ESTIMATION OF SLOPE LENGTH FACTOR (L) AND SLOPE STEEPNESS FACTOR (S) OF RUSLE EQUATION IN THE EUPHRATES RIVER WATERSHED BY GIS MODELING

Abstract

Specific effects of topography over any area watershed erosion are estimated through the LS factor as the product of slope length L and slope steepness factor S using RUSLE equation. The LS factor map of Euphrates watershed was derived from the raw Digital Elevation Model (DEM) by using of ArcMap 10.2 software, the DEM images were provided from United State Geological Survey (USGS) website. The DEM were consisting of sixteen images with cell resolution of 30m*30m, the DEM of Euphrates watershed is ranged from -100 m to 466 m, 98.83% of Euphrates basin area of DEM within the range 0 to 457 m. The slope in percentage rise map of Euphrates watershed is required to estimate the LS factor, the most of slope of this study was ranged from zero to five which represent about 93.12% from total area of basin. The LS factor of Euphrates basin is ranged from (0) to (8010.61), 94.25% of Euphrates watershed area have the LS factor of the range from (0) to (1). Furthermore, the LS factor values more than 500 of watershed have a small area, so the factor value can be considered up to 500 and neglect the other large values of LS factor. The LS values more than 3 were identified the lines of Euphrates river, distributary channel, rills, interrill and gully.