Evaluation of soil erosion by TOPSIS and SLEMSA method (Case study: Romeshgan, Iran)

The present study shows that very low erosion class (0.23 to 8 tons per hectare per year) Romeshgan watershed, most of the area to be included in the attrition levels low, medium, large and have too much. In general we can say the area is low to moderate ability erodible. SLEMSA model for estimating erosion, environmental conditions are examined. These factors in watershed erosion rates in different influence, its role in the model represent different values. Overlapping layers, rainfall, slope classes, geology, the land user, land type and Revealed that the maximum rate of erosion in areas with average precipitation of 600 mm, a range of plains and mountains of the terrace deposits and alluvial fans new and old, marl, limestone, siltstone, sandstone, conglomerate, and gypsum contains be. The slope factor, too, lands with slopes of 25 to 45 percent are devoted to the highest degree of erosion. Results using TOPSIS model in the survey also shows that factor eroding Romeshgan basin topography (slope) over other factors, basin was effective in erodible and has a major role. This model is also based on 1 sub basins in the north basin (with the highest similarity to the positive ideal), have the greatest vulnerability to erosion, then the sub basins 2, 4 and 3 are located. The reason for this can be achieved over all the heights and slopes of the basins is below. Looking at the situation of erosion and geomorphologic factors in the basin, we knew that the geomorphologic unit surface area plain, erosion of geological factors (alluvial deposits, marl, gypsum, shale, etc.) and land and units geomorphologic other variables in the same mountain slope, geology and rainfall is higher. Given the importance of the erosion zone and listed the conditions subject to wear and perform the necessary actions to protect resources and prevent soil erosion and loss it is necessary.