The deadliest landslides in Swiss history

A view of Brienz/Brinzauls, situated in southeast Switzerland, and the nearby crumbling mountain, May 12, 2023. Keystone / Gian Ehrenzeller

The eyes of the world are on the Swiss village of Brienz/Brinzauls, where a large section of the crumbling mountain broke off on June 16, narrowly missing the evacuated village in southeastern Switzerland. Here’s a look at some of the biggest landslide disasters in Swiss history.  

In mid-May the authorities in Brienz/Brinzauls evacuated all 86 residents of the small mountain village in canton Graubünden after warnings of a possible mountain collapse.

Experts said that two million cubic metres of rock could break loose and crash down on the village. On June 16, a huge landslide left a metre-high mass of rock on the cantonal road near the village school building. There have been no reports of damage in the village. 

It is unclear how much of the crumbling mountainside crashed down during the night or if there will be further landslides or rockfalls.

The dramatic evacuation and protection measures were taken at Brienz/Brinzauls to avoid a major catastrophe like those described below. 

Bondo, canton Graubünden

The village of Bondo after the massive landslide on August 23, 2017. Keystone / Gian Ehrenzeller

On August 23, 2017 three million cubic metres of rock crashed down from the Piz Cengalo mountain in eastern Switzerland, triggering a landslide into the valley. It was the largest landslide in Switzerland in over 130 years. 

Rubble and mud flowed down the valley to Bondo and the surrounding settlements of Promontogno, Sottoponte and Spino. Eight hikers were killed, and the homes of ten people were crushed. In all, 147 residents had to be brought to safety. Damage was estimated at CHF41 million ($46 million). 

YouTube video of the Piz Cengalo landslide in 2017 that hit the village of Bondo in canton Graubünden in south-eastern Switzerland.

The Swiss army helped with the rescue and clean-up operation and, later, most of the residents were able to return home. Dangers still exist, however. Protective infrastructure was therefore built after the disaster and a warning system will remain in place at least until 2024.  

Gondo, canton Valais 

Rescue and clean-up work in the destroyed village of Gondo in southern Switzerland, October 17, 2000. Keystone

Thirteen people lost their lives in 2000 when the tiny village of Gondo on the Swiss-Italian border was sliced in two by a 40-metre-wide swathe of mud and rocks loosened by three days of torrential rain. 

The landslide swept away ten houses, the school, shops and the road. Gondo was hardest hit, but other villages in Upper Valais were also cut off and houses were swept away.  

Randa, canton Valais

Workers try to clear a route through the landslide area near Randa, canton Valais, June 20, 1991. Keystone / René Ritler

In April and May 1991 two rockslides occurred from a cliff above the town of Randa in the Matter Valley in southern Switzerland. Almost 30 million cubic metres of rock and debris were released, burying rail and road links to the resort of Zermatt and damming the local river. There were no fatalities, but livestock, farmhouses and holiday homes were destroyed. 

Elm, canton Glarus

The devastation in the Glarus village of Elm after the landslide on September 11, 1881. Keystone

On September 11, 1881 a deadly rockslide occurred in Elm, canton Glarus. The rockslide was set loose when an open pit slate mine, dug into the side of a mountain, collapsed. It is estimated that ten million cubic metres of rock crashed down to the valley floor in a matter of seconds, burying people inside their homes and killing 114 of them. 

Goldau, canton Schwyz

Illustration of the landslide of Goldau, canton Schwyz. Keystone

On September 2, 1806, a huge rockfall from the Rossberg mountain in central Switzerland destroyed the village of Goldau, claiming 457 lives and killing hundreds of cattle. Over 300 houses and barns were destroyed. The easternmost part of the rock mass hit Lake Lauerz, triggering a 15-metre-high tsunami. Around ten people died in the resulting flood on the southern shores of the lake. 

According to research by the University of Geneva, in 563 a massive rockfall at the eastern end of Lake Geneva caused part of the Rhone delta to collapse and slide into the lake, triggering a tsunami that caused considerable destruction around the lake. 

Permafrost and monitoring

Switzerland is highly prone to natural hazards. Rockfalls and landslides occur everywhere in the mountains. The Federal Office for the Environment estimates that 6-8% of Switzerland’s territory is unstable and threatened by landslides and rockfalls, mainly in the Alps and lower Alpine regions. And around 7% of the Swiss population liveExternal link in areas that might be affected by avalanches, landslides, rockslides or rockfalls.  

Rising temperatures, melting glaciers and thawing permafrost are underminingExternal link the stability of mountain slopes. Settlements below permafrost zones must increasingly expect landslides and mudflows in the years ahead.  

In 2021 floods, landslides and rockfalls across Switzerland resulted in damage costs of about CHF450 million. 

Protective structures can help prevent risks, but they are complex to install and expensive, according to the authoritiesExternal link. In high-risk zones, monitoring technology may be used. At Brienz four different systems have been deployed to monitor the crumbling mountain.