Research on atypical evolution characteristics of convex bank of typical bend in lower Jingjiang river under changing environment

Abstract

Since Three Gorges Reservoir was put into operation, the water and sediment conditions have changed significantly, and the lower reach of the project have been adjusted to adapt to this change. The continuous bend of the Jingjiang section of the lower reach of the reservoir (Tiaoguan-Laijiapu) is selected as the research reach. The research methods of prototype data observation and physical model test were carried out, and the continuous erosion evolution and channel shape change characteristics of the reach are analyzed. The results show that the convex bank at the upper of the bend is eroded, the concave bank is deposited, the deep groove is moved to the right, widened and cut down, the deep groove at the lower of the bend is widened and brushed deep, the convex bank at the upper of the Laijiapu bend is scoured, the concave bank gradually deposited, and the deep groove of the whole bend is widened and deep scoured after Three Gorges Reservoir was built and used. The change of runoff conditions after the construction of the reservoir provide dynamic conditions for the continuous scouring of the convex bank. The main factors for the continuous erosion of the convex bank are the substantial reduction of sediment inflow downstream of the dam caused by reservoir sediment interception, sand mining and soil and water conservation. This study is universal and can provide reference for the research on evolution characteristics of the downstream bend reach of other large water conservancy projects.