Continuous measurements of valley floor width in mountainous landscapes

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 these landscapes. Various mechanisms have been proposed to spatial width floors, including climatic, tectonic, lithologic drivers. Attributing one drivers observed floor widths has hindered by lack reproducible, automated extraction methods allow continuous measurements at regional scales. Here, we present new method for measuring mountain from digital elevation models (DEMs). This first identifies based on thresholds slope compared modern channel uses extract centrelines. It then measures orthogonal centreline each pixel along channel. The result is measurement every valley, allowing us constrain how changes downstream. We demonstrate ability our accurately comparing with independent Quaternary fluvial deposit maps sites UK US. find extracts similar downstream patterns datasets site, mean difference 17–69 m. works best confined settings will not work unconfined where walls are easily distinguished floor. test current lateral erosion exploring relationship between drainage area Appalachian Plateau, USA, selected because its tectonic quiescence relatively homogeneous lithology. an exponent relating (cv=0.3±0.06) remarkably across region scales, suggesting evolution driven combination wall undercutting Plateau. Finally, suggest that, common metrics used explore vertical incision, provides potential act as network-scale metric response external forcing.