Geomorphometry
Geomorphometry - the measurement of the characteristics of the terrain surface - flourished during the quantitative revolution in Geography, but then fell into obscurity for a while. However it is enjoying something of a revival for two reasons:
- The widespread availability of DEM data and software to process it
- Renewed interest in long-standing geomorphological questions relating to long-term landform development, in the wake of the realisation that strong links exist between this and long-term climate and tectonic change
One of the key advances of the past 10 years has been the development of a number of surface process models (SPMs), which model tectonic and geomorphological processes and the interactions between them over timespans of tens of thousands of years. I am interested in the development of measures which might test how realistic the landscapes produced by these SPMs are.
Andrew Phillips, one of my research students has been working with Professor Chris Clark on this. He has been looking at the apparently simple task of distinguishing between landscapes which have been formed purely by fluvial processes, and those which have been glaciated.
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| Fluvial landscape |
Glacial landscape
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A number of standard geomorphometric measures, such as drainage density, grain and texture are relatively poor at making this distinction. Perhaps surprisingly, the textbook measure of valley cross-sectional shape ('V' versus 'U') when measured by the exponent of a curve fitted to profiles, is also poor at making this distinction when applied to a large number of DEMs from landscapes around the globe.
However, Andrew has shown that it is possible to achieve good separation when a number of measures are used in combination as shown in the graph. The two measures in this case are
- Valley width. This is essentially a measure of the amount of material removed from the landscape. Glacial valleys tend to be wider on average than fluvial ones, as a result of the greater erosional efficiency of ice.
- Mid-valley contour length. This measures the degree of fine-scale dissection of the landscape, and distinguishes between large glacially scoured valleys, with minimal erosion of the side walls since deglaciation and the fine drainage network of a fluvial system.
This work was presented at the AGU Fall Meeting in 2006 but has not yet been written up for publication.