Coastal Dunes
Ecosystems Functioning
Case Study 1 – Coastal Dunes
1. What are coastal dunes and how have they been formed?
Coastal Dunes are large accumulations of sand located immediately behind the active beach zone. They are formed when sand is deposited onto the shore by wave action, dries out and is blown to the back of the beach. This process is referred to as accretion.
2. Where are coastal dunes found globally? What role does the wind play in their formation?
Coastal dunes are found on all the worlds continental land masses, with the exception of Antarctica. They form wherever there is sand available for their construction. Windblown desert sand is usually finer than beach sand. The other significant factor is wind. It is the single most important factor in determining the shape and extent of coastal dunes. Dunes are most likely to develop in coastal regions that experience strong onshore prevailing winds.
3. List the 3 factors responsible for dune formation.
The movement of sand by the wind is referred to as Aeolian Transport. The volume of sand transported by wind depends on the size of the sand particles, the velocity of the wind, the local topography and the nature of the vegetation cover. Sand is most commonly moved by the wind via a process known as saltation. Very tiny particles of sand are moved by suspension.
4. Sketch and explain how a coastal dune system operates. Explain why the foredune is vulnerable (blow outs) to erosion.
Sand dunes are built up in calm weather by small waves and light winds. Dunes form where constructive waves encourage the accumulation of sand, and where prevailing onshore winds blow this sand inland. There need to be obstacles, for example, vegetation, pebbles and so on to trap the moving sand grains. As the sand grains get trapped they start to accumulate, starting dune formation. The wind then starts to affect the mound of sand by eroding sand particles from the windward side and depositing them on
Case Study 1 – Coastal Dunes
1. What are coastal dunes and how have they been formed?
Coastal Dunes are large accumulations of sand located immediately behind the active beach zone. They are formed when sand is deposited onto the shore by wave action, dries out and is blown to the back of the beach. This process is referred to as accretion.
2. Where are coastal dunes found globally? What role does the wind play in their formation?
Coastal dunes are found on all the worlds continental land masses, with the exception of Antarctica. They form wherever there is sand available for their construction. Windblown desert sand is usually finer than beach sand. The other significant factor is wind. It is the single most important factor in determining the shape and extent of coastal dunes. Dunes are most likely to develop in coastal regions that experience strong onshore prevailing winds.
3. List the 3 factors responsible for dune formation.
The movement of sand by the wind is referred to as Aeolian Transport. The volume of sand transported by wind depends on the size of the sand particles, the velocity of the wind, the local topography and the nature of the vegetation cover. Sand is most commonly moved by the wind via a process known as saltation. Very tiny particles of sand are moved by suspension.
4. Sketch and explain how a coastal dune system operates. Explain why the foredune is vulnerable (blow outs) to erosion.
Sand dunes are built up in calm weather by small waves and light winds. Dunes form where constructive waves encourage the accumulation of sand, and where prevailing onshore winds blow this sand inland. There need to be obstacles, for example, vegetation, pebbles and so on to trap the moving sand grains. As the sand grains get trapped they start to accumulate, starting dune formation. The wind then starts to affect the mound of sand by eroding sand particles from the windward side and depositing them on