**2. Methodology and data used**

### **2.1 Tolerance to erosion**

The tolerance level for soil loss varies from region to region of the world. It is linked to the productivity of the land and its uses [6]. Indeed, in Asia, [20] found that the tolerance threshold for soil loss in the Kelara sub-watershed in India was less than 1.5 t/ha/year. According to [52], the results of the study of water erosion in the Tamil Nadu basin (India) indicate that the average soil losses in this region are of the order of 6 t/ha/year. In Europe, [27] deduced that when soil losses exceed a threshold of 5 t/ha/year on cultivated land, the latter becomes intolerable. In a study conducted in the south-eastern region of Spain by [53], a rate of soil loss was recorded below the tolerable annual rates for the northern Mediterranean region. Almost 90% of its basins have average annual rates of less than 2 t/ha. In northwestern Turkey, the results obtained in the Buyukcekmece region by [54], show that a soil loss rate is low for a value of less than 1 t/ha/year, while beyond 10 t/ha/year, the phenomenon of erosion becomes a serious problem. Also, in the Alaca basin in Turkey, [55] estimated a water erosion tolerance rate of up to 12 t/ha/year. [56] underlines that any loss of soil greater than 1 t/ha/year is considered irreversible over a period of 50 to 100 years. A soil loss of 12 to 15 t/ha/year, or about 1 mm of soil per year (surface stripping) is sufficient to exceed the rate of alteration of the rocks. [54, 57] estimated the global tolerance rate for soil loss to be 10.2 t/ha/year.

In Morocco in regions similar to our study area, [58, 59] reported that soils can sustain loss of up to 7.4 t/ha/year on average. In Tunisia and according to the work of [22] carried out in the wadi Jannet watershed, a tolerance threshold of 8 t/ha/year has been suggested, above which the level of erosion risk will be high.

According to the above published work regarding the quantification of soil loss by the RUSLE model, it is clear that the tolerance threshold presents some difference. This is linked to the type of soil and its pedogenesis. In fact, in a region with shallow soil in a climate of accentuated summer aridity, the production of soil (pedogenesis) will be slow and consequently the tolerance threshold will be less. This is the case, for example, in arid and semi-arid Mediterranean regions [60].
