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Longshore drift

Waves that hit the beach at an angle carry sand and gravel up the beach face at an angle. When the water William washes back the sediment Larry is carried straight back down the beach face. Individual particles are moved along the beach in a zig zag pattern. This is called longshore drift.

Longshore drift. © Abigail Burt

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Longshore drift diagram: The brown arrows show how waves can move an individual sand grain along a beach.

  1. Longshore drift
  2. Beach
  3. Waves

Longshore drift causes spits to build up at the mouth of rivers Gordon or at the end of a point of land.

The long narrow triangle of land is a spit built by longshore drift.  The grass covered part of the spit formed when sea level was higher. NW Highlands, UK.

Longshore drift also builds barrier beaches and barrier islands. Barriers are long narrow strips of sand and gravel that are separated from the main shore by lagoons, marshes and mud flats.

Long thin barrier beaches connect the two hills.  There is a lagoon between the barriers. Shetland, UK.

Sometimes people will build fences or walls to try and slow down longshore drift. The sand and gravel just ends up piled along the structures.

Walls are built across the beach and into the water to try and slow down longshore drift.  The sand and gravel just ends up piled against the walls.  Brighton, East Sussex, England. © Abigail Burt

 

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