Since the 175 m test-operation of the Three Gorges Resevoir (TGR),the typical reach in the fluctuating backwater area has suffered navigation problems because of the pebble movements,among which the Sanjiaoqi reach is particularly serious.Located on the Jiulongpo harbor,Sanjiaoqi reach is a typical gully and branching reach,and the main channel is bend,narrow,shallow and dangerous.As a result of the change of the sediment movement law due to the impoundment of the TGR,new characteristics appear.The amount of sediment deposition is small,while the influence on the channel conditions is relatively large,and a lot of ships are stranded during the sluicing period.To improve the channel conditions,maintenance and dredging are extremely necessary.Based on the field measured data,we study the characteristics of sediment movements and discuss the dredging plan and effect.