coasts

• coastal management- no active intervention


  no intervention in defending against flooding or erosion whether or not coastal defences have existed previously
• coastal management- hold the line


  build or maintain coastal defences so that the position of the shoreline remains the same overtime, can be hard or soft engineering
• coastal management- managed retreat/realignment


  moving the line of defence further inland. actively removing coastal defences to allow areas to flood
• coastal management- advance the line


  build new coastal defences on the seaward side of existing coastline, usually involves land reclamation
• coastal management-hard engineering

  hard engineering

  the use of concrete and large artificial structures by civil engineers to defend land against natural erosion
• coastal management-hard engineering

  SEA WALL

  • physical barrier, along the back of the beach
  • recurved =more expensive but more effective (reflects waves energy back)
  • flat = cheap
  • steps to add stability
  • costs-£5000 per metre
  • last around 50-75 years

  advantage- protects the base of cliffs, land and buildings from erosion, can prevent coastal flooding

  disadvantage- expensive, high maintenance costs, overtime wall may begin to erode
• coastal management-hard engineering

  GROYNES

  • wooded/concrete structures that are built in the foreshore
  • 90' angle to beach
  • trap sediment transported by LSD
  • larger beach = better (absorbs energy)
  • costs £20000 each
  • last 20-40 years

  advantages- prevents movement of beach material, allows build up of beaches- naturally protects against erosion, tourism

  disadvantage- unattractive, costly to build + maintain, can increase erosion down the coast where its not protected
• coastal management-hard engineering

  ROCK ARMOUR

  • thousands of tonnes of huge boulders of hard rock (granite) that act as a barrier between the sea and the land - very effective
  • boulders = heavy - can't move
  • downwards slope - absorbs wave energy
  • £1000 per rock
  • short term

  advantage- allows build up of beach, large boulders absorb wave energy and reduce the power of the wave

  disadvantage- can be expensive to obtain and transport rocks, looks ugly, strong waves can undermine boulders
• coastal management-hard engineering

  GABIONS

  • steel wire cages filled with pebbles and rocks
  • placed on sandy beaches to create a wall-like structure
  • water enters the cage, rocks absorb the wave energy and reduces the rate of erosion
  • can be placed in front of cliffs- gives cliff stability and reduces risk of landslide
  • £110 per metre - last 25 years
• gabions

  advantage- use of smaller rocks give more flexibility with designs, less energy from waves, can use local materials to reduce visual impact

  disadvantage- unnatural appearance, if the wire cage breaks it becomes a hazard, short lifespan, ongoing maintenance cost
• coastal management- soft engineering


  soft engineering-

  working with natural processes to help restore beaches and coastal ecosystems
• coastal management- soft engineering

  BEACH NOURISHMENT

  • replace lost sediment
  • nourish beach = less waves reach cliffs - bigger beach = less erosion : 1. Recharge- take from a bay and place on a beach that is losing land 2. Recycle- sand removed from a down drift area- builds up sand
  • £20 per meter -last 1-10 years

  advantage- preserves beach resources, creates a large sand reservoir + pushes beach seaward, no negative effect on structure, relatively cheap

  disadvantage- doesn't remove physical forces causing erosion, requires constant maintenance
• coastal management- soft engineering


  DUNE REGENERATION

  • artificial creation of sand dunes or restoration of existing ones
  • act as a physical barrier between sea and land
  • absorb wave energy and water
  • £2000 per metre- long term if stable

  advantages- can attract tourist (make £), provide habitats, planting projects carried out by volunteers

  disadvantages- limited to small areas, takes about 3 years for grass to start to spread, no guarantee that the dunes will stabilize (may not stay in place)
• coastal management- soft engineering


  BEACH REPROFILING

  • artificial reshaping of a beach using existing beach material
  • in winter, a beach is lowered by destructive waves
  • after winter storms, bulldozers move shingle back up the beach
  • like beach nourishment, reprofiling ensures that the beach is large enough to be an effective buffer between land and sea
  • £200000 a year - lasts 1-10 years
• coastal management- soft engineering


  BEACH REPROFILING

  advantages- preserves beach resources, creates a larger sand reservoir and pushes shoreline seaward, beaches look natural, relatively cheap

  disadvantages- doesn't remove the physical force of cause of erosion, requires constant maintenance
• managed retreat- case study

  MEDMERY

  where - west Sussex - SSE of England

  why did it need it- high tides and storms were threatening the pebble beaches, endangering over 300 homes , the main road and water treatment works

  what was the scheme- in land flood banks- 7km in length, gradually let in the sea water into the site (water encroachment), aims: sustainably manage flooding, create intertidal habitats and community involvement and participation
• managed retreat- case study

  MEDMERY

  impacts:

  • locals feels safer and secure, reassured
  • locals gained jobs
  • found historical importance- bronze age remains, WW2 machines
  • freshwater habitats were created eg birds nests
• Holderness case study


  Holderness coast-

  • highest rate of erosion->1-2metres washed away every year
  • 29 villages lost to sea
  • farmers crops disappear
  • no protection for cliff at high tide from waves
  • sand = main defence
  • cliffs = soft rock
  • build sea defences = cheaper then moving main road
  • wall built - sand build up - sand takes energy from waves-protect
  • sea defences = 20 metres of land lost in 1 year due to defences
  • sea defences cause more problems down the beach->1 side = narrow - endangered, 1 side = fat - safe
• Holderness case study

  locations:

  Hornsea - tourist town with sea defences - stop LSD and deprive places further south of sediment

  wooded groynes, rock armour, sea wall (flat)

  Mapleton - village with farmland

  groynes (granite), rock armour

  Withernsea - wooden groynes, curved sea wall, rock armour

  Skipsea - tourist sight - NO DEFENCES - BAD EROSION

  Spurntlead - spit, LSD carries sediment down coast
• Beaches


  deposits of sand and shingle (pebbles) on a coast

  Pebble beaches are when waves wash away fine sand and leave behind the larger pabbles
• Sand dunes


  1. Embryo dunes form around deposited obstacles such as logs
  2. these develop and become stabilized by vegetation from foredunes and tall yellow dunes. Marram grass is adapted to the windy, exposed conditions and has long roots to find water. These roots bind the sand together and stabilize the dune
  3. in time, rotting vegetation adds organic matter to the sand making it more fertile, a greater number of plants colonise on these 'back' dunes
  4. winds form depressions in the sand called dune slacks, in which ponds can be formed

  
• 4 types of mass movement

  1. rockfall- materials break up and fall down a slope-result of freeze-thaw
  2. landslide- material shifts in a straight line
  3. mudflow
  4. slumping- material shifts with rotation (rotational slip)
• 4 types of erosion

  1. attrition
  2. hydraulic action
  3. abrasion
  4. solution
• hydraulic action 


  waves hit the side of the cliff, energy causes rocks to break down
• attrition


  rocks hit each other and break each other down
• abrasion


  when rocks are thrown at the cliff face, creating a scraping effect
• solution


  dissolved rocks
• rate of erosion depends on many factors

  • waves - strength, frequency, height, fetch
  • weather - frequency of storm conditions
  • geology of coastlines
• 4 types of transportation

  1. traction
  2. solution
  3. suspension
  4. saltation
• traction


  when boulders and pebbles roll along the river bed
• saltation


  materials carried by the river bounces along the bed
• suspension


  rocks carried by the river bed wear down the river bed and banks
• solution


  soluble materials is dissolved and carried by the river water
• the coastline is constantly being reshaped by wind, waves and the effects of weather

  where coastlines are made of hard and sheltered from the prevailing winds, changes happen slower

  if a coastline is made of softer rocks and exposed to the weather and powerful waves, then the whole area can change rapidly
• waves


  waves are the most significant force in changing the coastline

  1. the wave nears the coastline
  2. the base of the wave is in contact with the sea bed and friction lows it
  3. the crest of the wave breaks because its moving faster then the base
  4. the energy of the breaking wave pushes up the beach as swash
  5. when all the energy is used up, it runs back down the beach as backwash

  A) 1

  B) 3

  C) 4

  D) 5

  E) 2

  
• destructive waves


  a short steep wave that plunge into the beach with force

  weak swash, strong backwash

  
• constructive wave


  long, low wave that spills into the beach

  strong swash, weak backwash

  A) shallow gradient

  B) long wavelength

  C) beach build up

  
• weathering


  breaking down rock in situ (where it is)
• mechanical weathering


  the disintegration (break down) of rocks. Broken up rock fragments will be found at the bottom of cliffs
• chemical weathering


  the decomposition (eaten away) of rocks. caused by chemical change