Sand Dune

Sand dunes border long stretches of the World’s coastline and are best developed in temperate and arid zones (Bird 1984). They are formed when sandy shores dry out and sand grains are blown inland. Accumulations a few centimetres to 40m or more thick are formed by the combined action of wind and the stabilising effects of vegetation. Whilst most dunes show contemporary contact with the sea, on rising shorelines or where sand accumulation is extensive this contact may be discontinuous or absent. In Queensland, Australia, dunes exceeding 275m in height have developed through episodic migration (Bird 1984) and in Scandinavia land uplift has resulted in dunes occurring today far removed from the coast (Aartolahti 1973, Heikkinen & Tikkanen 1987). This chapter is concerned largely with dunes which are derived from sediments driven onshore by the action of the sea and subsequently moved inland by wind. Throughout reference is made to geomorphological issues though this is not dealt with in detail, but see Pye & Tsoar (1990), Nordstrom et al. (1990) and Bakker et al. (1990). The extensive barrier island coast of the eastern USA is mentioned only in relation to considering sea defence issues.