Abstract
We leverage on optical and radar remote sensing data acquired from the European Space Agency (ESA) Sentinels to monitor the surface deformation evolution on a large and very active instability located in the Swiss Alps, i.e., the Moosfluh rock slope. In the late summer 2016, a sudden acceleration was reported at this location, with surface velocity rates passing from maximum values of 0.2 cm/day to 80 cm/day. A dense pattern of uphill-facing scarps and tension cracks formed within the instability and rock fall activity started to become very pronounced. This evolution of the rock mass may suggest that the most active portion of the slope could fail catastrophically. Here we discuss advantages and limitations of the use of spaceborne methods for hazard analyses and early warning by using the ESA Sentinels, and show that in critical scenarios they are often not sufficient to reliably interpret the evolution of surface deformation. The insights obtained from this case study are relevant for similar scenarios in the Alps and elsewhere.
Highlights
The progressive evolution of a slope towards catastrophic failure is often associated to an exponential increase of ground displacements [1,2]
We leverage on optical and radar remote sensing data acquired from the European Space Agency (ESA) Sentinels to monitor the surface deformation evolution on a large and very active instability located in the Swiss Alps, i.e., the Moosfluh rock slope
When slope deformation suddenly increases, serious concerns are posed to elements at risk, such as population and/or infrastructures located within the area of influence of a potential landslide event [41]
Summary
The progressive evolution of a slope towards catastrophic failure is often associated to an exponential increase of ground displacements [1,2]. In addition to SAR imagery, optical and multispectral data acquired from a large number of orbiting satellites can be nowadays exploited to build time series spanning decades, and to detect surface changes associated to ground displacements [17,18] Likewise, in this case DIC approaches can be used to quantify offsets caused by the deformation. We take advantage of the ESA Sentinel-1 (radar imagery) and Sentinel-2 (multispectral imagery) to study the evolution of a deep seated gravitational slope deformation (DSGSD) located in the crystalline basement of Swiss Alps, near the tongue of the Great Aletsch Glacier (see Figure 1) This area, hereafter referred to as the Moosfluh rock slope instability, has shown evidences of slow but progressive increase of surface displacements during the past 20 years from about 4 cm/year during the 1990’s to more than 20 cm/year in 2008 [6,28].
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