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A dike protects the built-up area and land lying behind it against flooding. Dikes are most often established with a core of sand that is dressed with clay and then covered with grass or asphalt. The dimensions of the dike, and the choice of materials, depend on local conditions and the desired strength of the dike. A distinction is made between two types of dike: Sea walls and levees

A sea wall should be placed away from the coastline with foreland to minimise the risk of erosion from the direct impact of waves during normal and high sea levels. If a sea wall is placed as a protruding dyke, however, and without foreland, slope protection should be established, because the direct impact and resulting wear from waves will be considerable. Sea walls should generally be constructed with slightly slanting foreslopes, so that the energy of waves is evenly distributed over a larger area, and so the impact from the waves is reduced. This increases safety and reduces the risk of collapse and breaching.


Levees should be placed directly on the bank of the watercourse and are suitable near the mouth of watercourses in areas where elevated water levels are a frequent problem. Levees are typically established with a core of soil and are planted with grass.
Inspection and maintenance of dikes is vital to ensure the dimensioned strength of the dikes is maintained. Possible damage to the dike from human or animal activity should be minimised as far as possible, and the clay layer and a well-trimmed grass cover should be maintained. Dike reinforcement may be required and will typically be in the form of raising the height of the dike, evening out the foreslope, reinforcing the backslope and/or increasing the clay layer.



Foto: Kystdirektoratet

Senest redigeret: 04-02-2014