Coastal Dunes form where constructive waves encourage the accumulation of sand, and where prevailing onshore winds blow this sand inland. There need to be obstacles e.g. vegetation, pebbles etc. to trap the moving sand grains. As the sand grains get trapped they start to accumulate, this is the start of dune formation. The wind then starts to affect the mound of sand by eroding sand particles from the windward side and depositing them on the leeward side. Gradually this action causes the dune to “migrate” inland, as it does so it accumulates more and more sand. Dunes provide privacy and shelter from the wind.