三峡水库蓄水以来长江中下游干流河床沉积物粒度变化的初步研究

Variation in Grain Size of Sedimentin Middle and Lower Changjiang River Since Impoundment of Three Gorges Reservoir

于2008年在宜昌至徐六径之间的1600km干流河道进行30个横断面取样和分析,与前人于三峡水库蓄水前的取样分析资料进行对比。结果表明:①三峡水库蓄水以来坝下游约400km的干流河床(宜昌至城陵矶)沉积物出现全程粗化,越近大坝粗化越明显,这种沉积物粗化与水库蓄水后坝下游河床出现的强烈侵蚀密切相关;②蓄水前后城陵矶以下的1200km干流河床沉积物粒度的沿程趋势基本一致;③蓄水后河床沉积物仍保持沿程向下游变细且越近河口变化越缓慢的格局。

As the core of fluvial geomorphology,sediment parameters reflect the sedimentary environment in river system.The impoundment of the Three Gorges Dam （TGD） is a doubtless inducement of the erosion of the middle and lower Changjiang （Yangtze） River channel.Compared the sediment samples data collected before TGD and after TGD,we dig out some rules which reflect the impact of the TGD.The results show that 1） caused by the erosion,the grain size of sediment coarsened intensively from Yichang to Chenglingji.Where closed to TGD,the tendency of coursing behaves more apparent.2） The variation in grain size seems to be inconspicuous from Chenglinji to river mouth during 2002-2006.3） The sediment component tends to be finer along the river downstream to river mouth.