Modeling the Erosion and Sedimentation of Ghale Chai AjabShir Catchment Area By Satellite Data in GIS Environment

Soil erosion is one of the serious environmental issues in Iran. With respect to the high rate of general erosion in most geographical areas of the country, a great deal of efforts shall be made to decrease its hazards. Quantitative data are required for conducting such works in order to enable us to recognize and manage the critical areas which require the immediate protection.The performance of such works based on the traditional methods are costly and time consuming, and also give local information, therefore to perform a comprehensive and standard research, use of the new technology of remote sensing and GIS would be necessary.Ghale Chai catchment area is one of the basins of Sahand mountainous region with an area of about 249.5 km2, located in Ajabshir township. A dam is going to be constructed on its main tributary, so that, it is necessary to estimate the amount of soil erosion in the catchment area and sedimentation at the back of its dam. Therefore, for performing such work, experimental model of MPSIAC and the new techniques of remote sensing and GIS have been used. The required information levels including the geological maps, topography, soil science, ground coating, Land use, run off data, current situation of erosion, river erosion status by using the existing maps, satellite photos, the data of meteorological stations and hydrometry and field operations were provided and entered in to GIS environment and after preparing the information banks and weighting each one of layers, the erosion and sedimentation map of the catchment area based on MPSIAC model and hydrologic units have been derived.The results show that about 133,016 ton/year of the catchment area soil erodes each year. This figure is about 533 ton/km2 in a year. The final model shows this fact that the two factors of slope and ground covering has the main role in controlling erosion and sedimentation. From the view point of critical areas, the two sub- catchment areas of sb3 and sb7 have been recognized as having the greatest amount of sediment production in area unit but sb1 sub- catchment area has the lowest amount of sedimentation in area unit.