Abstract: While the reclamation project expands the land space to the coastal areas, it will also have a significant impact on the topographic changes of the project sea area. Based on the measured data and the results of the Delft3D mathematical modeling,  taking the eastern sea area of Ruian, Wenzhou as the research area in this study, the characteristics and dynamic mechanism of the topographic erosion and deposition changes caused by the Oufei Tidal Flat Reclamation Project were analyzed. Studies  show that the topography of the sea area has changed significantly after the implementation of the project, but the distribution characteristics of erosion and siltation in different areas are not consistent, and the dynamic mechanisms that cause changes are also different. From an overall point of view, the dominant feature of rising tides in the research sea area has been enhanced, and the coastal sea area maintains an overall siltation situation, and the siltation rate has increased slightly. From a local point of view, the vicinity of the dike bulge is affected by the effect of flip flow, which shows slow erosion, and at the concave corner of the dike affected by the blocking flow effect, it appears as rapid silting. The above results have important reference value for guiding the protection and utilization of Oufei Tidal Flat and other similar tidal flats.

Key words: reclamation project, Oufei Tidal Flat, erosion and deposition changes, dynamic mechanism