Mediterranean countries are increasingly confronted with decreasing rainfall, increasing droughts, and high demographic growth, which have severely contributed to the scarcity of water resources. Indeed, the construction of large dams is often considered the most effective solution to increase water availability and access. However, the reservoir sedimentation of the Lalla Takerkoust dam (Morocco) comes from the intense erosion of the watersheds from the N'fis slopes, especially during the flood period, representing a significant risk. The siltation reduces the reservoir storage volume and the useful life of the dam. Moreover, the trapped sediment release may cause damage to the hydromechanical equipment and a deterioration of the water quality. This study aims to quantify the erosion rates of the N'fis basin during extreme events and determine the processes influencing sedimentation. The data used can be classified into two categories, quantitative mapped data: soil characteristics, watershed morphology, vegetation cover, and measured data: rainfall, flow rates, siltation, and mineralogical composition of the studied reservoir silts. Approaches were implemented: (1) to identify the processes influencing the dams' sedimentation in the N'fis basin, (2) to use Revised Universal Soil Loss Equation (RUSLE) and GIS techniques to calculate soil erosion rates in the watershed, and (3) to examine the spatial and temporal variation of land use, extreme events, and snowmelt on soil erosion dynamics using remote sensing. This study demonstrated that with increased precipitation, soil erosion increases, which implies augmented sediment load in the dam. Therefore, predicting soil erosion rates in the N'fis basin and better soil management are excellent potentials to reduce the sediment load in the reservoir.