Mohammad Javanbakht - Department of Geology, Faculty of Science, Islamic Azad University - Mashhad Branch, Mashhad, Iran
Reza Moussavi Harami - Department of Geology, Faculty of Science, Ferdowsi University, Mashhad, Iran
Habibollah Torshizian - Department of Geology, Faculty of Science, Islamic Azad University - Mashhad Branch, Mashhad, Iran
Ehsan Sharifi - Department of Geology, Faculty of Science, Islamic Azad University - Mashhad Branch, Mashhad, Iran
Hamed Soukhtanlou - Department of Geology, Faculty of Science, Islamic Azad University - Mashhad Branch, Mashhad, Iran

Analysis of grain size parameters in rivers of Torogh Dam watershed, with gravelly bed, show three sedimentary links in Moghan-Kortian sub basin that isolated from each other by discontinuities. Sudden changes in slope gradient because of tectonic effects and tributaries are the most important factors causing changes in channel bed sediment texture and generation of different sedimentary links. Also studies indicate role of two important factors, Hydraulic sorting or selective transport and abrasion, in fining trend in this watershed basin. Sediment yield in a sub basin has been calculated using EPM method that, the amount of specific erosion of basin equal to ۷ tons per hectare per year and coefficient of sediment producing is ۶۸% and amount of specific sediment of basin is ۴.۸ tons per hectare per year.

EPM, Sedimentary Discontinuity, Sediment Yield, Torogh Dam, Watershed