Abstract: According to the adjustment characteristics of the downstream riverbed of dam after the operation of the Three Gorges Project, we developed a generalized mathematic model for predicting the longitudinal and lateral deformation of riverbed. The computational module of bed evolution is combined with that of bank retreat in this model. Taking cross-section Jing34 in the Upper Jingjiang Reach as a study object, we calculated the longitudinal and lateral deformation processes during the 2006 and 2008 hydrological years by using the generalized model. The predicated erosion volume of the riverbed, total bank retreat width and the failed bank profile were all in good agreement with the measured data. In addition, the effect of the riverbed evolution on the bank profile of cross-section Jing34 in 2006 was also investigated. Simulated results indicate that the position of river bed scouring is mainly concentrated in the low flow channel, and the maximum increase in height of river bank is about 1.9m induced by the river bed erosion. Moreover, the calculated total bank retreat width under the scenario with bed evolution is 20% greater than that under the scenario without bed evolution. Therefore, the bed evolution increases the relative bank height, which can reduce the safety factor of bank.

Key words: Upper Jingjiang Reach, composite riverbank, bank retreat process, longitudinal erosion and deposition, generalized simulation