长江口徐六泾节点段河槽稳定性及其影响因素

徐六泾节点段控制着长江口的物质通量和南北支的分流分沙,其河槽稳定性和变化趋势在长江口的演变中具有重要地位。采用实测资料分析和物理模型试验相结合的方法研究了长江口徐六泾节点段河槽的稳定性及其影响因素。研究结果表明:①徐六泾节点段1992年前河槽呈右移态势;1992—2018年间,河槽演变趋缓,平面上主要表现为小幅度的上提下挫,垂向上呈缓慢刷深之势。②徐六泾节点段未来滩槽格局基本稳定,河槽仍以冲刷为主,且有向下游发展趋势,大洪水作用下局部河床会出现较大的调整(2009—2018年+百年一遇水文年试验条件下,在现有的-30 m深槽下游约910 m 处出现一个新的-30 m槽)。③徐六泾节点段河槽整体稳定性前期主要受两岸圈围工程、上下游河势、大洪水等的影响,近年来主要受流域减沙的影响,局部河床稳定性的主要影响因素是大洪水和人类活动。

Channel Stability and Its Influencing Factors in Xuliujing Node Reach of Yangtze River Estuary

The channel stability and change trend of Xuliujing node reach are of pivotal importance in the evolution of the Yangtze River Estuary as it controls the material flux and the diversion and sediment distribution of the north and south branches of the Yangtze River Estuary. The stability of the channel in Xuliujing node reach and its influencing factors were studied via measured data analysis and physical model test. Results demonstrated that: 1) before 1992, the river channel in Xuliujing reach shifted to the right; from 1992 to 2018, the evolution of the river channel attenuated, displaying a small upward and downward trend on horizontal scale, and a slow downward trend on vertical scale. 2) In future, the pattern of shoal and trough in Xuliujing node reach would remain stable in general; the channel would be dominated by scour and develop towards the downstream; big floods will see conspicuous adjustments of local beds—a new -30 m trough will appear 910 meters downstream of the existing -30 m channel under the condition of 2009-2018 plus one-in-100-year hydrological years. 3) In early stage, the overall stability of Xuliujing reach is mainly affected by enclosure project, upstream and downstream river regime, and flood, while in recent years, it is mainly affected by sediment reduction of the river basin. Flood and human activities are major influencing factors of local riverbed stability.