节点广泛存在于分汊河段,对汊道的影响至关重要,研究节点对汊道演变的影响,对指导河道治理具有重要意义。长江下游马当河段为典型的微弯分汊河型,先后有骨牌洲、棉外洲、瓜子号洲等将河段多级分汊,依次有小孤山、彭郎矶、马当嘴、马当矶等山体形成控制节点。建立了马当河段二维水沙数学模型,在验证的基础上,从水流及河床冲淤变化的角度,结合河床演变,探索各个汊道分流比调整后对上下游河段的影响,分析了节点在汊道演变中的控制作用。研究结果表明:经过小孤山-彭郎矶节点的控制,马当河段进口边界条件较为稳定,上游河势发生较大变化时,马当河段河势变化微小;经过马当矶-马当嘴节点的控制,棉外洲左右槽分流比变化为23.3%~58.1%时,对节点下游主流和河床冲淤的影响主要集中在2~2.5 km以内,影响范围有限。通过采用数学模型和河床演变分析相结合的方法,探索汊道之间演变的相互影响,分析节点的控制作用,为河道治理提供指导意见。
Abstract
Nodes, widely exist in bifurcated channels, have essential impact on river bed evolution. We explored the impact of nodes on bifurcated channel evolution and provided guidance for river regulation by combining mathematical modelling and riverbed evolution analysis. Madang reach, which lies in the downstream of Yangtze River, is a typical slightly-bent and bifurcated channel. Many sandbars or shoals bifurcate this reach, such as Gupaizhou sandbar, Mianwaizhou shoal and Guazihaozhou sandbar. There are some nodes formed by mountains in Madang Reach, like Xiaogushan, Penglangji, Madangji, and Madangzui. A 2-D mathematical model of Madang reach was established and verified. From the perspective of water flow and riverbed evolution, the impact of sub-branches’ diversion ratio variation on their upstream and downstream channels, and the nodes’ influence on riverbed evolution were further analysed. Results reveal that by controlling the node of Xiaogushan-Penglangji, the incoming flow at the inlet of Madang reach is stable, and is slightly affected by its upstream variation. Due to the modification of Madangji-Madangzui node, when the diversion ratio of Mianwaizhou shoal varies from 23.3% to 58.1%, its impact on main flow and river bed erosion & deposition only covers a limited distance of 2-2.5km downstream of Madangji.
关键词
分汊河段 /
节点 /
分流比 /
马当河段 /
长江下游
Key words
bifurcated channel /
node /
diversion ratio /
Madang reach /
downstream of Yangtze River
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基金
国家973计划资助项目(2012CB417002);“十二五”国家科技支撑计划项目(2012BAB04B03)
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