| The Yangtze River is the biggest river in China,being the only well waterway transportation channel connecting the eastern the central and the western,with a superior navigation condition and huge potential for shipping.At present,the Yangtze River waterway maintenance-scale and the channel capacity can’t adapt to the economic development along the river basin.The channel in the middle reach of Yangtze River from Yichang to Hukou,where plenty of branching rivers such as ShaShi,JianLi,JiaYu,DaiJiaZhou,with complex river bed topography and dramatical sediment changes.Mainstream swinging,the bottomland changes,and main branches alternation are commen phenomenons in branching rivers.Combining with water storage and silt detention of Three Gorges Project,the chages of drainage of water and sediment conditions has caused more complicated changes in the dam downstream riverbed,such as clear-water flushing and beach-groove instability,also affectting channel condition.Therefore,branching river regulation technology research,has important theoretical meaning and engineering value.Since the 1990 s,the middle reach of Yangtze River has been the focus of construction of waterway maintenance,successfully regulating a lot obstruction navigation channels,A batch of regulation constructions aiming at key navigation-obstructing braided channel are implemented,such as ZhiJiang-JiangKou,ShaShi,MaJiaZui,YaoJian,LuXiKou etc,effectively relieving the obstruction navigation in the middle reach and resistance against dry season year after year.Before the year 2020,the Yangtze River channel regulation goal is increasing the downstream water depth,unblocking the middle reach,and extending the length of the upstream,to achieve this goal,the regulation principle for the middle reache should be continued adhering to that making branching regime stable,moderately reducing branches and rational utilization of bottomland,aiming at different types of branching channels,different regulation thoughts timing and measures etc.Main research contents in this article are as follows:(1)The navigation-obstructing characteristics and established projects of branching rivers are summarized,development status and trends of regulation structures,the mathematical model and regulation ideas are analyzed.(2)On the basis of the existing regulation projects in the middle reach of Yangtze River,aiming at the regulation technology of straight braided river JiePai section and curved braided river ShaShi section in this paper,the different types of branching channel regulation principle and ideas were put forward.(3)Combining the different types of branching channel regulation principle and ideas,taking Daijiazhou reach 2nd stage as background,the regulation principle and ideas during 2nd stage were put forward,based on the analysis summary of regulation effects after 1st stage construction and riverbed evolution in Daijiazhou reach,a two-dimensional mathematical model is established,simulating the regulation effects after loading different schemes,then finally determining the optimized scheme. |
