Coasts

• How waves form

  1. Wind blows over the surface of the sea

  2. Friction is created

  3. Producing a swell in the water
• Factors impacting wave size

  • Fetch - How long the wind has been blowing for (how far the wave has travelled)
  • Strength of the wind
• How sea stacks are formed


  1. Hydraulic action widens cracks in the cliff face over time

  2. Abrasion forms a wave cut notch between HT and LT

  3. Further abrasion widens the wave cut notch to from a cave

  4. Caves from both sides of the headland break through to form an arch

  5. Weather above/erosion below –arch collapses leaving stack

  6. Further weathering and erosion eaves a stump
• How bays and headlands are formed

  1. Waves attack the coastline

  2. Softer rock is eroded by the sea quicker forming a bay, calm area cases deposition

  3. More resistant rock is left jutting out into the sea. This is a headland and is now more vulnerable to erosion
• Hard engineering


  The use of artificial (man-made) structures to protect the coastline
• Soft engineering

  The use of natural methods to protect and manage the coastline
• Beach nourishment


  • Beaches built up with sand, so waves have to travel further before eroding cliffs
• Managed Retreat


  • Beaches built up with sand, so waves have to travel further before eroding cliffs
• How waves break

  1. Waves start out at sea

  2. As waves approaches the shore, friction slows the base

  3. This causes the orbit to become elliptical

  4. Until the top of the wave breaks over
• Characteristics of a constructive wave

  • Stronger swash than backwash (builds up a beach)
  • Long wave length (less frequent)
  • Smaller wave height (waves are small)
• Characteristics of a destructive wave

  • Stronger backwash than swash (destroys a beach)
  • Short wave length (frequent – more regular)
  • Large wave height (waves are big)
  • More energy
• How coastal spits are created

  1. Swash moves up the beach at the angle of the prevailing wind

  2. Backwash moves down the beach at 90° to coastline, due to gravity

  3. Zigzag movement (Longshore Drift) transports material along beach

  4. Deposition continues at a change in land directions causing the beach to extend out into open water

  5. Change in prevailing wind direction forms a hook

  6. Sheltered area behind spit encourages deposition, salt marsh forms
• How sand dunes are created

  1. As wind blows sand inland and embryo dune is formed round an obstacle (piece of wood or a rock)

  2. These them develop and become stabilised by vegetation (Marram grass is specially adapted to the conditions)

  3. In time rotting vegetation add organic matter
• Hard engineering techniques

  • Sea Wall
  • Groynes
  • Gabions or Rip Rap
• Sea Wall


  Concrete walls break up the energy of the wave. Has a lip to stop waves going over.
• Groynes


  Wood barriers prevent longshore drift, so the beach can build up.
• Gabions or Rip Rap


  Cages of rocks/boulders absorb the waves energy, protecting the cliff behind.
• Sussex Coastline (chalk):

  Sea stacks found at Seaford Head

  Wave-cut platform found at Seaford Head and Birling Gap