At the Wadden Sea in Southern Jutland, there are vast low-lying marshes, where humans have always struggled against sea flooding. It is from this area that the first examples of coastal protection in Denmark are known, and locally organized dike construction and operation have been carried out there since the middle ages.
As a consequence of the significant storm surges experienced in Denmark in 1976 and 1981, the Danish government subsequently decided to reinforce the existing dikes thoroughly and build an advanced dike in the Tønder marshland.
Today's dikes protecting Ribe and Tønder are built to resist a storm surge, which statistically occurs every 200 years, while the other dikes are built for storm surges that statistically occur every 50 years.
The dikes are operated and maintained by local dike associations, while the Danish Coastal Authority provides technical advice and handles the supervisory control of the dikes. Moreover, the Danish Coastal Authority continues to study the dikes in its efforts to develop new knowledge about the sea’s effect on the dikes and new technical methods and models for the assessment of dikes
Coastal protection in the Wadden Sea is carried out in close cooperation with the other countries of the Wadden Sea region. The Advanced Dike, also called the Danish-German Dike, has consequently been built in cooperation with Germany and stretches across the border between Denmark and Germany. The Danish Coastal Authority cooperates with the German federal state of Schleswig-Holstein in order to prevent flooding, including storm surge warning.
Since 1998, the Danish Coastal Authority has also participated in the trilateral Wadden Sea working group on Coastal Protection and Sea Level Rise, in which coastal protection, nature conservation, and planning authorities from The Netherlands, Denmark, and Germany meet to prepare common guidelines for e.g. coastal protection in the Wadden Sea. In 2010-2013, the Danish Coastal Authority held the working group presidency.
Apart from handling the supervisory control of the Wadden Sea dikes, the Danish Coastal Authority handles the technical supervisory control of the dikes on the islands of Lolland and Falster.