hard engineering

• hard engineering 


  the use of concrete and large artificial structures by civil engineers to defend land against natural erosion
• sea wall 


  physical barrier

  along the back of the beach

  recurved - more expensive but more effective as it reflects waves energy back into the sea

  flat = cheaper

  steps add stability

  costs - £5000 per metre

  last 50-70 years
• sea wall advantages

  • protects the base of the cliff, land and buildings against erosion
  • can prevent coastal flooding in some areas
• sea wall disadvantage

  • expensive to build
  • high maintenance cost
  • overtime, wall can fail due to wave scour
• groynes


  wooden or concrete structures that are rebuilt in the foreshore

  90' angle to the beach

  trap sediment by longshore drift

  larger beach = better - absorbs energy

  costs - £20000 each

  last 20-40 years
• groynes advantages


  prevents the movement of beach material along the shore via longshore drift

  allows the build up of sand

  tourism
• groynes disadvantages


  unattractive

  costly to build and maintain

  can increase erosion down the coast in area's not protected by defences
• rock armour 


  thousands of tonnes of huge hard rocks (granite) that act as a barrier between sea and land - very effective

  boulders = heavy = can't move

  downwards slope arrangement - absorbs water energy

  cost - £1000 per rock

  short term
• rock armour advantages


  large boulders absorb wave energy and reduce the power of the wave

  allows build up of a beach
• rock armour disadvantages


  can be expensive to obtain and transport rocks

  looks ugly

  strong waves can cause boulders to move
• gabions


  steel wire cages filled with pebbles and rocks placed on sandy beaches to create a wall-like structure

  water enters cages - this absorbs the wave energy and reduces the rate of erosion

  can be placed in front of cliffs - gives stability and reduces the risk of land slides

  costs - £110 per metre

  lasts 25 years
• gabions advantages


  use of the smaller rocks gives greater flexibility in designs

  less energy for erosion

  can use local beach material to reduce visual impact
• gabions disadvantages


  unnatural appearance

  unpleasant if mesh breaks - risk of injury

  short lifespan

  ongoing maintenance costs