GIS-Based Morphometric terrain analysis for watershed characterization: case study of Ain Leuh watershed, Morocco

Abstract. The Ain Leuh watershed occupies a strategic hydrogeographic position that favors surface water circulation and accumulation. Considering the persistent water stress affecting Morocco, a detailed characterization of this watershed is essential to support sustainable water resource management and to mitigate geohazards such as flooding and soil erosion. This study aims to characterize the Ain Leuh watershed using morphometric analysis based on the FABDEM (Forest and Buildings removed Copernicus DEM). Covering an area of 143.58 km², the watershed is geomorphologically young, well-drained, and characterized by significant surface runoff. Surface and linear morphometric include drainage density (2.96 km/km²), stream frequency (7.41 km⁻²), drainage texture (13.45 km⁻¹), elongation ratio (0.40), circularity ratio (0.29), and form factor (0.10). The values reflect a long, narrow basin with high runoff potential and limited infiltration capacity. Hypsometric contour mapping at 200-meter intervals highlighted a dominant NE–SW alignment, indicative of the region’s terraced geomorphology. Elevation data pointed to higher altitudes in the southeastern part of the basin and lower elevations in the northwest, while slope analysis indicated that low to moderate gradients are more dominant. These results were complemented by the relief parameters: the relief ratio (Rh), dissection index (Dis), and roughness number (Rn). The relief ratio (0.03) underscores the predominance of broad, low-relief areas such as floodplains and wide valleys. The dissection index (0.58) confirms considerable valley incision, implying a heightened risk of both fluvial and slope-driven erosion, while the roughness number (3.43) combines indicators of steep terrain and dense drainage to describe a rugged watershed with a significant susceptibility to surface water dynamics and erosion. The morphometric analysis identifies the Ain Leuh watershed as a young, elongated basin with efficient drainage, high surface runoff, and moderate to steep slopes. While its flood potential appears limited due to its geomorphological structure, the basin exhibits significant vulnerability to erosion. These findings provide valuable insights for regional water management strategies and underscore the need for erosion control measures to enhance the watershed’s resilience.