COMRISK - Common Strategies to reduce the risk of storm floods in coastal lowlands | Umweltbundesamt

Use of climate projections from the 3rd Assessment Report of the Intergovernmental Panel on Climate Change (IPCC 2001). Information on sea level rise from the CPSL project: Sea level rise of +1m (pessimistic scenario). In addition, failure and structural collapse probability scenarios for sea defence installations (e.g., dyke breaches) will be considered.

The climate change impacts considered are the increased risks of flooding and coastal erosion due to an accelerated sea level rise. One conclusion is that the coastal risks will increase even further as a result of increased land use intensity. In the event of a failure of the local coastal defence structures, the extent of the flooding and the size of the affected population vary greatly among different coastal areas in the North Sea region. Other climate change impacts considered include salt water intrusion into the ground water and dune erosion, for example on the East Frisian Islands.

The result is that all the countries and regions in the area under study see the climate change and the sea level rise associated with it as an important challenge. This means that, despite the existing uncertainties, most stakeholders in coastal defence have adopted a precautionary approach, taking into account higher values for dimensioning their defence measures. In addition, the policy-makers have registered that the sea level rise will entail an increase in the occurrence of extreme events and that this could make it necessary to adjust coastal defence strategies. How such strategies can be implemented in an institutional context, and what responsibilities the various national organization levels have, varies between the affected countries and regions.

A vulnerability analysis will be carried out to assess the possible extent of damages with the aid of so-called risk elements. The expected damage is analysed with the help of depth-dependent damage functions. Vulnerability is defined in terms of the loss of or damage to the risk elements in a specific area as a possible consequence of a specific hazard situation (here, in particular, a dyke breach with subsequent flooding of the protected area) The adaptive capacity of the population is not taken into account here, i.e., the expected damage determines the vulnerability. Risk awareness and risk acceptance are part of an integrated risk assessment and are considered accordingly.

A sensitivity analysis will also be performed with respect to the assessment of uncertainties in the input parameters and models of the overall failure probability statistics and failure mechanisms for the flood protection and coastal defence systems.

Coastal risk management needs to be able to reduce the natural hazards posed by the sea in the form of flooding and erosion, and to make them manageable. It must include - or better, integrate - the planning and construction of dykes and other defence structures, flood forecast and warning systems, evacuation plans and damage repair and rehabilitation plans after natural catastrophes. Many aspects of such a risk management strategy fall under the responsibility of government authorities, but individuals can also assume a significant role by being aware of the risks and knowing what to do in an emergency.

The aim of the analyses of the project is to improve risk management in coastal defence (so-called coastal risk management) by adapting to a rise in the sea level. In order to achieve a robust risk management strategy, a wider range of options need to be considered for integrative risk management. Apart from technical solutions, this includes spatial planning strategies and instruments, flood warning systems, self-help, and insurance/compensation.

Recommendations for a coastal risk management strategy are:

• Continued cooperation within the EU to ensure that common interests are fully exploited.
• Focus on further communication and mutual learning/understanding, rather than an enforced harmonization;
•  Improving information strategies and public perception of storm surges in order to increase the level of public risk awareness;
• Clear communication of coastal risks, rather than simply pointing to safety standards (for example, starting in schools);
• Use of advanced methods for addressing uncertainties and assurance that policy-makers are aware of the uncertainties in the data and findings.

Overall, risk management helps to broaden and improve the basis for decisions on adaptation measures for coastal defence.

Useful life of coastal defences (in some cases, up to 2100):

The United Kingdom and the Netherlands focus on a multi-generation time horizon in their coastal defence strategies. This illustrates the need for a long-term adaptation strategy for coastal defence planning. The other countries in the area of study will mostly limit themselves to assessing their current level of protection and studying the technical life expectancy of the coastal defence installations.

Conflicts of interest regarding land use in the coastal zones will be examined. Sustainability needs to be part of an integrated risk management (this is also a requirement of the Integrated Coastal Zone Management - ICZM).