Quantification and Evaluation of Water Erosion by RUSLE/GIS Approach in the Ykem Watershed (Western Morocco)
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Laboratory of Geosciences, Department of Geology, Faculty of Sciences, Kénitra, BP 133 Morocco
Department of Natural Resources and Environment, Hassan II Agronomy and Veterinary Institute, Rabat, 6202 Morocco
Laboratory of Geoscience and Applications, Faculty of Sciences, Hassan II University of Casablanca, Ben M’sik, 7955 Morocco
Department of Geology, Faculty of Sciences and Techniques Nouakchott El, Aasriya, Nouakchott, Mauritania
Mohameden Aoufa   

Laboratory of Geosciences, Department of Geology, Faculty of Sciences, Kénitra, BP 133 Morocco
Ecol. Eng. Environ. Technol. 2022; 5:42–53
The Water erosion of soils considered the main cause of soil degradation in Morocco. Soil erosion not only reduces agricultural productivity but also reduces water availability, and negatively contributes to the quality of drinking water sources. Consequently, the assessment of soil erosion risk has become the objective of several researches at the Moroccan level. It is in this context the purpose of this study is to assess the soil erosion risk using a Revised Universal Soil Loss Equation (RUSLE) / Geographic Information System (GIS) approach at the scale of the watershed of the Oued Ykem (western Morocco). (GIS) techniques were adopted to process the data obtained at the watershed scale, of reasonable spatial resolution (30 m) for the application of the RUSLE model. The latter is a multiplication of the five factors of erosion: the Rainfall erosivity (R), the Soil erodibility (K), the Slope length and steepness (LS), the Cover and management and the Support practice (P). Each of these factors has been expressed as a thematic map. The Oued Ykem watershed is an elongated coastal basin with an area of 516 km2. It is part of the Atlantic coastal basins of western Morocco. It is located southwest of the city of Rabat. Oued Ykem is characterized by a semi-arid climate with oceanic influence. Rare and irregular rains, mostly stormy in nature, combined with deforestation, cause erosion and irregular flow. Its flow-rate increases during the winter. Extreme flows-rate can be recorded after exceptional and very intense showers upstream of the basin. The resulting soil loss map, with an average erosion rate varying from 0 to 54 t / ha / year, showed low erosion. Areas with a strong erosion rate exceeding 30 t/ ha/ year cover about 3.8 % of the basin area. The analysis of the erosion risk map, in comparison with the maps of the different factors in the equation, showed a clear and important influence of the vegetation cover on the soil erosion (C factor is from 0.03 to 0.9), followed by the topographic factor, especially the slope (LS factor varies from 0 to 56.71).