Rock glacier monitoring with spaceborne SAR in Graechen, Valais, Switzerland

Spaceborne techniques to monitor the Earth and its processes have advanced significantly over the last thirty years. Sensor spatial resolutions have increased supporting more detailed measurements and shorter revisit times have given higher temporal resolutions. Notwithstanding such advances, understanding the Earth system as a whole remains challenging. The focus of this paper is on monitoring rock glaciers in a mountainous area in the municipality of Graechen, Valais, Switzerland using Envisat and TerraSAR-X data acquired in 2008, 2009 and 2010. Spaceborne Synthetic Aperture Radar interferometry (InSAR) is used to augment existing observations from borehole measurements, geodetic and photogrammetric methods. In the Graechen study area, significant phase differences are reliably observed in 11-day TerraSAR-X and 35-day Envisat differential interferograms related to movements of the “Distelhorn” rock glacier and the Ritigraben rock glacier. The number of visible fringes are a relatively clear indication for seasonal variations in the movement of the rock glaciers, being about a quarter of a fringe faster in autumn (September/October) than in summer (June, July).