For quantitative assessment of land degragation a watershed was selected with
35.5 ha acreage in lossinal hills in Gorgan River watershed located southeast of Kurdkoy with 6 Km distance and west of Ballajadeh village with 0.5 Km distance. The grid network was carried out with lOOm intervals , the Topographic map of the watershed was prepared by tacheometric method , the countour lines and three dimentional map was prepared with Isosurf software.The distribution of Cs137 on the corners of grids and on the elevated and depressional points between grid corners was determined with Gamma spectrometiy and was compared with predetermined CS137 fallout reference which was 3300 Bq n12 with Dejorg and Kachanovsky method. According to number of erosional or depositional points the area of these points was determined and the total erosion or deposition in (Ton ha1) were divided to the erosional or depositional acreage for determining the average erosion or deposition rate of the watershed .The gross erosion (Ton ha1) and deposition was calculated by dividing the total erosion or deposition (ton) to the total area of the watershed. The average erosion , deposition, gross erosion and gross deposition rate were 88, 172,58 , and 32 ton h1 a respectively , and the SDR was 45%. Revised Universal Soil Loss Equation (RUSLE) was selected for calculating the water erosion. The different parameters like R,K, IS, C and P were calculated according to standards of RUSLE, their value in this experiment were 40,0.3,13, 0.5 and 1 respectively . the water erosion was the produ1 of these parameters which was nearly 80 ton ha1 a1 .Tillage erosion according to tillage depth (Dp), bulk density (BD) , soil fluxe constant (A), slope of the correlation line (B) and inclination angle (0) was determined by Govers-Lindstrome relation as fallow:
Qdown=BD xDp(A+Bsin 0 )Tillage erosion using above parameters and relation was 20 ton ha1 a1. The total erosion mainly can be divided to water erosion and tillage erosion which constitute the 80% and 2Q% of the total erosion respectively. The splash erosion , and consolidation constitute only 1% of total erosion.
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