Résumé:
The erosion of upstream watersheds in all its forms is considered a crucial problem in Algeria. It is the source of the siltation of hydraulic structures and loss of capacity. In the watershed of Wadi Mina, marly zone is a typical example, it is an area particularly rich in forms of erosion, it is the largest supplier of sediment to the dam-Es Saada. According to studies done on this subject area of our work, there was a complex phenomenon of erosion, a significant heterogeneity of soils, vegetation cover very sparse or no rainfall and poorly distributed both in space in time. Of any anti-erosion management interventions required to maintain the irrigation scheme and dam downstream Es-Saada beginning to silt up at a rapid pace in recent years. The aim of our study is a priori, one-time spatialized model for assessing erosion USLE, the Geographic Information System (GIS) to map and quantify water erosion and locate the areas, sources of sediment. The universal equation of soil loss (USLE) was applied in RUSLE revised interactively with the GIS. The calculations are the result of modeling of the main factors involved in water erosion. The erosivity index R was calculated on the basis of the formula Arnoldus and Rango 1987, it ranged from 42.15 to 73.86. The values of soil erodibility factor K is between 0.059 and 0.463. A DEM of 30m resolution has been used to generate the topographic factor LS, calculations were made on the basis of the method proposed by Van Remortel et al, 2004.The values of C and P factors, which represent the vegetation cover and erosion control practices, respectively, were taken directly from the card cover and satellite images Google earth. Finally the map of soil loss was carried out following the crossing of different thematic maps through the GIS. The results show that the intensity of erosion and sediment loads produced vary substantially according to the present land use and the nature of the terrain and slopes. Priorities of management practices have been established on the basis of the risk of soil erosion and sediment transport downstream of the watershed of the Oued Mina.
