三峡水库蓄水后城陵矶至九江段河道冲淤调整机理.

The construction of a large-scale water conservancy project has caused the adjustment of the scouring and silting of the downstream river channel， which has a significant impact on the ecological environment， flood control and channel transportation. Since the trial experimental impoundment of the Three Gorges Dam in 2008， the down¬stream erosion of Chenglingji has intensified. To explore the adjust characteristics of scouring and silting and the driv¬ ing mechanism of tlie downstream erosion of a river channel during a water control project， the spatial evolution char¬acteristics and transverse morjDhological variation of the reach from Chenglingji to Jiujiang reach were analyzed. The results show that the scouring of the lowflowchannel in the Chenglingji—Jiujiang reach has intensified， and the mor¬phological changes since 2008 have mainly been concentrated in the medium flow channel， of which the proportion of the evolution volume accounts for more than 90% $ the transvers changes shows scouring and incising， while a sec¬tional view displays narrowingand deepening. On the basis of theestablished empirical relationship between the reach-scale medium channel dimensions and the accumulated sediment transport capacity in each discharge interval during 175 m experimental water storage period from 2008 to 2016，this paper indicates that the discharge of 29 000—31 000 m3/s at Luoshan Station and that of 31 000—33 000 m3/s at Hankou Station can be regarded as characteristic discharges corresponding to the average top levels of braided channel bars，which are of morphological significance in constraining the pasing flow in the medium flow channel and guaranteeing that tlie water transport ca¬pacity is the strongest. The geomorphic impact of flow below the characteristic discharge was more prominent during 2008 —2016 $ this impact resulted in the adjustment of scouring and silting being mainly concentrated in the medium flow channel. Moreover， river channel erosion has intensified because， in addition to the construction of waterway regulation projects， the volume of transported sediment with d > 0. 125 mm has largely diminished. [ABSTRACT FROM AUTHOR]