Coasts

• Inputs? sediment can be brought into the system in various ways. Energy inputs come from wind, tides and currents.
• Outputs ?

  sediment can be washed out to sea or deposited further along the coast.
• Flows/transfers?

  processes such as erosion, weathering, transportation and deposition which can move sediment within a system.
• Stores/components?

  landforms such as beaches, dunes and spits.
• Negative feedback?

  when a change in the system causes other changes that have the opposite effect.
• Positive feedback?

  when a change in the system causes other changes that have a similar effect.
• How is wind created?

  created by air moving from areas of high pressure to low pressure. During events such as storms, the pressure gradient is high and winds can be very strong.
• Prevailing wind?

  when wind is consistently blowing from the same direction and this causes higher energy waves compared to winds with directions that change frequently.
• How are waves created?

  by wind blowing over the surface f the water and the friction between the wind and the sea surface gives the waves a circular motion.
• Factors influencing wave effects on shore?

  wave height, wind speed, fetch of the wave. (A high wind speed and a long fetch create higher and more powerful waves)
• How do waves break?

  friction with the sea bed slows the bottom of the waves and makes their motion more eliptical and then the crest rises up and then collapses.
• Swash?

  water washing up the beach
• backwash?

  water washing back towards the sea
• Constructive wave?

  low frequency, low and long with an elliptical profile. The powerful swash carries material up the beach and deposits it.
• Destructive wave?

  high and steep, circular cross profile and higher frequency. Strong backwash removes material from the beach.
• Tides?

  the periodic rise and fall of the ocean surface caused by the gravitational pull of the moon and sun. Tides affect the position at which the waves break on the beach. The area between maximum high tide and minimum low tide is where most landforms are created and destroyed.
• Currents?

  Is the general flow of water in one direction, it can be caused by wind or by variation in water temperature and salinity. Currents move material down the coast.
• High energy coast?

  They receive high imputs of energy in the form of large, powerful waves. These can be caused by strong winds, long fetches and steeply shelving offshore zones. High energy coastlines tend to have sandy coves and rocky landforms. The rate of erosion is higher than the rate of deposition.
• Low energy coastline?

  Receive low inputs of energy in the form of small gentle waves, caused by gentle winds, short fetches and gentle sloping offshore zones. Often have salt marshes and mudflats and the rate of deposition is higher than the rate of erosion.
• Inputs of sediment into the coastal system?

  Rivers carry eroded sediment into the coastal system from inland. Sea level rise can flood river valleys, forming estuaries. Sediment is eroded from cliffs through waves, weathering and landslides. Sediment can be formed from the crushed shells of marine organisms. Waves, tides and current can transport sediment from offshore deposits.
• Sediment Budget?

  the difference between the amount of sediment that enters the system and the amount that leaves.
• positive sediment budget?

  more sediment enters than leaves
• Negative sediment budget?

  more sediment leaves than enters and the overall coastline retreats.
• Sediment cell?

  also called Littoral Cells. Pretty much entirely self contained for the movement of sediment. Processes going on in one cell don't effect another cell - closed coastal system.
• Cavitation?

  As waves recede, the compressed air expands violently exerting pressure on the rock and causing it to break
• Wave Quarrying?

  the energy of the wave as it breaks against a cliff is enough to detach bits of rock.
• Transportation processes?

  Solution, Saltation, suspension and traction
• Aeolian deposition?

  when sediment carried by the wind is deposited
• Why does deposition occur?

  sediment load increases, wind or water flow slows down therefore losing energy. Friction increases - if waves enter shallow water or wind reaches land. Flow becomes turbulent - if water or wind encounters and obstacle, flow becomes rougher and speed decreases. And if wind drops wave height, speed and energy will decrease aswell.
• Types of weathering?

  Salt weathering, freeze-thaw weathering, chemical weathering, wetting and drying.
• Types of mass movement?

  Slides, Slumps, Rockfalls and Mudflows.
• What causes mass movements?

  Unconsolidated rocks prone to collapse because there is little friction between particles to hold them together. Heavy rain can saturate unconsolidated rock. Runoff can erode particles and transport them downslope.
• Aims of coastal management?

  protect homes, businesses, and environment from erosion and flooding.
• How to choose places to defend?

  Cost-benefit analysis. Money available is used to protect large settlements and important industrial sites.
• Four options for coastal management?

  • Hold the line - maintain the existing coastal defences.
  • Advance the line - build new coastal defences further out to sea than the existing line of defence.
  • Do nothing
  • Managed realignment - allow the shoreline to move but manage retreat so it causes least damage
• Hard engineering defences?

  • Sea wall
  • Revetment (slanted structures built at the foot of cliffs)
  • Gabions
  • RipRap (boulders)
  • Groynes
  • Breakwaters (concrete blocks or boulders deposited off the coast)
  • Earth bank
  • Tidal barrier (built across river estuaries)
  • Tidal barrage (dams built across river estuaries and can generate electricity through the controlled release of water through turbines)
• Soft engineering?

  • Beach nourishment
  • Beach stabilisation (reducing the slop angle and planting vegetation)
  • Dune regeneration
  • Land use management (reducing vegetation loss which help to protect sand dunes by creating walkways and cycle routes)
  • Creating marshland (planting vegetation on mudflats to stabilise sediment and reduce the speed of waves - reduces flooding and removes waves erosive power on coastline)
  • Coastal realignment (allowing the sea to flood an area and let it become marshland)
• Benefits of soft engineering?

  Cheaper, requires less time and money to maintain. Designed to integrate with the natural environment and create important habitats
• Shoreline management plans?

  Each sediment cell on a coastline is given a plan to manage different areas with the aim of protecting sites without causing problems elsewhere in the sediment cell. Within each area of a cell, authorities can decide to hold, advance or retreat the line or do nothing.
• Integrated Coastal Zone Management?

  considers all elements of the coastal system. Aims to protect the coastal zone in a relatively natural state which allows people to use and develop it in different ways. The environment is viewed as a whole - the land and the water are interdependent. Different uses are considered. Local, regional and national authorities all have an input into the plan. Its a dynamic strategy where decisions are re-evaluated if the environment or demands on the area change.