The process of the hyperconcentrated flow of tributaries merges into the upper Yellow River as well as the deposition pattern in confluence was preliminarily studied through experiment. The results showed that the hyperconcentrated flow’s merging into the main stream caused higher backwater in the upstream of the junction and greater size of separation zone near the downstream junction corner.Strongly sediment diffusion and density current took place and moved upstream in the backwater area. The moving distance of the density current was a function of the main stream discharge and the momentum ratio of the tributary and mainstream flow. The deposition pattern in the channel displayed as three parts of a wedge-shaped sandbar with inverse slope in the upstream of the junction, a sandbar in the separation zone leaning the inner back,and a hole arrayed in the flow deflection area and high velocity area. The total incoming sediment of the tributary has great impact on the geometrical sizes of the sandbar which are well proportional to the total incoming sediment.
