Cansheng Zeng

A wave-current coupled mathematical model (MIKE21) was adopted in this paper to simulate the hydrodynamic changes (tidal level, tidal current, wave field) in the coastal waters surrounding the reclamation project of the Eastern Urban Economic Belt in Shantou, before and after the project implementation. The results show that: (1) Tidal level: After reclamation, the tidal level in the project area changed slightly within a range of 2~4 cm; the offshore low tidal level was 1~2 cm lower than pre-project. Shantou Port waterway’s high tidal level increased by 2~4 cm and low tidal level decreased by 2~4 cm, mainly caused by channel dredging. (2) Tidal current: The flood current velocity in the reclamation area increased with a changed direction; during ebb tide, the ebb current velocity increased at Xinjin and Waisha River estuaries, decreased along the reclamation coast, and increased in southeastern waters of Laiwu Island (flow direction unchanged). The reclamation had little impact on the waterway’s tidal current. (3) Wave field: Pre-project, natural horn-shaped coastline and barrier shoals induced nearshore wave refraction/breaking, with significant wave height of 0.0~0.2 m (nearshore) and 0.4~0.8 m (offshore). Post-reclamation, the straight artificial coastline and local sand extraction pits reduced wave energy loss, but the absence of shoals and topographic changes led to wave energy concentration in the reclamation front, with H₁/₃ increasing by 0.1~0.3 m (most notably at the two estuaries, rising from 0.0~0.2 m to 0.2~0.4 m). The research results reveal the influence mechanism of the reclamation project on the hydrodynamic environment of the coastal waters around the Eastern Urban Economic Belt in Shantou, and provide technical support for the feasibility evaluation of the construction project and the marine environmental risk management and control of the Eastern Urban Economic Belt in Shantou.

Based on field hydro-meteorological observations and sediment sampling data, this study analyzes sediment transport under normal conditions in the Fanshi offshore wind farm project area in Yangjiang, China. It was found that sediment transport in the engineering sea area is relatively stable, and seabed sediments are not easily mobilized. By building a tidal current–sediment mathematical model, the impact of wind farm construction on the erosion and deposition environment in the surrounding sea areas was studied. It was found that areas with significant accumulation are mainly located near the pile foundations of wind turbines. Furthermore, considering ocean dynamics, geological conditions, and wave–current interactions, different local erosion empirical formulas were used to calculate local erosion depth and range. The results show that Han Haiqian’s formula and the HEC-18 formula, which consider wave velocity, are very close and more suitable for the actual conditions of this project. As turbine pile diameters increase, local scour depths and ranges also increase. This study preliminarily analyzes the basic scour characteristics of deep-sea wind turbines off the western coast of Guangdong Province, offering important design parameters for the construction of this project, and also providing a systematic and scientific method for studying local scour at turbine pile foundations. This has great reference value for deep-sea wind farm construction projects.