Sand dune types - Europe
This article provides a description of the main sand dune types that occur along the coast of Europe.
Contents
General introduction
Coastlines occur in two broad categories: those with a predominantly cliffed landform and low-lying areas where the action of waves and wind moves sedimentary material to create intertidal or coastal terrestrial habitats. The erosion of the former (particularly cliffs made of soft glacial material) may provide an important source of sediment for the latter, notably saltmarshes, sand dunes and shingle beaches and structures. The type of sedimentary structure that develops depends on its physical location, the size, type and availability of sedimentary material and the method of transport.
Sand dune types
Sand dunes develop on coastlines with an adequate supply of material within the size range 0.2-2.0mms. The critical factor is the availability of a sufficiently large beach, which dries out at low tide and where sand grains are blown onto the land by the action of the wind. In most locations in the temperate regions of the world, vegetation plays an important role in the growth of the typical dune landscape, which is so familiar to anyone visiting the “seaside”, by facilitating the accumulation of sediment.
The figure opposite depicts the main types of sand dune that occur along the coastline of Europe. It also shows the other functional coastal formations associated with sand dunes.
The weather of the West European coast from Tarifa (Spain) to Skagen (Denmark) is especially suitable for the formation of dunes. Often a wind is blowing, varying widely in force and direction. The conditions are optimal for the formation of high and wide dune complexes, given a large supply of sand by the sea. The annual precipitation surplus is considerable for most of this coast. This favours the establishment of vegetation, and thereby it enhances dune formation. The short distance to the land-sea border causes strong gradients in several climatological parameters. These gradients lead to mesoscale effects, such as land-sea breezes and coastal fronts. The varying vegetation cover and the presence of slopes in all directions induce a strongly varying microclimate. However, this microclimate is not unique to the coastal dunes. Unique is the interaction with the wide range of ambient weather, which is inherent to the coast.
Dune types summary definition
These are described as follows:
Bay dunes are the most common and are found associated with indented coastlines often between headlands;
Hindshore dunes may become very large as both dominant and prevailing winds blow sand inland in sometimes massive waves. On especially exposed sites coastal cliffs may be covered with a veneer of sand blown up over the cliff to create ‘climbing dunes’. The machairs of the west of Ireland and Scotland are also a special kind of hindshore dune which occurs as a flat sandy plain;
Barrier islands tend to occur in exposed locations and may be built on shingle bars; examples include the Wadden islands of Denmark, Germany and Holland and the North Norfolk coast in eastern England;
Ness dunes, including cuspate forelands, occur where prevailing and dominant winds are in opposition. Sometimes progradation may be quite rapid and a series of low dune ridges occurs interspersed with wet hollows. These are also found in areas where sea level is rising relative to the land as in southeast Norway, northeast Scotland and Northern Ireland;
Spit dunes are formed when sediment is deposited at the mouth of an estuary. They occur in a variety of forms depending on the action of waves (longshore drift) and the force of the river flows to the sea. These include the dune forms associated with deltas in micro-tidal areas, especially in the Mediterranean.
References
- ↑ Ranwell, D.S. & Boar, R., 1986. Coast dune management guide. Institute of Terrestrial Ecology, HMSO, London.
See also
Please note that others may also have edited the contents of this article.
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