Prediction of recent bank retreat processes at typical sections in the Jingjiang Reach

Abstract

The Jingjiang Reach is experiencing continuous channel degradation owing to operation of the Three Gorges Project (TGP) in 2003. Significant retreat processes at composite riverbanks have occurred at local sites of this reach, which may influence the stability of the river regime and the effect of existing river training works. Therefore, bank retreat plays a key role in fluvial processes of the Jingjiang Reach, and it is necessary to predict the long-term processes of bank retreat at typical sections in the reach. In this study, various factors influencing bank retreat in the Jingjiang Reach are investigated, based on bank erosion processes at four sections and the corresponding flow and sediment conditions. It is discovered that fluvial erosion intensity is a dominant factor in controlling the processes of bank retreat in the reach, although other factors, such as bank soil properties, can also influence bank retreat. The bankfull width at a section with severe bank erosion since 2002 is defined as being equal to the sum of the bankfull width in 2002 and the accumulated bank retreat distance after 2002. The magnitude of the bankfull width can be expressed as an exponential function of the previous 5-year average fluvial erosion intensity during flood seasons. The accumulated distances of bank retreat at four sections over the period 2002–2012 are predicted using the proposed empirical relationships, with the calculated bank retreat processes agreeing well with observed data.