EGU General Assembly 2021
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

Rapidly eroding hilltops are surprisingly smooth: ridgetop curvature varies with the square root of erosion rate 

Simon M. Mudd1, Emmanuel J. Gabet2, Ryan W. Wood2, Stuart W. D. Grieve3, Steven A. Binnie4, and Tibor J. Dunai4
Simon M. Mudd et al.
  • 1University of Edinburgh, GeoSciences, Edinburgh, United Kingdom of Great Britain – England, Scotland, Wales (
  • 2Department of Geology, San Jose State University, San Jose, California, 95192, USA
  • 3School of Geography, Queen Mary University of London, London, UK, E1 4NS
  • 4Institute for Geology and Mineralogy, University of Cologne, Germany, 50674

The shape of soil-mantled hillslopes is typically attributed to erosion rate and the transport efficiency of the various processes that contribute to soil creep. While climate is generally hypothesized to have an important influence on soil creep rates, a lack of uniformity in the measurement of transport efficiency has been an obstacle to evaluating the controls on this important landscape parameter. We addressed this problem by compiling a data set in which the transport efficiency has been calculated using a single method, the analysis of hilltop curvatures using 1-m LiDAR data, and the erosion rates have also been determined via a single method, in-situ  ­cosmogenic 10Be concentrations. Moreover, to control for lithology, we chose sites that are only underlain by resistant bedrock. The sites span a range of erosion rates (6 – 1373 mm/kyr), annual precipitation (31 – 320 cm/yr), and aridity index (0.08 – 1.38). Surprisingly, we find that hilltop curvature varies with the square root of erosion rate, whereas previous studies predict a linear relationship. In addition, we find that the inferred transport coefficient also varies with the square root of erosion rate but is insensitive to climate. We explore various mechanisms that might link the transport coefficient to the erosion rate and conclude that present theory regarding soil-mantled hillslopes is unable to explain our results and is, therefore, incomplete. Finally, we tentatively suggest that bedrock processes may be responsible for the shape of hillslope profiles at our sites.

How to cite: Mudd, S. M., Gabet, E. J., Wood, R. W., Grieve, S. W. D., Binnie, S. A., and Dunai, T. J.: Rapidly eroding hilltops are surprisingly smooth: ridgetop curvature varies with the square root of erosion rate , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12536,, 2021.


Display file