Scouring and silting characteristics and dynamic mechanism of ebb and flow and spring-neap tidal cycles in Sansha Bay
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摘要:
潮滩不同尺度的变化规律一直是地表过程研究的核心之一。利用声学多普勒流速仪（ADV）、温盐深（CTD）、光学后向散射浊度计（OBS）对三沙湾潮滩涨落潮和大小潮冲淤及动力变化进行了高精度的观测。结果发现，潮周期内，潮滩冲淤呈现涨潮初期冲刷-落潮末期淤积-中间时段稳定的特征，涨潮初期水深<1 m 的30 min内平均冲刷4.05 mm，落潮末期水深<1 m 的30 min内平均淤积3.72 mm，中间时段动态稳定；大小潮周期内，呈现中潮到小潮平均淤积3.4 mm，小潮到大潮平均冲刷8.2 mm的特征。通过流速、紊动能、水深、悬沙浓度等因子与冲淤的相关性分析发现，潮周期内，流速和紊动能的增减决定涨潮初期冲刷和落潮末期淤积的变化；大小潮周期内，涨潮冲刷大于落潮淤积的特性决定了大潮到小潮阶段的冲刷， 涨潮冲刷小于落潮淤积决定了小潮到大潮阶段的淤积。涨落潮周期和大小潮潮周期的冲淤机制为潮滩动力地貌和动力沉积学研究提供了一定的参考。
Abstract:The variation rules of tidal flat at different scales has always been one of the main contents in the study of surface processes. The high-precision instruments ADV, CTD, and OBS were used to observe the scouring and silting characteristics of ebb and flow and spring-neap tide on May 26 to June 5, 2020 in Sansha Bay, Fujian, SE China. Results show that during the tidal cycle, the scouring and silting of the tidal flat are characterized by scouring at the beginning of rising tide, silting at the end of falling tide, and stabilizing in the middle period, the average scouring was 4.05 mm within 30 min when water depth is less than 1 m at the beginning of flood tide, and the average siltation was 3.72 mm within 30 min when water depth was less than 1 m at the end of ebb tide, and was in dynamic stability in the middle period. During the spring-neap tide period, the average siltation from mid tide to neap tide was 3.4 mm, and the average scouring from neap tide to spring tide was 8.2 mm. The correlation analysis on impact factors including velocity, turbulent energy, water depth, and suspended sediment concentration to the scouring and siltation showed that in tidal cycle, fluctuations in velocity and turbulent kinetic energy determined the changes of scour at the beginning of flood tide and siltation at the end of ebb tide. During spring-neap tides, the characteristics of more flood scouring than ebb siltation determined the scouring from spring tide to neap tide, and less flood scouring than ebb siltation determined the siltation from neap tide to spring tide. This study on scouring and silting mechanism in ebb and flow periods and spring and spring tides provided a reference for the study of tidal flat dynamic geomorphology and dynamic sedimentology.
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Key words:
- Sansha Bay /
- tidal flat /
- tidal period /
- scouring and silting /
- dynamic mechanism
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表 1 S1站观测数据
Table 1. S1 station observation data
潮周期序列 相对最高潮位/m 滩面距探头的
高程最大值/mm滩面距探头的
高程最小值/mm最大流速/（m/s） T1 3.18 −247.6 −251.1 0.326 T3 2.98 −247.4 −250.9 0.315 T5 2.85 −244.8 −249.3 0.297 T7（小潮） 2.85 −243.2 −248.3 0.286 T9 3.09 −244.4 −248.5 0.326 T11 3.19 −245.2 −248.1 0.361 T13 3.28 −246.4 −251.3 0.375 T15 3.51 −246.0 −256.8 0.367 T17（大潮） 3.67 −249.9 −254.6 0.400 T19 3.85 — — — 注：“—”为无数据。 
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表 2 S2站观测数据
Table 2. S2 station observation data
潮周期序列 相对最高潮位/m 滩面距探头的
高程最大值/mm滩面距探头的
高程最小值/mm最大流速/（m/s） T1 3.27 −291.9 −296.6 0.338 T3 3.22 −289.1 −293.0 0.298 T5 3.02 −290.3 −293.8 0.277 T7（小潮） 2.87 −290.2 −293.4 0.258 T9 2.89 −292.9 −294.9 0.218 T11 3.1 −287.8 −298.4 0.322 T13 3.25 −292.9 −299.9 0.331 T15 3.22 −292.8 −300.7 0.365 T17 3.56 –294.4 –301.0 0.384 T19（大潮） 3.64 −295.1 −302.6 0.432 T21 3.67 −292.7 −304.1 0.417
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