FLOOD RISK MAPPING IN ARID REGIONS BASED ON MORPHOMETRIC ANALYSIS AND GIS – CASE STUDY OF CHELLIF WATERSHED

Abstract

This study presents a comprehensive morphometric and flood hazard assessment of 36 sub-basins within the Cheliff watershed, located in north-central Algeria. Utilizing Geographic Information System (GIS) techniques and Digital Elevation Model (DEM) data, key morphometric parameters—such as area, slope, drainage density, shape factor, sinuosity index, circularity ratio, and Curve Number—were extracted and analyzed to evaluate their influence on hydrological behavior and flood susceptibility. The aim of the analysis was to evaluate the flood hazard degree across the watershed and identify basins with the highest vulnerability. The results reveal significant spatial variability, with several sub-basins—particularly O. Touil Aval, Daia el Firania, O. Ouassel Moyen, and O. Djidiouia—exhibiting morphometric characteristics associated with high flood susceptibility, such as steep slopes, compact forms, high drainage density, and limited infiltration capacity. Hazard classification maps were developed for each parameter and integrated into a final flood hazard map. The analysis indicates that more than 50% of the sub-basins fall into high or very high flood risk categories. These findings underscore the necessity of targeted watershed management strategies, including erosion control, land use planning, and flood mitigation measures, to reduce vulnerability and enhance resilience in the face of increasing hydrological extremes in the region.