Estimation and analysis of discharge, sediment transport and its effect on sedimentary processes of Alamut and Shahrud rivers (North of Qazvin Province)

Sediment transport from continents to oceans and seas via rivers is one of the most important processes regulating river-bank stabilization, soil formation, biogeochemical cycling of elements, crustal evolution and many other earth-related processes. Shahroud catchment is a part of Caspian Sea great drainage basin, located in North of Qazvin Province; its main tributaries are Alamoutrud and Taleghanrud rivers. As a structural point of view, the study area is part of Southern-Central Alborz structural zone which is mostly composed of Eocene volcanic units and Miocene terrigenous sedimentary rocks. In this research, water and sediment discharges (2013-2014 water year), grain size and mineralogical analysis of the sediment load were studied. Cyclic variation of discharge indicate a flood-dominated river; both water discharge and sediment load are controlled by the river tributaries and lithology of the catchment. This research shows (for the first time) that suspended load constitutes (mainly silt-size grains, composed of quartz, calcite, feldspar, muscovite/kaolinite) more than 99% of the sediment load. Bed-load materials are mainly volcanic- and carbonate-rock fragments. Erosion is the main process in upstream and transport/sedimentation is dominant in the river mid and downstream.