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受水动力条件、边界条件等影响,砂卵石分汊河段河床演变规律较为复杂.以长江中下游关洲-芦家河河段为例,分析了典型砂卵石弯曲分汊河段的演变特点.在此基础上,结合三峡蓄水后来水来沙、水动力轴线、泥沙粒径等河段变化特点,研究砂卵石分汊河段演变机理,并分析了砂卵石分汊河段的演变趋势.研究结果表明:自然情况下砂卵石分汊河段水沙输移主要特点为主流线随来流变化在两汊间摆动.在清水下泄河段总体冲刷背景下,河段冲刷主要以沙质河床部分为主,局部区域的淤积主要为推移质的淤积.蓄水后,关洲左汊将继续冲刷发展,芦家河水道沙泓进口淤积将有所发展,石泓的冲刷发展将相对较大,江心碛坝头部还将发生一定幅度的冲刷.
Under the influence of hydrodynamic conditions and boundary conditions, the evolution of the bed of sand and gravel in the Fenghuang section is complicated. Taking the Guanzhou-Lujiahe section in the middle and lower reaches of the Yangtze River as an example, the evolution characteristics of typical sand and gravel bend sections are analyzed Based on this, the evolution mechanism of sand-pebble sub-fluvial section is studied combining with the characteristics of water-sand transfer, hydrodynamic axis and sediment particle size after the Three Gorges Reservoir, and the evolution of sand-pebble sub-fluvial section Trend.The research results show that the main characteristics of water and sediment transport in sand and gravel distributary reach are as follows: The main part of the riverbed is sediment deposition in some areas, which is mainly siltation of sediment. After water storage, Guanzhou Zuojian will continue to scour and develop. Sedimentation of Shahong in Lujiahe channel will be developed, and the scour of Shihong will be relative Larger, Jiang heart moraine dam head will occur a certain amount of erosion.