Soil erosion and land degradation pose a persistent threat to semi-arid mountain catchments, where steep relief, erodible substrates, and concentrated seasonal runoff drive high sediment loss. This study prioritizes the 53 sub-watersheds of the Upper Sebou watershed (Middle Atlas, northern Morocco; 7368 km²) for soil and water conservation through quantitative morphometric analysis. Basic basin parameters were extracted from a digital elevation model (DEM) in ArcGIS, from which the linear, areal, and relief morphometric parameters were computed using established mathematical formulas. Each parameter was ranked across the sub-watersheds, and the ranks were averaged to obtain a compound parameter (Cp) expressing the relative erosion susceptibility and conservation priority of each unit. Compound parameter values ranged from 19.63 to 38 and were grouped into five priority classes; 12 sub-watersheds (≈23%) were classified as very high and 17 as high priority. The very-high units form a contiguous core along the upper Sebou channel in the center of the basin, together with a detached pocket on the eastern flank, where high drainage density and relief coincide with compact watershed shapes that favor rapid runoff concentration. The delineated gully-prone areas concentrate along the central drainage corridor and coincide spatially with the highest-priority sub-watersheds, providing field-based support for the ranking. Overall, the approach offers an effective, low-cost means of pinpointing land-degradation hotspots and prioritizing conservation interventions, readily transferable to other data-scarce semi-arid basins.