关键词: 河床演变, 长时间尺度, 分汊型河道, 镇扬河段, 长江下游

Abstract: As a typical bifurcating channel in the tidal reach of the lower Yangtze River(also known as the Changjiang River), the Zhenjiang-Yangzhou Reach has experienced long-term complicated evolution. By examining historical documents, ancient maps, modern topographic mapping, and hydrological data, we analyzed the long-term evolution of the Zhenjiang-Yangzhou Reach. According to our findings, prior to the Western Han Dynasty, the Zhenjiang-Yangzhou Reach served as the mouth of the Changjiang River. Sediment gradually accumulated in the ancient estuary, giving rise to the development of a sandbar along the north bank. The river channel generally shifted in a southerly direction, resulting in decreased river width. The sediment deposition eventually stabilized, forming the Shiye sandbar branching channel and the Hechang sandbar branching channel. Throughout history, hydraulic power and sediment transport characteristics played a key role in shaping and transforming the river. River nodes located on both the north and south banks played an essential role in controlling the river’s flow regime. Since the 1950s, the channel morphology of Zhenjiang-Yangzhou Reach has been in a relatively stable state. However, recent developments have shown adjustments in the flow regime within the branching channel. Human activities, such as the construction of various projects in the river, have become important external factors influencing the evolution of the riverbed.

Key words: fluvial processes, long-term scale, anabranching channel, Zhenjiang-Yangzhou River Reach, Lower Yangtze River