Mapping and Qualitative Assessment of Erosion in the Upper Guir Watershed. Supporting Measures to Prevent Siltation of the Kadoussa Dam (South-East Morocco)

Resumo

The study aims to map, assess, and spatialize the potential erosion risk in the Kadoussa dam catchment area, a crucial step in supporting the prevention of siltation and preserving its reservoir. The adopted methodology is based on the PAP/CAR erosion estimation ap proach and consists of establishing a qualitative zoning of erosion susceptibility. The results obtained show that the upper Guir watershed, which forms the dam’s catchment, is exposed to active and visible erosion with diverse forms ranging from simple sheet erosion to rills, gullies, and widespread deep ravines. The study also reveals that terrains with very high to medium erodibility classes cover 48% of the basin area, while 52% of the area is char acterized by low to very low erodibility. The findings of the study confirm that preventing siltation requires measures against particle detachment, which are particularly recommended in the most sensitive areas, such as torrent heads and ravines in the Jbel Mesrouh region, along with disrupting sediment transport towards the reservoir by constructing two hillside structures on the main tributaries of the basin, Oued Guir and Oued Asefti. The results of this study are low-cost and easily transferable to erosion and siltation assessments of other dam reservoirs under similar conditions.