Author(s): Ping Wang; Tian Hu; Yuanfeng Zhang; Suzhen Hou
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Keywords: Yellow River; Hyper-concentration flood; River confluence; Sand bar; Deposition morphology
Abstract: The hyper-concentration flood of the tributaries of the upper Yellow River in Inner Mongolia causes the forming of the sand bar in the confluence, choking the main stream of Yellow River. That is a special river converging phenomena and has great negative impacts on local river bed evolution, flood control and industrial water taking. The process of the hyper-concentration flood of the tributaries’ merging into the upper Yellow River as well as the deposition morphology in the confluence was preliminarily studied through experiment. The results shows the hyper-concentration flood from the tributaries and the flow in the main stream pushed mutually in the confluence causing backwater in mainstream upstream of the junction, the flow deflection zone in the middle, the high velocity flow following the deflected flow, the separation zone at the downstream junction corner and the flow recovery zone downstream of the separation zone. There was strongly sediment mixing the confluence. The density current was formed and moved backward in the backwater area. The moving distance of the density current was proportional to the discharge ratio. The sizes of the separation zone was also proportional to the discharge ratio, but restricted by the channel width. Corresponding to the different hydrodynamic zones in the confluence, the sand bar in the confluence can be divided into five parts with different deposition morphology: the wedge-shaped deposition body in the backwater area, the deposition body in the separation zone, the hole in the middle of the confluence, the deposition body in the downstream reach and the deposition body in the flood plain if it was overflowed. The geometrical sizes of all these sediment bodies as well as their volumes were well proportional to the total incoming sediment of the flood from the tributaries.
Year: 2013