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Bertrand Mareschal

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« on: April 08, 2020, 04:33:42 PM »
Assessment the Effects of Land-Use / Land-Cover Changes on Soil Loss and Sediment Yield Using WaTEM/SEDEM Model: Case study Ziz upper watershed in SE-Morocco.
Land use and land cover (LULC) are directly related to water erosion and sediment yields. A spatially distributed soil erosion and sediment delivery model can be used as a good tool to assess the effects of changes in land use on erosion processes. However, their calibration requires a lot of data, sometimes non-existent. In this work, WaTEM / SEDEM model of spatial distribution of sediments and their delivery to rivers was applied to a large basin (4435 km-2) in the Moroccan High Atlas. Model calibration was carried out based on a sediment yield recorded during the period from 1973 to 1990 at Hassan Eddakhil dam in the catchment outlet. Validation of the model results was made with a sediment yield recorded from 1991 to 2009. Three LULC scenarios were modeled by reproducing land use/ land cover in 1936 and in 1957 and then a hypothetical future scenario. The comparison of these simulations with the current situation of LULC shows that erosion rates increase from 1,503,066 t. yr-1 to 2,239,573 t. yr-1 and an increase in specific sediment yields from 0.37 t. ha-1. yr-1 to 5.6 t. ha-1. yr-1. These results can be explained by the interactions between bioclimatic factors and ecologically inadequate and destabilizing human interventions (deforestation). The great anthropogenic pressure on the natural resources which lasted in time ended by the outcropping of pavements of stones or soils exposed directly to the erosive processes.