Possibility of using land components for estimation of soil erosion (A case study, a watershed of second urban phase in Mashhad, Khorasan province, Iran)

In most parts of Iran, due to population growth, deforestation, over-grazing of pastures and other factors, soil erosion is more than the world s average and increases incredibly by time. Therefore, its correct evaluation is very important. The Mashhad-Chenaran is the biggest and most important sub-basin of Khorasan, with an extension of about 223989.7 ac. Hence, it was chosen for this study in the present investigation. Two models, the MPSIAC and the Gavrilovic method (EPM), used for evaluation of sediment amounts and soil erosion stations showed 2.74 t/ha per year. However, the MPSIAC model showed 1.56 t/ha, whereas the EPM model showed larger amounts of 5.73 t/ha per year. In soil erosion studies in watersheds, researchers have often introduced hydrological units of work. In this research, factors (geological factors, soil type, vegetation, slope etc) were utilized in the erosion estimation models used in addition to the hydrological units in the land components. In view of the availability of maps of land units and their components in many regions of Iran, the present study attempted to measure the erosion and sediment in hydrological units (sub-basins) and land components. The accuracy of estimates of erosion were tested; in order to ensure that the accuracy of the results or possibly the superiority of the homogeneous units to the hydrological units is ensured, it can be used in the same areas in the future.