Erosion of landscapes: recent advances in topographic analyses and impact of extreme events
Seminar Room 1, School of Geographical Science, University Road, Bristol, BS8 1SS
This Physical Geography Seminar will be given by Dr Mikael Attal (University of Edinburgh).
In this talk, I will present recent development in topographic analysis, including the use of new metrics describing hillslope and river geometry to infer erosion rates and tectonics. Data from California confirms the theory that hilltop curvature increases linearly with erosion rates and that the relationship between hilltop curvature and hillslope relief can reveal whether relief is growing or decaying. In rivers, geomorphologists have long relied on slope – area relationships to determine channel steepness and infer erosion rates; these relationships are however often blurred by high slope variability and uncertainty. The “integral approach to river profile analysis” presented by Perron and Royden (2013) does not utilise slope and offers the opportunity to identify subtle changes in steepness that may be interpreted in terms of change in erosion rates, tectonics and/or substrate. I will present a new statistical tool that has been developed to detect such changes. Finally, I will talk about the impact of extreme flood events on mountainous landscapes, with a case study in NE Iceland. 3He cosmogenic nuclide concentrations on abandoned fluvial surfaces reveal that the upper 5 km of the 100-m-deep Jökulsárgljúfur canyon (including Dettifoss, the most powerful waterfall in Europe) have been carved by two extreme floods triggered by subglacial volcanic eruptions 5 and 1.5 ka ago.
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