It is not just in Switzerland’s mountainous regions and near lakes and rivers that people are confronted with natural hazards, but all over the country. Because of urban development and climate change, the risks are increasing all the time, despite all the protection efforts. It is only by joining forces that the risks can be kept to a tolerable level for society.
Text: Nicolas Gattlen
Extreme natural events are a regular occurrence in Switzerland. We remember, for instance, the rock avalanche and debris flow in Bondo (GR) in 2017, the winter storm Lothar in 1999 and 100-year floods, like those of August 2005. However, the threat of hazards is not restricted to mountainous regions and areas near lakes and rivers. Every part of Switzerland is exposed to natural hazards and anyone could be affected. Data collected by the Federal Institute for Forest, Snow and Landscape Research (WSL), for instance, shows that in the past 45 years, four out of five Swiss communes have suffered damage as a result of debris flows or flooding. Landslides affected two in five communes in the same period.
Up to 100 billion Swiss francs
In Switzerland, earthquakes are the natural hazard with the largest potential for damage. The authorities estimate that an earthquake like the one that occurred in Basel in 1356, with an estimated magnitude of 6.6, would leave up to 2,000 people dead, 5,000 seriously injured and 20,000 with minor injuries, and would cause material damage costing 50 to 100 billion Swiss francs. Although powerful earthquakes are rare in Switzerland, history and research nevertheless show that they can still occur at any time and in any part of the country. A major earthquake (magnitude 6 or more) can be expected in any part of Switzerland every 50 to 150 years. However, the risk is highest is Valais, followed by Basel, Grisons and the Rhine Valley in St Gallen.
Heavy rainfall can also cause considerable damage anywhere in the country. This was seen in July 2017 in Zofingen (AG), where a three-hour storm left many basements, garages, gardens and underpasses submerged. Although the River Wigger burst its banks in some places, it was not the primary culprit. Rather, the huge volume of water was unable to drain away because of the ground being partially sealed. The surface runoff risk map shows that around two thirds of buildings could be affected by heavy rainfall. Surface runoff accounts for up to 50 percent of flood damage following heavy rainfall, and costs around 140 million Swiss francs per year. Rivers, streams and lakes bursting their banks cause the rest of the flood damage.
Switzerland is a densely populated country with a large number of rivers and lakes, so the flood risks are considerable: around 20 percent of the population lives in zones that could be affected by flooding. And these regions are home to 30 percent of the country’s workplaces and 25 percent of its material assets. The main risks are in the agglomerations. Between 1972 and 2018, floods, debris flows, landslides, rockfall processes accounted for around 305 million Swiss francs of damage per year on average. Over 90 percent of material damage is caused by flooding and debris flows, and just under 10 percent by landslides. Material damage caused by avalanches, rockfall processes is low by comparison. However, rockfall processes, landslides and avalanches often lead to loss of life.
More frequent and more intense
We can expect floods, debris flows, landslides and rockfall processes to become more frequent as a result of climate change. It is not just the frequency of natural hazards that is expected to increase, however, but also their intensity. Higher winter precipitation levels and the simultaneous rise in the snow line are increasing the risk of flooding in the winter months. Because of the expected increase in frequency and intensity of heavy rainfall, there is also likely to be a higher risk of flooding and, in particular, of damage caused by surface runoff at other times of the year as well. At the same time, Switzerland is facing more frequent forest fires and drought periods in the summer months when there is low rainfall. Higher temperatures are driving glacier melt in the mountains and thawing the permafrost, which is leading to a destabilisation of rocky mountainsides and scree slopes. In general, the hazard situation will change and intensify according to the season and region.
In addition, the risks from natural hazards are aggravated by more intensive land-use and the spread of settlements in hazardous zones. Building and infrastructure assets are constantly increasing in value, partly because of more expensive construction methods and larger dwellings. Sophisticated protective structures alone are not enough to prevent damage completely. In order to achieve and maintain an acceptable level of safety in the long term, there is also a need for risk-based land-use planning and for all stakeholders to work together. In Switzerland, natural hazard protection and emergency response management are joint tasks shared by the federal government, the cantons, the communes, insurance companies and private individuals. On the following pages we show which tasks are performed by which agents, and what contribution individuals can make to natural hazard protection.
Switzerland’s global involvement
In the years 2008 to 2018, the Red Cross recorded 3,750 natural disasters worldwide. Around two billion people were affected by the incidents and more than 700,000 lost their lives. Damage costing over 145 billion US dollars was caused each year. And the disaster risks will increase in future because of climate change, the destruction of the environment, population growth and poorly planned urbanisation. Switzerland has a great deal of experience in dealing with natural hazards and pursues a holistic approach to reducing risks – an approach that it also brings to bear in international committees and conferences, such as the Global Platform for Disaster Risk Reduction. This is the platform that regularly reviews progress in implementing the UN’s Sendai Framework for Disaster Risk Reduction and discusses new ideas for dealing with risks.
Disaster risk reduction is also a key part of the programmes of the Swiss Agency for Development and Cooperation (SDC) because natural disasters can destroy decades of development progress in one fell swoop. The SDC is also able to call on the FOEN’s experience and expertise in prevention and protection projects. For instance, the FOEN has carried out training sessions in Bolivia on hazard and risk assessment. In Jordan, it is currently assessing how a national flood hazard and risk-mapping programme could be implemented, and in China it is supporting implementation of an integrated risk management approach in a large torrent drainage basin.
Last modification 03.06.2020