EGU2020-10211
https://doi.org/10.5194/egusphere-egu2020-10211
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Controls on the lateral channel migration rate of braided alluvial channel systems

Aaron Bufe1, Jens Turowski1, Douglas Burbank2, Chris Paola3, Andrew Wickert3, and Stefanie Tofelde4
Aaron Bufe et al.
  • 1GFZ German Research Center for Geosciences, Section 4.6 Geomorphology, Department of Earth Science, Potsdam, Germany
  • 2Department of Earth Sciences, University of California, Santa Barbara, California, 93106, USA
  • 3Department of Earth & Environmental Sciences and Saint Anthony Falls Laboratory, University of Minnesota, Twin Cities, Minneapolis, Minnesota, USA
  • 4Institute for Earth and Environmental Sciences and Geography, University of Potsdam, 14476 Potsdam, Germany

Lateral movements of alluvial river channels control the extent and reworking rates of alluvial fans, floodplains, deltas, and alluvial sections of bedrock rivers. These lateral movements can occur by gradual channel migration or by sudden changes in channel position (avulsions). Whereas models exist for rates of river avulsion, we lack a detailed understanding of the rates of lateral channel migration on the scale of a channel belt. Here we develop, for the first time, an expression that describes the lateral migration rate of braided alluvial channels in non-cohesive sediment. On the basis of photographic and topographic data from laboratory experiments of braided channels performed under constant external boundary conditions, we first explore the impact of autogenic variations of the channel-system geometry (i.e., channel-bank heights, water depths, channel-system width, and channel slope) on channel-migration rates. In agreement with theoretical expectations, we find that, under such constant boundary conditions, lateral channel-migration rates scale inversely with the channel-bank height. Furthermore, when changes in channel-bank heights are accounted for, lateral migration rates appear independent of channel slope, channel-system width, and water depth. These constraints allow us to derive two dimensionally consistent expressions for lateral channel-migration rates under different boundary conditions. We find that migration rates are strongly sensitive to channel-bank heights and water discharges and more weakly sensitive to sediment discharges in braided equilibrium channel systems. In addition, the strong dependence of lateral migration rates on channel-bank heights implies that external perturbations (for example, perturbations of sediment and water discharges) that modulate the depth of channel incision and can indirectly affect lateral channel-migration rates.

How to cite: Bufe, A., Turowski, J., Burbank, D., Paola, C., Wickert, A., and Tofelde, S.: Controls on the lateral channel migration rate of braided alluvial channel systems, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10211, https://doi.org/10.5194/egusphere-egu2020-10211, 2020

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