长江中下游阻隔性河段特征及成因初步研究

Preliminary study on the characteristics and origin of barrier river reach in the Middle and Lower Yangtze River

长江中下游长河段长时段的演变资料分析表明河势调整往往会向下游传递,但是部分河段却能阻隔这种河势调整的传递效应,称之为阻隔性河段。统计表明,阻隔性河段应同时具有单一微弯的平面形态、凹岸抗冲性较强且中上段无挑流节点、河宽随水位变化率不超过45等三个特征。进一步分析表明,这种河段具有阻隔性的根本原因是其能够归顺不同流量级的主流平面位置,使得无论上游河势如何调整,其出流的主流平面位置基本稳定,为下游河段提供相对稳定的入流条件。河道整治过程中,宜抓住有利时机塑造阻隔性河段效果,无阻隔性影响的长河段宜自上而下系统规划整治,对大幅度崩岸、滩体大幅萎缩等可能破坏阻隔性的变化应及时整治,防止阻隔性丧失。

Analysis of long temporal and spatial riverbed evolution data shows that the adjustment of river regime in the Middle and Lower Yangtze River （MLYR） trends to pass downstream, but it＇s obstructed by some kind of reaches which is called barrier river reach （BRR for short）. Statistics indicates that barrier reach is generally a single-thread bend with strong resistance at the concave bank. There is no node de- flecting flow in the upper and middle reaches. In addition, BRR has narrow and deep cross-section and the change rate of river width with the water level is less than 45. Further analysis shows that the root rea- son of the barrier property lies in the ability to stabilize the mainstream planimetric positions of different flow levels. No matter how the upper river regime changes, the mainstream position of outflow basically re- mained stable, which provides relatively stable inflow conditions for the lower reaches. In the river regula- tion process, the good opportunity should be seized to shape BRR. The long river reaches without BRR should be planned and regulated systematically. The bank collapse and sandbar shrinking dramatically should be controlled timely to prevent barrier property from losing.