长江下游口岸直水道河床演变和碍航成因分析

Bed evolution characteristics and navigation obstructing mechanisms of the Kou′an straight reach of the Yangtze River

依据河道实测水文、地形资料对长江下游口岸直水道的河床演变、碍航特性和成因等进行了深入分析,初步提出了本河段航道治理的基本思路。分析表明:口岸直水道河势总体稳定;落成洲左汊主流右摆,洲头及其左缘持续冲刷,枯水河床展宽,浅区过渡段冲刷不力,航道条件向不利方向转化;鳗鱼沙心滩在不同水文年冲淤频繁,但受上游来沙减少的影响,总体上滩体冲刷萎缩,导致右汊航道条件变差,泰州大桥的兴建又使鳗鱼沙河段航道条件更趋复杂。航道治理的基本思路应在稳定落成洲头部和鳗鱼沙心滩的守护工程的基础上,以丁、潜坝配合守护工程适当增加浅区的冲刷能力。

Based on analysis of long-term topographic and hydrology data, the characteristics of the bed evolu-tion as well as the navigation obstructing mechanisms arising from it were thoroughly looked into at the Kou′anstraight reach of the Yangtze River. It shows that the river regime of the Kou′an straight reach is generally stable. Atthe area of Luocheng shoal, as the main flow in the left branch swings to the right, the head and left edge of the shoalare kept scouring, and the low-flow width of the bed continues to be broadened. However, due to the insufficient ero-sion at transitional shallow area, the navigation conditions will become worse. At the area of Manyusha sand bar, al-ternative erosion and deposition take place frequently in different hydrological years. As the sediment supply fromupstream reduces, the scale of the sand bar shrinks as well, which result in worse navigation conditions in the rightbranch. And furthermore, the construction of the Taizhou bridge deepened the complexity of the navigation condi-tion in downstream Manyusha reach. To deal with previously stated problems, the regulation principles for the im-provement of the Kou′an straight reach is presented as that, first to stabilize the river regime especially at the headof Luocheng shoal and the whole Manyusha sand bar, and then to enhance the erosive capability of the flow at theshallow areas with the measure of spur dikes and submerged dikes.