| Abstract
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Soil erosion is a complex, natural process that often is accelerated by such human activities as land clearance, agriculture, construction, and surface mining. Accurate soil erosion type/intensity maps can be effective tools in aid of soil erosion control efforts. The principal objective of this research was to use geographic information system (GIS) and remotely sensed data to extract and define erosion types/intensities over a large area (4,511.8 km2) in Iran. The study proceeded in three major steps: (i) a 10-m resolution digital elevation model (DEM), land slope, elevation range, and stream network pattern were created. These basic identifying parameters plus Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) images were used to differentiate various landforms, (ii) a land use and land cover map was created based on analysis of three Landsat Enhanced Thematic Mapper (ETM+) images from the growing season plus use of a landform map and climatic zones as ancillary information, and (iii) in order to extract and identify various erosion types/intensities, the difference in brightness combination over two growing season intervals derived from the Landsat ETM+ images were used. Further, land slope, landform, land use, and land cover layers were used to assist in the classification of the erosion types (interrill and rill). The approach presented produced soil erosion type/intensity maps with an overall accuracy of 93.4%. Considering only rangeland and forest a unique relationship exists between seasonal brightness combinations and erosion intensity. It was found that for the lower erosion levels it is the later season or second brightness combination (BJS) which indicates degree of erosion intensity, but for the areas of severe and very severe erosion it is the early season or first brightness combination (BMJ) that differentiates degree of erosion intensity. Further, this study illustrated that land use, land cover, landform, and land slope layers can be used for differentiating erosion types. The approach presented has been shown to be an effective tool for the creation of soil erosion maps over a large area of Iran and is expected to be useful for aiding in the development of soil conservation and watershed management plans in other areas. The main advantages of this approach are accuracy, lower demands on time and funds for field work and ready availability of required data for many regions of the world.
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