Preprints
https://doi.org/10.5194/esurf-2021-3
https://doi.org/10.5194/esurf-2021-3

  24 Feb 2021

24 Feb 2021

Review status: this preprint is currently under review for the journal ESurf.

Bedrock River Erosion through Dipping Layered Rocks: Quantifying Erodibility through Kinematic Wave Speed

Nate A. Mitchell and Brian J. Yanites Nate A. Mitchell and Brian J. Yanites
  • Indiana University, Bloomington, Indiana, USA

Abstract. Landscape morphology reflects drivers such as tectonics and climate but is also modulated by underlying rock properties. While geomorphologists may attempt to quantify the influence of rock strength through direct comparisons of landscape morphology and rock strength metrics, recent work has shown that the contact migration resulting from the presence of mixed lithologies may hinder such an approach. Indeed, this work counterintuitively suggests channel slopes within weaker units can sometimes be higher than channel slopes within stronger units. Here, we expand upon previous work with 1-D stream power numerical models in which we have created a system for quantifying contact migration over time. Although previous studies have developed theory for bedrock rivers incising through layered stratigraphy, we can now scrutinize this theory with contact migration rates measured in our models. Our results show that previously developed theory is generally robust and that contact migration rates reflect the pattern of kinematic wave speed across the profile. Furthermore, we have developed and tested a new approach for estimating kinematic wave speeds. This approach utilizes stream steepness, a known base level fall rate, and contact dips. Importantly, we demonstrate how this new approach can be combined with previous work to estimate erodibility values. We demonstrate this approach by accurately estimating the erodibility values used in our numerical models. After this demonstration, we use our approach to estimate erodibility values for a stream near Hanksville, UT. Because we show in our numerical models that one can estimate the erodibility of the unit with lower steepness, the erodibilities we estimate for this stream in Utah are likely representative of mudstone and/or siltstone. The methods we have developed can be applied to streams with temporally constant base level fall, opening new avenues of research within the field of geomorphology.

Nate A. Mitchell and Brian J. Yanites

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on esurf-2021-3', Sarah Boulton, 24 Mar 2021
  • RC2: 'Review of “Bedrock River Erosion through Dipping Layered Rocks: Quantifying Erodibility through Kinematic Wave Speed', Boris Gailleton, 21 Apr 2021

Nate A. Mitchell and Brian J. Yanites

Nate A. Mitchell and Brian J. Yanites

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Short summary
A landscape's appearance reflects the properties of the underlying bedrock. For example, strong bedrock can lead to steep slopes. Recent work has shown, however, that in areas with mixed rock types the stronger bedrock can have lower slopes. In this study, we use numerical models of bedrock river erosion to show why this change in behavior occurs. We also present a new approach for estimating bedrock erodibility. This new approach can allow for new opportunities in the field of geomorphology.