SUMMARY

Lack of information to prepare erosion maps for quantitative and qualitative sediment evaluation is a major need in watershed management in Iran. The goal of this study was to use EPM model and apply GIS to minimize the probable errors in evaluation of soil erosion and sedimentation in Ghareh Aghach watershed in central part of Iran. To achieve this goal, in the first step a topographic map in 1:25000 scale of the study area was digitalized by ILWISE program to provide a contour map. Using the contour map, the slope and aspect maps as well as the digital evaluation model (DEM) of the site were prepared. In the second step the satellite images, aerial photos of 1:40000 scale and data obtained from the field visits were used to provide with geological, geomorphologic, vegetation cover, peddological and land use maps of the study area. By integration of geological, geomorphology facieses and slope maps and classifying them in 5 categories (0-10%, 10-20%, 20-30%, 30-40 % and>40%), 21 homogenous uniform sampling units were identified to apply EPM model. Model information layers comprised of nine effective factors in erosion and sedimentation in the watershed site were obtained by digitalizing and classifying the basic information data in GIS program. In frequent field visits all the necessary data for EPM model were collected, checked and improved in 21 homogenous and uniform sampling units. Following of finalizing the informatio