EGU22-3896
https://doi.org/10.5194/egusphere-egu22-3896
EGU General Assembly 2022
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

Historic river floodplain engineering causes channel pattern shift from multiple to single-thread rivers

Annegret Larsen1, Charlotte Engelmann1, Alexander Fuelling2, Jasper Candel1, Hans-Rudolf Bork3, and Joshua Redder Larsen4
Annegret Larsen et al.
  • 1Soil Geography and Landscape, Wageningen University and Research, Wageningen, the Netherlands
  • 2Sedimentary Geology and Quaternary Research, University of Freiburg, Germany
  • 3Institute for Ecosystem Research, University of Kiel, Germany
  • 4School of Geography, Earth and Environmental Sciences, University of Birmingham, Great Britain

It is well-known that floodplain fine-grained alluvial sedimentation rates have been increasing due to human impact. In most catchments, the onset or acceleration of floodplain deposition is dated to medieval times, which has been attributed to increased hillslope soil erosion due to high population densities causing deforestation and slope instability. The also increasing river sediment load has then changed rivers into a single-thread, meandering channel pattern, which is now considered to be the ultima ratio in river restoration. In this presentation, we challenge this view and argue that current channel pattern and shape are related to historic channel engineering, and are hence not the product of fluvial processes associated with a meandering, or avulsing single-thread river system. Here, we present a study from a mountainous region in central Europe (Germany), in which we reconstruct the natural, pre-medieval channel pattern of two low order streams (3rd and 4th Strahler order), and their transition into the current, single-thread channel pattern which is characterised by meanders. This study is based upon a multi-proxy analysis of the chrono-stratigraphy, cross-valley ground penetrating radar, river surveying, analysis of historic maps, and hydrological data for channel pattern prediction. Finally, based on our analysis, we suggest that currently observed channel widening processes and island formation likely represent a tendency of the studied streams to re-create a braided channel pattern, which should be embraced by river management instead of forcing streams into a meandering pattern, as multi-thread, braiding channels are the most natural condition for these streams,  producing a sustainable and resilient river ecosystem.  

How to cite: Larsen, A., Engelmann, C., Fuelling, A., Candel, J., Bork, H.-R., and Larsen, J. R.: Historic river floodplain engineering causes channel pattern shift from multiple to single-thread rivers, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3896, https://doi.org/10.5194/egusphere-egu22-3896, 2022.