中文摘要：

通过分析渭河下游三个水文站点2002-2009年河道横断面及悬移质中值粒径的变化，发现渭河下游河道近期出现新的变化特点，河道展宽，平滩流量下河道容积扩大，悬移质中值粒径减小，河道冲刷。从水沙变化、潼关高程和中值粒径变化分析了河道近期发生冲刷的原因。结果表明：2003年多次的漫滩洪水，高含沙洪水与低含沙洪水的共同作用及洪水期流量一含沙量特殊的组合特征，拓宽了河道的容积，大大提升了渭河下游河道的行洪能力；来沙系数变化是渭河下游近期河道冲刷的主要原因；悬移质中值粒径的减小以及潼关高程的稳定也对河道冲刷有所贡献。

英文摘要：

Through analyzing the measured channel cross-sections at Xianyang, Lintong and Huaxian stations during the period of 2002 -2009, this study investigates the characteristics of fluvial processes of the Lower Weihe River in recent years and the driving forces for the changes. The results indicate that the river channel was broadened, the channel capacity at the bankfull discharge was enlarged, indicating that the channel of the Lower Weihe River was undergoing a change from deposition to erosion. Studies are made on the connections of channel changes with the changes of flow, sediment load, suspended sediment size, and Tongguan eleva- tion. The results show that the big floods occurred in the year of 2003 expanded the channel capacity, resulted in a great increase of the flood carrying capacity of the Lower Weihe River. Also, the low incoming sediment coefficient （the ratio of sediment concentration to water discharge） was another main cause of the channel scouring, and the larger sediment transport capacity of the river due to the decreasing median diameter of sus- pended sediment load and the declining and stable Tongguan elevation in recent years might be another cause for the recent channel adjustment.