Flood risk assessment in a semi-arid mediterranean basin using HEC-RAS hydraulic simulation: A case study of Oued Bounouara

Uncontrolled urban growth and change in climate have made urban flooding even more probable, particularly in urban areas with semi-arid climates that are characterized by quick and extreme changes in hydrological response. The study carries out a combined flood risk analysis of the Oued Bounouara watershed located in northeast Algeria and has an area equivalent to 181 km². The approach is considered the combination of high-resolution geomorphological analysis based on Geographic Information Systems (GIS) and empirical hydrological modeling (through Sokolovsky and Turazza methods) and sophisticated hydraulic modeling employing HEC-RAS to assess the dynamics of the floods due to different returns (10 to 1,000 years). The results indicate that the steep slope and the elongated form of the watershed predispose it to flash floods. A ten-year simulated return flood event (peak discharge = 56.09 m³/s) indicates widespread flooding of the alluvial plain, and the modeled flood depths are up to 7.68 meters. These findings must be similar to past flood records, and this fact attests to the credibility of the modeling framework.