长江中游戴家洲河段滩群联动演变及其对航道工程的响应机制

Evolution of the shoal group coupling and its response mechanism to waterway engineering in the Daijiazhou reach of the middle reaches of the Yangtze River

  • 摘要: 航道浅滩演变与滩槽形态调整具有强关联性,识别滩槽形态、河床冲淤与航道工程的响应关系,对评估航道工程实施效果具有重要意义。以长江中游戴家洲河段为对象,采用1954—2022年期间实测水沙和地形资料,解析滩群演变联动关系及对航道工程的响应机制。结果表明:①自然水沙阶段(2008年以前),巴河边滩与池湖港边滩关联性强,池湖港边滩淤涨并减弱了燕矶节点挑流作用,加速了戴家洲洲头低滩上延,而巴河边滩淤涨使得戴家洲洲头低滩冲刷,但流域来沙量减少增加了洲头低滩冲刷速率;戴家洲汊道分流关系不稳定且汉口站相同流量条件下的右汊分流比为减少态势,来沙量低的大水年份加速戴家洲右缘蚀退并为乐家湾边滩淤宽提供了空间。②航道工程影响阶段(2008年以来),航道工程实施使得戴家洲洲头低滩上延,其右缘冲刷应引起重视;戴家洲汊道进口段航道工程压缩了河道横向空间并加速了巴河边滩冲失趋势,池湖港边滩侧蚀使得分汊段水流分散程度增加,不利于汊道进口段浅滩水动力的稳定或增强;戴家洲右缘洲体守护后的完整性增强,乐家湾边滩由淤涨转为冲刷过程形成的分离体进入航槽并碍航,6m水深航道工程实施后乐家湾边滩完整性增强,右汊中下段浅区航道条件改善。

     

    Abstract: The evolution of shoals and the adjustment of channel morphology have a strong correlation. Identifying the relationship between the impact of channel engineering on shoal morphology, riverbed scouring and siltation is valuable for evaluating the effectiveness of channel engineering implementation. This study focuses on the Daijiazhou reach in the middle reaches of the Yangtze River, analyzing the coupled evolution of the shoal group and its response mechanisms to channel engineering using 60 years of measured water, sediment, and topographic data. In the natural water and sediment stage (before 2008): the Bahe shoal and the Chihugang shoal exhibited a strong associations. The deposition of the Chihugang shoal weakened the diversion effect of the Yanji node, accelerating the upstream extension of the low shoal at the head of Daijiazhou. The deposition at the Bahe shoal led to scouring of the low shoal at the head of Daijiazhou, while the reduced sediment supply increased the scouring rate of the low shoal. The distribution of flow between the branches of Daijiazhou was unstable, and the proportion of flow into the right branch showed a decreasing trend under the same Hankou station flow conditions. In high-flow years with low sediment supply, the erosion of the right bank of Daijiazhou was accelerated, providing space for the widening of the Lejiawan shoal. In the channel engineering impact stage (since 2008): the implementation of channel engineering further extended the low shoal at the head of Daijiazhou; however, the scouring of its right bank requires significant attention. The channel engineering at the inlet of the Daijiazhou branches compressed the lateral space of the river and accelerated the disappearance of the Bahe shoal. As the Chihugang shoal eroded, the degree of flow dispersion increased, which was detrimental to enhancing the hydrodynamics at the inlet of the branches. After the right bank of Daijiazhou was protected, its integrity improved. However, the separated portion of the Lejiawan shoal, resulting from the transition from deposition to scouring, entered the channel and obstructed navigation. The implementation of the 6m depth channel engineering strengthened the integrity of the Lejiawan shoal, significantly improving navigation conditions in the middle and lower reaches of the right branch.

     

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