中文摘要：

以荆江监利河段为例,采用三维水沙模型与二元结构岸滩崩塌力学模式相结合,构建了考虑边岸、洲滩崩塌的分汊型河道演变三维数值模型。依据2003年11月～2006年7月监利河段的实测资料对模型进行了验证,模拟结果与实测结果吻合较好,能够模拟岸滩崩塌及深槽摆动的特点。以此为基础,对三峡水库蓄水运用初期,该河段在不同岸滩抗冲性条件下的演变进行了概化模拟分析,结果表明：上游水库蓄水运用后,该河段河床将会进一步产生冲刷;岸滩可冲条件下,河道冲刷的同时还伴随着岸滩坍塌、河道摆动的发生;岸滩不可冲时,将以河床下切为主,横断面形态逐渐向窄深方向发展;在一段时期内,右汊将仍维持为主汊。

英文摘要：

A 3-D mathematical model of braided channels with bank failure was developed for the Jianli reach of the middle Yangtze by using a 3-D flow and sediment transport module and a bank erosion module with composite structure. This model was verified with the in-situ observed data of bed deformation from Nov. 2003 to July 2006, and its calculations agree well with the measurements. It was applied to simulation of morphological changes in this reach under different bank erodibility conditions at the initial filling stage of the Three Gorges reservoir （TGR）. Results demonstrate that at this stage, a decrease in sediment load brought forth river bed scour. As a result, failure of high-erodibility bank caused river bed degradation and lateral channel migration, while in the reaches of strong bank anti-scour ability, only bed degradation occurred, forming narrow and deep cross-sectional profiles. During the early filling of the TGR, the right branch of Jianli reach has remained as the main channel.