三峡水库运用后武汉天兴洲分汊河段演变规律及趋势

Regularity and Trend of the Evolution of Tianxingzhou Braided Channel in Wuhan after Three Gorges Reservoir Operation

利用武汉天兴洲分汊河段的水文与地形等实测资料,分析了水沙变化条件下本河段分流区水流动力轴线、流速与含沙量分布等变化特点,阐述了本河段水沙运动与河床演变的相互作用机制,预测了本河段的演变趋势。研究结果表明:本河段分流区水流动力轴线随流量增加而逐渐偏向左侧变化,其变化规律形成了左汊的有利进流条件与较长时间维持本河段分汊的河势格局,但因上游来沙的大幅度减少,右汊冲刷幅度较左汊大,有利于右汊继续维持主汊地位。

According to observed data of hydrology,sediment and topography of the bending braided channel at Wuhan＇s Tianxingzhou reach in the middle Yangtze River,we analysed the changes of flow dynamic axis,flow velocity and sediment concentration distribution in the presence of varying flow and sediment. We also expounded the interaction between runoff and sediment load and fluvial processes,and predicted the evolution trend. Results suggest that the flow dynamic axis in river diversion zone shifts to the left with the flow increasing,giving rise to favorable conditions for the left branch and a long-term braided river pattern. But as the incoming sediment from the upstream reduces remarkably,erosion in the right branch is more severe than that in the left branch,favorable for the right branch to maintaining as the main branch.