Low-frequency waves with infragravity and very-low-frequency bands have been found to induce coastal flooding and erosion on low-lying reef islands under storm conditions. The aim of this study is to investigate the dynamics of low-frequency waves around an atoll reef island in the South China Sea, Dongsha Island, during a large typhoon event. A Boussinesq-type wave model, FUNWAVE-TVD, is applied to reproduce nearshore wave dynamics that caused severe erosion on the southern coast of the island. The interactions between waves with different incident directions and the localized atoll topography are examined. Modeled alongshore significant wave heights, wave setups, infragravity waves and very-low-frequency waves on the southern coast are first examined. The results show that alongshore low-frequency waves increase, and wave setup decreases as incident wave angles decrease. Eastward low-frequency edge waves are dominant in all incident wave directions. Comprehensive two-dimensional wave variations are further used to illustrate the interplay between incident waves and the localized atoll geometry. Infragravity and very-low-frequency waves are energetic around the eroded position of the shoreline with nearly shore-normal incident waves. Specifically, the shapes of very-low-frequency waves are highly asymmetrical, suggesting that very-low-frequency waves play a crucial role in affecting erosion and sedimentation during the typhoon events.

已发现具有超引力和极低频段的低频波在风暴条件下会导致低洼礁岛的沿海洪水和侵蚀。本研究的目的是调查南海东沙岛一个环礁岛在大型台风事件期间低频波的动态变化。Boussinesq 型波浪模型 FUNWAVE-TVD 用于重现导致该岛南部海岸严重侵蚀的近岸波浪动力学。检查具有不同入射方向的波与局部环礁地形之间的相互作用。首先检查了南部海岸的沿海显着波高、波浪设置、次重力波和极低频波的建模。结果表明，沿岸低频波增加，并且波设置随着入射波角的减小而减小。东向低频边缘波在所有入射波方向上占主导地位。进一步使用综合二维波变化来说明入射波与局部环礁几何形状之间的相互作用。次重力波和极低频波在海岸线的侵蚀位置周围充满能量，几乎与海岸法线入射波相同。具体而言，极低频波的形状高度不对称，表明极低频波在影响台风事件期间的侵蚀和沉积方面起着至关重要的作用。进一步使用综合二维波变化来说明入射波与局部环礁几何形状之间的相互作用。次重力波和极低频波在海岸线的侵蚀位置周围充满能量，几乎与海岸法线入射波相同。具体而言，极低频波的形状高度不对称，表明极低频波在影响台风事件期间的侵蚀和沉积方面起着至关重要的作用。进一步使用综合二维波变化来说明入射波与局部环礁几何形状之间的相互作用。次重力波和极低频波在海岸线的侵蚀位置周围充满能量，具有接近海岸法线的入射波。具体而言，极低频波的形状高度不对称，表明极低频波在影响台风事件期间的侵蚀和沉积方面起着至关重要的作用。