As human activity increases, coastal ecosystems are becoming increasingly vulnerable to a range of challenges. Oyster reefs are coastal ecosystems that provide habitats for a diverse range of marine species while also purifying water and providing natural coastal defense. However, because of human activity, global oyster reef areas have drastically diminished and are in grave danger. Simultaneously, it is impossible to determine the negative impact of human engineering activity on oyster reefs, due to the lack of intuitive and quantitative study methodologies. To address this issue, we applied a hydrodynamic model to analyze the impact on oyster reefs. First, we considered that human engineering activity, that is, coastal engineering, mainly affects the development of Liyashan Oyster Reefs by influencing hydrodynamics, sediment concentration, and bed-level evolution. We then applied MIKE3 to establish and validate a 3D hydrodynamic model of the southern part of the Yellow Sea around oyster reefs. Results showed that regional variations in flow velocity and suspended sediment concentration occurred in oyster reef waters, but the magnitude of these variations was limited. However, seabed elevation increased substantially in the Center Protection Area, which had a negative impact on oyster reefs. In general, our study provided a paradigm for analyzing the degree of impact on oyster reefs, showed the advantages of hydrodynamic models in quantitatively analyzing impact factors, and had reliable results.

Waves are one of the most important factors affecting offshore marine engineering. Accurate calculation of wave distribution is an important prerequisite to ensure the safety of coastal engineering construction. Due to the influence of complex topography, hydrological conditions, and marine structures on the propagation of waves offshore, slowly varying topography, refraction, diffraction, reflection, shallowness, and other phenomena may occur. This article combines the MIKE21 Spetral Waves (SW) wave model and the MIKE21 Boussinesq Waves (BW) wave model which are developed by Danish Hydraulic Institute (DHI) for a joint application (SW–BW nested model). It simulates the hydrodynamic environment of the Yanwo Island scenic area, located in Zhoushan, in both large and small ranges. In addition, wave height distribution and berthing stability of different breakwater planning schemes are calculated to optimize the layout of the breakwater. Through the analysis of simulation results, it is concluded that the hydraulic performance of Scheme 2 (the broken line section on the west side is 100 m long, and that on the east is 1200 m long, and the breakwater is rotated 8 degrees counterclockwise along the axis on the basis of Scheme 1) is better than that of Scheme 1 (the broken line section on the west side is 100 m long, and that on the east is 1100 m long), which can provide a more reliable construction reference for the construction of the Yanwo Island scenic area.