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Earth Surface Dynamics An interactive open-access journal of the European Geosciences Union

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https://doi.org/10.5194/esurf-2018-39
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
14 May 2018
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Earth Surface Dynamics (ESurf).
Long-Profile Evolution of Transport-Limited Gravel-Bed Rivers
Andrew D. Wickert1 and Taylor F. Schildgen2,3 1Department of Earth Sciences and Saint Anthony Falls Laboratory, University of Minnesota, Minneapolis, Minnesota, USA
2Institut für Erd- und Umweltwissenschaften, Universität Potsdam, 14476 Potsdam, Germany
3Helmholtz Zentrum Potsdam, GeoForschungsZentrum (GFZ) Potsdam, 14473 Potsdam, Germany
Abstract. Alluvial and transport-limited bedrock rivers constitute the majority of fluvial systems on Earth. Their long profiles hold clues to their present state and past evolution. We currently possess first-principles-based governing equations for flow, sediment transport, and channel morphodynamics in these systems, which we lack for detachment-limited bedrock rivers. Here we formally couple these equations for transport-limited gravel-bed river long-profile evolution. The result is a new predictive relationship whose functional form and parameters are grounded in theory and defined through experimental data. From this, we produce a power-law analytical solution and a finite-difference numerical solution to long-profile evolution. Steady-state channel concavity and steepness are diagnostic of external drivers: concavity decreases with increasing uplift, and steepness increases with increasing sediment-to-water supply ratio. Constraining free parameters explains common observations of river form: To match observed channel concavities, gravel-sized sediments must weather and fine – typically rapidly – and valleys must widen gradually. To match the empirical square-root width–discharge scaling in equilibrium-width gravel-bed rivers, downstream fining must occur. The ability to assign a cause to such observations is the direct result of a deductive approach to developing equations for landscape evolution.
Citation: Wickert, A. D. and Schildgen, T. F.: Long-Profile Evolution of Transport-Limited Gravel-Bed Rivers, Earth Surf. Dynam. Discuss., https://doi.org/10.5194/esurf-2018-39, in review, 2018.
Andrew D. Wickert and Taylor F. Schildgen
Andrew D. Wickert and Taylor F. Schildgen
Andrew D. Wickert and Taylor F. Schildgen

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Short summary
Rivers can raise or lower their beds by depositing or eroding sediments. We combined equations for flow, channel geometry, and gravel transport, to learn how changes in climate and tectonics shape profiles of river-bed elevation downstream. Rivers steepen when they receive more sediment (relative to water) and become straighter with tectonic uplift. Weathering and valley widening are required to produce gradually widening rivers with concave-up profiles that are often observed in the field.
Rivers can raise or lower their beds by depositing or eroding sediments. We combined equations...
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