Summary
1. Climate Change and Natural Disasters
Serious worldwide consequences associated with climate change are expected unless greenhouse gas emissions are significantly reduced. For Switzerland, the impact of natural disasters - especially flooding, which tends to cause particularly high levels of damage - is a key issue. In this Report, we discuss the frequency and potential economic impact of heavy precipitation events and droughts in Switzerland.
2.Climate, Extreme Precipitation, and Runoff
Over the last few years, research has provided an improved understanding of the processes leading to extreme precipitation and flooding. Thanks to modern climate models, accurate estimates of changes in the average climate in the average future climate are achievable. However, these models do not provide definitive statements concerning future extreme precipitation events. Nevertheless, weather forecasting models allow detection of the formation of such events days in advance.
At present, the processes that cause prolonged droughts in the Alpine region are poorly understood.
3. Frequency of Precipitation and Flood Events
According to climate models, intensification of the hydrologic cycle due to anthropogenic climatic warming is likely. Indeed, recent studies based on the 100 year observational record in Switzerland confirm model-based predictions: There has been an increase of up to 30% in autumn and winter precipitation in the Alps, and we may well see a further rise in the future. As a result, the frequency of flood events in the Swiss Central Plateau (Mittelland) and southern Switzerland in the winter half-year is expected to increase.
Little change in the magnitude of summer precipitation has been observed, and its future pattern is uncertain. This makes it virtually impossible to predict the impact on the flow patterns of Alpine rivers, which flood primarily in response to summer storms.
4. Economic Impacts of Extreme Precipitation Events
The economic impact can be assessed on the basis of three scenarios:
- A seasonal drought would not have serious economic consequences, as Switzerland has sufficient water reserves.
- If regional flooding were to increase, we should expect costs to rise by several hundred million francs per year. Broadly speaking, existing insurance schemes, reinsurance agreements and solidarity agreements should be able to absorb this additional risk.
- Historical climate records indicate that extreme precipitation events could occur on a far greater scale than they have in recent years. The resulting damage-related costs would far exceed current insured amounts. However, since such events are rare, this issue cannot be linked to climate change.
5. Measures to Minimize Future Damages
Measures for preventing flood-related damage can be directed at different points in the precipitation formation/flooding/damage chain of events.
- Switzerland is well advanced in terms of construction-related measures. However, there is a clear need for overall evaluation when new investments are being planned.
- Land-use planning is likely to become more important as the risk of flooding grows, since effective planning reduces the potential for damage.
- Unilateral reduction of greenhouse gas emissions in Switzerland will not have any direct impact. Switzerland can best serve environmental policy needs by becoming involved at the international level in efforts to reduce greenhouse gases. This includes reducing emissions at the national level.
6. Synthesis
Various institutions should make efforts to respond to increases in the frequency of flood events:
- Research institutions should make further improvements in their climate, weather forecasting and natural disaster models. In addition, improvements are required in the basic principles of damage-related cost estimates and cost-benefit analyses relating to protection measures.
- Insurance companies should, among other things, reassess their coverage levels and develop risk-based premiums.
- Government is challenged on all levels:
- At the municipal level, land-use planning should take into account flood protection measures;
- At the cantonal level, guidelines and funds for flood protection measures should be used more effectively;
- At the national level, land-use planning must be coordinated more effectively. Funds for construction-related flood protection measures should be used more effectively. In addition, the government should undertake diplomatic initiatives with the aim of forging international environmental and climate agreements.
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