Abstract

The low-water braided reach is a type of river pattern that the channel is braided by shallow central bar in low-water period, while in flood period, as rise of the water level, the central bar is submerged by flow and the channel transforms to be single. It is relatively sensitive to the variation of the water, sediment and boundary conditions. The impoundment of reservoir has been markedly changed the amount and process of the post-dam incoming discharge and sediment. This change may induce the deposition or erosion, especially on the central bar, therefore it may bring to the variation of the split flow point and the braided pattern in low-water period. According to the variation of braided pattern, the mainstream as well as the thalwag may transfer as adjustment. In this paper, taking Yidu reach for example, based on the analysis and contrast of scouring and silting characteristics and flow movement characteristics pre- and after the reservoir impoundment, the influence on low-water braided bending reach after reservoir impoundment as well as impacts to navigation have been studied.

Keywords: low-water braided reach, reservoir impoundment, Yidu reach, river evolution