RAPID: Collaborative Research: Floodplain Sedimentation from an Extreme Event: The 2011 Lower Mississippi River Flood

RAPID：合作研究：极端事件造成的洪泛区沉积：2011 年密西西比河下游洪水

• 批准号: 1151719
• 负责人: Franklin Heitmuller
• 金额: $ 3.45万
• 依托单位: University of Southern Mississippi
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-09-01 至 2012-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1151719&HistoricalAwards=false
• 关键词: RAPID; Collaborative; Research; Floodplain; Sedimentation

This rapid-response research project will examine the impact of extreme events on the geomorphology of large river floodplains by analyzing overbank deposits associated with the 2011 flood in the lowermost reaches of the Mississippi River alluvial valley in Louisiana and Mississippi. The investigators will draw on and seek to contribute to two bodies of knowledge in physical geography, fluvial geomorphology, and sedimentology: (1) the role of extreme events on sedimentation processes and floodplain construction of large lowland, embanked, meandering rivers and (2) the modern geomorphic adjustment of the Lower Mississippi River in response to flood control. They will gather materials and date to examine possible answers to the following research questions: How do sediment thicknesses and textural characteristics of overbank deposits derived from the 2011 flood directly compare with a previous, large-scale flood (1973) in the study area? Do overbank sedimentation thicknesses differ for floodplain transects of various embanked (leveed) widths? Do advective (longitudinal) or diffusive (lateral) sedimentation mechanisms control overbank deposition along embanked floodplains? They will engage in field work, laboratory analyses of overbank sediments, geographic information system-based evaluations of LiDAR-derived floodplain elevations, and quantitative analyses. They will determine overbank sediment thickness at locations identical to a published study documenting the 1973 flood. They will infer overbank flow direction from preserved sedimentary structures, quantify sediment texture, associate sedimentary characteristics with floodplain elevation and distance from the channel, and compare the 2011 data with data from the 1973 flood. Their work will focus on a reach of the Lower Mississippi that is the only location to receive drainage from all tributaries and has the highest discharge within the Mississippi River basin, thereby sampling flood deposits associated with record flood stages from one of the largest recorded discharge events in North America. The field study design will permit a direct examination of the impact of flood-control levees on sedimentation. In contrast to the western side of the river, the eastern floodplain reach is not embanked, which permits unimpeded overbank sediment transport from the river to the valley wall. The study area is upstream from the most important flood-control structure in North America, the Old River Control Structure, whose function is partially dependent on stage-discharge relations that adjust with floodplain elevation. Furthermore, the study reach has been shown to have increasingly high stages for a given flood discharge since the 1980s.While it is rare to have an opportunity to sample overbank deposits from large floods on large rivers, it is unprecedented to have the opportunity to sample overbank deposits from two large floods within the same reach, this project will resample the exact locations from one of the most cited studies in the flood sedimentation literature (Kesel et al, 1974). The results of this project therefore are expected to have broader relevance for environmental scientists, including hydrologic and hydraulic engineers, physical geographers, riparian biologists, geologists, and instream-flow specialists. The project will provide field-, lab-, and computationally based education and training experiences for graduate and undergraduate students, and it will provide valuable information and insights to floodplain managers and policy makers.

这个快速响应研究项目将通过分析路易斯安那州和密西西比州密西西比河冲积谷的2011年洪水范围内与2011年洪水相关的超银行沉积物来研究极端事件对大型河流洪泛区的地貌的影响。 研究人员将借鉴并寻求为物理地理学，河流地貌学和沉积学方面的两个知识物体做出贡献：（1）极端事件在沉积过程中的作用和大小低地，弯曲的河流，蜿蜒的河流和（2）下层密西西比河的现代地貌调节的作用。 他们将收集材料和日期，以检查以下研究问题的可能答案：从2011年洪水中衍生出的过度银行沉积物的沉积物厚度和质地特征如何直接与研究区域中以前的大规模洪水（1973年）相比？ 在各种堤防（伸出的）宽度的洪泛区样带上，超银行沉积厚度有所不同吗？ 对流（纵向）或扩散（横向）沉积机制是否控制了沿路堤洪泛区的银行沉积？ 他们将从事现场工作，对银行沉积物的实验室分析，基于地理信息系统的基于LIDAR衍生的洪泛区高程的评估以及定量分析。 他们将确定与1973年洪水的公开研究相同的位置上的堤岸沉积物厚度。 他们将从保存的沉积结构中推断出堤岸的流动方向，量化沉积物纹理，将沉积物特征与洪泛区高程相关联和距离通道的距离，并将2011年数据与1973年洪水的数据进行比较。 他们的工作将集中在密西西比州下部的覆盖面上，这是唯一接收所有支流排水的地点，并且在密西西比河河流域内的排放量最高，从而抽样了与北美最大记录的排放事件之一相关的与创纪录的洪水阶段相关的洪水沉积物。 现场研究设计将直接检查洪水堤对沉积的影响。 与河的西侧相反，东部洪泛区河流没有堤防，这允许从河流到山谷墙的不受阻碍的超银色沉积物运输。 研究区域是北美最重要的洪水控制结构，即旧的河流控制结构，其功能部分取决于阶段解散关系，该关系与洪泛区高程有关。 此外，自1980年以来，该研究的影响范围已经显示出给定洪水的阶段越来越高。尽管很少有机会从大河流上的大洪水中品尝过育的沉积物，但没有前所未有的机会可以有机会品尝从同一项目中的两个大洪水中的两次大洪水中的过度银行沉积物，这将在同一项目中从一项洪水中分散了一项洪水的定期。 因此，该项目的结果有望与环境科学家，包括水文和液压工程师，物理地理学家，河岸生物学家，地质学家和仪表流专家具有更广泛的相关性。 该项目将为研究生和本科生提供基于现场，实验室和计算的教育和培训经验，并将为洪泛区经理和政策制定者提供有价值的信息和见解。