SANDDUNE - Sand dunes occur when prevailing winds blow sediment to the back of the beach and therefore the formation of dunes requires large quantities of sand and a large tidal range. This allows the sand to dry, so that it is light enough to be picked up and carried by the wind to the back of the beach. Frequent and strong onshore winds are also necessary. The dunes develop as a process of a vegetation succession:
○ Embryo dunes – Upper beach area where sand starts to accumulate around a small obstacle (driftwood, wooden peg, ridge of shingle)
○ Yellow dunes – As more sand accumulates and the dune growns, vegetation may develop on the upper and back dune surfaces, which stabilises the dune. The tallest of the dune succession.
○ Grey dunes – Sand develops into soil with lots of moisture and nutrients, as vegetation dies, enabling more varied plant growth.
○ Dune slack – The water table rises closer to the surface, or water is trapped between hollows between dunes during storms, allowing the development of moisture-loving plants (e.g. willow grass)
○ Heath and woodland – Sandy soils develop as there is a greater nutrients content, allowing for less brackish plants to thrive. Trees will also grow (willow, birch, oak trees) with the coastal woodland becoming a natural windbreak to the mainland behind