Characteristics of coastal erosion, siltation, and future development in Yazhou Bay, Sanya

The geological survey data of the coastal zone from 2018 to 2022 in Yazhou Bay, Hainan Province, South China, were analyzed, based on which the characteristics of shoreline evolution and seabed scouring and siltation were revealed by modeling. Results indicate that in recent years, erosion along the Yazhou Bay coast was mainly concentrated in the section east of the Yanzao River estuary and east of the wave barrier of the Yazhou Bay Central Fishing Port. Siltation along the coast took place mainly in the wave shadow area of the Moon Island (artificial island) and the area of the Yazhou Bay Science and Technology City. Shoreline evolution predictions show that in future 20 years, the maximum retreat distance of the Yazhou Bay coast will be approximately 33 m in the east side of the Yanzao River estuary; and the maximum siltation distance will be approximately 99 m in the western side of the Moon Island bridge. Scouring and siltation change predictions indicate that the maximum scouring intensity of the seabed is approximately 0.14 m/a, located in the outer waters of Moon Island; the maximum siltation intensity is approximately 0.07 m/a, located in the nearshore waters of the Science and Technology City. The main reason is the construction of the Moon Island, the Central Fishing Port, and Nanshan Port, which have altered the local sediment transport direction and subsequently changed hydrodynamic conditions, thus affecting the overall scouring and siltation pattern.