Abstarct: Among significant issues in river engineering are scouring, sedimentation, and alterations in riverbed topography in the location of the river’s bend. The setup and behavior of flow in river bends are more complicated in comparison with a straight course. Due to the centrifugal force and its interaction with lateral pressure gradients caused by lateral slope of water surface in the bend, a secondary flow forms. By an interaction between the secondary flow and non-uniform profile of longitudinal velocity a particular flow pattern known as spiral flow forms that causes great changes in the bend’s flow pattern in comparison with flows in straight channels.This phenomenon has a significant effect on riverbed topography, its alterations, and scouring and sedimentation in inner and outer banks. An understanding of the topography of the bed in bends is necessary for determination of scouring and sedimentation areas in order to decide the most appropriate location to construct hydraulic structures such as groynes and basins, and also to manage organizing the rivers. In regard of studying flow and sediment transport patterns in river bends, numerous field and laboratory studies have been carried out, but only a few numerical studies are available. Currently, various numerical models have been developed for simulation of hydrodynamics and sediment transport in open channels. In this thesis CCHE2D – a depth-averaged two dimensional model – was utilized. Furthermore, the main purpose of this thesis is modeling sediment transport in bends using the CCHE2D numerical model. In order to achieve this goal, results from two available laboratory-baxsed references that have examined the pattern of flow and sediment transport in sine-generated meandering channels were used for verification of the CCHE2D model. Also, utilizing the CCHE2D software, effects of geometrical parameters (including bend radius, bend angle, and longitudinal slope of the channel bed) and hydraulic conditions (including flow discharge, depth, flow velocity, and Froude number) on flow pattern and topography of the bed were investigated. Results from the numerical model show that: • By reducing the bend radius alterations in bed’s topography, the amount of sedimentation, and scour increase. • By increasing the bend angle, the amount of sedimentation and scour increase. • Also by increasing the longitudinal slope of channel’s bed, the amount and depth of scouring in the outer bank increase and the distance between two scouring holes increases too. In contrast, sedimentation in the inner bank decreases and also sedimentation pile shifts to the bend’s exit. In order to study the effect of the bend’s inflow conditions on the bed’s topography, simulations were carried out for different values of U/Uc ratio (U is the inflow velocity, and Uc is the critical velocity for transportation of the sediments) in the straight course leading to the bend’s entrance. Results show that for U/Uc<1, only one scouring hole forms near the bend’s exit. When 1<U/Uc<1.1, two scouring holes form near each other or in a merged state at the outer wall. And when 1.24<U/Uc<1.33, two scouring holes form at the outer wall of the bend.