Comparing Efficiency of Hill Slope Erosion Model (HEM) in Dry and Abandoned Land (Case Study: Khosbijan Research Center, Arak

Soil erosion and sediment yield from watersheds confine sustainable use of land resources and is supposed as one of the most critical environmental issues. Prediction of storm wise soil erosion and sediment yield is very important, especially in arid and semiarid regions due to small number of events and high intensity of rainfall. Evaluation of soil erosion by existing models is needed as an important tool for managerial purposes in designation proper water and soil conservation technique. Sometimes inappropriate use of the model causes very high or low estimate. The present study aimed to assess the applicability of Hillslope Erosion Model (HEM) for prediction of storm related sediment yield in Khosbijan by using soil erosion standard plots in two common land use in semi arid region i.e. dry land and abandoned land. In order to run the model, runoff depth, land surface cover, soil texture, slope steepness and length were determined for 16 storm events. In calibration stage, 75% o f data were used and 25% used in validation stage. The results showed that the uncalibrated HEM didn’t simulate the observed sediment yields, properly in two selected land use. While it could successfully predict the soil erosion rate in plots on dry and abandoned land by calibrating soil erodibility parameter with determination coefficient of 0.61, 0.78 and estimate error of 38 and 25 percent, respectively. The results also, clearly showed that HEM better efficiency in abandoned landuse.