中文摘要：

沙市河段为三峡水库下游第一个沙质河段,对水库蓄水拦沙的响应较为明显,且河道内洲滩密集,消长频繁,为长江中游典型的滩群河段。通过分析三峡水库蓄水前后沙市河段内滩群演变特征的异同,并结合实测水力因子、参考实体模型试验成果,探讨了蓄水前后滩群演变差异的原因。结论表明：该河段滩群内部通过此消彼长、散乱发展等形式进行着局部格局的调整,但右岸腊林洲边滩始终在滩群演变中居于主导地位,其他滩体则是该边滩在不同水流条件下的另一种表现形式,这一特征不会因上游水库蓄水拦沙而改变;水库蓄水后14 000~20 000 m3/s流量持续时间延长,是导致滩体散乱化发展的主要原因。

英文摘要：

Mutual influences and interdependences of deposited bars in alluvial river are very complicated,which vary with river boundaries and income water and sediment. This paper deals with evolution processes of the multiple bars taking example of Shashi reach,the first sandy sub-reach downstream from Three Gorges Dam. Referring with results of physical model,difference of bars evolution between pre-dam and post-dam,and its causes are studied through field data analysis. Result shows that partial adjustment occurs on the bars taking form of enlarging-shrinking and dispersing under the new flow and sediment regime. The evolution processes are dominated on the Lalin sidebar,which will take form of mid-channel bar and point bar under different fluvial condition. The progresses of this reach is mainly caused by sediment deposition of the upsteam reservoirs impoundment.