Kandersteg: Geoprevent monitors Spitze Stei with radar and deformation camera

Sep 3, 2020News, Rock

The rock slope named “bim spitze Stei” above world-famous Lake Oeschinen in the Swiss Alps has always seen movement (Office for Forests and Natural Hazards of the Canton of Berne). Heavy precipitation often increases slope movement and in recent years the slope has accelerated. The unstable area covers about one square kilometre and has been monitored since summer 2018. GPS and total station measurements have been recorded at specific locations since and we ran a first testing phase with the georadar in late 2019. Subsequently, monitoring was intensified with further measurement technologies. We installed the first high-resolution PRO Cam for monitoring of the uppermost section in summer 2019 and a second device in spring 2020. PRO Cam automatically takes pictures in regular time intervals and uploads the images to the online data portal. This allows natural hazards experts to inspect the area remotely at any time and verify measured displacements or collapses or view slope details.
 

The upper part of Spitze Stei collapses.

In December 2019, PRO Cam recorded a rockfall of approximately 15,000 cubic metres. The uppermost part of the prominent pillar at Spitze Stei had collapsed.

Since June 2019, Geoprevent has also been monitoring the entire north-western slope with an interferometric radar as well as a second PRO Cam. The interferometric radar measures continually scans the slope and measures displacements in the mm range. Measurement data is automatically uploaded to the online data portal for anytime access for authorized users.

Georadar measurements from the Rosshubel site.

The interferometric radar reliably measures slope movements in the mm range in all visibility and weather conditions. Radar and PRO Cam are located on the opposite slope at a distance of more than 2.7 km to Spitze Stei.

Spitzen Stei slope monitoring

View of the snow covered Spitze Stei slope from the radar and PRO Cam location. The red circle marks the prominent pillar of the Spitze Stei slope.

The second PRO Cam is mainly used for visual inspection of the selected section of the monitoring area and allows remote viewing with a high level of detail. As example, the before-after camera images of 20/21 June 2020 show a small rockfall. The deposited material is under the rock where it collaped.

The media release of the municipality of Kandersteg dated 7 August 2020 inlcudes all monitoring devices used at Spitze Stei.