Abstract
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 rate, and steepness increases
with an 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 typically should 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.
Funder
Deutsche Forschungsgemeinschaft
Subject
Earth-Surface Processes,Geophysics
Cited by
36 articles.
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