Based on the long-term hydrological and sediment observation data and the measured topographic data, this paper analyzes the characteristics of water and sediment and riverbed erosion and deposition in the Yizhi reach after the impoundment of the Three Gorges Reservoir. The results show that after the impoundment of the Three Gorges Reservoir, the runoff volume of the Yizhi reach changes little, only 4 % lower than that before the impoundment, the sediment volume decreases by more than 92 %, and the coarse sediment content increases significantly. The total amount of scoured sediment in the flat-beach channel of Yizhi reach is 164.2 million m3, mainly in the dry channel, and the scour is primarily located in the downstream of Yidu reach, accounting for 89 % of the total amount of scour. Restricted by the boundary conditions on both sides of the river, the riverbed is mainly incised by longitudinal erosion.

river evolution;Yizhi reach;Three Groges Reservoir