The Influence of Hillslope Length and Direction on Runoff and Soil LossUnder Natural Rainfall in an Arid Region

   Analyzing variability of measured runoff and soil loss data under different condition of measurement system, are critical for advancing erosion science, evaluating hydrologic models, and designing erosion experiments. For this purpose, the current study aimed to evaluate how runoff and soil loss are influenced by hillslope direction and length in Sangane arid rangeland, Razavi Khorasan Province, Iran. To achieve the goals of this research, 5 plots with length of 5, 10, 15, 20 and 25 meters were established on the north and south facing hillside. The analysis of 20 storms events causing soil erosion, indicted that one event produced about 70% and 34% of soil loss in southern and northern slopes, respectively. The results also, showed that in northern slopes duo to poor vegetation cover, hydrological response to subsequent rainfalls and hail are different from the northern slope. Finally, in current study, a decreasing non-linear relationship between area specific runoff and soil loss as well as plot length were founded.