Under what conditions and for what reasons do coastal sand dunes develop? With the aid of examples examine the impact of sand sunes on economic activities.

    The particles have to be of a certain size so that they can be moved. I the particles are too small then they will not be deposited soon enough o form sand dunes. But also if the particles are too large they will not be able to be moved at all. The particles, which are the right size, are often moved by saltation. This is where the particles are moved only by the strongest winds blow and soon come back down to the ground when the wind is slowed. The particles therefore move in a hopping movement. Another method of transport is surface creep. This occurs when the larger particles are thrown by the wave and whilst landing throw the nearby sand particles forward. This is a very slow movement.

    Once the sand particles are being moved they need the wind flow to be blocked or stopped. Any obstacle such as plants, litter and walls can do this. If there is no common obstacle and the sand simply relies on lack of wind to stop moving then the deposition of sand would be too varied for a sand dune to form.

    When there is an obstacle to block the wind flow and the saltation process, the wind will slow and deposit any sand particles it is carrying. When a substantial amount of sand has been dropped this creates a bigger obstacle and therefore encourages more sand to be deposited and causes a bigger obstacle. The bigger the sand dune the less vulnerable it is as the centre of the sand dune will be moist and more stable so the winds will only be able to damage the outside layer of the sand dune.

    For a sand dune to survive it needs to be stabilised. This is done most effectively by vegetation developing on it. Colonising species such as sand twitch are able to survive here due to their long roots which are needed to hold the sand together and go deep into the sand dune to get water. The roots of the plants act as an anchor to the sand particles so that the dune doesn’t move. The vegetation over time adds nutrients to the soil and allows more species to develop there. AS more and more species develop the sand will continue to develop and the sand will slowly start to become of more of a soil.

                                        There are two main types of sand dunes vegetation sand dunes and transverse sand dunes. Transverse sand dunes are constantly on the move in the direction of the prevailing winds as there is no vegetation to keep them together. Vegetation sand dunes are more stable and do not move this is because plants are able to grow here and hold the sand together However the vegetation cover can sometime be broken if the vegetation cover is poor. Burrowing animals such as rabbits can also cause problems as they can dig through the vegetation and weaken the sand dune that can now be damaged by the wind and water.

Transverse sand dunes can often cause problems. This is because they are able to move freely in the direction of the prevailing winds covering everything in their way. This has obvious consequences on the people and environment nearby. Transverses sand dunes are common in dry environments as the sand is nearly always dry so can be transported easily. Mobile sand dunes cause many problems. Crops can be destroyed as well as people’s homes t is therefore important for governments and individuals to try and control the sand dunes.