Coastal processes

The action of waves

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  • Created by: Leanne
  • Created on: 27-04-11 12:54

Coastal processes

Waves can be destructive or constructive.

When a wave breaks, water is washed up the beach - this is called the swash. Then the water runs back down the beach - this is called the backwash. With a constructive wave, the swash is stronger than the backwash. With a destructive wave, the backwash is stronger  than the swash.

Destructive wave

The effects of a high wave (

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  • destructive waves are created in storm conditions.
  • are created from big, strong waves when the wind is powerful and has been blowing for a long time.
  • occur when wave energy is high and the wave has travelled over a long fetch.
  • tend to erode the coast.
  • have a stronger backwash than swash.
  • have a short wave length and are high and steep.

Constructive waves

The effects of a low wave (

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  • constructive waves are created in calm weather and are less powerful that destructive waves.
  • break on the shore and deposit material, building up beaches.
  • have a swash that is stronger than the backwash.
  • have a long wavelength, a low height.

The sea shapes the coastal landscape. Coastal erosion is the wearing away and breaking up of rock along the coast. Destructive waves erode the coastline in a number of ways:

Hydraulic action.-Air may become trapped in joints and cracks on a cliff face. When a wave breaks, the trapped air is compressed which weakens the cliff and causes erosion.

 Abrasion- Bits of rock and sand in waves grind down cliff surfaces like sandpaper.

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  • Attrition. Waves smash rocks and pebbles on the shore into each other, and they break and become smoother.
  • Solution. Acids contained in sea water will dissolve some types of rock such as chalk or limestone


There are various sources of the material in the sea. The material has been:

  • eroded from cliffs.
  • transported by longshore drift along the coastline.
  • brought inland from offshore by constructive waves.
  • carried to the coastline by rivers.
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