Flood hazard mapping using gis and multi-criteria decision analysis (MCDA): A case study of Afgooye District, Webi Shabelle River Basin, Somalia

Abstract

Identification of the flood hazard hotspot is critical for disaster risk management. Floods are one of the world’s most severe hydrometeorological hazards, often aggravated by rapid land-use change, geomorphic change, and extreme rainfall events. The Afgooye District in the Webi Shabelle River Basin (WSHRB) in the southern part of Somalia has experienced frequent flood events, but a systematic, geospatially integrated flood susceptibility, vulnerability, and risk assessment has been lacking. This study introduced an integrated approach for mapping the flood risk priority areas using GIS and MCDA, applicable to flooded regions. The results indicate hazard class distribution patterns across the study area. To validate the model, the intensity of historical flood events was compared against the identified critical zones. The results showed that our hazard maps fell into the actual flood historical events' spatial patterns, suggesting validity and consistency with the practical reality. About 26.52% and 13.43% of the study areas are exposed to very high flood susceptibility, while 19.78% and 6.69% are high to very high flood vulnerability. Elevation, slope, TWI, rainfall, distance from the river, drainage intensity, and soil were highly correlated with flood risk. Also, population density, LULC, distance to the roads, and NDVI had a great influence on flood vulnerability. To validate the flood hazard mapping of this study, the area under the Curve (AUC) approach was used to confirm the flood risk map, which showed a high degree of accuracy (0.88). Thus, this study suggests that integrated GIS-MCDA could be used as a tool for rapid identification of flood risk areas and guide a strategic management intervention. The results of this study provide valuable insights for monitoring and estimating the probability of floods in the Afgooye District.