粤东南澳岛青澳海滩侵蚀退化风险评价及其安全调控

分析了南澳岛海滩资源储量、空间分布及其开发利用现状,开展海岛海滩侵蚀风险评价,选择青澳海滩开展岸滩及其海湾海床地形、沉积物、动力泥沙调查,分析探讨了青澳海滩泥沙动力沉积特征,灾变退化过程机制,并从海滩稳定性和游客安全角度给出安全调控建议。结果表明:1)南澳岛海滩资源储量与侵蚀风险区域分异特征明显,其中青澳海滩旅游活动频繁、开发强度大,侵蚀退化风险等级高,人为破坏干扰抑制滩海泥沙交换,无序无度占滩开发与利用破坏了海滩自然演化进程,短期过量旅游活动加速海滩侵蚀退化进程;2)青澳湾沉积物以粗粒砂为主,沙源供给不足,不同岸段岸线进退与岸滩蚀淤与海滩方位、波浪动力强度强弱关系密切,具有明显的纵向沉积地貌分带特征。湾内落潮优势流(SE)优于涨潮(NW),对泥沙输运进入湾内具有抑制作用,潮周期海湾泥沙自湾内向湾外输运,泥沙以外输为主单宽输沙为3 400 t;3)青澳海滩存在严重的"无序占滩建筑,污水肆意排放,管理不规范"等问题,监测评价亦表明侵蚀退化风险巨大,游客安全面临着风险隐患,建议青澳海滩实行以生态化养护开发和"游客为中心"为理念的安全调控措施,设立红线及安全标示。该研究为岛礁生态建设、海岛保护及修复提供科学依据。

Erosion Risk Assessment and Safety Regulatory of Qing'ao Beach in the Nan'ao Island,Guangdong Province

Beach resources with excellent quality and mature development are widely distributed in the Nan’ao Island. After the completion of the Nan’ao Bridge in 2015, rapidly increasing visitors to the Island have led to the obvious erosion degradation of some beaches of the Island, which have potentially threatened the safety of tourists. On the basis of analyzing the quantity, distribution and development status of Nan’ao Beach, this study performed the risk assessment of beach erosion, and investigated the beach and seabed topography, sediment and tide in the Qing’ao Bay of the Island, and analyzed the characteristics of the dynamic deposition of the Bay and the degradation process and mechanism of the Qing’ao Beach, and proposed the regulation measures for beach stability and tourist safety. The results showed that,(1) the regional differentiation characteristics of Nan’ao Beach resources and their erosion risk are obvious, and the trend of erosion and degradation of Qing’ao Beach are at the high risk grade. Some factors such as unordered development of beaches, inhibited sediment supply, and overloaded tourists, accelerated the beach degradation.(2) Sediments in the Qing’ao Bay are mainly sand. The coastal variation(shoreline retreat and section erosion) has obvious longitudinal regional differentiation and lateral differentiation. The predominant flow(SE) of the ebb tidal current(NW) in the Qing’ao Bay significantly inhibited the sediment transportation from the outside bay, and the tidal cyclical sediment transportation is dominated by single-wide transport of-3400 t;(3) Because the Qing’ao Beaches and tourists faced the serious safety risks and hidden dangers, there existed many problems such as disordered beach-buildings, sewage wanton emissions, unstandardized safe-management. Finally we suggested that the beach eco-system should be developed and utilized scientifically, and the red line and safety mark should be set up. The results obtained in this study will provide a scientific basis for the construction and protection and restoration of island and reef.