近60年渭河下游自然裁弯成因分析

渭河下游是典型的弯曲型河道,过去60年频繁地发生自然裁弯,其触发原因、形成过程和演变规律缺少深入的研究。渭河下游的裁弯是河湾横向演变到一定阶段后在汛期洪水冲刷作用下发生临界突变,直接影响河道平面形态、上下游河床冲淤和局部河段的防洪安全。基于原型观测、水沙数据(1960-2013)和遥感影像(1990-2015),分析了渭河下游裁弯事件的水沙条件、影响因素和裁弯时空演变过程及其原因。渭河下游发生的18次裁弯的主要原因是受三门峡建库后渭河下游边界条件的改变,包括潼关侵蚀基准面淤积抬高,凸岸边滩及内侧平原缺少粘性成分,抗冲性差,同时也受渭河下游来水来沙条件的变化及其高含沙洪水的影响。

Study on meander cutoffs of the Lower Wei River in recent 60 years

The lower reach of Wei River is a typical meandering channel,where natural cutoffs frequently occurred since 1950s.Meander cutoff is a critical mutation event under the effect of floods when the transverse migration to a certain stage,which directly affects the fluvial processes of the meandering channel of upstream and downstream,and flood control.Influence factors and spatial-temporal evolution of 18 meander cutoffs in the lower Wei River last 60 years are systematically analyzed,using previous observations,hydrological data (1960-2013) and remote sensing images (1990-2015).Results show that three primary factors control the frequency of meander cutoffs in Low Wei River,including the change of boundary conditions induced by the Sanmenxia Reservoir impoundment (i.e.,base level of the Tongguan elevation rising,lack of clay contents,lower resistant-erosion),variation of incoming water and sediment,and the hyperconcentration flood.