Investigating the Effect of Land use Optimization on Decreasing the Erosion and Sedimentation in Cham Gardalan dam Watershed by Using GIS

Today, environmental degradation is one of the problems of human communities due to mismanagement in watersheds. Land use optimization is one of the appropriate strategies for achieving sustainable development and reduction of resources lose.The present study taken place in Cham Gardalan dam watershed of Ilam province with area of 46822 ha and in order to determine the most appropriate combination of land use, including gardens, irrigated cultivation, rainfed cultivation, rangeland and forest for the minimization of soil erosion. In this study, Based on objectives, intially, maps of topography, slope, direction elevation levels map, geology and etc. were prepared by using a GIS software.Then, the first two primary maps were prepared by ovelaying elevation levels on direction map and geological map on slope map, respectively. The primary maps were overlaid to obtain the basic map with 190 homogenous units.Then, at first, the rate of specific erosion and sedimentation and erosion severity was determined using the EPM model in the GIS environment. Present land uses and optimum ones that were detemined by a systematic land use evaluation and planning method were used in the model. The study showed that with adapting appropriate watershed management practices and land use planning, the total erosion and sedimentation rate may be lowered to around 401276 ton per year(about 54%) in the watershed. Therefore, if proper and compatible usages with natural and environmental conditions and to the aim of optimum use of nature be presented and selected, erosion in the watershed and finally the produced sediment in the watershed will decrease greatly.