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Research title Paraglacial bedrock river incision: the Scottish Highlands. Summary of research What happens to glaciated landscapes after the glaciers have gone? How does the form of the landscape change when the main agent of erosion and transport of rock and sediment switches from glaciers to rivers? Can river erosion make a ‘glacial’ landscape look ‘fluvial’ again, and if so, how long would that take?
The first step towards addressing these questions is to quantify bedrock river erosion in postglacial landscapes and assess what controls it. Research has shown that bedrock river erosion is the key link between climate, tectonics and landscape form in areas that are not glaciated. This is because rivers form the lower boundary of hillslopes, any lowering of the river bed steepens adjacent hillsides, influencing hillslope processes across whole catchments. In glaciated landscapes, rivers are not only influenced by active climatic, and in some areas tectonic, control factors, but also by the inheritance of landscape form and sediment deposits conditioned by the preceding glaciation. In postglacial areas, changing river discharge and declining ‘paraglacial’ sediment flux have the potential to drive spatially and temporally variable fluvial incision into bedrock. In addition, rivers inherit complex valley floor slopes, and may be affected by base level change driven by glacio-isostatic uplift. All these factors combine to prime landscapes for bedrock river erosion. The challenge is to quantify the distribution and rate of erosion and how they vary with time, and assess which factors are the main drivers and constraints on the process.
My research is quantifying the distribution and rate of bedrock incision in postglacial rivers in the hard-rock, post-orogenic terrain of the northern Scottish Highlands, last glaciated during the Main Late Devensian glaciation (LGM ~20 ka) and Younger Drays stadial (12.9-11.5 ka). The distribution and form of bedrock channels in the northern Highlands are being assessed through field mapping and GIS-based topographic analysis of three catchments ranging from 30-300 km2. The timing and rate of bedrock incision is being quantified using cosmogenic nuclide exposure-age dating of strath terrace surfaces at 5 sites across the Highlands. Variations in the rate of incision and changes in the distribution and form of bedrock channels over time indicates that rivers are responding to evolving control factors, especially declining sediment flux.
Supervisors Dr John Jansen
Professor Paul Bishop
Dr Derek Fabel
Dr Ruth Robinson (University of St. Andrews) Recent research grants Fabel, D., Bishop, P., Jansen, J.D., Whitbread K. 2010. Postglacial bedrock river incision, £13k (NERC Cosmogenic Isotope Analysis Facility Allocation 9088.0410). |
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