The Danish Coastal Authority The Danish Coastal Authority (Kystdirektoratet) – a division of the Ministry of Transport – is the state authority responsible for the construction and maintenance of coastal protection on the west coast of Jutland. Other responsibilities include harbour operation, dredging and storm surge alerts for the west coast of Jutland and the tidal flats. Coastal protection on the west coast The west coast of Jutland is constantly affected by the waves and currents of the North Sea. The Danish state has carried out coastal protection on the west coast to protect valuable resources from erosion and flooding since 1875.
On particularly vulnerable sections of the coast, such as the Harboøre sandbar and the cliffs at Bovbjerg, the Danish Coastal Authority has built a number of groynes to combat the immense power of the sea. There are now approximately 100 granite and concrete groynes on the west coast, the largest rocks in the groynes weighing more than 15 tons. The first groyne was built at Bovbjerg in 1875.
The groynes cannot completely stop coastal erosion but for almost 100 years they were the only viable method of protection.
In 1974 the method of coast nourishment was introduced. In coast nourishment sand is pumped onto the beach or in near-shore areas to compensate for lost sand. Coast nourishment has reduced erosion on the west coast significantly and in some areas brought it to a standstill.
The groynes on the west coast are still maintained and in addition concrete revetments have been built into or in front of the seawall as a reinforcement on critical sections, e.g. Ferring Lake. Coast nourishment In 2009 the west coast were nourished with approximately 1.7 million m3 of sand, the expenses shared by the Danish state and the appropriate regions and coastal districts.
A custom-built dredger pumps sand from the seabed approximately 5-10 kilometres from shore and ships it to the near-shore holding area. Here the dredger is coupled to a large rubber tube through which the sand is then pumped either onto the seabed close to land or onto the beach itself. These operations are known as “near-shore nourishment" and "beach nourishment” respectively.
The beach itself is not affected and remains open to the public while work is in progress but handling the large tube can involve the use of heavy machinery; therefore in the interest of public safety people have to remain at some distance while the machines are operating.
Without coastal protection roughly 1 metre of the west coast would disappear each year. Surveys show that there has been no recession of the coastline in recent years, so we can safely say that coast nourishment has neutralized the natural erosion of the coastline.
The sand-pump dredger is coupled to a tube floating on the surface of the sea. The sand is mixed with water and pumped through the tube onto the seabed near the shore.
A custom-built vessel (the sand-pump dredger) pumps sand into its hold from the seabed 20 metres below it, approximately 5 kilometres from the coast. The vessel has a capacity of approximately 2000 m3 and has a loaded draught of approximately 5 metres.
