Erosion Risk Assessment by Applying the GIS/RUSLE Approach and Python Web Application: Impact on the Silting up of the Sidi Salem Dam (Northern Tunisia)

The phenomenon of water erosion is one of the main factors in the de-gradation of the natural environment. In the absence of protective structures, this phenomenon can threaten socio-economic assets such as: (i) road infrastructure due to landslides, (ii) hydraulic structures due to siltation of dams and dams on hillsides, and (iii) the demolition of habitats on slopes. In Tunisia, the process of water erosion is very frequent and changes dynamic aspect according to the evolution and spatial variation of the lithological nature of the mother rocks, the geomorphology of the landscapes, the geometry of the watersheds, and their bioclimatic situation. The study of the interaction of these factors and their spatio-temporal evolution on the scale of the Medjerda Middle Valley (Jendouba-Bou Salem plain) allowed us to establish a cartographic zoning by class improvement of the study area into several areas according to their degree of susceptibility to erosion and an approximate quantification of soil loss. The objective of this study is to develop an open source GIS application, using the RUSLE methodology to estimate the rate of erosion at the watershed level of the Middle Medjerda Valley and provide the same application via a web access (web application). This model is the product of the five erosion factors: rainfall aggressiveness, soil erodibility, slope and slope length, plant neck density, and erosion control practices. Each of these factors was expressed in the form of a thematic map, the product of which corresponds to a resultant map representing soil losses with different rates of erosion: low, medium, and high and their corresponding areas having, respectively, 40%, 20%, and 40%. It was also concluded that the heavily eroded areas are related to high slope values, bare soil, and the highest P and C values. These threatened regions are mainly located around the Sidi Salem dam, which leads to a significant production of sediment deposited directly in the dam’s reservoir.