Applied research
Applied research
 
 
 

Rock slope response to contemporary deglaciation

Displacement fields measured on the Great Aletsch Glacier and Moosfluh rock slope instability using a portable radar interferometer.

 
 

“Climate change affects glaciated areas worldwide. Hazards associated with catastrophic landslides in recently de-glaciated valleys increasingly affect human society and critical infrastructure. Our study provides new insights in the interaction between deglaciation and rock slope response and is important for both scientific and practical reasons. We show that critically unstable slopes are sensitive to glacier ice loss, the slope response is significantly faster than previously reported, and landslide response brought on by rapid deglaciation may be enhanced as a result of climate change” (Kos et al 2016).

In 2007,  a long term study was initiated on the paraglacial response of the Moosfluh rock slope instability located at the terminus of the Great Aletsch glacier in Canton Wallis, Switzerland.

The glacier has been undergoing rapid retreat and volume decrease, and as a consequence, a number of rock slope instabilities around the glacier’s terminus are responding directly those rapid changes (see MSF and DSF in the accompanying landslide distribution map).

For the first time, we quantified the spatial and temporal relationship between the lowering of glacier ice and the acceleration of a landslide response, which was previously thought to occur over much longer time frames.

The data acquired for this study was one of the first times that satellite, airbourne, and ground-based remote sensing was combined with in situ monitoring data and field mapping to provide an unprecedented insight into paraglacial slope processes.

The publication is available on the Geophysical Research Letters website, via this external link.

 

 
 

Key outcomes of the study:

  • A clear acceleration of the slope occurs in the 1990s, with catastrophic failure occurring within a decadal period (see accompanying graph).
  • We identified and documented an increase in rock fall activity at the toe of the rock slope – a key indicator of impending large scale failure.
  • The failure response initiated at the toe of the slope and extended several kilometers up to the ridge crest (see supplementary information in Kos et al 2016).
  • Pre-failure activity included increased landslide activity on the outer flanks of the landslide area, imaged using a portable radar interferometer (see supplem.

 

 
 

The Piz Cengalo Rock slope Instability

The Piz Cengalo rock slope instability failed catastrophically on 23 August, 2017. During the period 2012-2017 terrasense was monitoring the rock slope using terrestrial radar interferometry as part of an AlpArge project.

 
 

A timely early warning…

Based on time series displacement maps from the period 2012 to 2017, we identified that the rock slope underwent a transition from a sub-critical to critical stability state. Several weeks prior to the catastrophic failure, an early warning was issued to Cantonal authorities.

Following the rock avalanche event of August 23, Terrasense was contracted by the Canton Graubünden (AfWN), in collaboration with Bonanomi Ltd to measure and support interpretation of the stability state of the rock slope. Our inputs played a central role in decision-making during the post-crisis intervention by local authorities.