The sand dunes lie at right angles to the prevailing wind and form a series of ridges, running roughly north-south, with lower lying areas between their crests. The long, linear depressions formed when a length of beach has been enclosed by newly formed dunes are known as "swales", whilst the smaller hollows are called "slacks".
The fixed dunes were once mobile dunes, like those nearer the sea. Over time, new dunes have formed to seaward and interrupted the supply of fresh sand. The once dominant Marram grass and Lyme grass have been replaced by new plant communities and thin, impoverished soils have developed on what was raw sand.
The foredunes are the first dunes to form in the dune system and the develop above the line of wave-deposited debris (strandline) where only the strongest waves during very high tides will reach.
About 15 years ago, a number of ponds could be found in the dune slack areas. These areas remained wet throughout most of the year, supporting wetland plants such as Marsh Pennywort, the less common Narrow-Leaved Reedmace, Meadowsweet, Wild Mint and three or four species of orchid, including the Heath-Spotted Orchid and the Marsh Helleborine.