三亚湾东段海岸侵蚀与海滩养护

海岸侵蚀是当前沿海地区普遍所面临的挑战之一,许多城市景观海滩区沿海景观和旅游休闲功能已受到海岸侵蚀的直接影响,侵蚀性景观海滩的人工养护对保持海滩品位和促进旅游可持续发展具有重要意义。在分析三亚湾东段动力泥沙环境和岸滩自然特征基础上,根据卫星遥感影像资料、固定断面测量资料对比分析了该岸段的侵蚀特征和成因,提出以增加沙源有效供给和增强海滩抗冲刷能力为目标的海滩养护修复途径,设计了海滩养护方案。根据海滩养护工程实施后的地形断面监测对比,海滩养护后海滩范围扩大,达到修复目标。补沙工程一年半后,岸滩整体较为稳定,补沙后的泥沙流失量未有显著增加,达到预期效果。

Beach erosion and nourishment in the east section of Sanya Bay,China

Coastal erosion is one of the major challenges in coastal zones. Coastal landscape, tourism and leisure functions have been seriously affected by coastal erosion in many tourist sand beaches. Artificial nourishment on regular tourist beaches is of great importance for maintaining beach grade and promoting sustainable tourist development. Based on analysis of coastal dynamics, sediment and beach conditions, as well as comparison of remote sensing images and beach profiles, erosion conditions and origins of erosion are examined on the east section of Sanya Bay, Hainan Island, China. Artificial beach nourishment that does not shift coast nature was proposed for restoration and preservation of the beach, concerning the scenic urban area. By analyzing beach landform, dynamics, native and borrowed sand conditions, we designed a beach nourishment project, with the goal of proving resistivity to erosion and increasing the material sediment supply of the beach. Comparison of satellite images and fixed beach profiles before and after beach nourishment shows that the beach was restored and broadened as designed. Profiles measured one and a half years after nourishment show that the nourished beach face and berm were relatively stable, without an obvious increase in the rate of sand loss. The east section of Sanya Bay is a relatively calm area sheltered by the Luhuitou Peninsula. Beach erosion is mostly induced by a decrease in foreign sand supply and enhancement of local dynamic forces due to sandbar reclamation, construction of hard structural revement and artificial islands. Weakening dynamic forces to reduce sand loss and/or adding an effective supply of foreign sediment by artificial measures are necessary ways to restore and protect the beach. However, hard structures like groins and breakwaters will have a negative effect on both the coastal landscape and tourists' safety. The proposed beach nourishment project does not modify the beach nature, which is a reliable choice for beach restoration in Sanya, a famous tropical tourist city in China. Practice of the beach nourishment project indicates that beach nourishment with suitable location, range and borrowed sand following the natural coastline, landform and hydro-dynamics is effective for restoration of beach erosion of the east section of Sanya Bay. However, beach nourishment is not efficacious forever. Sand loss is still inevitable after nourishment, because the hydrodynamics have not changed. Further sustained re-nourishment is necessary to maintain the dynamic stability of the beach. Meanwhile, no strong typhoon hit the area during the surveys after nourishment, further response of the beach to storm waves are to be concerned.