Doctoral Dissertation Research: Investigation of Interactions Among Near-Bank Turbulence, Flow Structure, and Bank Retreat in a Compound Meander Loop

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The interaction among channel morphology, turbulent flow structure, and sediment transport often produces complex meander planforms that evolve through lateral and downstream channel migration. As meanders migrate, they tend to increase in sinuosity and curvature, often forming elongate bends with multiple curvature maximums otherwise known as compound loops. Flow moving through simple meander bends is highly three dimensional, but the relationship among 3-D flow structure, turbulence characteristics, and planform evolution in compound loops is poorly understood. In particular, knowledge of the structure of turbulence near the outer bank of meandering rivers, which should be closely related to the erosional forces acting on the bank, is incomplete. The doctoral dissertation research project will conduct a systematic, process-based field investigation of the interactions between near-bank turbulence, the mean flow field, and bank erosion in a compound loop in Central Illinois. Field data on bed and bank morphology, time-averaged flow structure, and near-bank instantaneous flow velocities will be collected at the study site for several flow stages. Monitoring of changes in channel morphology, including bank retreat, will be coupled with repeat flow measurements to facilitate exploration and interpretation of the influence of morphology, flow structure, and the spatial structure of turbulence on the morphodynamics of a compound meander loop. The change in bank position, channel morphology, flow structure, and structure of turbulence will be documented, and the interactions among these processes will be identified.The results of this project will help fill existing gaps in basic understanding regarding how interactions among meander planform, flow movement through a bend, and bank erosion relate to the development and evolution of complex meander forms. The project will provide high-quality field data to evaluate theoretical models river scientists use to understand and predict planform evolution. In addition to providing new information and insights for basic researchers, greater knowledge of meander planform evolution will have practical utility because of the impacts planform change has on human welfare, such as the threat to structures located along meandering rivers and potential property loss caused by channel migration. Increasing human proximity to meandering rivers is creating a greater need for informed river management practices. By improving scientific understanding regarding how flow stage and near-bank flow turbulence influence bank erosion and channel migration, this project will inform management and policy decisions, including river and habitat restoration practices in or near meandering river systems. As a Doctoral Dissertation Research Improvement award, this award also will provide support to enable a promising student to establish a strong independent research career.