landscapes

• The coast as a system?

  • As with any geographical system, the coast, as a system, has inputs, stores, transfers and outputs
  • The system constantly strives to be in a state of dynamic equilibrium
  • The coast can be viewed as both an open system and a closed system 
  • It is an open system because it receives inputs from the lithosphere, atmosphere, hydrosphere, biosphere and cryosphere
  • However, during research and coastline management the coast can be seen as a closed system where a specific sediment cell is examined
• What is an example of positive feedback at the coast?

  • As waves erode the cliff, material is released
  • This material abrades the cliff which results in even more cliff erosion 
• What is an example of negative feedback at the coast?

  • As the shore is eroded, the material makes the wave-cut platform wider
  • This can absorb wave energy and reduce the impact at the base of the cliff
• What are 2 long term factors that affect coastal systems?

  Geology

  Changes in sea level
• What is geology?

  a long term factor that affects coastal systems

  • The geology is the characteristics of the land which includes both:
  • Rock type
  • Rock structure
  • Coasts can be classified as:
  • Rocky
  • Sandy
  • Estuarine
  • They can also be classified as: 
  • Concordant - where different rock types run parallel to the coast
  • Discordant - where different rock types run at right angles to the coast
• What is sea level change?

  a long term factor that affects coastal systems

  • Sea level change can occur as a result of:
  • Global warming - natural and enhanced
  • Tectonic activity - which can lead sections of land to rise or subside
  • Longer-term sea level change can be:
  • Eustatic - when the sea level itself changes 
  • Isostatic - when the land rises or falls relative to the sea
  • This leads to coasts that are either emergent or submergent
• What short term factors affect coastal systems?

  Waves

  Tides

  Rivers

  Storm events
• • Coasts can also be categorised by short-term factors:
  • Waves - can be constructive or destructive
  • Tides - tidal range is the difference between high and low tide
  • Rivers
  • Storm events
  • These create coastlines that can be:
  • Retreating or advancing which depends on whether erosion or deposition dominates
  • Dominated by land-based processes (primary coasts) or marine processes (secondary coasts)
  • Large or small tidal range 
  • High or low-energy 
• What are characteristics of high energy coasts?

  destructive waves

  exposed to strong winds and long fetches

  higher rates of erosion than deposition

  tend to be rocky coasts

  steep cliffs- marine cliff profile

  less steep cliffs- subaerial cliff profile

  headlands

  wave-cut platforms
• What are characteristics of low energy coasts?

  constructive waves

  sheltered locations with short fetch

  higher rates of deposition than erosion

  sandy beaches, salt marshes, estuarine and tidal mud flats

  gentle relief

  sediment from land and sea

  beaches, spits and coastal plains
• Rocky coasts?

  • Rocky coasts form where there is more resistant geology - in the UK this is mainly in the north and west of the country
  • Cliffs of varying heights and steepness can be found along rocky coastlines:
  • Steep cliffs tend to be found in high energy environments
  • Cliffs with a gentler slope tend to be found in low energy environments
  • Erosion is more dominant than deposition
• What are the 2 types of erosion that dominate along rocky coastlines?

  • Marine erosion - the action of waves
  • Sub-aerial erosion weathering and mass movement
• Coastal plain landscapes?

  • Coastal plains usually occur where the land gradually slopes down towards the sea
  • Tend to be low relief
  • Coastal plains include both:
  • Sandy coastlines
  • Estuarine coastlines
  • These are usually low energy coastal environments
  • They form due to coastal accretion - when deposition is greater than erosion
• Where does sediment for deposition comes from at coastal plain landscapes?

  • Offshore sources
  • Terrestrial sources
• At coastal plain landscapes:

  • Dunes form, helping to stabilise the coast and reduce erosion
  • Wetlands and marshes form due to poor drainage
  • Estuarine coastlines form at the mouths of rivers and are formed from clay and silt
• What is a positive feedback mechanism at the coast?

  People walking over sand dunes destroys vegetation growing there and causes erosion.

  As the roots from the vegetation have been holding the sand dunes together, damaging the vegetation makes the sand dunes more susceptible to erosion.

  This increases the rate of erosion.

  Eventually the sand dunes will be completely eroded leaving more of the beach open to erosion taking the beach further away from dynamic equilibrium.
• What is a negative feedback mechanism at the coast?

  A negative feedback loop will balance this excess of inputted sediment:

  When the destructive waves from the storm lose their energy excess sediment is deposited as an offshore bar.

  The bar dissipates the waves energy which protects the beach from further erosion.

  Over time the bar gets eroded instead of the beach.

  Once the bar has gone normal conditions follow and the system goes back to dynamic equilibrium.