Hydrodynamics of fluvial wakes past large in-stream natural objects and their implications for riverbed morphology

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The diversity of natural river environments is presently understood throughout the degree of spatial heterogeneity in abiotic factors controlled by river flow structures. Central to this topic is flow heterogeneity produced by natural in-stream obstructions such as boulder clusters, log jams, patches of riparian and aquatic vegetation and their various combinations. Specific flow types forming around and downstream of in-stream obstructions are called wakes, which dynamics are still incompletely understood because of complexities in natural environments and processes. The proposed research aims at the improvement in knowledge of wake flows hydrodynamics by providing fundamental theory-based insight into controlling factors and their implications for river morphology. In this project, complex environmental flows generated in shallow, rough-bedded river environments by porous in-stream obstructions will be assessed directly in the field at a range of hydrological conditions. Dynamics of these wake flows then will be further understood by comparing field observations with the results of lab experiments, which up-scaling issues will be examined by carrying out scale-independent field-based experiments and numerical simulations. These studies will be also complemented by in-situ surveys of porosity in natural obstructions and sampling of the riverbed substrate. These surveys will deliver presently unavailable knowledge on fundamental properties of in-stream obstructions and direct quantification of erosion/deposition processes due to fluvial wakes. Furthermore, the collected data will estimate the wakes’ contribution into the bulk hydraulic characteristics at a river reach scale.