Abstract
AbstractThe geometry of channels controls the erosion rate of rivers and the evolution of topography following environmental change. We examine how sediment, slope, and substrate interact to constrain the development of channels following deglaciation and test whether theoretical relationships derived from streams reacting to tectonic uplift apply in these settings. Using an extensive data set of channel geometry measurements from postglacial streams in the Scottish Highlands, we find that a power law width‐drainage area scaling model accounts for 81% of the spatial variation in channel width. Substrate influences channel form at the reach scale, with bedrock channels found to be narrower and deeper than alluvial channels. Bedrock channel width does not covary with slope, which may be due to downstream variations in sediment flux. Bedrock channel width‐to‐depth ratios increase with discharge (or area) and sediment flux, consistent with increasing bed cover promoting lateral widening. We find steep, wide, and shallow bedrock channels immediately below lakes, which we interpret as the result of limited erosion due to a lack of sediment “tools.” Where sediment supply is sufficient to exceed transport capacity, alluvial channels develop wider, shallower geometries constrained primarily by flow hydraulics. Our results indicate that simple scaling models of channel width with drainage area are applicable at regional scale, but locally, channel width varies with substrate, and in the case of bedrock channels, with sediment flux.
Highlights
Bedrock channel geometry controls fluvial incision rates and the mechanisms by which hillslopes are affected by channel bed lowering, thereby influencing landscape evolution in response to environmental change [e.g., Hartshorn et al, 2002; Whipple, 2004]
Using an extensive data set of channel geometry measurements from postglacial streams in the Scottish Highlands, we find that a power law width-drainage area scaling model accounts for 81% of the spatial variation in channel width
Our results indicate that simple scaling models of channel width with drainage area are applicable at regional scale, but locally, channel width varies with substrate, and in the case of bedrock channels, with sediment flux
Summary
Bedrock channel geometry controls fluvial incision rates and the mechanisms by which hillslopes are affected by channel bed lowering, thereby influencing landscape evolution in response to environmental change [e.g., Hartshorn et al, 2002; Whipple, 2004]. In many landscape evolution models, variations in channel geometry are approximated by scaling with discharge or drainage area [e.g., Howard et al, 1994; Whipple and Tucker, 1999]. Recent studies have shown that substrate [Allen et al, 2013; Turowski et al, 2007], slope [Amos and Burbank, 2007; Finnegan et al, 2005; Whittaker et al, 2007], and sediment flux [Finnegan et al, 2007; Yanites and Tucker, 2010] may influence the channel cross section, and debate continues over the factors that control bedrock channel form. Scaling factors that relate discharge to catchment area and width to discharge (or area) are widely used to estimate shear stress and stream power in natural streams as a function of drainage area (which can be estimated from topographic data): Q 1⁄4 kqAc;
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
