Spatiotemporal evolution characteristics of river channels of Dangqu River Basin in source region of Yangtze River

Abstract

[Objective] In the context of global climate warming, both temperature and precipitation in the source region of the Yangtze River have shown increasing trends, leading to enhanced glacier melt and snowmelt and intensified river evolution. Clarifying the spatiotemporal evolution patterns of plateau river channels under climate change is of great significance for the enhanced understanding of response and evolutionary characteristics of plateau rivers and for the conservation of ecological environment. [Methods]Based on remote sensing imagery of the Dangqu River Basin in the source region of the Yangtze River and temperature and precipitation data from three nearby meteorological stations from 1990 to 2023, the spatiotemporal evolution patterns of river channels in the Dangqu River Basin were quantitatively investigated. This was achieved by the MNDWI method, channel centerline method, Mann-Kendall trend analysis, and maximum value composite(MVC) method. Additionally, interannual variations in curvature, width, and lateral migration rates of river channels from 1990 to 2023 were analyzed. [Results] The result showed that within the 152 km river section of the Dangqu River Basin, straight channels accounted for approximately one-third, while meandering channels accounted for two-thirds. Over the past 34 years, the average curvature of river channels in the Dangqu River Basin was 1. 14, exhibiting only a 2% decrease during this period. The river width of the Dangqu River continued to increase, with an average growth of 9. 4% and an annual increase of 0. 4 m/a. The normalized lateral migration rate of the river channels [= total lateral migration distance/m（year of migration × river width）]decreased by 48%, with an average annual reduction of 0. 014 over the 34-year period. [Conclusion] The river width and normalized lateral migration rate are significantly influenced by temperature and precipitation. Increased glacier melt and snowmelt induced by rising temperatures, combined with higher precipitation, jointly lead to higher river discharge and elevated water levels, thereby promoting the widening of river channels in the Dangqu River Basin. In addition, these changes in hydrological conditions are favorable for vegetation growth, which strengthens bank stabilization and suppresses lateral channel migration, resulting in a decreasing trend in the normalized lateral migration rate.

Keywords

meandering river / river channel evolution / lateral migration / source region of Yangtze River / spatiotemporal evolution / Dangqu River Basin / remote sensing interpretation / climate change