One in six Swiss homes exposed to natural hazards

The village of Brienz in canton Graubünden is threatened by a rock avalanche. Around 1.2 million cubic metres of debris are moving down the valley and threaten to bury the mountain village. Keystone-SDA

One in six homes in Switzerland is located in a zone threatened by natural hazards, a new study by Zürcher Kantonalbank (ZKB) has revealed.

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The mountain village of Brienz in canton Graubünden has been evacuated twice in recent times because of landslide threats. Meanwhile, in summer 2024 several people lost their homes in the Misox region in canton Graubünden and in the Maggia Valley in canton Ticino due to violent storms.

A study published by ZKB on Tuesday shows that many homeowners in Switzerland are potentially affected by such events.

There are many potential cases in canton Glarus in central Switzerland: almost half of all residential buildings there are exposed to at least one natural hazard. It is followed by cantons Valais (36%), Schwyz (30%), Graubünden (29%) and St Gallen (27%).

The hazard level is mostly low (62%) or medium (34%). However, every 125th residential building is located in zones with significant hazards, according to the study.

Floods pose the greatest risk

Researchers studied the threat to residential buildings using the hazard maps of 21 cantons. The results show that flooding is by far the greatest threat.

The second most common danger is landslides. These even threatened numerous residential buildings in canton Basel Country, a region in northwestern Switzerland where this would not be expected due to the nature of the terrain. This is due to the prevailing layers of clay and marl.

Heavy rainfall is particularly problematic in the mountains, as it can trigger debris flows and landslides as well as flooding.

In canton Ticino comparatively few residential buildings are located in endangered zones. However, if they are located in such areas they are often (46%) at “medium” or even “considerable” risk. This means that the extent of the potential damage could be particularly high. Only cantons Valais and Neuchâtel have an even higher proportion of potential risk (around 50% each).

According to ZKB, many risks could be prevented through measures on buildings or protective structures in the terrain, such as flood protection dams, rockfall nets or similar infrastructure.

However, these are associated with considerable financial expenditure. ZKB says that more than CHF1 billion ($1.2 billion) are invested in protection against natural hazards in Switzerland every year.

Translated from French by DeepL/sb

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