564 / 2024-07-31 22:25:27

Research on the Characteristics and Influencing Factors of Split Pattern  Changes in the Tongling reach of Lower Yangtze River

Lower Yangtze River; Tongling Reach; Diversion pattern; Channel evolution; Cause analysis

Subtheme 7: Sediment Regulation and Management > Topic 6: River- Lake Evolution and Ecology Rehabilitation

The Tongling Reach of the Lower Yangtze River, located downstream of the tidal reach and upstream of the Heishazhou Reach, is one of the key reaches in the Yangtze River Basin. Historical records show that numerous sandbars, including Chengdezhou Continent and Tingjiazhou Continent, have formed distinct channel patterns since 1865. Following the construction of the Three Gorges Reservoir, the Tongling Reach has undergone significant adjustments in its shoals and channels, altering its diversion pattern and affecting navigation conditions. This study analyzed the changes in the diversion patterns of the Chengdezhou Continent and Tingjiazhou Continent channels using topographic and hydrological data from 1998 to 2023. The results indicate that (1) the left branch of Chengdezhou Continent was the dominant channel from 1967 to 1998, but its diversion ratio sharply decreased to about 42.4% in 2023, resulting in a switch between the main and secondary channels; the left branch of Tingjiazhou Continent has remained the dominant channel since 1967, although its diversion ratio has gradually decreased in recent years, it still holds the position of the main channel. (2) The changes in the annual flow process under the regulation of the Three Gorges Reservoir are the main reasons for the alternation of the main and secondary channels of the Chengdezhou Continent channel, with the main flow shifting to the right and the right channel experiencing intensified erosion. (3) The deep channel of the right branch of Tingjiazhou Continent has shown an overall rising trend. After the impoundment of the Three Gorges Reservoir, the unevenness of the riverbed incision along the course led to a decrease in the riverbed gradient, which promoted the increase in the diversion ratio of the channel.