Coastal processes


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Coastal processes

  1. 1. COASTAL PROCESSES Coasts are shaped by the sea and the action of waves. The processes that take place are erosion, transportation and deposition.
  2. 2. The action of waves The power of waves is one of the most significant forces of coastal change. Waves are created by wind blowing over the surface of the sea. The size and energy of a wave is influenced by: • strength of wind • how long the wind has been blowing • How far the wave has travelled
  3. 3. Types of waves Waves can be destructive or constructive. • Constructive waves – have limited energy; – move material up the beach (deposition).
  4. 4. Types of waves • Destructive waves – larger and have more energy; – tend to erode the coast; – used by backwash to move material down the beach
  5. 5. Coastal erosion • • • • 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 Corrasion/ abrasion Attrition Corrosion/ solution
  6. 6. Coastal erosion • Hydraulic action: as waves break against the cliff face, the pressure of the breaking wave can compress air in cracks. This compressed air gradually forces open the crack in the rock - as this process continues, the rock becomes increasingly weakened. • Corrasion: (also known as abrasion) rock fragments are hurled at cliffs by breaking waves, gradually scraping away at the cliff face. • Attrition: rock fragments carried by the waves hit against each other and gradually wear down to form sand and silt. • Corrosion (also known as solution): occurs where the salt water is able to dissolve some of the chemicals in rocks.
  7. 7. Factors affecting coastal rosion
  8. 8. Transport • • • • 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.
  9. 9. Transport Waves can approach the coast at an angle because of the direction of the prevailing wind. The swash of the waves carries material up the beach at an angle. The backwash then flows back to the sea in a straight line at 90 degrees. This movement of material is called transportation. Continual swash and backwash transports material sideways along the coast. This movement of material is called longshore drift and occurs in a zigzag.
  10. 10. Transport Longshore drift is the process by which sand and pebbles are moved along a beach by the movement of the waves.
  11. 11. Transport
  12. 12. Deposition When the sea loses energy, it drops the sand, rock particles and pebbles it has been carrying. This is called deposition. Deposition happens when the swash is stronger than the backwash and is associated with constructive waves.