TOPOGRAPHIC CHARACTERIZATION AND MAPPING OF SOIL EROSION IN THE DIARHA WATERSHED USING RUSLE, RS AND GIS.

Mapping of erosive risk is a prerequisite in an erosion control approach. It makes it possible to locate the sectors most vulnerable to erosive processes. The establishment of the erosive risk map results from the spatialization of the Revised Universal Soil Loss Equation (Rusle). This equation is combined with Geographic Information Systems (GIS) and Remote Sensing techniques to estimate and map average rates of soil loss. This study was conducted in the Diarha watershed and its sub-basins to determine their morphometric characteristics and map the main factors involved in soil erosion processes. The results showed that soil erosion risk varies according to the topographic and climatic gradients of the watershed. The Diarha catchment area covers an area of 759.3 km?. Its compactness index of 1.5 indicates an elongated shape SE-NW. The altitudes vary from 576 m in the South to 55 m in the North with an average of 315.5 m. The LS topographic factor varies from 0 to 30. Potential soil losses vary between 0 and 1873 t/ha/year depending on the sector. The assessment yielded an average of 36.4t/ha/year and a standard deviation of 105.3t/ha/year. Annual soil losses in the entire Diarha catchment area are estimated at 31.882t/year; with a specific degradation of 42t/km?/year.