supporting sustainable development goal 11( SDG 11 ) and climate adaptation strategies. The framework offers a applicable approach for data scarce regions, with recommendations for higher-resolution DEMs, validation using observed flood data, and the evaluation of structural mitigation measures like retention ponds. This comprehensive assessment provides actionable insights for urban flood management and resilience planning.