摘要
长江沙卵过渡带位于三峡水库出口至江汉平原之间,其对水沙变化的响应关系着长江中游河道的防洪、航运规划和生态栖息地功能。基于大量实测数据,系统研究了1955~2021年变化水沙条件下长江沙卵过渡带冲淤演变及水动力变化特征。结果表明:1955~2021年长江沙卵过渡带年径流量变化较小,而输沙量变化显著,推移质输沙量和悬移质输沙量分别于1982年和2003年发生锐减;从冲刷时间分布来看,长江沙卵过渡段的冲刷调整主要集中在1975~1991年葛洲坝独立运行(施工)期和2003~2008年三峡水库蓄水初期,2016年后冲刷幅度明显减小。从冲刷空间分布来看,1975~1991年沙卵过渡带的冲刷部位集中于平滩河槽以下,2003年三峡水库运行后其冲刷特征则转变为“滩槽均冲”,且随着时间推移,主槽附近河床趋于稳定,河道冲刷变形集中在远离主槽的边滩、支汊等部位。上游次饱和水流下泄导致的沿程冲刷以及下游枯水位下降、河床沿程不均匀下切等引起的溯源冲刷是建坝后长江沙卵过渡带冲刷变形的主因。在河道整体冲刷背景下,1975~2021年沙卵过渡带洪水水面线形态相对稳定,受河道冲刷,床面糙度增加以及洞庭湖顶托作用联合影响,宜昌—枝城段洪水比降略微增大,沙市以下洪水比降略微减小;相比之下,枯水水面线形态变陡,且随着河床比降趋陡以及下游水位的持续下降,局部水面比降显著增大,其中毛家花屋—陈家湾段平均水面比降增幅超1,枯期水流输沙能力明显增强。
Changjiang gravel-sand transition was located between the Three Gorges and Jianghan Plain,and its response to the altered flow-sediment regimes showed a significant implications for flood control,navigation,and the ecological health of the middle Changjiang River.Based on detailed field observations,we systematically examined the river evolution and dynamic adjustments of the gravel-sand transition in altered flow-sediment regimes from 1955~2021.The results indicated that the annual runoff exhibited minimal variation,fluctuating slightly between years,whereas the annual sediment supply underwent abrupt changes,with a sharp decline in bed-load supply in 1982 and in suspended load supply in 2003.Regarding temporal erosion patterns,significant erosion within the gravel-sand transition was most pronounced during 1975~1991,coinciding with the operation of the Gezhouba Dam,and at the early stages of the Three Gorges Reservoir operation from 2003 to 2008,with the erosion intensity markedly decreasing after 2016.Regarding spatial erosion patterns,the intensive channel erosion was primarily concentrated in the bankful channel from 1975 to 1991.However,following the operation of the Three Gorges Reservoir in 2003,the erosion shifted to full-section down-cutting.As the bed material in the main channel became coarser,the riverbed became increasingly resistant to erosion,causing the intensive erosion to gradually shift to areas such as shoals and secondary branches away from the main channel.In the dammed Changjiang gravel-sand transition,erosion was driven primarily by the streamwise erosion from upstream to downstream induced by the clear erosive water released from the dams,and the headcut erosion from downstream to upstream caused by lowering downstream water levels and varying degrees of riverbed down-cutting.Despite the channel degradation,the flood flow level water surface profile remained relatively stable from 1975 to 2021,with a minimal inter-annual variation.The combined effects of riverbed down-cutting,bed surface coarsening,and backwater from Dongting Lake resulted in a slight increase in water surface slope during flood flows between Yichang and Zhicheng,and a slight decrease downstream of Shashi.Conversely,at low flows,the water surface profile steepened year by year.As the bed profile steepened and downstream water levels lowered,the local water surface slope increased,with an average slope rise of 1 in the Maojiahuawu to Dabujie region,thereby enhancing the low flow competence.
作者
何子灿
郭小虎
孙昭华
渠庚
邹宇雄
HE Zican;GUO Xiaohu;SUN Zhaohua;QU Geng;ZOU Yuxiong(River Research Department,Changjiang River Scientific Research Institute,Wuhan 430010,China;State Key Laboratory of Water Resources Engineering and Management,Wuhan University,Wuhan 430072,China;Key Laboratory of River and Lake Regulation and Flood Control in the Middle and Lower Reaches of the Changjiang River of Ministry of Water Resources,Changjiang River Scientific Research Institute,Wuhan 430010,China;Changjiang Survey,Planning,Design and Research Co.,Ltd.,Wuhan 430010,China)
出处
《水利水电快报》
2025年第3期25-32,共8页
Express Water Resources & Hydropower Information
基金
中央级公益性院所基金项目(CKSF2023343/HL,CKSF2024326/HL)
国家自然科学基金项目(52409080,U2240206)。
关键词
冲淤演变
水动力变化特征
长江沙卵过渡带
三峡水库
deposition and erosion evolution
dynamics adjustments characteristics
Changjiang gravel-sand transition
Three Gorges Reservoir
