近期长江荆江河道演变特点

River channel evolution characteristics of Jingjiang reach of the Yangtze river in the late period

从长系列资料看,上游来水量无趋势性增大或减少,来沙量自20世纪90年代以来明显减少。入洞庭湖三口分流分沙呈减少趋势,尤其以藕池口衰减最为突出。1998年大水造床作用明显,上荆江滩槽皆冲,以冲滩为主;下荆江表现为冲槽淤滩,总体呈淤积状态。还对重点河弯,如沙市、石首河段,自1998年大水以来的最新演变情况作了详细分析,主要特点表现为沙洲移动、主流线摆动,顶冲点普遍下移,崩岸时有发生。

From long series of data,the water coming from upstream of the Jingjiang reach of the Yangtze river has no increasing trend and the sediment has decreased obviously since 1990s. The flow and sediment diverted into the Dongting lake through 3 diversion outlets presented decreasing trend, especially for Ouchi diversion outlet. 1998 big flood had obvious influence on river bed evolution. Both the river channel and beach of upper Jingjiang reach were scoured and the beach scouring was more serious. For the lower Jingjiang reach, the river channel was scoured and the beach was silted up, and in general, the lower Jingjiang reach presented silting state. This paper analyses emphatically the evolution of the main river reaches since 1998 big flood, such as Shashi and Shishou reaches. The change characteristics of the river channel are sediment shoal movement, main streamline swing, the head-on scouring site moving downstream generally and bank collapse occurring frequently.