关键词: 三亚湾, 砂质海滩, 海岸侵蚀, 海滩养护

Abstract:

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.

Key words: Sanya Bay, sandy beach, coastal erosion, beach nourishment