Geological evaluation and analysis on erosion intensity of depositproduction at the upper acquiferousbasin ofAlborz dam and preparing a dispersion map in GIS environment

ABSTRACT: Undesirable effects of erosion phenomenon may not be very noticeable in short time, but these effects become significant in long term. Erosion and wasting of soil is one of major effective factors on reduction of soil fertility, reduction of product,deposition of materials in waterways,in irrigation canals and in rivers, decreasing the capacity of dams reservoirs and their lifetimes, flood occurring, environmental pollution and closing of ways. The object of this research was examination and analysis on erosion intensity at the upper acquiferous basin of Alborz dam and we prepared a dispersion map by using geographic information system(GIS).As aresult, the major reason of soil erosion at the upper lands is the excessive traffic of domesticated animals and devastation of plant covering by them. Furthermore, construction of roads in forest for exploiting from coal mine and woods transportation increases soil erosion in lands of that region’s forest.Generally,the annual average of deposition in basins of this station is estimated 630 tons per kilometer. Lack of control and management in an acquiferous basin, increasing erosion and deposition can decrease the lifetime of Alborz dam(Lafour-PashKola) significantly. Examinations show that the mean of deposit production in all five acquiferous basins is 4/45 tons annually, and the most amount of deposit Production is related to the down of those basins which their most surfaces are formed by Pastures.