| Abstract from DBPedia | Barrier islands are coastal landforms and a type of dune system that are exceptionally flat or lumpy areas of sand that form by wave and tidal action parallel to the mainland coast. They usually occur in chains, consisting of anything from a few islands to more than a dozen. They are subject to change during storms and other action, but absorb energy and protect the coastlines and create areas of protected waters where wetlands may flourish. A barrier chain may extend uninterrupted for over a hundred kilometers, excepting the tidal inlets that separate the islands, the longest and widest being Padre Island of Texas, United States. Sometimes an important inlet may close permanently, transforming an island into a peninsula, thus creating a barrier peninsula, often including a beach, barrier beach.The length and width of barriers and overall morphology of barrier coasts are related to parameters including tidal range, wave energy, sediment supply, sea-level trends, and basement controls. The amount of vegetation on the barrier has a large impact on the height and evolution of the island. Chains of barrier islands can be found along approximately 13-15% of the world's coastlines. They display different settings, suggesting that they can form and be maintained in a variety of environments. Numerous theories have been given to explain their formation. A human-made offshore structure constructed parallel to the shore is called a breakwater. In terms of coastal morphodynamics, it acts similarly to a naturally occurring barrier island by dissipating and reducing the energy of the waves and currents striking the coast. Hence, it is an important aspect of coastal engineering.バリアー島（英語: barrier island）とは、海岸線よりも海側に岸と並行に伸びる、礫や砂でなるいくつかの細長い高まりの連なりを指し、陸を海から守るような姿からこう呼ばれる。バリアー島の海側には砂浜が発達し、多くの島で低い砂丘と灌木等の植生が見られる。また、バリアー島と陸地との間にはラグーン（lagoon）と呼ばれる潟をもち、バリアー島同士の間にはラグーンと外洋とをつなぐ潮流口（tidal inlet）がある。上げ潮・下げ潮の度にラグーンと外洋の海水が潮流口を行き来するので、上げ潮の際にはラグーン側に、下げ潮の際には外洋側に三角州状の地形ができる。これは潮汐三角州（tidal delta）と呼ばれる。また、このラグーンは時間が経過すると潮流口がふさがり、塩沼となることもある。 (Source: http://dbpedia.org/resource/Barrier_island) |
