PROBLEM OF WATERSHED ERODIBILITY IN THE HIGH ATLAS OF MARRAKECH (MOROCCO) AND ITS IMPACT ON WATER RESOURCES

The watersheds on the northern flank of the High Atlas Mountains, which drain to the Atlantic Ocean, act as a water tower for the arid plains surrounding the city of Marrakech (Morocco). These watersheds have short-term torrential flows and a significant drainage density. Frequent, violent floods cause erosion, which results in siltation of reservoirs. The area is dissected by rugged slopes and the rocks have been deformed by thrusting. The study area is characterized by a very complete lithological series ranging from Precambrian to the present. The resistance or susceptibility to erosion varies with rock type.

In this study, GIS and remote sensing have been used to map soil types, drainage networks and directions of flow on the Piedmont of the High Atlas of Marrakesh. The obtained results highlight the hydrographic phenomena and their effects on water resources. In particular, this study has enabled the mapping of zones that are vulnerable to erosion.