Keywords:
barrier dune
artificial dune
coastal erosion
sand nourishment
Contact: W.D. Kamp. Ministry for rural areas, agriculture,
food and tourism. State of Schleswig-Holstein. P.O. Box 1440.
25804 Husum. Germany.
Location: Germany, Schleswig-Holstein, North Sea
The island of Sylt
The west coast of Sylt with a length of 40 km tends into the North
Sea and is therefore affected by storm and wave forces. The island
originated from a round oval moraine, which was located several
kilometres further west than today. With the rising of the sea
level after the last ice-age, the nowadays existing long shape
with the core of former mainland and the adjoining dunes in the
north and in the south developed. The island’s base rises gradually
from the deeper sea ground, where a sandy reef in the foreshore
zone is located. Shore and reef together function as a transportation
mean. While waves and tides continuously erode and move away material
from the sandy shore and foreshore area, dune cliffs are only
affected in irregular intervals during storm surges. The average
annual retreat at the west coast from 1870 to 1950 has been 0.9
m but has increased during the past 35 years. For the protection,
seawalls of a total length of 3 km along the coast were constructed
between 1907 and 1954, but erosion in front of the construction
and lee-erosion at the edges appeared.
Management
As a result of the storm surges of the past years, the managing
state agency in Husum has developed the project ‘Coastal protection
on Sylt’, in which the solution offered by the latest developments
and technologies (e.g. solid constructions: every kind of bank
revetment, groynes) and sand nourishment were examined. It turned
out, that continuously repeated sand nourishments are an appropriate
solution from the technical, economical and environmental point
of view. The sand nourishments consists of backfill material and
a 60 m wide artificial dune in front of the erosion line, that
functions as a stockpile of sand. In the case of extremely severe
storm surges, this recession depot will be eroded. The artificial
dune has to be restored in certain time periods with new material,
which is excavated by automatic trailing suction dredgers out
of an area, which is located 7 – 10 km in front of the island’s
west coast with an average water depth of 14 m. No impact on the
island is expected from this sand borrowing.
Future Research
The sand nourishments were accompanied by a research program with
the aim to improve knowledge about the development at the west
coast of Sylt and to optimize the method. Therefore the State
Schleswig-Holstein, with support of the German Ministry for Research
and Technology (BMFT), has launched a large research program ‘Aims
of the optimisation of Coastal Protection on the Island of Sylt’,
in which several institutions participated. The program ended
in 1994.
Nourishment profile
References
- Kamp, W.D. & P. Wieland (1993): Case Studies for Coastal
Protection: Dithmarschen; Eider Estuary; Sylt. In: Coastlines
of the Southern North Sea. The American Society of Civil Engineers.
New York. (18.3.9).
