Water Erosion between the Vulnerability of Environmental Balances and Prospects for Sustainability: The Case of El Abed and Tlagh Watersheds (North-Eastern Morocco)

Abstract

Water erosion is one of the serious threats to the physical environment and human stability. The watersheds of Wadi El Abed and Wadi Tlagh (Morocco) have been factors to this phenomenon for a long time. Thus, the problem of this study focuses on erosion and its evaluation in these two basins. So, we have analyzed the data available and carried out measurements in the field by simulating rain. Soil loss was estimated using the Universal Soil Loss Equation. The inventory of the various manifestations and forms of water erosion clearly shows that it is a strong morphodynamic activity characterized by diffuse and concentrated runoff, gullies and side extensions of the valleys. After calculating the various USLE factors, it was found that 4% of the surface of El Abed watershed and 13% of Tlagh watershed would be heavily eroded. The average specific degradation was estimated at 38.71 t/ha/year. Rain simulation measurements showed clear differences between land uses. Indeed, the runoff coefficients are low in the plots covered with vegetation and those cultivated parallel to the contour lines. On the other hand, on bare ground and steep slopes, this coefficient is high. The quantities of detached soil vary from 0.01 t/ha for the covered plots to 29.05 t/ha for those bare and with a steep slope, with an average of 3 t/ha.