Morphodynamics of gravel-bed rivers

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The overall research goal is to analyze the dynamics of rivers to contribute to understanding of the response of rivers to environmental change and human modification, and to the development of methods for restoration of impacted rivers. This requires an understanding of the processes that create particular types of river form and dynamics. At the heart of this is the idea that rivers are transporters of sediment and that this sediment transport also creates the river form. If we can understand these sediment transport processes we can explain why rivers with different morphology occur and how rivers change in morphology over time. The classical approach to analysis of sediment transport is to develop mathematical functions that predict transport rate from the hydraulics of the flow. But this hydraulically-based analysis does not directly explain differences in river form and the local processes creating this form, and ignores the possibility that there are elements of the transport process that are not directly related to local hydraulics but are inherent properties of morphological instability. I am exploring an alternative approach which is to measure rates and 'styles' of morphological development - morphodynamics - that are the outcome, and driver, of spatial and temporal patterns of sediment transport. By measuring the morphological change we can make a direct link between the sediment transport processes and differences in river form and dynamics. This also leads to development of new methods for predicting sediment transport rate in rivers. Because the morphological dynamics of rivers is relatively slow we use small-scale physical models in an experimental flume to observe the development of channel morphology, measure rates of change and the volumes of erosion and deposition (using photogrammetry to map bed topography), and observe the way in which morphology develops from the statistics of the collective displacement of bed material particles. The outcome of the research will be a new way of analyzing river morphology and sediment transport, and of understanding variations in river morphology and morphological change, with practical application in river management and fluvial sedimentology.