CPSL - Coastal Protection and Sea Level Rise | Umweltbundesamt

Three scenarios are used for the sea level rise: +10 cms, +25 cms and +50 cms. Two geomorphological scenarios were devised for the future development of the Wadden Sea.

The climate change effects on selected physical, biological and socio-economic parameters of the Wadden Sea are analysed Characteristic elements of the Wadden sea system are the barrier islands, the tidal inlets, the ebb-tidal deltas, the tidal channels, the tidal flats and the salt marshes, and there is a constant sediment exchange between these elements.

For the scenario with +25cms of sea level rise by the year 2050 no significant changes in the Wadden Sea ecosystem (geomorphology and biology) are expected. However, the costs for coastal defence could rise by between 5 and 15%. For the scenario with +50cms of sea level rise by the year 2050, the capacity of the Wadden Sea to balance changes in the system through sediment distribution could be exceeded. Consequently, the tidal basins could evolve into coastal lagoons comprising large, permanently flooded areas. Such a geomorphological development would significantly affect and change the biological systems. Also, the costs for coastal defence could double in this scenario, if current safety standards were to be maintained.

The vulnerability issue is limited to the (natural) resilience and adaptive capacity of the ecosystems in the Wadden Sea, the adaptive capacity of the resident population is not taken into account.

The Wadden Sea is characterized by a strong natural variability and has a high natural resilience to changes. However, because of this, developments away from the existing dynamic equilibrium are difficult to detect, and some uncertainties exist on the so-called "breakpoints" of Wadden Sea basins, above which new ecosystems and biotope changes may become established.

Adaptive capacity: The study expects that a breakpoint exists between the two scenarios for the sea level rise up to 2050 (+25cms and +50cms), above which the adaptive capacity of a tidal basin will fail. This breakpoint is, however, dependent on the rate at which the sea level rises, and will vary between the individual tidal basins.

The urgency with which adaptation measures will be required mainly depends on the speed and extent of the sea level rise.

Sustainable coastal defence measures (so-called "Best Environmental Practices") will be selected that are suitable for guaranteeing that the current safety standards can be maintained in the future. Since the measures considered differ strongly with respect to their technical effectiveness, it is obvious that there is cannot be one single solution that fits all the demands of the whole Wadden Sea. Therefore, the group will recommend particularly those measures that best suit the coastal defence purposes while taking account of the ecological consequences.

The following points should be observed in coastal protection measures and strategies:

1. Spatial planning for coastal zones should include buffering and flood hazard areas (compliance with ICZM principles). Coastal defence and climate change should be duly considered in relation to each other. The feasibility of such plans should be investigated by a group of nature conservation, spatial planning and coastal defence experts.
2. Sand nourishment should be applied, wherever feasible, to combat erosion along sandy coastlines.
3. A study should be carried out on the extent to which sand nourishments will be able to balance the sediment deficit of the Wadden Sea tidal basins under an increased sea level rise.
4. Regional salt marsh management plans should be established to harmonize the demands of coastal defence and nature conservation.
5. An assessment the present-day coastal defence measures should be carried out to determine their suitability for guaranteeing that the current safety standards can be maintained in the future, with respect to their feasibility and ecological consequences.

Above all, conflicts exist between the interests of coastal defence, nature conservation and tourism. Sustainable coastal defence measures that comply with the ICZM principles can help reduce these conflicts.