Abstract: Since the operation of the Three Gorges Dam (TGD), sediment deposition occurred primarily at the wide and curved reaches in the permanent backwater region, while no deposition occurred at the gorge reaches. Based on the measured data, sediment carrying capacities were calculated during the Pre-TGD (2001) and Post-TGD (from 2003 to 2011) period, indicating that the sediment carrying capacities decreased gradually due to the rising of the water level after the impoundment, and the deposition ratio increased step by step. The sediment carrying capacities at the wide reaches reduced greatly to the values smaller than the sediment concentrations, thus deposition occurred. While the reduction of the sediment carrying capacities at gorges was relatively small, and the sediment capacities were still bigger than sediment concentrations, no cumulative deposition happened consequently. The bigger the flow discharges, the smaller the sediment carrying capacities at the wide reaches were than the sediment concentrations, but the opposite at the gorge reaches, demonstrating that deposition at the wide reaches occurred mostly during the flood season and erosion occurred at gorges. Because of the flocculation and big erosion resistance of the fine cohesive particles, the best estimation of deposition amount was obtained when the recovery saturation coefficient was 1 for deposition and 0.01 for erosion. The estimated sedimentation at the curved reaches didn't agree with the measured values, indicating that the flow velocity had two-dimensional characteristics, and the one-dimensional sediment carrying capacity was not applicable for calculating the deposition at the curved reaches.