三峡水库蓄水后上荆江不同河床组成江心洲的演变过程及其机制  

Evolution process and mechanism of mid-channel bars composed of different bed materials in the Upper Jingjiang Reach after the Three Gorges Project operation

作　　者：毛禹 夏军强[1] 周美蓉[1] 邓珊珊[1] Mao Yu;Xia Junqiang;Zhou Meirong;Deng Shanshan(State Key Laboratory of Water Resources and Hydropower Engineering Science,Wuhan University,Wuhan 430072,P.R.China)

机构地区：[1]武汉大学水资源与水电工程科学国家重点实验室,武汉430072

出　　处：《湖泊科学》2023年第2期673-683,共11页Journal of Lake Sciences

基　　金：国家自然科学基金项目(51725902,U2040215,52109098,52009095);博士后创新人才支持计划项目(BX2021228)联合资助。

摘　　要：三峡及上游梯级水库群运用后,大坝下游江心洲以冲刷为主,直接影响分汊河段河势条件及航道边界的稳定性。本文采用卫星遥感影像、实测水沙及固定断面床沙级配等资料,分析上荆江枝江、沙市河段中不同河床组成江心洲的演变过程及其机理。结果表明:(1)三峡水库蓄水后(2003-2019年),沙市段沙质江心洲较枝江段卵石夹沙质江心洲萎缩更为显著,出露面积的减幅分别达31%和24%。(2)以关洲和金城洲分别代表卵石夹沙质和沙质江心洲,三峡工程运用后关洲洲头形态较为稳定,受无序采砂的影响其沙质组成的洲尾面积显著减小,而金城洲面积萎缩程度更大。(3)床沙组成对江心洲冲刷程度差异具有重要影响,关洲洲头较金城洲抗冲性更强,与其床沙在年内达到起动条件的数量更少、时长更短有关;建立了江心洲面积与水流冲刷强度及相对水深的定量关系,该关系能综合考虑水沙变化与床沙组成调整的影响,能更好地反演近期江心洲的面积变化特点。After the operation of the Three Gorges cascade reservoirs(TGP),the mid-channel bars(MCBs) downstream of the dam were generally scoured and shrank,which directly affects the river regime in ana-branching reaches and the stability of the navigation channel boundaries.The morphological evolution processes and mechanisms of MCBs in the Zhijiang(ZJ) and Shashi(SS) sub-reaches of the Upper Jingjiang Reach were analyzed,using the remote sensing images,the hydrological data and the measured riverbed compositions.The results indicate that:(ⅰ) During the post-TGP period(2003-2019),the sandy MCBs in the SS subreach shrank more significantly than the one in the ZJ subreach.The total exposed area of the former decreased by 31%,while the latter decreased by 24%;(ⅱ) Guanzhou(GZ) and Jinchengzhou(JCZ) were taken as the representative sandy-gravel and sandy MCBs,respectively.During the post-TGP period,the head zone of the GZ MCB was relatively stable,and the reduced area was mainly in the bar-tail zone due to the illegal sand mining,while the JCZ MCB had a more obvious erosion trend;(ⅲ)The bed-material composition had an important influence on the erosion degree of MCBs.The GZ MCB had a stronger anti-erosion capacity than the JCZ MCB,which was related to the less amount and duration of bed material that can reach the incipient condition in a hydrological year.Moreover,different empirical relationships were developed between the exposed area of MCB,fluvial scour intensity,and relative water depth.It is found that comprehensive consideration of the effects of flow-sediment condition and bed-material composition adjustment can better explain the recent variations in the exposed areas of MCBs.

关 键 词：江心洲演变 河床组成 上荆江河段 三峡工程 

分 类 号：TV147.5[水利工程—水力学及河流动力学]