Study of Changes in Sediment Concentration and Soil Loss and Its Temporal Variation in Different Conditions of Slope and Rainfall Intensity

Study of factors that affecting soil erosion and its temporal variation is prerequisitethe for management of soil and water resources. The purpose of This study was to determine susceptibility of soils to erosion and its temporal variations in three soil textures (clay loam, loam and sandy loam) on different slopes (5, 10, 15, 25, and 30 degree) under simulated rainfalls (40, 60 and 80 mm h-1). The experiment done by flume (160 cm × 65 cm) and in a completely randomized design with two replications. Soil losses measured at various times (0/5, 1, 1/5, 2, 3, 4, 5 10, 15, 20, 30, 40,50 and 60 minutes) to achieve steady-state flow of surface runoff. There was a Significant difference between  the soils in  terms of soil loss (p< 0.01). Clay loam was the most susceptible on to soil erosion. In this soil, Most of erodible soil particles eroded by surface runoff at the beginning of rainfall and soil loss decrese with continuing of rain. Soil loss in soils was strongly influenced by slope gradient and rainfall intensity (p< 0. 01). by increasing slope gradient,due to lower rain water retention on the surface, runoff was occurred quickly, and then soil loss increased. in soil loss of sandy loam,Slope steepness and rainfall intensity showed dominant roles in soil losses. The results revealed that in erodible soils, sensitivity to erosion by changing the slope and rain intensity is lower, and these two factors (slope steepness and rainfall intensity) has greatest impact on soil loss in highly resistant soils to erosion .