The Zhenjiang-Yangzhou reach of the Yangtze River is located at the top of the Yangtze River Delta, which is one of the most dramatic changes in the lower reaches of the Yangtze River. The study on the migration characteristics of the channel centerline is crucial for a comprehensive understanding of the river channel changes in the Zhenjiang-Yangzhou reach. In this study, a detailed calculation method is proposed to extract the channel centerline of the Zhenjiang-Yangzhou reach by using old maps and remote sensing satellite map and decompose it into seven parts. The spatial and temporal changes of Net Shift Distance (NSD), Cumulative Moving Distance (CMD), Migration Rate of Channel Centerline (MRCC) and Linear Regression Change Rate of channel centerline (LRCR) from 1865 to 2019 on the cross-section scale are studied. The results show that: (1) from 1868 to 2019, the channel centerline of the Zhenjiang-Yangzhou reach kept shifting. The average net displacement distance of the section is 1103.47 m on the right bank, and the average cumulative displacement distance of the section is 2790.51 m. (2) According to the NSD and CMD data of each part, the long-term movement direction of the channel centerline is basically the same, and a small part of the channel centerline has periodic reverse swing. The probability of channel centerline moving right is about twice that of moving left. At the same time, some rivers have high erosion risk. (3) Through MRCC and LRCR data, the total number of channel centerline moving left and right is 156 and 329, respectively, and the erosion risk level of the near half of the shoreline is high. (4) The change of river boundary conditions and hydrodynamic force will affect the migration rate and direction of channel centerline. (5) This study proposes a method to extract channel centerline from a braided reach and study its changes, which can be applied to other similar reaches with a long history of human activities and high density. The results enrich people’s understanding of the long-term changes of a braided reach in the lower reaches of the Yangtze River and have certain guiding significance for river regulation, navigation safety, and revetment construction.

中文翻译：

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基于档案和当代数据集的长江镇江至扬州河段航道中心线变化及影响

长江镇江至扬州河段位于长江三角洲顶端，是长江下游变化最为剧烈的地区之一。研究河道中心线迁移特征对于全面了解镇江-扬州河段河道变化具有重要意义。本研究提出了利用旧地图和遥感卫星图提取镇江-扬州河段航道中心线并将其分解为7个部分的详细计算方法。净位移距离（NSD）、累积移动距离（CMD）、通道中心线迁移率（MRCC）和通道中心线线性回归变化率（LRCR ) 从 1865 年到 2019 年在横截面尺度上进行了研究。结果表明：（1）1868—2019年，镇江—扬州河段航道中心线不断偏移。右岸断面平均净位移距离为1103.47 m，平均累计位移距离为2790.51 m。(2)根据各部位的NSD和CMD数据，河道中心线长期运动方向基本一致，小部分河道中心线有周期性反向摆动。通道中心线向右移动的概率大约是向左移动的两倍。同时，一些河流具有较高的侵蚀风险。(3) 通过MRCC和LRCR数据显示，河道中心线左右移动总数分别为156条和329条，近一半岸线的侵蚀风险等级较高。(4)河流边界条件和水动力的变化会影响河道中心线的迁移速度和方向。(5) 本研究提出了一种从辫状河段中提取河道中心线并研究其变化的方法，该方法可应用于其他人类活动历史悠久、密度高的类似河段。研究结果丰富了人们对长江下游辫状河段长期变化的认识，对河道整治、航行安全、护岸建设具有一定的指导意义。