Subwatersheds prioritization using the compound parameter method: A case study of Drâa basin (morocco)

Water induced risks are major concern in arid and semi-arid regions, like Drâa basin, where unpredictable rainfall and slope increase the threat. In this study, a GIS-based morphometric analysis was conducted to prioritize the three major subwatatersheds—Upper Drâa, Middle Drâa and Lower Drâa— in Drâa basin (south-southeast of Morocco). Digital Elevation Model- derived morphometric parameters were computed first, including basin length (Bl), compactness index (KG), overall slope index (Ig), specific elevation gain (Ds), drainage density (Dd), stream frequency (Fs), gradient ratio (Rg), basin relief (H), time of concentration (Tc) and torrentiality coefficient (Tcoef). After, the sub-watersheds were ranked using the compound parameter method (CPM). The results show that Upper Drâa is most sensitive to water induced risks due to steep slopes, high elevation range and short water concentration time. This study helps identify areas with a priority for water induced risk management, such as flash floods and soil erosion.