三峡水库的运行显著改变了河流原有的水动力条件,引起江心洲形态冲淤调整。为进一步探究三峡水库蓄水对江心洲形态调整的影响,选取库区5个典型江心洲为研究对象,采用Landsat遥感影像以及三峡水库2003—2017年实测的地形和水沙资料,定量分析了不同阶段江心洲的形态调整及时空演变特征。研究表明:伴随三峡库区水位波动,江心洲出露面积逐渐减少,河床呈现累计淤积态势,加快了江心洲的冲淤变化,其中156 m蓄水高程(2006年10月—2008年10月)的淤积强度最大,而2012年后淤积显著变缓;在空间尺度上,距离大坝越远,江心洲淤积强度越小,变动回水区江心洲因受采砂影响,河床局部地形出现不规则变化;同时,受三峡回水影响,江心洲发育模式改变,洲尾顺水流朝下游发育淤长,洲头受清水冲刷垮塌。
Abstract
The operation of the Three Gorges Reservoir has significantly altered the original hydrodynamic conditions of the river and led to adjustments in the morphology of central bars. To further investigate the effects of Three Gorges Reservoir impoundment on the morphological adjustments of central bars, we selected five typical central bars in the reservoir area as study objects. Using Landsat remote sensing images and terrain and water-sediment data from 2003 to 2017, we quantitatively analyzed the spatial and temporal evolution characteristics of the morphological adjustments of the central bars at different stages. Results showed that with the fluctuation of the water level in the Three Gorges Reservoir, the exposed area of central bars gradually decreased, and the riverbed showed an accumulated siltation trend, which accelerated the morphological changes of central bars. The strongest siltation occurred at a water storage elevation of 156 m (October, 2006 to 2008), while siltation significantly attenuated after 2012. At spatial scale, the further away from the dam, the smaller the siltation intensity of central bars. Due to sand mining, central bars in the area affected by the backflow of the reservoir were subjected to irregular changes in local riverbed topography. Meanwhile, the backflow of the Three Gorges Reservoir changed the development mode of central bars. Specifically, the downstream end of the bars developed and was silted towards the downstream, while the upstream end was eroded by clear water flow.
关键词
江心洲 /
冲淤调整 /
水沙变化 /
Landsat遥感影像 /
形态时空演变 /
三峡水库
Key words
central bar /
scouring and silting adjustment /
flow-sediment variation /
Landsat remote sensing image /
morphological spatial and temporal evolution /
Three Gorges Reservoir
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基金
国家自然科学基金项目(51779241);中国科学院青年创新促新会项目(2018417,2021385);三峡后续工作科研项目(5000002021BF40001);重庆科技局中央引导地方科技发展专项(2021000069)
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