Sediment yield and study of fining trend in Torogh Dam watershed with emphasize on Moghan-Kortian sub basin

Abstract

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 7 tons per hectare per year and coefficient of sediment producing is 68% and amount of specific sediment of basin is 4.8 tons per hectare per year.