ABSTRACT
The Jingjiang Reach in the Middle Yangtze River is experiencing continuous channel degradation due to the operation of the Three Gorges Project (TGP) in 2003, and 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 the 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 fluvial and non-fluvial factors influencing bank retreat in the reach have been investigated, based on the corresponding flow and sediment conditions, and it is discovered that non-fluvial erosion factors such as the bank soil properties can influence bank erosion, but fluvial erosion intensity is a dominating factor in controlling the processes of bank retreat in the reach. The bankfull width at a section with severe bank erosion since 2002 is regarded to equal the sum of the bankfull width in 2002 and the accumulated bank retreat distance after 2002, with the magnitude being expressed by an exponent function of the previous 5 -year average fluvial erosion intensity during flood seasons. The accumulated distances of bank retreat at two sections over the period from 2002 to 2012 were predicted using the proposed empirical relations, with the predictions agreeing well with the observed data.
