Keywords:
artificial dune
barrier dune
morphology
vegetation
dune creation

Contact:  Peter Vestergaard, Botanical Institute, University of Copenhagen, Øster Farimags-gade 2 D, DK 1353 Copenhagen, Email: peterv@bot.ku.dk

Location:  Denmark, Baltic Sea, southwest of Copenhagen

The construction of Køge Bay Seaside Park
In 1975 the Ministry of Environment decided to establish a beach park facility situated in the Køge Bay, southwest of Copenhagen. The Køge Bay developed during the last stage of the Pleistocene Age and can be characterized as a low wave energy environment. The new land with shores, dunes, grasslands and plantings was built as an 8 km long stretch in 1977-79, using the structure of a natural barrier system, located more southernly in the Køge Bay, as a model. The backbone of the park is a ca. 7 km long and 300 m wide artificial barrier, built of marine sand, pumped up mainly upon sandy barrier islands. The water area behind the barrier was transformed into two systems of brackish la-goons. The shore and the dune were built of sand, the area behind the dune row was formed of mate-rial of a finer texture, the uppermost 30 cm mixed with clay to improve growth conditions for the plants. The dunes with their slopes were planted with Ammophila arenaria. The area behind the dune row was partly planted with trees and shrubs, partly sown with a mixture of grasses. After the period of establishment in 1977-1980, where the planted and sown areas were fertilized and controlled, the area was mainly given to spontaneous vegetation developments.

Morphological changes
Investigations at the coast indicate no retreat of the coastline, the nearshore terrace appears relatively stable with an even positive trend in material exchange. Investigations along a transect shows, that the relief in the inner part of the dune and behind it, remained fairly unchanged, but in front of the dune the relief changed very markedly. The planned 45 m broad beach, unusual for the landscape in Køge Bay, changed into a normal beach of approximately 10-15 m width over its whole length. It is bordered by an almost continuous and marram grass covered mobile dune ridge, formed from marine deposits by eolian transport.
Further a considerable accretion has taken place on a 3 km long coastal stretch southwest of the beach park. Several barrier islands and lagoons have emerged, and in some sections the coastline is displaced more than 100 m in a seaward direction. However, it is not known, if this results from the beach park itself or if it’s a natural barrier development, just started during the time, when the beach park was built.

Changes in vegetation
Along the investigated transect, the number of species increased both on the beach and in the dune zones. This results from an influx of diaspores, judged from the initial absence of terrestrial species in the seed bank. The planted Ammophila arenaria dominated during the first years, but declined in the dune zone because of the establishment of grassland species, mainly of Festuca rubra. Plants of A. arenaria and A. baltica spread both vegetatively and by seed on the beach zone, still playing an im-portant role in the formation of foredunes. In the dune area, the dominance of therophytes has changed to a dominance of hemicryptophytes. In 1994 altogether 220 species were found in the whole area.
All in all, there was a parallel displacement of the mobile dune from the position of the man-made dune seaward, while the man-made dune developed into dune grassland. After 13 years naturally established plants seemed to be prevalent and the artificial dune is comparable with natural dunes in respect to its species composition, whereas the artificial grasslands differ from natural salt meadows.
 
 

 Køge Bay Beach Park

References

• Andersen, U. V. (1995): Invasive Aliens: A Threat to the Danish Coastal Vegetation?. In: Healy & M. Doody (eds.). Directions in European Coastal Management. Samara Publishing Limited. Cardigan. (PC95).
• Andersen, U. V. (1996): The influence of human trampling on the vegetation on artificial dune and coastal grassland in Denmark. In: A.H.P.M. Salman, H. Berends & M. Bonazountas (eds.). Coastal Management and Habitat Conservation. EUCC. Leiden. The Netherlands. (PC96).
• Nielsen, N. (1990): Construction of a recreational beach using the original coastal morphology, Koege Bay, Denmark. In: P. Fabbri (ed). Recreational uses of coastal areas. Kluwer Academic Publishers: 177-189. (DRC90).
• Hansen, K. & P. Vestergaard (1986): Initial establishment of vegetation in a man-made coastal area in Denmark. Nordic Journal of Botany 6: 479-495. (32BNT86).
• Vestergaard, P. & K. Hansen (1992): Changes in morphology and vegetation of a man-made beach-dune system by natural processes. In: Carter, Curtis & Sheehy-Skeffington (eds.). Coastal Dunes: 165-176. Balkema. Rotterdam. (BNd92).