Scientists monitor Bavaria’s most rockfall-prone mountains

A potential major rockfall at Hochvogel in the Allgäu could involve about 400,000 cubic metres of rock, and researchers are tracking the mountain closely, BR reported. Scientists say several other mountain areas in Bavaria are also prone to rockfalls.

Researchers from the Technical University of Munich have monitored Hochvogel for 12 years. They previously estimated that about 260,000 cubic metres of rock could fall on the uninhabited Austrian side. Professor Michael Krautblatter, who leads the university’s chair for slope movements, now puts the possible volume at around 400,000 cubic metres, or about half the summit.

Krautblatter expects the debris could dam two mountain streams in the Hornbachtal valley on the Tyrolean side. That could affect infrastructure such as paths and bridges, but settlements would not be directly affected, he said. The area, including the Bäumenheimer path from the valley to the summit, has been closed since 2014.

Thawing can weaken rock

Krautblatter’s team also tests how rock strength changes at different temperatures. In laboratory tests, researchers compress rock samples and have found that nearly every type of rock loses about 20 per cent of its strength when it thaws. Ice in small cracks adds strength while frozen, the geologist said.

The samples came from rockfalls in permafrost areas, including Fluchthorn in Tyrol, Blatten in Switzerland and Zugspitze. A rockfall on the north face of Zugspitze in September involved around 13,000 cubic metres of rock. The Wetterstein range, which includes Zugspitze, is highly prone to rockfalls, Krautblatter said, with small and medium-sized falls occurring every year. Researchers also monitor the Karwendel range, which has several large, unstable rock faces.

Monitoring also covers areas 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 researchers have placed the most measuring equipment at Hochvogel and in the Wetterstein range.

A new monitoring project is planned in Franconian Switzerland, near Pottenstein and Tüchersfeld in the Upper Franconian district of Bayreuth. Dolomite rock formations there stand close to buildings and the B470 road. These rock towers are harder to assess, Krautblatter said, because the last ice age did not reshape the area as extensively as it did the Alps. Researchers plan to test early-warning systems similar to those used in the Alps.