Costal

• Waves

  Caused by friction generated when wind blows across the surface of the sea
• Wave reaching the beach

  1. Water running up the beach is called the swash

  2. As the wave loses energy, the water begins to run back down the beach to the sea, and is called the backwash
• Types of waves


  • Destructive waves
  • Constructive waves

  
• Destructive waves

  • Strong winds, powerful waves and cause coastal erosion, tall and steep, backwash is stronger than the swash so material is carried out to sea
• Constructive waves

  • Light winds, not powerful and cause deposition, stronger swash so material is carried up the beach and deposited
• Erosion


  A wave removing material from the coastline
• Attrition


  Small rocks that the waves are carrying, collide into one another, the rocks break up, becoming smaller and rounder, until the rock becomes sand
• Abrasion


  Rocks that the wave is carrying are thrown against the coastline, wearing away the coastline over time
• Hydraulic action


  Large waves break against the cliff, the water is forced into faults/cracks in the cliff, which causes immense pressure, when this pressure is released, it produces a force that makes the crack larger

  
• Solution

  Sea water has lots of different chemicals, and these can sometimes react with the rock, causing the rock to dissolve, occurs most frequently with limestone
• concordant coastline

  Bands of rock run parallel to the coastline, limestone (resistant rock) runs along the entire length of the coast

  
• Discordant coastline


  Bands of differing rock strengths (resistant and less resistant) run perpendicular (in the opposite direction) to the coastline, a mixture of clay (less resistant), chalk and limestone (resistant) run perpendicular to the coastline

  
• Headland


  Along a discordant coastline, the rocks of higher resistance erode at a slower rate to the rock of lower resistance, resulting in the high resistant rocks protruding out from the coastline

  
• Bay


  Along a discordant coastline, the rocks of lower resistance erode at a faster rate than the rocks of higher resistance, resulting in the rock eroding back more quickly to produce bays, constructive waves often bring sediment to form a beach
• arch

  waves erode thecave, via the process of hydraulic action and abrasion, with rocks and pebbles swirling within the cave. If the cave sits in a narrow headland, waves eroe through the cave, creating an arch

  
• stack

  Continued erosion of the base of the arch wekeans the structure, until a point where the roof collapses due to instability, leaving a stack, separated from the main land.

  
• Cave formation


  Destructive waves break against the cliff face, weaknesses in the rock are attacked, hydraulic action widens the crack, eventually forming a cave

  
• Arch formation


  Waves erode the cave via hydraulic action and abrasion, if the cave sits in a narrow headland, waves erode through the cave, creating an arch
• Stack formation


  Continued erosion of the base of the arch weakens the structure, until the roof collapses due to instability, leaving a stack separated from the mainland
• Happisburgh, Norfolk has eroded by almost 90m over the last 10 years, due to a failure in coastal defences
• Processes that change coastlines

  • Mechanical (freeze thaw)
  • Chemical
  • Biological
  • Mass movement (slumping, rock falls, sliding)
• In the UK, winter storms can bring torrential rain and winds in excess of 100mph, increasing erosion rates
• Longshore drift


  Waves approach the beach at an angle equal to the prevailing wind, material is moved up the beach at an angle (swash), returning perpendicular to the coast, along the south coast of the UK, the prevailing wind is from the South West, moving material from west to east
• Bar


  A ridge of sand or material that extends across a bay or river mouth, creating an enclosed water body, forms through the same process as longshore drift
• Spit


  A narrow ridge of sand or shingle, that stretches out from the coastline, into a gap in the coastline, forms due to longshore drift
• How humans affect the coastline

  • Settlement
  • Tourism
  • Infrastructure
  • Construction
  • Agriculture
• Many people choose to live near the coastline in the UK due to the economic, environmental and social benefits it brings
• Sea level in the English Channel is expected to rise by 15cm by 2030 due to global warming
• A storm surge is a large increase in sea level due to a storm, strong winds drive the waves, whilst low pressure allows the sea level to rise up to 3m above normal in the UK, these events can last for days and cause significant harm and loss of life
• In January and February of 2014, the UK was hit by a series of low pressure systems, bringing heavy rainfall and extremely strong winds, the south west of England was worst hit, with some areas having their wettest January since records began
• Coastal management strategies


  • No intervention
  • Hold the line
  • Managed realignment
  • Advance the line
• Advantages and disadvantages of coastal defences

  • Sea wall (protects base of cliff, expensive and unattractive, restricts access)
  • Groynes (maintains wide beach, attracts tourists, high cost of maintenance, can impact other areas)
  • Beach replenishment (looks natural, attracts tourists, cheap, material easily eroded, needs constant replenishment)
  • Slope stabilisation (prevents mass movement, safer for people, difficult to install, very expensive)