EGU2020-15211
https://doi.org/10.5194/egusphere-egu2020-15211
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Planform deviations in river channel alignment due to active landsliding in the High Himalaya of Bhutan

Larissa de Palézieux, Kerry Leith, and Simon Loew
Larissa de Palézieux et al.
  • ETH Zurich, Geology, Earth Sciences, Zurich, Switzerland (larissa.depalezieux@erdw.ethz.ch)

Large rock slope instabilities affect river channels both due to catastrophic failures and long-term creep. The relationship between rock slop instabilities and processes in the adjacent river system are typically assessed in terms of channel profile perturbations and cross-sectional morphology, e.g. excess topography. However, such relationships can also be evident in planform changes of the channel alignment, e.g. in landslide dams and long-term channel migration. Large scale creeping rock slope instabilities can be considered point sources which introduce sediment laterally to a river channel. In cases in which sediment production from one side of the channel exceeds that of the opposing side, the course of the river can be shifted towards the less active hillslope. The deviation of the channel from its original course may therefore be used as a proxy for relative sediment input of the two opposing hillslopes.

In order to characterize the planform morphology of the river channels, we treat them as signals fluctuating around a smoothed channel and use a fast Fourier transform to extract characteristic wavelengths and amplitudes of the stream network. We observe a consistent increase in amplitude of planform deviation with increasing wavelength with a variability of two orders of magnitude at the shortest wavelength (101 m) and less than one order of magnitude at longer wavelengths (103 m).

When comparing characteristic channel morphologies based on these analyses to the deviation of channels adjacent to mapped landslides, the amplitude of the deviation appears higher than those naturally occurring in the river system at wavelengths similar to twice the landslide width.

How to cite: de Palézieux, L., Leith, K., and Loew, S.: Planform deviations in river channel alignment due to active landsliding in the High Himalaya of Bhutan, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-15211, https://doi.org/10.5194/egusphere-egu2020-15211, 2020

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