关键词: 分汊河道;河床演变;河势;如皋沙群河段;

Abstract: Rugao sand shoals reach is located in Jiangyin-Nantong reach of Changjiang River. The channel is wide and multi-branched, and the scouring and silting law in the shoal is complex. It is of great significance to study the channel evolution and its influencing factors for the treatment and protection of this reach. Based on the measured data from 1977 to 2018, we systematically analyzed the recent changes of erosion and deposition, thalweg, shoal channel and typical cross-sections of Rugao sand shoals reach and discussed the main factors of the channel evolution in the reach. The results showed that in recent years, the river bed of Rugao sand shoals reach had shown a general trend of scouring development, and the thalweg had shifted to the left generally, especially the maximum deviation range in the right branch of Rugao reach had reached 900 m. The left and right edges of Shuangjian shoal protection part were slightly silted, the end of Minzhu shoal slightly moved down, and the beach surface of Henggang shoal was obvious silted. From 2011 to 2018, the average siltation elevation of Henggang shoal in the riverbed above -5 m of Jiuweigang increased by 0.62 m, the variation range of deep grooves and typical cross-sections tended to be smaller, showing a trend of slowly scouring deep, and rise and deepening of deep grooves in plain view. The overall stability of Rugao sand shoals reach was affected by river boundary conditions, flood, incoming water and sediment, and human activities, among which human activities had a greater impact. The implementation of relevant regulation projects made the overall river regime of the section stable.

Key words: braided channel; riverbed evolution; river regime; Rugao sand shoals reach