Nourishing the coast with sand 

Every other year or so, part of the 13 kilometre long stretch of coast in
Denmark gets ‘beach nourishment’ from the sea. This ensures that local holiday homes are still able to enjoy their sea view and sandy beach.

The north Funen coastline in Denmark is home to 2,000 holiday cottages along a 13 kilometre stretch offering enviable views. Maintaining the beach costs them each about EUR 200 a year in fees, which they pay to the North Funen Coast Protection, Dyke and Drainage Association.

The money ensures that the holiday homes can maintain their safe position on the coast and an attractive sandy shore. The coastline is protected by rock structures and beach nourishment as the sea would otherwise get closer and closer.

Photo: Rohde Nielsen A/S
The idea of beach nourishment is to replace sand that is eroded by waves. Here, a dredger
pumps sand along the west coast of
Denmark.


Nourishing the shore

Every other year, the shore is nourished by a fresh supply in the form of approximately 20,000 cubic metres of sand, which is shipped from the seabed by a special vessel called a dredger, and which sails close in to the coast and pumps the last bit up onto the beach through a pipeline to reform the beach.

"The idea of beach nourishment is to replace the sand which is being eroded by the waves and lost along the coast. It’s a never-ending job. However, rock structures have been installed at the most exposed sections in order to reduce the loss of sand and hence the need for recharging," says Christian Helledie, a coastal morphologist at cowi, who has been involved in the project for several years.


Second chance In 1996, the Danish Coastal Authority began upgrading the coast protection defence along a number of sections of the Danish waters. Some 25 sections with serious coastal problems were selected, including North Funen, where the sea had eroded most of the sandy beach over the years. The following year, COWI began the new coastal protection works at North Funen. The coast was already protected by a number of small, run-down groynes and other rock structures, which made the coast look messy and aesthetically unpleasant.

"The old structures were incapable of retaining the sand on the beach, which had largely disappeared as a consequence. And that created an increased risk of a sea dyke breach and flooding," Christian Helledie explains.

By replenishing the beach with 113,000 cubic metres of sand, spread out over a stretch of 2.2 kilometres, the goal was to advance the beach
some 25 metres in relation to the original beach, which had vanished completely in a number of locations. Beach nourishment was chosen in order to restore a natural, attractive sandy beach while simultaneously protecting he nearby sea dyke from erosion. In addition, it was decided to leave the old groynes in position in order to retain the sand which was being heaped up across the beach.

By Gitte Roe Eriksen,  cht@cowi.com
Published: 12.08.2008