Multi-Layer Safety Kampereilanden
A study has been conducted into solution strategies for short-term and long-term flood risk management of the Kampereilanden polders. Building blocks have been developed from the multi-layer flood risk management perspective. These building blocks are linked to the three “layers” of the multi-layer flood risk management model. The study focused on societal costs, comprising the risk and the costs of measures. Flood risks have been assessed using the multi-layer flood risk management tools. The costs of risk-reducing measures have been estimated on the basis of the cost indicators of the Expertise Centrum Kosten (Cost Expertise Centre, ECK). In addition to the risks and costs, additional criteria such as the efficiency of investments, support among stakeholders, spatial quality, Nature, and ecology have been used to assess the measures, in accordance with the recently formulated multi-layer flood risk management evaluation system (Foundation for Applied Water Research, STOWA).
Results
Absolute safety cannot be guaranteed in the Kampereilanden polders, as the risk cannot be reduced to zero. However, multi-layer flood risk management will enable the composition of a package of measures that is acceptable in terms of costs and which will reduce the risk. This consideration focuses on efficiency, but also on other criteria such as Nature and ecology, or the perspectives for the agricultural sector. An application of the multi-layer flood risk management evaluation framework has facilitated the comparison and discussion of alternative strategies, as has the approach adopted, involving design sessions and analyses to gain insight into the risks, the costs, and the other values.
In order to substantiate the collaboration between authorities and with the residents of the Kampereilanden polders, it is important to point out that there is an (acceptable) flood risk, and on the other hand, what measures are being taken to establish and contain that risk. The question of what is deemed acceptable and what measures would be acceptable is one to be addressed by politics/society.
Various multi-layer flood risk management strategies have been formulated for the Kampereilanden polders, whose pros and cons have been mapped out by reference to an evaluation framework. The elaboration provides a suitable basis for administrative assessment and decision-making.
Prevention (first layer) is the most effective and efficient risk-reducing measure, compared to second and third layer measures. There is something to be said for combining measures across the different layers; this would involve preventative measures supplemented by measures from the third and possibly the second layers.
Organising disaster management and enhancing the capacity of individuals to cope efficiently with disasters are relatively cheap measures that are considered useful complements to prevention. An essential component, however, is that it must be made clear that the government cannot guarantee the safety of all people and animals; the residents also have a responsibility of their own.
The area has only limited linkage opportunities (linking flood risk management to other spatial developments). This is due to the relatively low degree of spatial development in the Kampereilanden polders. Furthermore, multi-layer flood risk management strategies turn out to hold limited benefits for other values.
The Kampereilanden polders have been designated as a peak water storage area. This designation is, however, debatable. From the perspective of a risk-based approach, it could be stated that the low degree of flood risk management ensues from the value of the area: surrounding areas have a higher economic value and thus are better protected. From an equality perspective, on the other hand, the Kampereilanden region needs additional measures, supplementary to prevention, because the area is more prone to flooding. A multi-layer flood risk management strategy could substantiate this.
Spatial interventions aimed at raising ground and adopting different construction methods are neither effective nor cost-efficient. Neither is utilising the old sea wall as a partition dyke. This does not hamper the voluntary raising of ground, but such measures do call for proper insight into what may happen if things go wrong.