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Hilltop Curvature Increases with the Square Root of Erosion Rate
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  • Emmanuel J. Gabet,
  • Simon Marius Mudd,
  • Ryan Wood,
  • Stuart William David Grieve,
  • Steven A. Binnie,
  • Tibor J. Dunai
Emmanuel J. Gabet
San José State University, San José State University

Corresponding Author:manny.gabet@sjsu.edu

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Simon Marius Mudd
University of Edinburgh, University of Edinburgh
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Ryan Wood
San Jose State University, San Jose State University
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Stuart William David Grieve
Queen Mary University of London, Queen Mary University of London
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Steven A. Binnie
Universität zu Köln, Universität zu Köln
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Tibor J. Dunai
Universtiät zu Köln, Universtiät zu Köln
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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 – 922 mm/kyr), mean annual precipitation (39 – 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 processes occurding in the bedrock (e.g., fracture generation) may play a role in the shape of hillslope profiles at our sites.
May 2021Published in Journal of Geophysical Research: Earth Surface volume 126 issue 5. 10.1029/2020JF005858