Laung
A Laerung is a bank protection system . These are mostly double rows of wooden stakes that are built into the sea in the shore area with bushes tied in between, so-called fascines . Depending on the depth, current and subsoil, gabions are also used successfully here . The approximately 60–80 cm high parapets enclose fields of approximately 100 m × 200 m in size.
In Germany, Lahnungen are often built on the banks of the Wadden Sea . The resulting floodplain fields are drained through ditches , so-called clumps or clumps . These are up to 2 m wide, a few decimeters deep and divide a Lahnungsfeld into up to 10 m wide beds. The groups are excavated in a linear fashion and mostly run at right angles to the coast. The excavated soil is thrown sideways onto the parapet fields. At high tide, the water flows onto these fields, where it comes to rest and the suspended solids can settle. This promotes sedimentation and silting up .
If the fields are silted up sufficiently high, the groups are dredged again, whereby the excavation is used to further increase the mudflat between the groups. At the same time, it also improves the drainage of the soil between the trenches. In this way, the ground elevation is up to 10 cm per year, after one to two decades salt marshes have emerged from the sea floor with a foreland level that is above the normal flood level.
The use of parapets for the purpose of land reclamation often takes place in three stages. In front of a Schardeich a first floodplain field is built in which sediments are deposited. After a few years a second field will be built in front of the first on the lake side. There sediments are deposited again, while pioneer plants emerge in the first field . Finally, a third floodplain field is set up, while the second is now overgrown by pioneer plants and the first has already become salt marshes in the foreland of the dike.
This type of coastal protection not only gains land, but also makes the hinterland safer, because during storm surges the force of the waves against the dikes is weakened.
literature
- Petra Witez: Final report on the research project MTK 0608 (03 KIS 3160): Programs for the long-term conservation of the Wadden Sea - Prowatt , ed. from the Federal Ministry of Education and Research, Laboe 2002, p. 32 ff.
