Deltas in particular are susceptible to phenomena such as climate change, sea level rise and natural disasters. Therefore, coastal defense is important in these areas. Experience has shown that natural solutions are more resilient to resist disturbances. The lectorate Building with Nature investigates how to make maximum use of nature in coastal defense, so that in addition to safety it also offers opportunities for recreation.
Much of the Netherlands has a sandy coast of beaches and dunes. Such a coast can be maintained by the interplay of sand, wind, waves and currents. An example of a Building with Nature approach is to replenish the shortage of sand after which it is left to nature to maintain the coast. An added benefit is being able to recreate on the beach.
Restoration of salt marshes
In addition to sandy coasts, the Netherlands has dikes. Examples of Building with Nature solutions in such areas are artificial oyster reefs or the restoration of salt marshes that reduce wave impact on the dike.
The research group also conducts research into increasing natural values on the dikes themselves. The researchers work a lot on site, in the field or in the laboratory.
Wietse van de Lageweg is lector Building with Nature. He delivered his inaugural address on Nov. 3, 2022: 'Future Shores'.
Behind the research facility of NIOZ in Yerseke lie 12 concrete basins that are flooded during high tide and easy to reach during low tide. Within these basins experiments are performed on how biodiversity can be enhanced on subtidal, hard structures like dikes or pillars of wind farms. To meet current safety standards dikes need to be reinforced. In subtidal parts this is usually done through adding a layer of rock material or steel slag (a waste product of the steel industry with a high density). These reinforcements are often applied in soft sediment areas or on dikes with a high nature value. These locations often receive special protection due to their high natural value. The hard structures provide shelter for the European lobster and other important target species. Dike reinforcements can only take place when this natural value is preserved or compensated. The aim of Rijkswaterstaat is to protect the nature value of the subtidal parts of the dike through the addition of 'eco-tops'. These eco-tops exist of a ridge or pile of rocks which facilitate the reestablishment of the target species as well as a sheltered area that allows a faster sediment deposit.
The narrow strip of beach and dunes form an important part of the coastal protection system around the world. Even though it only makes up about 4% of the earths total landmass. They protect the hinterland from flooding, provide freshwater filtration and storage services and add unique wetlands and landscapes which provide many touristic and recreational functions. However, these areas are experiencing heavier erosion each year. Therefore, innovative measures created by the Building with Nature and Living Shorelines philosophies will be put to use in order to halt and reverse ongoing erosion. The solution proposed is the addition of sand suppletions to areas that show high erosion rates. The volume of the nourishments is determined by predicting the erosion rate on current knowledge gained by monitoring. Two large-scale nourishment projects have been created (Sandmotor and Hondsbossche Dunes) and form the living labs for the project C-SCAPE. Examining natural and anthropogenic drivers of the coastal landscape is the key to high quality data on erosion and effectiveness of the sand suppletions. On the two locations not only physical experiments will be done, but also societal factors will be taken into account. The objective of C-SCAPE is to develop the knowledge and tools needed to assess the feasibility and benefits of sandy strategies for coastal climate adaptation.
Sea level rise puts pressure on the safety, ecology and economy of the coast and delta waters. The traditional response from the manager is then to reinforce flood defences. History has shown that this is effective, only it is often a costly operation, takes up a lot of space and only serves water safety. Innovations in coastal management are necessary and urgent to develop new concepts for the levee zone that provide flood safety, increase spatial quality (creating valuable nature and other societal benefits) and give substance to climate-neutral and circular operations. This challenge is already in play in the near future because the new water safety assessment requires a substantial reinforcement task for the dykes of the Western and Eastern Scheldt to be realised by 2050. BwN solutions offer a promising action perspective for our handling of sea level rise, but require more research for optimal incorporation on a large scale.
