Fluvial Dynamics of Cutoffs and Abandoned Channel Development on Meandering Rivers

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This project will advance the understanding of the mechanics of meandering river cutoffs, a ubiquitous, yet poorly understood feature of rivers. Meandering rivers are among the most recognizable landforms on the earth's surface, and their complex spatial patterns have been of interest to geographers and other earth scientists for a long time. A characteristic feature of meandering rivers is the development of cutoffs, where curved channels migrate close enough to one another for a new channel to developt across the interior portion, or neck, of a tight bend. The development of cutoffs typically produces oxbow lakes as sedimentation occurs at the bend entrance and exit, the river follows the path of the new cutoff channel, and flow through the abandoned bend ceases. Despite an abundance of past work on meandering rivers, knowledge of the mechanisms by which bend cutoffs develop is incomplete. As a consequence, the capacity to accurately model and predict the spatial and temporal dynamics of meandering rivers is limited. In response to this research need, this project will address questions concerning cutoff channel evolution after they have been initiated, the patterns of the flow structures and how these impact sedimentation and erosion patterns, and how flow structures in the main channel as well as sedimentation and erosion patterns change after the cutoff has been initiated. To address these questions, the investigators will use state-of-the-art field measurement techniques to capture, at a high resolution, how three-dimensional flow structure and patterns of erosion and deposition interact at an evolving cutoff of the Wabash River along the Illinois-Indiana border just upstream from the confluence of the Wabash and Ohio rivers. They also will conduct a series of laboratory experiments in a physical model of a bend cutoff to examine three-dimensional flow structure, bed morphology, and channel change for a variety of cutoff configurations. Finally, they will develop numerical models to simulate cutoff dynamics, using field and laboratory data to condition and validate the computational models. The validated and fully tested models will then provide an advanced theoretical tool for predicting cutoff dynamics along meandering rivers over an extended range of boundary conditions. This project will enhance knowledge about meandering rivers by contributing to basic theoretical understanding of the processes involved in the development of bend cutoffs and by providing the basis for improved predictive capabilities for modeling the dynamic behavior of meandering rivers. The project also will yield practical knowledge relevant to river management, including sedimentation problems associated with cutoffs that can impede commercial navigation, the conservation of riparian habitat at the sites of cutoffs and oxbow lakes, and river restoration activities that include maintaining or establishing connectivity between oxbow lakes and the main river channel, especially where rivers have been channelized. The project will contribute to interdisciplinary training for graduate and undergraduate students at the University of Illinois at Urbana-Champaign (by incorporating findings into courses. It will also expose high school students, including students from underrepresented groups, to cutting-edge scientific research that advances theory and serves society at the annual Illinois Science Olympiad and at the National Science Olympiad, which will hosted by the state of Illinois in 2014.