Monitoring of the Kleines Nesthorn and the Birch Glacier during the rock avalanche in Blatten

Summary

Abstract

On May 28th 2025, a massive rock avalanche buried the village of Blatten under 9 million m3 of ice and rock. Thanks to the expertise of many specialists and continuous monitoring with measurement systems in the field, it was possible to detect this danger in advance and to protect the life of many people. The Birch Glacier was already monitored before this tragic landslide. These monitoring systems revealed the upcoming collapse of the Kleines Nesthorn. Consulting expert Geoformer and local authorities mandated Geoprevent to install an interferometric radar which was done at the day, when Blatten was evacuated. Our radar solution provided valuable data about the displacement of the entire region around the Birch Glacier and helped the authorities to manage the situation. This system records even small movements of the mountain independent of rain, snow, fog or darkness and can therefore see things that a human eye cannot. It can be used up to distances of 4 km and to monitor areas of up to 5 km2. One day before the collapse of the glacier our team installed a camera on the Eastern moraine of the Birch Glacier to monitor it from the top. These images revealed a dramatic picture during the last hours and showed a rapid movement of the glacier. With this camera-based technology and the help of complex algorithms, our monitoring system was able to provide data about the displacement to the experts for their risk assessments and for monitoring and evaluating the situation continuously. Currently, the installation is changing from an emergency project to a mid- and long-term monitoring solution which should provide safety for the clearance and construction works. Additional cameras and GPS systems were installed by our team to provide an even deeper insight into the instabilities and deformations around the Kleines Nesthorn.