In addressing the uncertainties regarding the laws of riverbed erosion-deposition,flow division ratio,and river channel volume changes before and after the implementation of the west waterway of Tongzhou Sand Shoal regulation project within the comprehensive regulation of the Chengtong Reach in the lower Yangtze River,and the need to ensure the safe operation of the 12.5 m deepwater navigation channel,we integrate riverbed evolution analysis and project impact assessment methodologies to systematically study the impacts of the west waterway regulation project (from 2011 to 2016) on the channel flow distribution pattern,erosion-deposition distribution,and volume variation relying on measured hydrological and topographic data from 2010 to 2023.The results reveal that the regulation project has effectively curbed the atrophy trend of the west waterway,stabilized the head of Tongzhou Sand Shoal,transformed the middle reach from a wide-shallow morphology into a single deep channel,and increased the flow division ratio to a stable range of 10%-12%.However,current siltation in the inlet and lower reaches restricts inflow conditions,leading to a slow overall silting trend in the west waterway.This trend currently exerts no significant adverse effects on the operation of the 12.5 m deepwater channel.The research outcomes provide field-measured data support for navigation channel maintenance in Chengtong Reach and effectiveness evaluation of similar river engineering regulation projects.It is recommended to enhance monitoring of sediment deposition in the inlet section and optimize the dredging scheme to maintain channel flow capacity in future practices.