DYNAMICS AND MODELLING OF LARGE-SCALE RIVER ADJUSTMENTS OF EQUILIBRIUM

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This research program combines the theoretical and experimental research of mechanisms of flow and sediment transport involved in the deformation of bed and banks of alluvial streams with the development of physically-based, high-accuracy numerical models for the simulation and prediction of river morphological changes. These changes may occur naturally or as a response to direct or indirect human river interventions. The proposed research focuses on: 1- large-scale turbulence coherent structures and their morphological consequences; and 2- bed morphological changes and bank migration in meandering streams. An extensive series of experiments will be carried out in a 21m-long straight channel having an adjustable width from 1m to 2m. In these experiments, events of generation, growth and decay of large-scale coherent structures and their morphological consequences will be recorded. This study is expected to yield a better understanding of the development of large-scale bed forms (alternate and multiple bars), and of incipient stream deviations from straight alignment eventually leading to meandering or braiding. It will also constitute a foundation for the future modelling of these processes. Additionally, the mechanisms of flow and sediment transport involved in bed and bank deformation in meandering streams will be investigated. For this purpose, initial (non-equilibrium) laboratory meandering streams lying on a 21m-long, 7m-wide sand basin, will be subjected to a variety of flow conditions and their time-evolution will be monitored. The new data and insights will be used to develop a combined 2D/3D numerical model for the simulation and prediction of coupled meandering bed deformation and lateral migration over time. This model is expected to constitute a valuable tool to assess the impact on the physical environment of both natural and man-induced meandering morphological changes. The proposed research will result in the training of 4 Ph.D., 2 M.Sc. and 5 B.Sc. students, who will acquire highly desired, advanced skills with application in river engineering research and practice.