Submerged dikes were frequently built in curved estuarine channels to improve navigational conditions. A three-dimensional numerical model of tidal motions was developed to simulate flows through the submerged dike alignment in curved estuarine reach of complex bathymetry on the basis of satisfactory calibrations. Through the analysis of the morphological characteristics of the curved channel of the Huangpu River mouth in the Yangtze River Delta, a submerged dike alignment project was examined. The effect of the navigation channel improvement project and its influence on the flow regimes, the navigational conditions, the flood control and the operating conditions of harbours within the adjacent water area were evaluated, and the technical feasibility of the navigation channel improvement scheme was demonstrated. Submerged dikes were frequently built in curved estuarine channels to improve navigational conditions. A three-dimensional numerical model of tidal motions was developed to simulate flows through the submerged dike alignment in curved estuarine reach of complex bathymetry on the basis of satisfactory calibrations. Through the analysis of the morphological characteristics of the curved channel of the Huangpu River mouth in the Yangtze River Delta, a submerged dike alignment project was examined. The effect of the navigation channel improvement project and its influence on the flow regimes, the navigational conditions, the flood control and the operating conditions of harbors within the adjacent water area were evaluated, and the technical feasibility of the navigation channel improvement scheme was demonstrated.