2022 CSDMS meeting-048

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Concavity controls on river incision in precipitation-dominated settings

Marina Ruiz Sánchez-Oro, (She/her),The University of Edinburgh Edinburgh , United Kingdom. marina.ruiz.so@ed.ac.uk

Simon Mudd, The University of Edinburgh Edinburgh , United Kingdom. simon.m.mudd@ed.ac.uk

Boris Gailleton, GFZ Potsdam Potsdam , Germany. boris.gailleton@gfz-potsdam.de

Fluvial incision patterns help us understand the role of precipitation in river formation and evolution. The effects of drainage area, sediment supply and precipitation are closely linked and disentangling them is a challenging task.

In this study, we model different precipitation scenarios and use the stream power law to analyse river profiles. We focus on the analysis of the χ coordinate, a transformation of the stream-power law to capture changes in slope with distance downstream. The value of this coordinate is controlled by the concavity index, θ, which sets the steepness of the rivers downstream. Similar χ profile shapes can be caused by different precipitation patterns, tectonic forcings or lithologies. However, choosing different θ coefficient values will lead to patterns similar to those arising from the natural forcings above, distorting the original physical signal.

In this study, we use the modelling framework Fastscape to generate landscapes that evolve to steady state under different precipitation scenarios. We test multiple precipitation models and calculate the χ profiles of the resulting simulated rivers using LSDTopoTools. We complete the analysis by comparing the model results to real topographic data from sites featuring a strong precipitation gradient, such as the Pyrenees, the Alburz mountains and the Andes.

This piece of research provides further insight on the importance of constraining the θ coefficient in χ profiles, in particular when disentangling the role of precipitation in river incision mechanisms.