To protect the rich resources of tidal flats, a project involving two groins was set up to stabilize and promote tidal flat deposition in the southern coast of Hangzhou Bay. In this study, an unstructured mesh system was set up for numerical simulation to investigate the effect of the groins on hydrodynamics and morphology. A well-validated model was used to simulate the current. It was found that the groins were almost perpendicular to the current direction, directly affecting the movement of the current. Thus, the current significantly decreased between and outside the groins and increased at the heads of the groins. This characteristic finally caused a deposition of 0.25–0.60 m at both toes and between the groins and heavy erosion reaching 0.30–0.40 m at both heads of the groins. Finally, the simulation of the suspended sediment induced by riprap demonstrated that the suspended sediment was transported to an area larger than 29 km2 with concentrations above 10 mg/L within and around the engineering region.