GROSSE GRABE (VS)
Active rock glacier / Landslide (Sackung) / Rockslide
Elevation: 2420-2760m - Massif: Valais Alps (Mischabel) - Commune: St-Niklaus (VS)
The Grosse Grabe rock glacier, located on the orographic right side of the Mattertal, is one of five rock glaciers that were found to be destabilized in the middle of the years 2000 using satellite interferometry (InSAR). Its dynamic changed significantly between 1982 and 1995. The tongue of the rock glacier was inactive between 1969 and 1982 (no or only very little movement). One or several rock fall events from the rock wall in the northern part of the Grosse Grabe cirque occurred during the period 1982-1995 and overlaid most of the rock glacier tongue, reactivating the terminal tongue, which separated from the upper intact part of the rock glacier. Between 1995 and 2010, the lower (terminal) part showed velocities reaching more than 5 m per year. The movements have then decreased. A reverse development has occurred in the uppermost part of the rock glacier, which is crossed by the Europaweg: velocities have increased since 2010. The whole rock mass in the center of the Grosse Grabe cirque (by pt. 2671, visible on the right on the webcam images) is also moving (around 0.1 m/a). Since 2019, numerous rockslide failures have occurred from the rock wall at the northern edge of the cirque. The first displacement measurements (DGNSS) were performed at Grosse Grabe in 2007.
Measurements and observations
Remote sensing (webcam, aerial images, Lidar)
Current images of the unstable rockwall.
Current image of the rock glacier.
Timelapse based on selected webcam images.
Measured horizontal flow field (annual velocity).
Annual surface velocity. Mean of a set of points selected in various parts of the rock glacier.
Kanton Wallis – Dienststelle für Wald, Flussbau und Landschaft (DWFL)
ID eletronic SA
Delaloye, R., Morard, S., Barboux, C., Abbet, D., Gruber, V., Riedo, M. and Gachet, S. (2013). Rapidly moving rock glaciers in Mattertal. In: Graf, C. (ed.) Mattertal – ein Tal in Bewegung. Publikation zur Jahrestagung der Schweizerischen Geomorphologischen Gesellschaft 29. Juni – 1. Juli 2011, St. Niklaus. Birmensdorf, Eidg. Forschungsanstalt WSL. 21-30. (pdf)