Аннотация:Understanding the processes of displacement and redistribution of soil particles caused by different erosion types is consideredan efficient sediment management tool in various scales from the field plot to the watershed. The rainfed agriculture practices on highgradient slopes are one of the main sources of accelerated soil erosion due to the disturbance of soil structure by tillage processes.Therefore, the present study aimed to investigate the synergistic effect of rainfed agriculture practices and slope gradient on soil erosionusing the activity concentrations of 137Cs fallout in Khamsan experimental watershed, western Iran. The diffusion and migration modelwas used for undisturbed soils and mass balance equation type II was used for agricultural lands. The distribution map of soil erosionand deposition of the watershed was prepared using 137Cs method and the interactions between rainfed agriculture and slope gradient(as the most effective geomorphological factor) on erosion rate and sediment redistribution were evaluated. The results indicated thatthe highest rates of soil erosion in rainfed agriculture (11.46 t ha–1 year–1) and rangeland (1.27 t ha–1 year–1) were recorded in the slopegradient classes of 20%–30% and >60%, respectively. In addition, the maximum sedimentation in rainfed agriculture (5.78 t ha–1 year–1)and rangeland (0.89 t ha–1 year–1) occurred in the slope classes of 30%–60% and in >60%, respectively.