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

Author:

Seelig SimonORCID,Wagner Thomas,Krainer Karl,Avian Michael,Olefs Marc,Haslinger KlausORCID,Winkler GerfriedORCID

Abstract

Abstract. A rapid sequence of cascading events involving thermokarst lake outburst, local rock glacier front failure, debris flow development, and river blockage hit Radurschl Valley (Ötztal Alps, Tyrol) on 13 August 2019. Compounding effects from permafrost degradation and drainage network development within the rock glacier 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. We present a systematic analysis of destabilizing factors to deduce the failure mechanism. The identification and evaluation of individual factors reveals a critical combination of topographical and sedimentological disposition, climate, and weather patterns driving the evolution of a thermokarst drainage network. Progressively changing groundwater flow and storage patterns within the frozen sediment accumulation governed the slope stability of the rock glacier front. Our results demonstrate the hazard potential of active rock glaciers due to their large amount of mobilizable sediment, dynamically changing internal structure, thermokarst lake development, and substantial water flow along a rapidly evolving channel network.

Funder

Bundesministerium für Land- und Forstwirtschaft, Umwelt und Wasserwirtschaft

Karl-Franzens-Universität Graz

Amt der Steiermärkischen Landesregierung

Amt der Kärntner Landesregierung

Salzburger Landesregierung

Landes Tirols

Amt der Vorarlberger Landesregierung

Publisher

Copernicus GmbH

Subject

General Earth and Planetary Sciences

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