Introduction
Soil erosion is highly significant as a spatiotemporal phenomenon in many countries (Fistikoglu and Harmancioglu, 2002; Hoyos, 2005; Pandey et al.,2009). Soil erosion is a natural process, where the extent and magnitude of soil loss are controlled by various environmental determinants, such as topography, climate, soil and vegetation (Wischmeier and Smith, 1978; Renard et al., 1997; Mutua et al., 2006; Butt et al., 2010). There are several factors that increase water erosion which are: rainfall, soil type, slope, vegetation type and presence or absence of conservation measures (Khalid chadli, 2016).
In Morocco, soil erosion has been increasing annually. Indeed, in recent decades, the agricultural areas has undergone considerable changes, with specific degradation and soil loss rates, varying from region to another and mainly ranging from 5 to 20 t/ha/year (Ghanam, 2003).
To date, most studies on soil erosion at large scale have used numerous soil erosion and sediment transport models. In fact, modeling provides quantitative estimation of soil loss in a reasonable time-frame under a wide range of conditions, compared to the field-based methods. In Morocco, research works dealing with soil erodibility and erosion risk were undertaken at different scales. El Garouani et al. (2005) used the USLE in the Oued Jemaa basin (Pre-Rif zone in the North of Morocco). For large scale mapping, El bouqdaoui et al. (2005) used the expert-based model LEAM (Land Erodibility Assessment Model), based on the USLE and satellite imagery to evaluate soil loss rates in the Oued Srou Basin.
Universal Soil Loss Equation (USLE) (Wischmeier & Smith, 1978) and Revised Universal Soil Loss Equation (RUSLE) (Renard et al., 1997) are the most widely used models because of their simplicity, robustness and transparent model structure, minimal data requirement, easy input data availability as well as the compatibility with geospatial platforms (Millward & Mersey, 1999; Merritt et al., 2003). Despite the inherent limitations of USLE and RUSLE, the versatility of these models integrated with GIS was demonstrated in a wide range of environmental settings and at various spatial scales (Prasanna-kumar, Vijith et al., 2011; Prasannakumar, Shiny et al., 2011; Ranzi, Le, & Rulli, 2012; Mhangara, Kakembo, & Lim, 2012; Panagos et al., 2015; Pradeep et al., 2015; Magesh & Chandrasekar, 2016; Abdo & Salloum, 2017; da Cunha, Bacani, & Panachuki, 2017 ; Haregeweyn et al., 2017).
The objective of the present study is to assess the amount of soil loss at Ben Ahmed watershed based on USLE method and GIS (Geographical Information System) techniques, and to prepare potential soil erosion maps of the Ben Ahmed watershed.