A comparison of three terrain parameters that may be used to identify denudation surfaces within a GIS: A case study from Wales, United Kingdom

The study of denudation surfaces has long formed a major theme within geomorphic and tectonic research. This paper describes the computational methods used to identify these surfaces through three terrain parameters within a GIS. The investigated parameters are slope angle, relative relief, and the elevation–relief ratio. The study area under consideration is that of Wales, United Kingdom. The SRTM DEM forms the basis of this investigation, with all data interrogation undertaken in ArcMap 9.3. The computational methods are described in detail and then the results relating to each terrain parameter are compared. The denudation surface maps based on slope angle and relative relief both clearly show that the most widespread surfaces are associated with coastal plateaux and valley lowlands. However, the altitude–frequency plots that pertain to relative relief are better able to constrain the altitudinal range of the individual surfaces than those that pertain to slope angle. The denudation surface maps based on the elevation–relief ratio are able to differentiate between concave and convex topography. It is, thus, possible to differentiate between coastal plateaux and valley lowlands at low elevations. However, the major advantage of this parameter is that it is able to clearly identify more dissected surfaces at higher elevations. Taking the results together, the region is characterised by four widespread denudation surfaces at 45–100 m asl, 155–245 m asl, 370–430 m asl, and 500–560 m asl. There are certain similarities and certain differences between the results presented here and those of previously studies. Nonetheless, the accurate characterisation of denudation surfaces is of fundamental importance to those studies that use them to constrain the magnitude of uplift events. Further studies are required in order to better understand the significance of these surfaces in relation to the geomorphic and tectonic development of the region.

► Denudation surfaces may be used to constrain the magnitude of uplift events.
► DEMs give far greater objectivity to the mapping of such surfaces.
► Three techniques for accurately characterising denudation surfaces are detailed.
► Widespread surfaces should be mapped using slope angle or relative relief.
► Heavily dissected surfaces should be mapped using the elevation–relief ratio.