Mass movements

Knowledge of processes and factors affecting slope instability is essential for detecting and monitoring potentially hazardous slopes. The overall aim of this study is to detect and characterize different slope movements in alpine periglacial environments, with the ultimate goal to understand the broad range of phenomena and processes encountered.

GPS (Global Positioning System) devices combined with two inclinometers have been developed and deployed to continuously measure the velocity of slope movements within an Alpine study site (Field site Matter valley). Our measurement-setup allows continuously measuring highly accurate positions and tilt-angles of moving boulders with high temporal resolution and coverage (potential to operate for several years). Next to the GPS-measurements, air-temperature, near ground-surface temperature and precipitation is measured at the study site. The high temporal resolution and coverage of our measurements makes it possible to identify both velocity variations (a) within a short period (e.g. week or season) and (b) between different years. The large number of measurement points, located upon various slope movement types, will help to find common characteristics of cryosphere-related slope movements in high mountains. Detecting the timing of acceleration and deceleration of various measurements points allows building and testing hypotheses concerning influencing factors, such as meltwater infiltration.

To derive velocity from GPS-positions a method has been developed that propagates uncertainties from different sources (GPS-solutions, inclinometer-measurements) and adapts the time-granularity depending on the strength of the signal. With this procedure changes in velocity can be detected for fast and slow movements. 

Each GPS-station includes a GPS-antenna and two inclinometers to measure the mast-tilt.

Horizontal velocity of a rock glacier. The slow reduction in velocity during winter as well as the acceleration in spring with several peaks is visible. In grey the standard-deviation of the velocity is plotted.

Based on inclinometer-measurements a tilt of the GPS-mast within hours can be detected and removed from the actual displacement.