Abstract: The geomorphology of the Dagu River mouth is formed by the interaction of the river hydrodynamics and sediment. But the downstream of the Dagu River has gradually transformed from rive-dominated to tide-dominated in recent years. The original river morphology is no longer suitable for the hydrodynamics and sediment conditions. In this paper, new regulation schemes are proposed. And a quasi-3D numerical river dynamics model is used to simulate the water flow and sediment dynamics of the Dagu river in the different schemes. Effects of the location of dike, the shape of river bank, the width of rubber dam and the shape of t wharf section are all studied separately. The best regulaton scheme is then selected, with the least flood risk and minimum sediment fluvial volume, which can reach the standards of 50-year flood control. The research results suggest that for those rivers with large change of hydrodynamics and sediment, new regulation schemes should be designed and the quasi-3D numerical model can be used in the schemes optimizing process.