Coastal erosion
Coastal erosion or (geological) abrasion is the gradually advancing change of (marine) coasts due to erosion caused by tides , waves and weather influences such as wind , rain and temperature differences , natural events such as hurricanes or earthquakes , but also due to effects on the environment, for example due to the damage to the uppermost soil layers by human influence or global warming .
Coastal erosion is a natural mechanical- physical process: The damage to vegetation through human use makes the coast more susceptible to the forces of the wind and facilitates the penetration of water and z. B. related frost blasts , as was the case with the chalk cliffs on the island of Rügen in winter 2004/2005.
Coastal erosion affects all forms of coastline : on steep coasts , cliffs are eroded and collapse. Sandy beaches are washed away by the waves or carried away by the wind. In general, coastal erosion is less effective on hard-rock coasts. On cliffs, the speed of erosion also depends on how quickly debris is removed by the water and thus the cliff behind it becomes unprotected again.
Thereby causing storm surges and tsunamis great damage. Investigations by NOAA showed that Hurricane Katrina in the Mississippi Delta damaged the natural coastal protection of the mangroves . The 2004 Indian Ocean tsunami changed a number of islands significantly.
According to the European Commission , around a fifth of the coastlines within the European Union (excluding Bulgaria and Romania) were affected in 2004 . The front runners are Poland (55.0 percent) and Cyprus (37.8), least of them Finland (0.04), Estonia (2) and Sweden (2.4%). The coasts of Finland and Sweden in particular are characterized by granite cliffs , which make a very large part of the coastline practically non-erodible.
As a countermeasure, considerable financial resources are invested in coastal protection through dykes , groynes , breakwaters , lahnungen or sand flushing. However, these also have the effect that, although coastal erosion is slowed down on the respective coastline, the erosive effects are intensified on other coastlines due to the change in the flow behavior of the water.
The negative consequences of coastal erosion are the loss of areas with a high level of biodiversity or important ecosystems , of economically used areas and objects, the abandonment of endangered houses on the demolition edges, the growing danger for residents near the coast and damage to natural or artificial coastal protection.
One factor that makes coasts more prone to erosion is the shrinkage of sandy beaches or sandbanks , since sand washed away by waves and currents is no longer sufficiently filled by sedimentation . These are either removed as building material or are left behind behind embankments and barricades.
The global warming and the associated changes as the global sea level rise , changes in waves or the destabilization of Arctic coasts, which make up more than a third of the world's coastline, by thawing permafrost and decreasing sea ice cover provide many coastal an increasing erosion risk.
Added to this is the loss of natural coastal protection , e.g. B. through the destruction and damage of mangrove forests ; the destructive effect of storm surge waves and tsunamis on human settlements on the coast can be reduced by intact mangrove forests in front of them.
Web links
- EU press release: European Commission makes coastal erosion a key issue
- European Commission website on coastal erosion (English / French / Spanish / Portuguese)
Individual evidence
- ↑ Sean Vitousek, Patrick L. Barnard, Patrick Limber: Can beaches survive climate change? In: Earth and Space Science . April 2017, doi : 10.1002 / 2017JF004308 .
- ^ Michael Fritz, Jorien E. Vonk, Hugues Lantuit: Collapsing Arctic coastlines . In: Nature Climate Change . January 2017, doi : 10.1038 / nclimate3188 .
- ↑ Andrea Naica-Loebell: Mangroves as a tsunami brake. In: Telepolis. November 2, 2005, accessed December 5, 2014 .
- ↑ Kandasamy Kathiresan, Narayanasamy Rajendran: Coastal mangrove forests mitigated tsunami. In: Estuarine, Coastal and Shelf Science. Vol. 65, No. 3, 2005, ISSN 0272-7714 , pp. 601-606, doi : 10.1016 / j.ecss.2005.06.022 .