Assessement of soil erosion by fallout 137Cs in the Abdelali basin (Rif of N Morocco)

Abstract

In the Rif, Northern Morocco, the severity of soil erosion threatens the sustainability of landscapes and agroecosystems. The climatic, lithologic and edaphic factors determine the fragility of this Mediterranean environment and the antrohopic impact due to intensive soil use, grazing and deforestation are the main factors causing important soil losses. In the Abdelali catchment, fallout 137Cs is used to identify the main areas supplying sediment and to quantify soil erosion under different soil uses and slopes. The highest losses of 137Cs, compared to the reference inventory, are found in the steepest cultivated soils where erosion rates reach 42 t/ha/year, followed by matorral areas scarcely vegetated. More stable soil conditions and less erosion are found in more densely vegetated shrubs and forests. Soil movement in the catchment is very intense and particles accumulate at the lower part of the hillslopes, where 137Cs gain has been measured. The magnitude of erosion is reflected by the total siltation of the small dam at the catchment outlet, occurred shortly after it was build. The severity of soil erosion in the area requires to establish strategies for soil conservation.