Coastal protection structures

Groynes

• are obstacles built into the water at a right angle to the shoreline or the direction of the water flow (wall- or dam-like structures)
• are used as a basic element in the coastal protection since they break currents, surf and reduce the extent of erosion significantly
• usually wooden posts rammed into the seabed; have a durability of 40-60 years
• timber is well-suited, can be exposed to great dynamic load due to its elastic properties
• one of the major enemies of wooden groynes, especially of those made of local timber, is the Teredo navalis, called shipworm, it feeds on wood, infests the timber, makes it porous, as a resultl groynes will no longer resist the pressure of water and ice
• tropical timber from plantations is an alternative because the Teredo navalis cannot penetrate this extremely hard wood so easily
• to enter groynes is prohibited for the sake of safety, moreover they are usually very slippery
• dangerous currents can occur around groynes
• Keep away from the groynes when swimming!

Breakwaters

• are shore- parallel structures consisting of large natural stone blocks designed to minimize the wave`s intensity.
• stone blocks with a weight up to 7 tons are heaped up in a water depth of two to four meters, transported by excavators, helicopters or lighters (small, often broad barges with shallow draft - well suited for the transport of bulk material), stone blocks are placed in 50 - 200 meter long lines, 50 - 200 meters far from the coast
• especially built in places where there is a great danger of coastal erosion
• used to accumulate large quantities of sand behind the breakwaters

Dune, Dunes

• dunes are for coastal protection
• are sand mounds planted with beach grass
• purposes of planting beach grass:
  1. to increase the stability of the dunes by binding the sand due to a deep and a well-branched root system (2 to 3 meters deep)
  2. to prevent the dunes` surface from being eroded by the wind and prevent the sand from being carried into the hinterland
  3. to support the dune`s height growth by trapping sand grains and amassing the moving sand
• Please use beach accesses only, do not enter dunes. Their reconstruction is of great effort and of high costs.

Dikes

• To brave storm surges people began to build dikes some centuries ago
• a dike is mostly located behind a dune or a higher area formed by different soil layers
• initially dikes were simple mounds of marsh soil only covered with grass turf
• but from repeating levee breaches and ensuing floods the constructors learnt how to protect the coastal region better, the dikes became higher and also wider in their cross-sections

Coastal protection forests

• coastal protection forests complete the protection of coastal areas and prevent damage from water that would float landwards too rapidly in case of storm surges
• coastal forests offer protection from:
  1. the erosion of sand and stones by the wind
  2. sun or desiccation of the soil or any damage by the powers of the water
  3. 1.damage by the cold or severe frost

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