Climate-proofing and flood-proofing the island of Schouwen-Duiveland

Results

The study shows that the vulnerability of Schouwen-Duiveland can be reduced by taking measures in the context of multi-layer flood risk management.

In accordance with the “flood risk management regional pilots” (National Water Plan), strategies have also been drawn up for the Schouwen-Duiveland pilot. The strategies focus on the goal of “flood-proofing the road structure (2050-2100)”. They have been established on the basis of the typical features of Schouwen-Duiveland, field trips, and the various aspects of Multi-Layer Flood Risk Management (National Water Plan, 2009). Three strategies have been proposed:

1. “Traditional plus” – The current flood risk management philosophy will be continued. The flood risk is reduced by reinforcing the two relatively vulnerable locations near the foot of the Brouwers dam and the Oosterschelde storm surge barrier. This is expected to contribute significantly to the promotion of safety. Wherever possible, adjustments to flood defence systems will be linked to other functions, such as recreation, Nature, or a road on top of the dyke. For that reason, a flood defence system that is generously dimensioned both in height and in width would be preferable.

2. “The backbone” – The elevated backbone runs from east to west and has sufficient capacity for evacuation traffic. This generates a flood-proof road that, in the near future, will provide a positive impetus to the economic activities on the island and that will continue to be flood-proof in the more distant future as well. On account of the elevation of the road, a combination with other functions would be a logical choice. Emergency relief locations will be sought in the more elevated sections, with corresponding evacuation routes.

3. “Infrastructure follows landscape structure” – This involves the realisation of a flood-proof infrastructure that follows the island’s landscape structure. Wherever possible, the elevated, flood-proof routes are located on dykes or more elevated terrain. The openness of the mostly open polder is not interrupted. The road will only be widened, not raised. Emergency relief locations will be sought along the flood defences along the coast, and in the more elevated sections of the island.

Additionally, the flood-resilience of Schouwen-Duiveland may be enhanced by:

• Raising awareness among residents and improving their coping capacity (how high is my house located, where is the nearest emergency relief location, how do I get there, what does an emergency kit contain?);
• Improving safe flood relief locations with sufficient capacity. Both in residents’ own homes (water-proofing, flood-proof construction, floating homes) and providing emergency relief locations on the island of Schouwen- Duiveland. New emergency relief locations may be linked to various functions, including flood risk management (flood defence), infrastructure (roads), recreation (vantage points), sports facilities, et cetera;
• Promoting the realisation of new developments on more elevated terrain, and/or factoring in evacuation routes to a safe location, as well as the prevention of damage;
• Protecting vulnerable areas (vital infrastructure or villages) by, e.g., a partition dyke or by temporarily collecting water elsewhere and subsequently discharging it at an accelerated rate in order to relieve the vulnerable areas.

The report also sets out a number of recommendations pertaining to multi-layer flood risk management policy and planning:

• A multi-layer flood risk management ambition supported at the national, regional, and local levels, including financial substantiation and responsibilities;
• Calculation / assessment methods, including the elaboration of the impact of flooding on these measures;
• Participatory process / promotion team with district water board, municipality, Province, national government, and project developers;
• Providing transparency regarding and raising awareness of the risks in the event of a flood, for both the current situation and when making new plans;
• Realising an accessible data bank with potential measures against flooding, pluvial flooding, heat and drought, with their typical features (including benefits for the quality of the living environment and economic value).