Earth Science Frontiers ›› 2023, Vol. 30 ›› Issue (5): 553-566.DOI: 10.13745/j.esf.sf.2023.2.73

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Estimating bedload transport at the eastern entrance to the Qiongzhou Strait by numerical simulation

TONG Changliang1,2,3(), ZHU Yu1,3, WU Xiangbai4,*(), MO Yingming2, WANG Xuemu3   

  1. 1. Hainan Key Laboratory of Marine Geological Resources and Environment, Haikou 570206, China
    2. Hainan Geology Detection and Research Centre, Haikou 570206, China
    3. Marine Geological Institute of Hainan Province, Haikou 570206, China
    4. School of Naval Architecture and Ocean Engineering, Jiangsu University of Science and Technology, Zhenjiang 212100, China
  • Received:2022-01-01 Revised:2023-01-01 Online:2023-09-25 Published:2023-10-20
  • Contact: WU Xiangbai

Abstract:

The widespread tidal ridges at the eastern entrance to the Qiongzhou Strait are mainly controlled by east-west tidal currents of four types, i.e., eastward/westward flood or ebb. According to the numerical simulation, the speed of tidal currents is relatively fast in the central waterway, the north shore and shoals, where the average vertical speed can reach 0.7-1.0 m/s, whilst elsewhere it is about 0.3-0.5 m/s. In general, the eastward current speed is faster than the westward counterpart, but the opposite is true at the north shore due to the western Guangdong coastal current. This characteristic is especially obvious during spring tides where the current speed is generally 1.5-2.0-fold faster compared to during neap tides. The study area is dominated by sandy and gravel deposits distributed mainly in the central waterway, shoals and the north shore, where the average particle size of sediment is 2.67Φ areawide, with poor sorting overall. The critical starting rate of bedload transport ranges between 0.12-0.79 m/s—above 0.6 m/s in the central channel to shoals in the southwest, and generally 0.35-0.45 m/s in sandbanks. However, in muddy areas of the eastern shelf, the starting rate is generally less than 0.22 m/s. Using the Bagnold transport model, the north shore has the highest transport rate, followed by the central waterway and shoals. Within a tidal cycle, sediment is transported westward along the north shore but mostly eastward elsewhere, and the net transport volume between spring and neap tides can differ by an order of magnitude. According to the cross-section calculation, the net amount of bed materials transported through the eastern entrance to the Qiongzhou Strait is on the order of 108 kg per month.

Key words: sedimentary dynamics, bedload, transport volume, tidal current simulation, east entrance of Qiongzhou Strait

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