Morphodynamics of Complex Meander Bends on Large Rivers

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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.