Catastrophic Potential of Over 400,000 Cubic Metres of Rock Collapsing into the Valley

Rockslide Watch: The Looming Threat of Hochvogel

By: Dirk Walter

Gossip Corner

The Hochvogel, a towering beauty in the Allgäu, is under close monitoring. And there's a darn good reason: A whopping 400,000 cubic meters of rock could crash from the summit.

No need to freak out just yet—a devastating Alpine-style landslide like the one in Switzerland is off the cards for now. But make no mistake, Hochvogel is harboring some unstable mountain slopes.

Standing tall at 2,592 meters, Hochvogel looms west of Oberstdorf, on the Bavarian-Tirol border. A team spearheaded by Prof. Michael Krautblatter of TU Munich has been deploying sensors and cameras on the mountain. Crack-ridden Hochvogel is a ticking time bomb, posing the threat of a potential massive rockslide. This issue isn't exactly new; the mountain has seen its fair share of rockslides, with one as far back as 1935. Since 2014, Hochvogel has been under Krautblatter's microscope, specifically the TU chair for landslides he oversees. Back in 2014, around 140,000 cubic meters of rock came crashing down. Don't go messing about with the south-facing Baumenheimer Way; it's been off-limits since the rockslide, and venturing there is a one-way ticket to danger.

Expect the Unexpected

It looks like the amount of rock at risk might be more significant than initially thought. Geologists have re-calculated the potential mass that could pile into the valley. Previously, around 260,000 cubic meters of rock was assumed, a figure still occasionally tossed about in the media. But now, we're looking at 400,000 cubic meters—roughly enough to match a tenth to a twentieth of the mass that buried the Swiss village of Blatten[1]. The Hochvogel has been restless since 2014; in fact, the cracks and fissures are growing ever deeper and wider[1]. Water seeping into these cracks acts like a catalyst, further eroding the mountain after frost. A crack near the summit cross is a cause for particular concern—it expanded by several centimeters last summer[1]. With such progression, partial collapse is a real possibility.

While no precise prediction can be made, Krautblatter's prognosis is that the cracks would swiftly expand a few days before the total collapse, perhaps by several centimeters daily. Then, he'd receive a warning on his mobile phone and alert the authorities and the mayors of the neighboring communities of Hindelang in the Allgäu and Hinterhornbach in Tirol. At least: Even with 400,000 cubic meters, "no residential areas will be affected," says Krautblatter. However, any impeded wild streams, such as the Hornbach, would need to be swiftly cleared to prevent flooding.

Eyes on the District

The researchers also have their eyes on neighboring regions, like the Garmisch-Partenkirchen district. Last week, a laser was installed at the Ferchenbach above the Partnach Gorge. An early warning system will now measure whether the stream is obstructed by landslides, potentially causing a surge wave through the Partnach Gorge. The adjacent Höllentalklamm has been monitored since 2016. If a rock shifts, the gorge would become impassable due to acute rockfall danger. They've already had to clamp shut two sections of the path and reroute hikers through tunnels in the mountain[1].

Embrace the (Past) Crisis

In 2015, the slope at Grafenaschau in the Murnauer Moos experienced a landslide. The event buried forest roads, uprooted trees, and flowed over an area of 60 hectares. The slope hasn't been entirely calm since. Once a year, the landslide is assessed using a drone[1].

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The Hochvogel's instability has gained more attention than ever before—likely fuelled by international coverage of rockfall events like the one in 2022 at the Marmolada in Italy's Trentino, which claimed the lives of eleven mountaineers, or the recent event in Switzerland[1]. When Krautblatter started, his chair had just two employees; today, there are 20. This month, an expedition to the Hochvogel is planned, itching to install additional measuring instruments.

Catastrophic Potential of Over 400,000 Cubic Metres of Rock Collapsing into the Valley