Natural Hazards Cause Billions in Damage – Development Not Linear
The Swiss time series since 1972 shows extreme year-to-year fluctuations. Few major events cause a large part of the total damage.
Natural Hazards Cause Billions in Damage – Development Not Linear
The Swiss time series since 1972 shows extreme year-to-year fluctuations. Few major events cause a large part of the total damage.
Since 1972, the Swiss Federal Institute for Forest, Snow and Landscape Research (WSL) has recorded damage from floods, debris flows, landslides, and rockfall processes on behalf of the federal government. The Federal Statistical Office (BFS) time series now extends to 2025. It shows one main fact: The financial consequences of natural events fluctuate greatly. Single catastrophes can shape a decade's damage balance.
Key Facts
- Since 1972: WSL systematically records damage from floods, debris flows, landslides, rockfall, and falling rocks.
- Around 17.5 billion Swiss Francs: This is the inflation-adjusted total damage from recorded events since 1972.
- 2024: With approximately 905 million Swiss Francs, the year was the costliest since 2005 and the fifth most expensive in the 53-year observation series.
- 2005: The August flood caused around 3 billion Swiss Francs in damage, making it the costliest event in the database.
- Important: The time series does not cover all natural hazards. Avalanches, earthquakes, hail, storms, and drought are not included.
17.5 Billion Swiss Francs in Over Five Decades
The figures initially convey a vast dimension. Since systematic data collection began in 1972, damages totaling around 17.5 billion Swiss Francs have accumulated. These values are inflation-adjusted, making them comparable over decades.
However, the total sum is not distributed evenly across the years. The WSL explicitly states that a few major events cause a significant portion of the total damage sum.
This makes the time series particularly interesting. It does not simply show a steadily rising damage curve. Instead, it displays a sequence of relatively low-damage years and individual extreme spikes.
2005 Remains the Exceptional Year
This effect becomes particularly clear with the floods of August 21 and 22, 2005. This event caused damages of approximately 3 billion Swiss Francs. It is the costliest flood in the Swiss database.
The severe weather year of 1987 also proved costly. Inflation-adjusted damages then totaled more than 1.1 billion Swiss Francs. Together with other major events, this shows how strongly individual catastrophes influence long-term statistics.
The WSL therefore reaches an important conclusion: A large part of the total damage sum stems from comparatively few major events.
2024 Was the Fifth Costliest Year
The most recent year with significant damage was 2024. Floods, debris flows, landslides, and rockfall processes caused damages of around 905 million Swiss Francs.
Thus, 2024 was the most expensive year since 2005. It ranked fifth in the 53-year observation series. Almost 85 percent of the estimated damage occurred in June alone.
Affected areas included Valais, Misox, Maggia Valley, and later also the Bernese Oberland. Over 60 percent of the total annual damage occurred in Valais. Damages to the aluminum industry in Sierre alone accounted for almost a quarter of the total.
This also highlights an important characteristic of the statistics: A single, particularly costly damage to an industrial facility can significantly influence the annual balance.
What the Time Series Does Not Prove
The data are impressive. However, they do not provide simple proof that climate change causes greater damage every year.
There are several reasons for this. The extent of damage depends not only on how frequently or intensely a natural event occurs. Crucial factors include which buildings, transport routes, industrial facilities, and infrastructures are located in vulnerable areas.
If more construction occurs in a hazardous area, and the value of property there increases, the same natural event can cause significantly higher financial damage today than decades ago.
The damage statistics therefore measure more than just the intensity of natural hazards. They also show how exposed society is to these dangers.
Damage Figures Alone Are Not Enough for a Climate Assessment
To assess climate change, damage data must be combined with other measurement series. These include, for example, precipitation, discharge volumes, temperature trends, the frequency of extreme events, and changes in land use.
The situation is complex, especially concerning floods. Climatic changes can influence heavy rainfall and other hydrological processes. Simultaneously, settlements, infrastructure, and protective measures also change.
The WSL has therefore already investigated how damages can be normalized. This considers social and spatial changes, among other factors. Only such analyses allow for better distinguishing changes in natural hazard risk from changes in exposed assets.
Floods Dominate the Damage Balance
Not all natural events contribute equally to the total sum. Floods and debris flows cause by far the largest share of recorded damages.
The WSL points out that floods alone have caused damages amounting to approximately 14 billion Swiss Francs since 1972. Few major events account for a particularly large proportion.
Landslides and rockfall processes are also relevant. However, they reach significantly lower values in the long-term total sum.
An Important Limitation of the Time Series
The statistics do not cover all natural hazards. Damages from avalanches, snow pressure, earthquakes, lightning strikes, hail, storms, and drought are not included, among others.
The term "damage from natural events" should therefore not be equated with all natural disaster damages in Switzerland.
Additionally, there is a methodological peculiarity: Rockfalls and falling rocks have only been included in the BFS time series since 2002. This change in the data collection basis must be considered for comparisons over the entire period.
Figures Are Partially Based on Estimates
The damage sums are also not equivalent to an exact accounting for all of Switzerland. The WSL database relies significantly on the systematic evaluation of media reports. Property, infrastructure, forest, and agricultural damages are recorded.
The method is therefore primarily intended for long-term observation and comparison of events. It does not reflect every single Swiss Franc actually spent after a natural event.
Especially for major events, damage sums are subsequently further processed. The values should therefore be understood as estimates of economic damages.
Why the Data Are Important for Switzerland
Despite these limitations, the time series holds significant practical value. The WSL describes its severe weather damage database as an important basis for hazard assessment. Authorities and expert bodies can derive insights into the spatial distribution, extent, and causes of past events.
Such information informs hazard maps and the planning of protective measures, among other things. These include flood protection, protective forests, retention facilities, and structural measures against debris flows and landslides.
The principle is simple: The better known where which natural hazards have already caused damage, the more targeted risks can be reduced.
Natural Hazards Meet a More Densely Used Switzerland
Long-term development must therefore be viewed from two perspectives. On the one hand, natural hazards are changing. On the other hand, land use is increasing and intensifying.
In a densely populated country like Switzerland, natural events can therefore become particularly costly. Transport routes, power plants, industrial facilities, residential areas, and tourist infrastructure are partly located in regions where natural hazards are known.
Damage development is thus also a question of spatial planning. Where construction takes place helps determine how costly a future event can become.
The Main Statement of the Time Series
The statistics, covering more than five decades, do not show that damages continuously increase every year. They show something else – and something at least as important for risk planning.
Individual extreme events can cause billions in damage within a few days.
2005 stands for this, as does 1987. 2024 has shown that even today, a single severe weather year can cause damages of almost one billion Swiss Francs.
At the same time, the time series clarifies that a single annual figure is insufficient to assess long-term developments. For this, natural hazards, climate data, settlement development, asset values, and protective measures must be considered together.
What Switzerland Can Learn from 53 Years of Data
The most important insight from the BFS and WSL time series is not that natural hazards are simply becoming "ever more expensive." The development is too strongly influenced by individual extreme events for that.
Instead, the data shows how vulnerable a highly developed and densely utilized society is to natural hazards. Even if a major event remains rare, its financial consequences can be enormous.
For Switzerland, this means prevention remains a long-term task. Hazard maps, protective structures, spatial planning, and early warning systems must be regularly reviewed and adapted to changing climatic and societal conditions.
The time series since 1972 provides the memory for this. It shows what has already happened – and why the question of protection against the next major event should not only arise when the water is already rising.
Sources
- Federal Statistical Office (BFS): "Damage from Natural Events – Floods, Debris Flows, Landslides, Rockfalls, and Falling Rocks – Million Swiss Francs – 1972–2025"
- Swiss Federal Institute for Forest, Snow and Landscape Research (WSL): Severe Weather Damage Database Switzerland
- WSL: "Severe Weather 2024: Many Casualties and High Costs"
- WSL: "Severe Weather Damage in Switzerland 2024", Water Energy Air, 2025
