Understanding the relationship between unbalanced riverbed scouring or deposition and the evolution of central bars in natural conditions and human activity is useful for river regime control and waterway improvement ...Understanding the relationship between unbalanced riverbed scouring or deposition and the evolution of central bars in natural conditions and human activity is useful for river regime control and waterway improvement projects.Toward this end,we utilized the Yangzhong reach in the lower reaches of the Yangtze River as a case study and evaluated runoff,sediment content,and topographical data measured over the past 70 years(1951–2021).With the decrease in the amount of incoming sediment in the river basin,the Yangzhong reach exhibited a continuous state of scouring.The cumulative riverbed scouring volumes of the low-water and flood channels from 1981 to 2021 were 3.97×10^(8)and 4.14×10^(8)m^(3),respectively,with the riverbed scouring volume of the low-water channel accounting for 95.9%of that of the flood channel.Under quasi-natural runoff–sediment conditions,the evolution of the central bars in the Yangzhong reach was highly correlated with the amount of scouring or deposition.In particular,the Luochengzhou reach could be characterized as a meandering river with scouring on concave riverbanks and deposition on convex riverbanks.In the context of reduced incoming sediment,the beach area of the Yangzhong reach decreased by approximately 9.9%(from 2003 to 2021)and the central bars of the straight section areas decreased.Moreover,following operation of the Three Gorges Reservoir,both the Luocheng central bar and Jiangyin beach areas could be characterized as meandering rivers with convex riverbanks and beaches.In the quasi-natural period before the implementation of the waterway improvement project,the trend of high scouring intensity and increased fluid diversion ratio in the right branch of the Luocheng central bar was in accordance with the law that the short branch of the length is in a developing state under the condition of decreasing river sediment volume.With the control of riverbank protection and the construction of waterway improvement projects in the Yangzhong reach,the shapes of the riverbanks and central bars were effectively stabilized,and the linkage relationship formed in the quasi-natural period was interrupted.Overall,these findings provide a strong foundation for understanding riverbed scouring or deposition and the evolution of central bars under the influence of natural conditions and human activities,and will inform future river management and waterway dimension planning.展开更多
基金National Natural Science Foundation of China,No.52279066Fundamental Research Funds for Central Welfare Research Institutes,No.TKS20230206The CRSRI Open Research Program,No.CKWV2021862/KY。
文摘Understanding the relationship between unbalanced riverbed scouring or deposition and the evolution of central bars in natural conditions and human activity is useful for river regime control and waterway improvement projects.Toward this end,we utilized the Yangzhong reach in the lower reaches of the Yangtze River as a case study and evaluated runoff,sediment content,and topographical data measured over the past 70 years(1951–2021).With the decrease in the amount of incoming sediment in the river basin,the Yangzhong reach exhibited a continuous state of scouring.The cumulative riverbed scouring volumes of the low-water and flood channels from 1981 to 2021 were 3.97×10^(8)and 4.14×10^(8)m^(3),respectively,with the riverbed scouring volume of the low-water channel accounting for 95.9%of that of the flood channel.Under quasi-natural runoff–sediment conditions,the evolution of the central bars in the Yangzhong reach was highly correlated with the amount of scouring or deposition.In particular,the Luochengzhou reach could be characterized as a meandering river with scouring on concave riverbanks and deposition on convex riverbanks.In the context of reduced incoming sediment,the beach area of the Yangzhong reach decreased by approximately 9.9%(from 2003 to 2021)and the central bars of the straight section areas decreased.Moreover,following operation of the Three Gorges Reservoir,both the Luocheng central bar and Jiangyin beach areas could be characterized as meandering rivers with convex riverbanks and beaches.In the quasi-natural period before the implementation of the waterway improvement project,the trend of high scouring intensity and increased fluid diversion ratio in the right branch of the Luocheng central bar was in accordance with the law that the short branch of the length is in a developing state under the condition of decreasing river sediment volume.With the control of riverbank protection and the construction of waterway improvement projects in the Yangzhong reach,the shapes of the riverbanks and central bars were effectively stabilized,and the linkage relationship formed in the quasi-natural period was interrupted.Overall,these findings provide a strong foundation for understanding riverbed scouring or deposition and the evolution of central bars under the influence of natural conditions and human activities,and will inform future river management and waterway dimension planning.
