Preprints
https://doi.org/10.5194/egusphere-2022-567
https://doi.org/10.5194/egusphere-2022-567
 
22 Jul 2022
22 Jul 2022
Status: this preprint is open for discussion.

The role of thermokarst evolution in debris flow initiation (Hüttekar Rock Glacier, Austrian Alps)

Simon Kainz1, Thomas Wagner1, Karl Krainer2, Michael Avian3, Marc Olefs3, Klaus Haslinger3, and Gerfried Winkler1 Simon Kainz et al.
  • 1Institute of Earth Sciences, NAWI Graz Geocenter, University of Graz, Heinrichstrasse 26, 8010 Graz, Austria
  • 2Institute of Geology, University of Innsbruck, Innrain 52, 6020 Innsbruck, Austria
  • 3Central Institute for Meteorology and Geodynamics, Hohe Warte 38, 1190 Vienna, Austria

Abstract. A rapid sequence of cascading events involving thermokarst lake outburst, rock glacier front failure, debris flow development and river blockage hit Radurschl Valley (Ötztal Alps, Tyrol) on 13 August 2019. Compounding effects from multivariate permafrost degradation and drainage network development initiated the complex process chain. The debris flow dammed the main river of the valley, impounding a water volume of 120,000 m3 that was partly drained by excavation to prevent a potentially catastrophic outburst flood. Since the environmental forces inducing the debris flow evolved under ambiguous conditions, potentially destabilizing factors were analyzed systematically to deduce the failure mechanism and establish a basis for multi hazard assessment in similar settings. Identification and evaluation of individual factors revealed a critical combination of topographical and sedimentological disposition, climate, and weather patterns driving the evolution of thermokarst and debris flow. Progressively changing groundwater flow and storage patterns characterizing the hydraulic configuration within the frozen sediment accumulation governed the slope stability of the rock glacier front. The large amount of mobilizable sediment, dynamically changing internal structure, and substantial water flow along a rapidly evolving channel network eroded into the permafrost body, render active rock glaciers complex multi hazard elements in periglacial, mountainous environments.

Simon Kainz et al.

Status: open (until 02 Sep 2022)

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Simon Kainz et al.

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Short summary
We analyze the environmental conditions initiating cascading events in permafrost-affected terrain. The sequence includes lake outburst, slope failure, debris flow development, and river blockage. We identify the rapid evolution of a thermokarst channel network as the main driver for initiating the process chain by draining the lake and transferring the water to the debris flow. These results highlight the need to account for permafrost degradation in hazard assessment studies.