Recent and historic low-frequency, high-impact events have demonstrated the flood risks faced by exposed coastal areas in Europe. Risk can be defined as the product of the probability of a hazard and its consequences. Both are likely to increase in the future. The hazard probability may go up due to a changing climate with more frequent and violent hazards of surge-driven floods, wind damage, erosion, overtopping and rain-driven flash floods. Also, the consequences will increase.
These consequences (or impacts) are composed of two factors: the direct exposure (the density of receptors, e.g. number of people and buildings in an affected area) and vulnerability (receptor value and their sensitivity to experience harm). The number and value of receptors in the coastal area increases due to continued economic development and population growth. The sensitivity is also increasing e.g. due to unsuitable building types. Moreover, due to ripple effects of disasters, indirect impacts will affect the EU hinterland since coastal areas are gateways to Europe.
This projected increase in risk along coasts requires a re-evaluation of coastal disaster risk reduction (DRR) strategies and a new mix of prevention (e.g. dike protection), mitigation (e.g. limiting construction in flood-prone areas) and preparedness (e.g. Early warning systems, EWS) measures. Finally, in the longer term, the use of relief funds and provision of flood insurance are effective means so that an affected community can recover and restore its functions more quickly, i.e. increase resilience. Even without a change in risk due to climate or socio-economic changes, a re-evaluation is necessary in the light of i) shrinking public works budgets which drives cost-efficiency, and ii) a growing appreciation of ecological and natural values which drive ecosystem-based approaches. One step further is the “Building with Nature” approach, which in effect uses natural processes and environments to help protect the hinterland. In addition, as free space is becoming sparse, coastal DRR plans need to be spatially efficient, allowing for multi-functionality. This can be achieved, for instance, by using ecosystem services as flood defence or by combining coastal protection with benefits for tourism.
DRR should be viewed as an integrated chain of actions. This chain starts with understanding the present and historic situation and context in an area, assessing coastal risk for present and future hazard probabilities, identifying critical (hot spot) areas of higher risk, designing DRR plans including suitable prevention, mitigation and preparedness measures (such as EWS) to reduce coastal risk, and building trust and societal acceptance of these measures. In this way effective DRR solutions can achieve a strong societal basis and become part of the culture. Developing methods and tools to decrease risk and increase resilience requires an interdisciplinary approach which is too expensive and knowledge-intensive to be borne by individual countries or jurisdictions. Rather a supranational effort is required.