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首页> 外文期刊>Journal of geophysical research. Earth Surface: JGR >Suspension of bed material over sand bars in the Lower Mississippi River and its implications for Mississippi delta environmental restoration
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Suspension of bed material over sand bars in the Lower Mississippi River and its implications for Mississippi delta environmental restoration

机译：密西西比河下游沙洲上的河床物质的悬浮及其对密西西比三角洲环境恢复的影响

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Understanding specific pathways for sand transport in the lower reaches of large rivers, including the Mississippi, is a key for addressing multiple significant geologic problems, such as delta building and discharge to the oceans, and for environmental restoration efforts in deltaic environments threatened by rising sea levels. Field studies were performed in the Mississippi River 75-100 km upstream of the Gulf of Mexico outlet in 2010-2011 to examine sand transport phenomena in the tidally affected river channel over a range of discharges. Methods included mapping bottom morphology (multibeam sonar), cross-sectional and longitudinal measurements of water column velocity and acoustic backscatter, suspended sediment sampling, and channel-bed sampling. Substantial interaction was observed between the flow conditions in the river (boundary shear stress), channel-bed morphology (size and extent of sandy bedforms), and bed material sand transport (quantity, transport mode, and spatial distribution). A lateral shift was observed in the region of maximum bed material transport from deep to shallow areas of subaqueous sand bars with increasing water discharge. Bed material was transported both in traction and in suspension at these water discharges, and we posit that the downriver flux of sand grains is composed of both locally- and drainage basin-sourced material, with distinct transport pathways and relations to flow conditions. We provide suggestions for the optimal design and operation of planned river diversion projects. Key Points There are two distinct sources of sand in the lower Mississippi River Feedback occurs between flow, bed morphology, and bed material suspension These results are relevant to planned river management projects
机译：了解解决包括密西西比河在内的大河下游沙流的具体途径，对于解决多个重大地质问题（例如三角洲建设和向海洋排放）以及在受到海平面上升威胁的三角洲环境中的环境恢复工作方面至关重要。水平。在2010-2011年，在墨西哥湾出口上游75-100公里的密西西比河中进行了实地研究，以研究在一系列排放量中受潮汐影响的河道中的沙土运输现象。方法包括测绘底部形态（多束声纳），水柱速度和声反向散射的横截面和纵向测量，悬浮沉积物采样和河床采样。观察到河流的流动条件（边界剪切应力），河床床形（沙质床形的大小和范围）和床物质砂的运输（量，运输方式和空间分布）之间存在实质性的相互作用。随着排水量的增加，在最大床层材料从水下砂棒的深部到浅部输送的区域中观察到横向偏移。在这些排水处，床层物料既有牵引力又有悬浮液的运移方式，我们认为，沙粒的下游通量是由本地和流域盆地来源的物料组成的，它们具有独特的输送路径和与流动条件的关系。我们为规划的引水工程的优化设计和运行提供建议。要点密西西比河下游有两种不同的沙源：在流量，河床形态和河床物质悬浮之间发生反馈。这些结果与计划中的河流管理项目有关

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