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

Rock instability in high mountain areas poses an important risk for man and infrastructure. At 3 p.m. on 18 August 2012 a rock slide event was documented at the Kitzsteinhorn, Austria. The release zone was detected on a north-exposed rock face below the cable car summit station (3.029 m). Analysis of terrestrial laser scanning (TLS) data delivered an accurate identification of the release zone yielding a rock fall volume of approximately 500 m3. Cubic Blocks with lengths of up to 4 m and block masses of up to 125 t were released during the event. The failure plane is located in a depth of approximately 3–4 m and runs parallel to the former rock surface (mean inclination 47°). Comparison with borehole data located less than 50 m from the release zone shows that failure plane depth is consistent with active layer depth. The event documentation is supplemented with observations of rock and air temperature, data on precipitation and snow depth, electrical resistivity tomography data, observed active layer depth and geological/geotechnical background data. The comprehensive ambient data suggests the influence of high temperatures and water availability for the triggering of the rock slide.