长江下游新生洲洲头分流段演变特征及洲头守护措施

洲头分流段的河床演变对河势控制与稳定起着承上启下的关键作用，历来受到工程界的广泛关注。长江新生洲洲头分流段处于苏皖交界，是长江南京河段的门户。通过分析历史及近年上游小黄洲汊道、下游新生洲汊道及新生洲洲头分流段的河床演变特征，揭示了上下两个汊道分流比变化及洲头冲淤、汊道兴衰的内在关联性，论证了洲头控制对汊道水动力变化及主支汊演变的重要性，指出在三峡水库新运行的水沙条件、河势变化及汊道河势稳定性要求下，守护新生洲洲头的治理措施应以恢复近年洲头冲刷后退前的滩势为原则，修建长度、方向、高程合理的洲头导流坝，并辅以护底及洲头两缘的护岸工程，以及对小黄洲洲尾右侧至洲尾滩脊进行局部疏浚。成果可为该河段的全面系统治理提供有益参考。

Evolution characteristics and protection measures for diversion section of Xinshengzhou shoal head in lower Yangtze River

The river channel process of the bifurcating section of a shoal head plays a vital role in river regime control and stability, and this issue has been a widespread concern in the water conservancy and water transport engineering. The object of the analysis, the bifurcating section of the shoal head of the Xinshengzhou, situated at the Yangtze River reach adjoining Jiangsu and Anhui Provinces, is the gateway to Nanjing reach of the Yangtze River. In this study, the river channel process characteristics of the bifurcating section of the shoal head of the lower Xinshengzhou and the Xiaohuangzhou bifurcating channel are analyzed to reveal the inherent relations between the two upper and lower two inlet's diversion ratios, and between the scour and siltation along the shoal head, and to demonstrate the importance in controlling the evolution characteristics and hydrodynamic changes of the shoal head and the main or branch channels. Analysis results show that regulation measures should be taken for controlling the significant effects of the shoal head on the hydrodynamic conditions and the river channel process of the adjacent branches. Considering the new water-sediment conditions, river regime changes and stability due to the operation of the Three Gorges project, the regulation measures for the Xinshengzhou shoal head should be as follows: the training walls and groynes which have the reasonable lengths, directions and heights must be placed in front of the shoal head to control the flow regime, and the local dredging should be carried out on the right side and the shoal ridge of the Xiaohuangzhou shoal in order to avoid persistent erosion. Meanwhile, the other protection works must be constructed on the riverbed and along the riverbank. These research results can provide a useful reference for the comprehensive regulation of the river reach.