Primary research on the erosion adjustment of the alternant braided reach in the mid-down yangtze river after Three Gorges dam impoundment

The impoundment of Three Gorges Project has changed the incoming water and sediment conditions of downstream, leading to corresponding erosion adjustment of the riverbed. Because the dynamic axis of flow replace between branches, the evolution of annual alternant braided reach is different from non-alternant ones. Guanzhou braid reach is a typical annual alternant braided reach in the mid-down Yangtze River. With field data, this paper researches the evolution law of the annual alternant braided reach after the Yangtze River Three Gorges Reservoir. Results show that, the erosion adjustment of main branch in flood season is more obvious than that in dry season, and its flow diversion ratio also increases with time, which has an adverse affect on the stability of the river.