Floods, debris flows, landslides, and rockfall events caused damage of around 75 million Swiss francs in 2023. This was the result of the annual evaluation of the storm damage database by the Swiss Federal Research Institute WSL.
Locally, there was major damage in 2023. Looking at Switzerland as a whole, 2023 was a rather low-damage year compared to the long-term average and median. Thanks to good preventive measures, there were fortunately no fatalities caused by floods, debris flows, landslides, and rockfall events. In the 52-year observation series, 2023 ranks 37th, with a damage amount of 75 million Swiss francs. The largest share of the estimated damage costs (around 66 %) was caused by landslides, followed by floods (21 %), rockfall and rock avalanches (7 %) and debris flows (6 %). The main causes were continuous rain (67 %) and rain in combination with snowmelt (18 %).
Many and long-lasting evacuations ¶
The year of damage 2023 was dominated by the events in Schwanden (municipality of Glarus Süd). On 29 August 2023, a large landslide reached the settlement area, destroying several houses and making others uninhabitable. The village of Brienz/Brinzauls in the municipality of Albula GR also experienced an unusual situation. After weeks of evacuating the village population, the expected rockfall/landslide occured on 15 June without causing any damage to the village itself.
In both villages, the population affected was evacuated in time so that nobody was injured. In Brienz/Brinzauls, the over 80 residents were able to return to their village after seven weeks. In Schwanden, only a few of the over 100 evacuees were able to return to their homes. Forty people have been permanently evacuated due to the damage.
Floods ¶
Continuous rainfall at the end of August led to tense flood situations, particularly in Ticino and eastern Switzerland, but the damage was limited. In November and December, persistent precipitation combined with melting snow led to flooding, debris flows, and landslides, particularly in western Switzerland, Valais, the Bernese Oberland, and around the Jura border lakes.
Location, extent, and type of damage events in 2023 (Map basis: FSO GEOSTAT / Federal Office of Topography swisstopo).
Distribution of the various damage processes in the total costs for the period 1972 - 2022 (adjusted for inflation) and for 2023. (Graphic: WSL)
Annual damage amounts for the various processes for the period 1972 - 2023 (adjusted for inflation, basis 2023). The arithmetic mean (solid, CHF 304 million) and median (dashed, CHF 101 million) are marked with horizontal lines. (Graphic: WSL)
The Swiss Federal Research Institute WSL has been systematically collecting information on storm damage since 1972. The database, compiled with the support of the Federal Office for the Environment FOEN, contains information on damage caused by floods, debris flows, and landslides as well as rockfall, rock avalanches, and rockslides. Damage caused by avalanches, snow pressure, earthquakes, lightning, hail, and storm winds is not included in the analyses. Estimates of damage to property, infrastructure, forests, and agriculture are mainly based on media reports. The data is available to experts on request and forms an important basis for risk assessment. The WSLs storm damage survey is used for environmental reporting by the Federal Office for the Environment FOEN.
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