Morphodynamics of Complex Meander Bends on Large Rivers

该项目将结合最先进的现场测量技术和河流过程的数学建模，探索大型河流复杂曲流弯曲中水流、泥沙运动和河道变化之间的相互作用。这项研究将解决以下问题：弯曲形状的复杂性如何影响水流和沉积物的运输，这些影响如何随不同的流量水平而变化，以及这些影响如何结合起来决定大型曲流弯曲形状的长期变化。位于伊利诺斯州和印第安纳州交界处的沃巴什河，是美国最后一条几乎不受管制的自由流动的蜿蜒河流之一，将作为试验点。这项研究将使用新的声学技术，测量水运动的三维模式，沉积物的运输和不同形状的曲流弯曲在一定范围内的水流水平变化的河床形态。现场测量将用于开发、校准和测试先进的计算模型，这些模型将允许在更大范围的曲流形状和流量水平上进行曲流弯曲动力学的数值模拟。曲流是河流景观中最容易辨认和最常见的特征之一，几个世纪以来一直吸引着科学家、艺术家和作家。大型蜿蜒河流的泛滥平原也是世界上人口最多的地区之一，对这些地区的人类基础设施的管理往往至关重要。此外，曲流河沉积物形成的岩石可能含有大量具有重要经济价值的石油、天然气、水和矿物，对这些过去环境的重建依赖于对现代曲流河过程的了解。目前，大多数关于曲流河流的水流模式、泥沙运动和河道变化的知识都来自于实验室和野外对小弯的研究，以及形状相对简单的弯的研究。该项目将改变我们对大型、复杂形状的河曲的形式和动力学的理解，并允许测试有关河道几何的假设，这些假设长期以来一直被提出用于较小的河曲，但从未在大型河曲中进行过测试。该研究将量化大沃巴什河（约250米宽，10米深）中水的三维运动，沉积物的运输和河流弯曲的演变，并利用这些数据开发和测试曲流弯曲流动和侵蚀的数值模型。这种结合现场数值的方法将直接用于解释复杂的河流弯曲是如何演变的，以及它们未来的表现。这将对社会科学和应用科学的许多领域产生重大影响，这些领域涉及大型蜿蜒河流泛滥平原内的基础设施和人口管理，以及未来对河岸侵蚀、河道迁移和蜿蜒河流废弃的预测。

This project will combine state-of-the-art techniques in field measurement and mathematical modeling of river processes to explore the interactions among flow, sediment movement and channel change in complex meander bends along large rivers. The research will address questions of how the complexity of bend shape affects flow and sediment transport, how these effects vary with different flow levels, and how these effects combine to determine long-term changes in the shapes of large meander bends. The Wabash River on the border of Illinois and Indiana, one of America's last virtually unregulated free-flowing meandering rivers, will serve as the field site. The research will measure, using new acoustic technologies, three-dimensional patterns of water movement, sediment transport and changing riverbed morphology within meander bends of different shape over a range of flow levels. Field measurements will be used to develop, calibrate and test advanced computational models that will allow numerical simulations of meander bend dynamics over a wider range of meander shapes and flow levels than is possible in the field. Meanders are one of the most recognizable and common features of river landscapes, and have fascinated scientists, artists and writers for centuries. The floodplains of large meandering rivers are also among the most populated areas in the world, and management of human infrastructure in these locations is often of critical importance. Additionally, rocks formed from the deposits of meandering rivers may contain economically-important quantities of oil, gas, water and minerals, and reconstruction of these past environments relies on knowledge of processes in modern meandering rivers. At present, most knowledge concerning patterns of flow, sediment movement and channel change in meandering rivers stems from studies of small bends, in the laboratory and field, and bends that have relatively simple shapes. The project will transform our understanding of the form and dynamics of large, complex-shaped, river meanders and allow testing of hypotheses concerning channel geometry that have been long-proposed for smaller river meanders, but never tested in large river bends. The research will quantify the three-dimensional movement of water, transport of sediment and evolution of river bends in the large Wabash River (c. 250m wide, 10m deep), and use this data to develop and test numerical models of meander bend flow and erosion. This combined field-numerical approach will be of direct use in explaining how complex river bends have evolved and how they may behave in the future. This will have significant impact in many realms of social and applied science concerned with the management of infrastructure and populations located within the floodplains of large meandering rivers, and in future predictions of bank erosion, channel migration and meander abandonment.