Core Viewpoint - The article discusses the severe impact of Typhoon "Haikashan" on coastal areas such as Zhuhai, Hong Kong, and Macau, leading to significant seawater inundation due to storm surges combined with astronomical tides [1][3][4]. Group 1: Causes of Seawater Inundation - Seawater inundation occurs when seawater enters land through surface or underground pathways, often exacerbated by geological structures, tides, and typhoons [1]. - The phenomenon is driven by two types of tides: astronomical tides caused by lunar and solar gravitational forces, and storm surges resulting from strong winds and low atmospheric pressure during typhoons [1][5]. - During the impact of Typhoon "Haikashan," the coastal areas were experiencing astronomical high tides, which contributed to the abnormal rise in water levels [3]. Group 2: Impact of Typhoon "Haikashan" - The maximum storm surge recorded in Guangdong's coastal areas reached 278 centimeters, with the most affected region being the Pearl River Estuary [3]. - In Zhuhai, the storm surge combined with astronomical high tide resulted in a peak water level of 328 centimeters, exceeding the red alert level by 43 centimeters [3]. - The coastal areas experienced significant wave heights, with effective wave heights recorded at 6.5 meters, leading to damage to coastal defenses and further exacerbating seawater inundation [3]. Group 3: Historical Context - Similar seawater inundation events occurred in Guangdong last November due to Typhoon "Wangyi," which, despite being weaker, still caused tidal levels to exceed warning thresholds when combined with astronomical tides [5]. - It is noted that typhoons are not the sole cause of seawater inundation; astronomical tides also play a critical role in these events [5]. Group 4: Prevention and Mitigation Strategies - Effective storm surge warnings are crucial for coastal areas to prepare and mitigate the impacts of seawater inundation [6]. - Recommendations include preemptive measures such as installing flood barriers, sealing underground drainage systems, and preparing emergency response plans [6]. - In areas already affected by seawater inundation, immediate evacuation and drainage efforts are essential to minimize damage [6].