Wadden Sea Area
The Wadden Sea area is the most natural part of the Dutch coast. Every year tens of thousands of tourists visit the area to spend time on one of the quiet beaches, explore nature and enjoy cultural events. In terms of coastal protection, the Wadden area is essential for the safety of our country’s northern region. Tidal mud flats and tidal marshes minimize the impact of sea waves on the dikes.
Above all, the Wadden area is an internationally famous and extremely valuable nature reserve. Millions of migratory birds use the area as a halting place between their wintering habitats and breeding grounds. Unfortunately these qualities of the Wadden Sea are threatened. Rising sea levels and land subsidence increase the depth of the Wadden Sea, amplifying the impact of waves on the coast, and damaging shoreland ecosystems.
To preserve the functional significance of the Wadden area for the Netherlands, the supply of sand and sediments to the area must be increased, and erosion and sedimentation processes must be given free rein. Only this way the Wadden Sea and tidal marshes can grow along with the rising sea level and keep sea waves from impacting the coast. The following measures could help to reach this goal:
- optimise offshore sand supplementation in the North Sea and Wadden Sea for adequate sediment supply to the Wadden island shores and Wadden Sea;
- improve sediment trapping: experiment with seagrass fields and mussel banks;
- make the transition between land and water more gradual, to cushion the impact of waves and reduce flooding risks for Friesland and Groningen. The feasability of double seawalls, dikes resistant to overflow, and ‘wash-overs’ (areas without dunes or dikes, which are periodally flooded by the sea) should be considered;
- restore the hydrological connections between the Wadden Sea and the IJsselmeer, Lauwersmeer and Binnen-A, to facilitate movement and exchange of organisms.
The coast of Holland
The coast of Holland, i.e. the west coast of the Netherlands, along the North-Holland and South-Holland provinces, is our most important recreation area. Under natural conditions, a rising sea level would move the coastline further inland. The coastal dunes would ‘wander’ further inland as well. Every sea level change would recreate a new equilibrium. However, the sandy coastline of the Netherlands is fixed, to protect the cities and towns behind the dunes.During the last few decades, the fixed coastline has weakened in several places. As the sea currents do not bring enough sand, the beach narrows and the coast steepens. Intensive maintenance of the coastline by yearly sand supplementation is required to prevent further damage. Due to climate change, coastal maintenance costs will go up as increasingly more sand will be needed. This is inevitable. Climate buffers along the coast will draw on natural processes that allow the coast to grow along with the expected sea level rise.
Offshore sand supplementation should help to restore the sediment balance. Concrete plans for ‘Sand Motors’ have already been worked out. ‘Sand Motors’ are large, concentrated offshore sand supplementations. Sea currents will pick up the sand and deposit it on the beaches. This way, sand supplementation stimulates and reinforces the process of natural dune formation. This will benefit the endangered dune plant and animal communities.
The estuaries of the Rhine, Maas and Scheldt are among the most productive ecosystems on earth. By nature these estuaries produce enormous numbers of shrimp, mussels and oysters; they are the nurseries and breeding grounds for many fish species and marine mammals. The islands of the Zeeland Delta are among the most popular holiday destinations of Western Europe.
The Zeeland Delta is world famous for the Delta Works: a series of dams, sluices, locks, dikes, and storm surge barriers that protect the area from the sea. However, it is now becoming clear that these structures prevent the delta from naturally adapting to rising sea levels. In the long run, this will undermine the safety of the area. Additional problems associated with the Delta works are their huge maintenance costs and negative effects on water movement and circulation. For instance, the Volkerak Zoommeer lake suffers from eutrophication and algal blooms because there is hardly any water movement to transport fertilizer runoff elsewhere.
Furthermore, the shores of the various inlets have become unstable because dams and dikes limit tidal movement and natural sand supply. This problem is most acute in the Oosterschelde estuary. And finally, it will become increasingly difficult to drain the swelling rivers via the Haringvliet sluices. Natural climate buffers offer a sustainable solution for the problems of the Zeeland delta.
The sea dikes along the shores of the Westerschelde should be moved further inland, to allow sandbars and salt marshes to grow along with the sea. The Oosterschelde must be reconnected to the North Sea and the Scheldt river, to increase the natural supply of sand and sediment in the Oosterschelde. This will have a favourable impact on the production of fish, shrimp and shellfish, and increase the stability of shores and sea dikes.
A return of tidal movement will also benefit the shore stability and ecosystems of the Grevelingen (a former estuary that became a lake after the Delta works were built). The Volkerak-Zoom lake should be reconnected to the Haringvliet and Oosterschelde inlets and the Grevelingen lake to improve tidal movement and water quality. Sluice capacities must be increased to keep up with the swelling rivers. These measures will boost recreation and tourism, and open up possibilities for climate-proof housing developments. The gates of the Haringvliet sluices should be permanently open (except during extreme weather) to restore the natural freshwater-saltwater gradient. The return of natural dynamics will also positively affect the habitat quality of many migratory and coastal bird species.