Abstract: The operation of the Three Gorges Project (TGP) had changed the condition of discharge and sediment. Curved reaches in the Jingjiang River all witnessed erosion in convex bank and deposition in concave bank, detrimental to channel navigation. In order to study the evolution characteristics and influence factors of curved reach, we analyzed the evolution causes and estimated the future changes of Jingjiangmen reach of lower Jingjiang River as an example according to measured topographic data in recent 15 years after the impoundment of TGR via logic reasoning and statistical analysis. Results demonstrated that after the operation of TGP, the convex bank of Jingjiangmen reach showed a trend of continuous scouring year by year, and the position of scouring moved downwards continuously, which deteriorated the channel navigation condition. When the duration of bank-full discharge (20 000~25 000 m³/s) was longer than 15 days in a year, convex bank was scoured and moved backwards, while on the contrary, when the duration of bank-full discharge was shorter than 15 days of the year, the convex bank was silted. The annual variations of convex bank had a good corresponding relationship with sediment concentration, especially fine sand content (d<0.125 mm), synchronously increasing or decreasing. After the first phase implementation project of Jingjiang Reach in 2014, given the discharge and sediment conditions, convex bank wound continue scouring, giving rise to double-groove in dry season and more deteriorated navigation condition. In conclusion, changes in discharge and sediment conditions are the major causes of bend reach evolution. In years of long flood duration with small sediment discharge, Jingjiangmen reach would most likely experience navigation obstruction. These conclusions provide reference for the governance of meandering channels in lower Jingjiangmen reach.

Key words: relationship between bank and groove, convex bank, characteristics discharge, duration, water and sediment process, navigation channel change, lower Jingjiang River, Jingjiangmen bend reach