Scientists track how Blatten landslide debris cone is changing
Sunday 23rd August 2026 on 20:30 in
Switzerland
More than a year after the landslide at Blatten, the resulting debris cone continues to shape the rear Lötschental valley, SRF reports. Scientists are using drones, surveys and sensors to measure how the mass of rock, sand and ice is changing.
Mario Studer, a surveying engineer at Terradata, monitors the debris cone to help plan reconstruction. An autonomous drone launches from a box at the edge of the landslide zone, flies over the cone and takes several hundred images.
Terradata uses the images to create geometrically accurate aerial photographs, elevation profiles and three-dimensional models of the surface. The repeated measurements show how much the debris cone moves, settles and breaks down. In some places, it has subsided by only a few centimetres over the past year; in others, by several metres. The debris rises as high as 35 metres above the valley floor in some locations, while the layer of sand and rock is only a few centimetres thick elsewhere.
The drone flew over the cone daily shortly after the landslide. More than a year later, flights take place every 14 days.
Terradata has also drilled several holes up to 25 metres deep into the debris cone. Highly sensitive sensors measure temperatures inside it, showing where remnants of the landslide remain frozen and where no ice is left. Under a rock layer that can be as high as a house, ice from the collapsed Birch Glacier may still be up to 15 metres thick, Studer said.
In other places, researchers found that the ice had shrunk from six metres to three metres where the protective layer of rock above it was only two or three metres thick. As the ice melts and only rocks and sand remain, the debris cone settles.
Gleb Kabakovitch and Andreas Hüni from the Geographical Institute of the University of Irchel in Zurich are also studying the cone. Using spectrometers, they examine the size of the rubble on the surface and just below it. Their measurements produce images showing the composition of the surface, with fine material deposited after the landslide appearing in purple.