Longshore drift

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Diagram demonstrating longshore drift
1=beach
2=sea
3=longshore current direction
4=incoming waves
5=swash
6=backwash

Longshore drift is the process of the ocean currents forcing sand and other material down a beach, eventually washing it all out to sea. The material is first pulled into the currents by the backwash (the water going out to sea) and is then pushed back up the beach by the swash (the water going onto the beach.) Longshore drift always moves in the direction of the main wind. If longshore drift continues for a long time, beaches can be destroyed which would reduce the amount of money coastal resorts get.

  • The waves carry the rock material up the beach at an angle. (waves move at an angle – wind)
  • The backwash carries the material directly down (gravity) into the sea or it stays there.
  • This process goes again.

There are, however, many inexpensive and effective ways of controlling longshore drift. The most common method is groynes (wooden walls that the sand builds up in.) Some people dislike the groynes because they are not very nice to look at.

Longshore drift is the net movement of sand grains move across a beach in a zig-zag motion.