人民长江 ›› 2021, Vol. 52 ›› Issue (3): 1-8.doi: 10.16232/j.cnki.1001-4179.2021.03.001

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边界条件对荆江监利河段枯水河槽形态调整的影响

林芬芬,夏军强,周美蓉,邓珊珊   

  • 出版日期:2021-03-28 发布日期:2021-04-23

Influence of boundary conditions on low-water channel geometry adjustments of Jianli Section, Jingjiang Reach of Changjiang River

LIN Fenfen, XIA Junqiang, ZHOU Meirong, DENG Shanshan   

  • Online:2021-03-28 Published:2021-04-23

摘要: 受三峡工程运用及洞庭湖出流顶托的影响,荆江监利河段的进口水沙过程及其出口侵蚀基准面发生改变,河床调整剧烈,枯水(5 000 m3/s流量)期河槽形态发生变化,对航道条件产生了一定影响。基于监利河段实测水沙及断面地形资料,首先通过一维水动力学模型计算了该河段2002~2017年各固定断面的枯水河槽形态参数(枯水河槽面积、宽度、水深及宽深比),其次采用河段平均方法计算了监利河段尺度的枯水河槽特征值,最后建立了以上特征参数与上下游边界条件之间的综合关系。结果表明:(1)受大规模护岸及护滩工程控制,近期监利河段枯水河床调整以水深变化为主,2002~2017年河段尺度的水深累计增加了0.49 m,相应宽深比减小了8%,河床趋于窄深,航道条件整体改善;(2)在部分过渡段与急弯段(如大马洲及七弓岭河段),边滩冲刷剧烈,断面趋于宽浅,航道条件恶化;(3)枯水河槽形态调整受上下游边界条件的共同控制,其中河段枯水河槽水深、面积及宽深比与前5 a汛期平均水流冲刷强度(上边界条件)以及上下游水位差(下边界条件)密切相关。定量分析了在上下游边界条件共同作用下,近期监利河段枯水河槽调整过程及其对航道条件的影响,建立的经验公式可用于预测该河段枯水河槽形态的变化过程,研究成果有助于定量评估监利河段的航道条件。

关键词: 监利河段; 枯水河槽; 一维水动力模型; 航道条件; 上下游边界; 三峡工程;

Abstract: Owing to combined effects of the upstream operation of the Three Gorges Project(TGP),and the downstream confluence of the Dongting Lake, the flow-sediment input and local base-level of the Jianli Section, Changjiang River Jingjiang Reach were changed, which caused remarkable adjustments in the low-water channel geometry and thus affected the navigation condition.Based on the measured hydrological and topographic data, low-water channel geometry variations in section and reach scale(area, width, depth and width-depth ratio) from 2002 to 2017 were quantified by a one-dimensional hydrodynamic model and a reach-averaged method.Finally, the empirical relationships between the reach-scale variables and the boundary conditions were proposed.Calculated results indicated that:(1) Because of various bank protection works, the channel evolution in Jianli Section was mainly characterized by the variation in the depth with an increase of 0.49 m in the reach-scale low-water depth and a 8% reduction in the width-depth ratio from 2002 to 2017,leading to a narrower and deeper channel geometry and thus an improvement for the navigation condition;(2) However, the width-depth ratios at low water increased in local transit reaches or sharp bends such as Damazhou and Qigongling due to the dramatic erosion of the central-bar and convex point-bar, which resulted in the deterioration of the navigation condition in these local reaches;(3) Variation in the low-water channel geometry was controlled by both the upstream and downstream boundary conditions, and the reach-scale low-water channel dimensions(depth, area and width-depth ratio) could be expressed by a power function of the previous five-year average fluvial erosion intensity(upstream control) and the corresponding water level difference between the inlet and the outlet(downstream control).Recent channel evolution of the Jianli Section, Jingjiang Reach and its effect on the navigation condition were investigated quantitatively under upstream and downstream controls.The proposed empirical relationships can be used to predict the channel geometry adjustments in the study reach.These findings are applicable to estimating the navigation condition in the Jianli reach.

Key words: Jianli reach; low-water channel geometry; one-dimensional hydrodynamic model; navigation condition; upstream and downstream boundary; Three Gorges Project;