Hochvogel could lose 400,000 cubic metres of rock

Scientists estimate that about 400,000 cubic metres of rock could break away from the Hochvogel in the Allgäu Alps, BR reports. Researchers from the Technical University of Munich have monitored the mountain for 12 years. A crack at its summit is up to six metres wide and 70 metres deep.

The rock is expected to fall on the Austrian side, in an uninhabited area. Geologist Michael Krautblatter, who heads the university’s chair of slope movements, said the collapse could dam two mountain streams in the Hornbachtal valley with sediment. This could affect paths and bridges, but settlements are not directly at risk, he said. The area, including the Bäumenheimer Weg trail to the summit, has been closed since 2014.

Krautblatter’s team also tests how temperature changes affect rock strength. Laboratory tests show that rock loses about 20 per cent of its strength as it thaws, because ice in small cracks adds strength while it is frozen. Samples came from rockfalls in permafrost areas, including Fluchthorn in Tyrol, Blatten in Switzerland and the Zugspitze.

A rockfall of about 13,000 cubic metres hit the Zugspitze’s north face in September. The Wetterstein mountains, which include the Zugspitze, are particularly prone to rockfalls, Krautblatter said. Small and medium-sized falls occur there every year. Researchers also closely monitor the Karwendel mountain range, which has many large, unstable rock faces.

Monitoring also covers places with substantial infrastructure and visitor numbers, including the Höllental and Partnach gorges and the area around Königssee in Berchtesgaden National Park. Last year, 20 hikers were rescued by helicopter after a rockfall in the park. The Hochvogel and Wetterstein mountains have the largest number of measuring devices.

Researchers are planning a new early-warning project near Pottenstein-Tüchersfeld in the Franconian Switzerland region. Dolomite rock towers there stand close to buildings and the B470 road. The formations are difficult to assess, Krautblatter said, and the team plans to test warning systems similar to those used in the Alps.