The expansion of sand-dredging activities in Lingding Bay has an unknown impact on the distribution of suspended sediment in the surrounding sea area. In this paper, an accurate formula was proposed for calculating suspended sediment concentration(SCC) based on GF-1 satellite images and mass filed data of SSC in Lingding Bay. First, the plane distribution of surface SSC of Lingding Bay are acquired and the distribution and transporting characteristics of SSC in Lingding Bay are analyzed, and then, the possible influence of turbidity water with high SSC caused by sand-dredging activities is discussed. The results were shown as follow: The plane distribution characteristics of surface SSC in Lingding Bay were generally "westen higher than eastern", "northern higher than southern", "shoals higher than troughs", and the main transport direction of suspended sediment was generally from north to south; Large-scale sand-dredging activities had significantly increased the SSC value in the middle shoal of Lingding Bay; The turbidity water with high SSC values can transport to Lingding Channel and Tonggu Channel with tidal flow, and its influence on the back siltation of the navigating channel deserves more attention.

Research on Suspended Sediment Characteristics of Lingding Bay based on GF-1 Remote Sensing Images

Consisting of a 28.9-km-long bridge, two 6.7-km-long man-made islands, and a 5,664-m-long immersed tube tunnel, the Hong Kong-Zhuhai-Macao Bridge is a super large-scale transportation project in the Lingding Bay of the Pearl River Estuary. The construction of the immersed tube tunnel involved arranging 33 tunnel elements from west to east in an excavated foundation trench. The installation was forced to stop, which was a difficult problem for the project team to solve immediately due to the abnormal deposition for tunnel element 15 during floating installation on November 15, 2014. In this article, the hydrodynamic and sediment environment, the topographic and geomorphic features, suspended sediment concentration caused by sand-dredging activities, and flow field near deep foundation trench were analyzed for the purpose of research. Overall, the cause of abnormal deposition was very complicated. Large-scale sand-dredging activities on the north side of Neilingding Island directly led to an increase in the suspended sediment concentration. With tunnel element 15 as the boundary, the topographical and geomorphic differences between the east and west sides were the reason that silting firstly occurred for tunnel element 15 but not for tunnel elements 1–14. Finally, the complex vertical circulation structure was another factor of abnormal deposition caused by the project itself. In a word, the cause of abnormal deposition for tunnel element 15 is very complex, including the joint influence of human and natural factors.

Han Zhi-yuan

Papers

Research on Suspended Sediment Characteristics of Lingding Bay based on GF-1 Remote Sensing Images

Cause Analysis of Abnormal Deposition of Hong Kong–Zhuhai–Macao Bridge in Pearl River Estuary, China