TY - GEN

T1 - Foreland development along the advanced seawall at Højer, the Danish Wadden Sea

AU - Vestergaard, Peter

N1 - Key words: Foreland, geomorphology, management, monitoring, salt marsh, tidal flat, vegetation

PY - 2006

Y1 - 2006

N2 - As part of the advanced seawall at Højer, built in 1979-1981, a marsh foreland, 150 mwide and sloping from +2.45 m DNN to +0.20-0.30 m DNN, was designed. The aimwas to provide protection of the seawall and to create a green environment as a replacementof the salt marsh areas, which would be lost between this and the oldseawall. The foreland was founded by marine sand, and the innermost part wassown with grasses. To enhance sedimentation, a coherent row of sedimentation fieldswas established along the foreland in 1986-1988. The development of the forelandhas been monitored with irregular intervals since 1981. In this paper I present observationsof changes in profile and vegetation, and I compare the state of the forelandin 2004 with mature marsh forelands.The main trends observed so far have been: 1) the species richness of vascularplants has increased, 2) Glasswort (Salicornia) and Common Cord-Grass (Spartina)have established widely on tidal flats in the sedimentation fields, 3) At the inner partof the tidal flat a Common Salt-Marsh-Grass (Puccinellia maritima) salt marsh hasgradually established, 4) the foreland landwards to the tidal flat has currently beennarrowed by erosion, but has also been influenced by sand accretion, 5) the vegetationof the outer part of the foreland is still open and characterized by beach anddune species, 6) the vegetation of the inner part of the foreland is slowly developingtowards a typical Wadden Sea high marsh.In conclusion, the planned foreland has not yet been achieved after 23 years, andthe development of the foreland has differed somewhat from what was originallyexpected. This is probably caused by the circumstance that the advanced seawall wasbuilt on a relatively low-lying tidal flat. The vegetation zonation developed so farindicates, however, that a typical marsh foreland may be formed along the advancedseawall during the coming decades on the basis of the technical support carried outuntil now and a continuation of the current management of the foreland. Establishmentof extra brushwood groynes

AB - As part of the advanced seawall at Højer, built in 1979-1981, a marsh foreland, 150 mwide and sloping from +2.45 m DNN to +0.20-0.30 m DNN, was designed. The aimwas to provide protection of the seawall and to create a green environment as a replacementof the salt marsh areas, which would be lost between this and the oldseawall. The foreland was founded by marine sand, and the innermost part wassown with grasses. To enhance sedimentation, a coherent row of sedimentation fieldswas established along the foreland in 1986-1988. The development of the forelandhas been monitored with irregular intervals since 1981. In this paper I present observationsof changes in profile and vegetation, and I compare the state of the forelandin 2004 with mature marsh forelands.The main trends observed so far have been: 1) the species richness of vascularplants has increased, 2) Glasswort (Salicornia) and Common Cord-Grass (Spartina)have established widely on tidal flats in the sedimentation fields, 3) At the inner partof the tidal flat a Common Salt-Marsh-Grass (Puccinellia maritima) salt marsh hasgradually established, 4) the foreland landwards to the tidal flat has currently beennarrowed by erosion, but has also been influenced by sand accretion, 5) the vegetationof the outer part of the foreland is still open and characterized by beach anddune species, 6) the vegetation of the inner part of the foreland is slowly developingtowards a typical Wadden Sea high marsh.In conclusion, the planned foreland has not yet been achieved after 23 years, andthe development of the foreland has differed somewhat from what was originallyexpected. This is probably caused by the circumstance that the advanced seawall wasbuilt on a relatively low-lying tidal flat. The vegetation zonation developed so farindicates, however, that a typical marsh foreland may be formed along the advancedseawall during the coming decades on the basis of the technical support carried outuntil now and a continuation of the current management of the foreland. Establishmentof extra brushwood groynes

M3 - Report chapter

SN - 978-87-7772-921-8

T3 - Technical Report No. 573

SP - 123

EP - 132

BT - Monitoring and assessement in the Wadden Sea.

PB - National Environmental Research Institute

CY - Kalø

ER -