Preprints
https://doi.org/10.5194/esurf-2022-2
https://doi.org/10.5194/esurf-2022-2
 
01 Feb 2022
01 Feb 2022
Status: a revised version of this preprint was accepted for the journal ESurf and is expected to appear here in due course.

Continuous measurements of valley floor width in mountainous landscapes

Fiona Jane Clubb1, Eliot Francois Weir1,2, and Simon Marius Mudd2 Fiona Jane Clubb et al.
  • 1Department of Geography, Durham University, UK
  • 2School of GeoSciences, University of Edinburgh, UK

Abstract. Mountainous landscapes often feature alluviated valleys that control both ecosystem diversity and the distribution of human populations. Alluviated, flat valley floors also play a key role in determining flood hazard in these landscapes. Various mechanisms have been proposed to control the spatial distribution and width of valley floors, including climatic, tectonic and lithologic drivers. Attributing one of these drivers to observed valley floor widths has been hindered by a lack of reproducible, automated valley extraction methods that allow continuous measurements of valley floor width at regional scales. Here we present a new method for measuring valley floor width in mountain landscapes from digital elevation models (DEMs). This method first identifies valley floors based on thresholds of slope and elevation compared to the modern channel, and uses these valley floors to extract valley centrelines. It then measures valley floor width orthogonal to the centreline at each pixel along the channel. The result is a continuous measurement of valley floor width at every pixel along the valley, allowing us to constrain how valley floor width changes downstream. We demonstrate the ability of our method to accurately extract valley floor widths by comparing with independent Quaternary fluvial deposit maps from sites in the UK and the USA. We find that our method extracts similar downstream patterns of valley floor width to the independent datasets in each site. The method works best in confined valley settings and will not work in unconfined valleys where the valley walls are not easily distinguished from the valley floor. We then test current models of lateral erosion by exploring the relationship between valley floor width and drainage area in the Appalachian Plateau, USA, selected because of its tectonic quiescence and relatively homogeneous lithology. We find that an exponent relating width and drainage area (cv = 0.3 ± 0.06) is remarkably similar across the region and across spatial scales, suggesting that valley floor width evolution is driven by a combination of both valley wall undercutting and wall erosion in the Appalachian Plateau. Finally, we suggest that, similar to common metrics used to explore vertical incision, our method provides the potential to act as a network-scale metric of lateral fluvial response to external forcing.

Fiona Jane Clubb et al.

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on esurf-2022-2', Helen Beeson, 04 Mar 2022
    • AC1: 'Reply to RC1', Fiona Clubb, 08 Mar 2022
  • RC2: 'Comment on esurf-2022-2', Matthew Morriss, 14 Mar 2022

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on esurf-2022-2', Helen Beeson, 04 Mar 2022
    • AC1: 'Reply to RC1', Fiona Clubb, 08 Mar 2022
  • RC2: 'Comment on esurf-2022-2', Matthew Morriss, 14 Mar 2022

Fiona Jane Clubb et al.

Fiona Jane Clubb et al.

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Short summary
River valleys are important components of mountain systems: they are the most fertile part of landscapes, and store sediment which is transported from mountains to surrounding basins. Our knowledge of the location and shape of valleys is hindered by our ability to measure them over large areas. We present a new method for measuring the width of mountain valleys continuously along river channels from digital topography, and show that our method can be used to test common models of river widening.