To systematically address navigation safety issues arising from adverse flow patterns such as cross-flow,recirculating flow,boil vortices,and overtopping flow in the Changshou waterway of the upper Yangtze River,a movable-bed physical model test is conducted to predict and evaluate the effects of the navigation regulation project.Based on the natural flow and sediment processes from May 2018 to November 2019,model calibration and scale determination are completed,and a high-precision flow-sediment physical model is established.To systematically analyze the response of flow structure and riverbed topography after project implementation,simulations are conducted for four characteristic discharges during flood,medium and dry water periods as well as under typical hydrological year conditions.Results indicate that after regulation,the flow velocity in the central part of Xiaojiashipan decreases by 29.9%,and the maximum flow velocity in the dredged area increases by 34.2%.The angle between the oblique flow in the left branch and the navigation channel is reduced from 39° to 4°,the transverse velocity decreases by more than 85%,and the adverse flow patterns such as boil vortices and overtopping flow are significantly weakened.After scouring and adjustment over a sequence of hydrological years,the riverbed tends to be stable.The left branch navigation channel maintains a designed water depth of 4.5 m,and its width is expanded from less than 110 m to more than 150 m,resulting in significantly improved navigation conditions.The study confirms that the project effectively optimizes the flow patterns and channel dimensions in the rapid reach,and the relevant methods and conclusions can provide theoretical and technical support for the regulation of similar mountainous waterways.