Long-Profile Evolution of Transport-Limited Gravel-Bed Rivers

  • Wickert A
  • Schildgen T
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Abstract

<p><strong>Abstract.</strong> 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 &amp;ndash; typically rapidly &amp;ndash; and valleys must widen gradually. To match the empirical square-root width&amp;ndash;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.</p>

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APA

Wickert, A. D., & Schildgen, T. F. (2018). Long-Profile Evolution of Transport-Limited Gravel-Bed Rivers. Earth Surface Dynamics Discussions, 1–41. https://doi.org/10.5194/esurf-2018-39

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