Topographic factor (LS)
Topographic factor represents the influence of slope length and slope steepness on erosion process. LS is calculated using the formula mentioned in the methodology section, using an ASTER type digital terrain model with a spatial resolution of 30 m. LS values obtained in the Ben Ahmed watershed range from 0 to 4.25 (Figure 1).
Figure 1 here

Cropping management factor (C)

Currently, due to the variety of land cover patterns with spatial and temporal variations, satellite remote sensing data sets are used for the assessment of C –factor (Karydas et al., 2009). Based on our land cover mapping, the results showed that the C factor ranged from 0 to 1. The land use-land cover of the Ben Ahmed watershed was classified with three land cover classes, namely, agriculture land which represent 74,5% (C=0,1), bare land representing 22,4% (C=1) and built-up (C= 0) representing 3,1%. These land use-land cover features are represented in Table 1 and Figure 2.
Table 1 here
Figure 2 here

Rainfall-runoff erosivity (R) factor

Several studies (Jain et al., 2001; Dabral et al., 2008) revealed that the soil erosion rate at the watershed level is more sensitive to rainfall. In Ben Ahmed watershed, the mean annual rainfall is 548.83 mm. It is calculated by reporting the average annual precipitation values measured between 1969 and 2002 in the surrounding catchment area. The R-value of Ben Ahmed watershed obtained from annual and monthly precipitation averages is 75.67 (MJ * mm / ha * hour) (Table 2).
Table 2 here

Support practice (P) factor

The most conservative practices of soils are contour crops, alternating strips or terraces, reforestation in banquettes. According to the Wischmeier equation, P is equal to 1 if none of these practices exist in watersheds, which is the case of our study area.