Permafrost-Related Mass Movements: Implications from a Rock Slide at the Kitzsteinhorn, Austria

Keuschnig, Markus; Hartmeyer, Ingo; Höfer‐Öllinger, Giorgio; Schober, Andreas; Krautblatter, Michael; Schrott, Lothar

doi:10.1007/978-3-319-09300-0_48

Cited by 14 publications

(15 citation statements)

References 3 publications

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“…As a consequence, hydrostatic pressures increase until cleftwater pours out through open fractures. Similar forcing has been observed before the triggering of a recent rock slide detachment below the ERT transect (Figure ; Keuschnig et al, ).…”

Section: Discussionmentioning

confidence: 99%

Automated Electrical Resistivity Tomography Testing for Early Warning in Unstable Permafrost Rock Walls Around Alpine Infrastructure

Keuschnig

Krautblatter

Hartmeyer

et al. 2016

Permafrost and Periglac. Process.

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Subsurface monitoring of permafrost conditions at depths up to 20–30 m is crucial to assess the safety and reliability of mountain infrastructure, because permafrost degradation critically affects rock slope stability in high mountains. Electrical resistivity tomography (ERT) provides a straightforward tool for monitoring near‐surface bedrock permafrost at monthly or longer intervals. But as rockfalls are often prepared over periods of hours or days, ERT for early warning purposes should also detect short‐term triggering events such as pressurised water flow. Here, we present the first approach to monitor steep permafrost rock walls quasi‐continuously with ERT. We measured ERT every 4 h at the up to 67° steep rock wall below the Kitzsteinhorn cable car, Austria. Wenner datasets (n = 996) were analysed from February 2013 to February 2014 in terms of data stability, raw data characteristics and measurement errors coinciding with potential disturbing factors. Strong resistivity changes coincided with rapid freezing or water inundating rock fractures. Automatically detected periods with large resistivity changes produce ERT time series with low resistivities extending from the bottom upwards during times of snowmelt. We infer that flow of pressurised water in fractures warms the surrounding rock in an upward direction, based on fracture inventories, visual observations of cleftwater and near‐surface temperature measurements. We develop a strategy for ERT monitoring suitable for potential early warning systems, where high apparent resistivity changes in 4 h intervals may precede critical hydrostatic events confined by permafrost rocks. Copyright © 2016 John Wiley & Sons, Ltd.

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Section: Discussionmentioning

confidence: 99%

Automated Electrical Resistivity Tomography Testing for Early Warning in Unstable Permafrost Rock Walls Around Alpine Infrastructure

Keuschnig

Krautblatter

Hartmeyer

et al. 2016

Permafrost and Periglac. Process.

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“…The Kitzsteinhorn hosts an extensive research site to investigate the consequences of climate change on high-alpine infrastructure and rock stability ('Open-Air-Lab Kitzsteinhorn'). Measurements performed at the Kitzsteinhorn focus on rockfall activity (Keuschnig et al, 2015), subsurface temperature changes (Hartmeyer et al, 2012), geophysical monitoring with ERT (Supper et al, 2014;Keuschnig et al, 2016), rock mass pressure using anchor load plates (Plaesken et al, 2017) and fracture dynamics monitoring 115 with crackmeters (Ewald et al, 2019).…”

Section: Study Areamentioning

confidence: 99%

Enhanced rockwall retreat and modified rockfall magnitudes/frequencies in deglaciating cirques from a 6-year LiDAR monitoring

Hartmeyer

Keuschnig

Delleske

et al. 2020

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Cirque erosion contributes significantly to mountain denudation and is a key element of glaciated mountain topography. Despite long-standing efforts, rates of rockwall retreat and the proportional contributions of low-, mid-and high magnitude rockfalls have remained poorly constrained. Here, a unique, terrestrial LiDAR-derived rockfall inventory (2011-2017) of two glaciated cirques in the Hohe Tauern Range, Central European Alps, Austria is analysed. The mean cirque wall retreat rate of 1.9 mm a -1 ranks in the top range of reported values and is mainly driven by enhanced rockfall from the 15 lowermost, freshly deglaciated rockwall sections. Retreat rates are significantly elevated over decades subsequent to glacier downwasting. Elongated cirque morphology and recorded cirque wall retreat rates indicate headward erosion is clearly outpacing lateral erosion, most likely due to the cataclinal backwalls, which are prone to large dip-slope failures. The rockfall magnitude-frequency distributionthe first such distribution derived for deglaciating cirquesfollows a distinct negative power law over four orders of magnitude. Magnitude-frequency distributions in glacier-proximal and glacier-distal rockwall 20 sections differ significantly due to an increased occurrence of large rockfalls in recently deglaciated areas. In this paper we show how recent climate warming shapes glacial landforms, controls spatiotemporal rockfall variation in glacial environments and indicates a transient signal with decadal scale exhaustion of rockfall activity immediately following deglaciation crucial for future hazard assessments.

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“…Recent instability is presumably initiated by deglaciation of this part of the headwall where foliation dips out of the slope and favours sliding failures. Resulting debuttressing is considered a preparatory factor of a recent rockslide of considerable magnitude (Keuschnig et al, 2015).…”

Section: Implications For Rock Slope Stabilitymentioning

confidence: 99%

“…Here, we investigate the deformation regime of an open fracture, which is of direct geotechnical relevance for a popular cable car station. The fracture is situated immediately up slope of the detachment zone of a recent rockslide (2012) (Keuschnig et al, 2015) and was glacially covered until the 1980s. The present study focuses on the need for quantitative data from unstable, recently deglaciated rock slopes, essential for better understanding the increasing risk on high-alpine infrastructure.…”

mentioning

confidence: 99%

Fracture dynamics in an unstable, deglaciating headwall, Kitzsteinhorn, Austria

Ewald

Hartmeyer²,

Keuschnig³

et al. 2019

Preprint

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Abstract. Processes destabilising recently deglaciated rockwalls, driving cirque headwall retreat, and putting high alpine infrastructure at risk are poorly understood due to a lack of in situ monitoring data. Deglaciation initiates internal stress redistribution and drastically increases atmospheric forcing rendering cirque headwalls particularly prone for rock slope failure. Here we present quantitative data from an unstable, recently deglaciated cirque headwall. We monitor the dynamics of a fracture at the north face of the Kitzsteinhorn (3203 m a.s.l.) over a period of 2.5 years. Two crackmeters measure horizontal and vertical crack deformation with a resolution of ±0.003 mm and are complemented by crack top temperature measurements. To decipher thermo-mechanical from cryogenic forcing, thermal expansion coefficients for both horizontal and vertical directions are calculated to derive purely thermo-mechanical deformation. Our data shows that fracture dynamics are dominated by thermo-mechanical expansion and contraction of the inter-cleft rock mass during snow-covered and snow-free periods. Significant deviations from thermo-mechanical behavior occur due to freeze-thaw action during spring and autumn zero curtain periods. Exceptional vertical deformation during these periods is triggered by rainfall events providing liquid water into the fracture system. Subsequent refreezing rather than hydrostatic pressure build-up is to the most likely cause of the mechanical response. Lower magnitude horizontal deformation occurs in autumn and early winter due to ice segregation. Irreversible fracture opening was not observed, however, enhanced cryogenic deformation in spring and autumn may lead to shallow, low magnitude rock detachments. Our results highlight the importance of liquid water intake in combination with subzero-temperatures on the destabilisation of glacier headwalls. We conclude that intense frost action and ice segregation are common processes in randkluft systems, serving as important preparatory factors of paraglacial rock slope instability.

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Permafrost-Related Mass Movements: Implications from a Rock Slide at the Kitzsteinhorn, Austria

Cited by 14 publications

References 3 publications

Automated Electrical Resistivity Tomography Testing for Early Warning in Unstable Permafrost Rock Walls Around Alpine Infrastructure

Automated Electrical Resistivity Tomography Testing for Early Warning in Unstable Permafrost Rock Walls Around Alpine Infrastructure

Enhanced rockwall retreat and modified rockfall magnitudes/frequencies in deglaciating cirques from a 6-year LiDAR monitoring

Fracture dynamics in an unstable, deglaciating headwall, Kitzsteinhorn, Austria

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