Investigation of the relationship between sediments of small dams and their sources using tracing method in Semnan province

For implementation of soil conservation and sediment control plans in drainage basins، the recognition of the main sediment sources and erodible area is necessary. In this research the relationship between sediments of small dams which are constructed on drainages of Ebrahim-Abad and Royan Catchments in Semnan Province، with the upland sources was determined using composite and quantitative Tracing Method. The aim of research has been the differentiation of sediment sources and determination the contribution and the relative importance of each source in sediment production. By field investigation، the combination of both surface areas under different lithology and sub surface sources (gully walls) were selected as sediment sources and source differentiation was evaluated using 15 fingerprinting properties and by Kruskal Walis and Diffraction Function Analyses. Finaly the contribution of each sediment source was determined by calculating multivariate mixing models. The results have shown good differentiation of sediment sources، so that in Ebrahim-Abad Catchment، an optimal composition of illite، Mg and Organic Carbon with 95. 8% and in Royan Catchment، Cholorit، XFD، N and Organic Carbon with 92. 9% differentiation power could differentiate sediment sources. The results of calculation using composite multi-variate statistical methods have show that Quaternary units and Shemshak، Dalichay، Hezar-Dareh، Karaj and Lar Formations in Ebrahim-Abad Catchment and Quaternary units، gully erosion and Karaj، Shemshak، Upper Red and Lar formations in Royan Catchment are the most important sources of sediments، respectively.