Theme 4 - coastal hazard and their management

• Sea walls (hard):

  • concrete barrer build at foot of cliffs. It has curved face to reflect the wave back and disrupt the next wave.
  • adv: excellent defence with long life span
  • disadv: expensive, affect access, increase erosion
• Groynes (hard):

  • Trap sand being transported by lonshore drift. This result in wider beach, absorbs wave energy and reduce the rate of cliff erosion.
  • adv: cheap
  • disadv: further coastline starved beach material
• Rip rap (hard):

  • Large boulder of hard rock are placed on the base to absorb wave energy
  • adv: cheap + efficient
  • disadv: unattractive, difficult access
• Gabions (hard):

  • steel cages absorb the energy of waves
  • adv: cheap and efficient
  • disadv: unattractive and shorter life span
• Revetment (hard):

  • allow seawater and sediment to pass through but structure absorb sea energy
  • adv: cheap + less erosion of beach material
  • disadv: short life span + unsuitable when wave energy is high
• Beach nourishment (soft):

  • beach are made higher and wider by importing sand durther along the coast or from sea bed
  • adv: cheap + retains natural look
  • disadv: increase erosion in other areas + replenishment is necessasry on a regular basis increase cost
• Sand dune stabilisation (soft):

  • natural defence against coastal flooding and erosion
  • adv: maintain natural ecosystem + accessible to tourist
  • disadv: time consuming + expensive
• Manage retreat (soft):

  • create a new intertidal zone as a natural buffer against storm and rising sea level
  • adv: natural balance of coastal system + encourage development of beach
  • disadv: people lose their livelihoods + cost of compensation
• Vulnerable coastline in HICs: Thames Gateway UK

  risk:

  • isostatic change, area sink into sea 2 mm per year
  • rise in sea level 3 mm per year

  vulnerable:

  • London CIty Airport
  • UK largest centre of economic
• Vulnerable coastline in developing country: Nile Delta, Egypt

  Risk:

  • 50% of people live in informal housing
  • have few saving and insurance

  vulnerable:

  • densely populated
  • lost of fertile agriculture land

  == protected with sand belt 1-10 km wide
• Hold the line: Borth

  Impact:

  • property worth 10 million
  • sand dunes attract tourist --> local business will suffer if don't hold

  Strategy:

  • rock groynes
  • beach nourishment
• Manage retreat: Medmerry

  Impact:

  • many money are spent on maintaining bank, it will save the maintance cost
  • allow green tourism (natural reserve)

  Streategy:

  • remove sea wall
  • redrawn coastline 2 km further inland
• Human intervention made coastline worst: Holderness coast

  Impact:

  • Cliff retreat a lot, village are lost
  • sea defence has increase the erosion further e.g. groynes trapped the sand and starved the beach, exposed the cliff to full force of wave

  Risk:

  • lost of village and fertile farmland

  Strategy:

  • groynes
  • rip rap
  • sea wall
• Shoreline management plan: assessment of risk associate with coastal processes

  Cost - benefit analyse: beenfit and action vs cost

  Integrated coastal zone managment: aims to develop sustainable solution