Mapping surface water erosion potential in the Soummam watershed in Northeast Algeria with RUSLE model

The present study aims to estimate the annual soil loss in the Soummam watershed in the northeast of Algeria, using the Revised Universal Soil Loss Equation(RUSLE), geographic information system(GIS), and remote sensing(RS). RUSLE model has been used for modelling the main factors involved in erosive phenomena. The Soummam watershed covers a surface area of 9108.45 km2 of irregular shape, northeast –southwest towards southeast. It is characterized by an altitude varying between 2 m in the northeast and 2308 m in the northwest. Results showed that the average erosivity factor(R) is 70.64(MJ·mm)/(ha·h·year) and the maximum value reaches 140(MJ·mm)/(ha·h·year), the average soil erodibility factor(K) is 0.016(t·h·ha)/(MJ·ha·mm) and maximum values reach 0.0204(t·h·ha)/(MJ·ha·mm) in the southeast regions of the watershed, the average slope length and steepness factor(LS) is 9.79 and the mean C factor is estimated to be 0.62. Thematic maps integration of different factors of RUSLE in GIS with their database, allowed with a rapid and efficient manner to highlight complexity and factors interdependence in the erosion risk analyses. The resulting map for soils losses, with an average erosion rate of 6.81 t/(ha·year) shows a low erosion(<7.41 t/(ha·year)) which covers 73.46% of the total area of the basin, and a medium erosion(7.42 to 19.77 t/(ha·year)), which represents 17.66% of the area. Areas with extreme erosion risk exceeding 32.18 t/(ha·year) cover more than 3.54% of the basin area. The results can certainly aid in implementation of soil management and conservation practices to reduce the soil erosion in the Soummam watershed.