Engineering techniques

Engineering techniques

1. Hard

   • Rip-Rap
     • Large rocks placed in front of the cliff
     • Advantages
       • Dissipates wave energy
       • Cheap (depending on the rock type)
       • Lasts long
     • Disadvantages
       • Unattractive
       • Can make beach inaccessible
       • Not effective in storm conditions
     • Cost: 300 GBP/metre
   • Recurved sea wall
     • Usually made of concrete
     • Cost: 3000 GBP/metre
     • Modern ones have a recurved face
     • Disadvantages
       • Ugly- less tourism
       • Expensive
       • Can cause scouring if not positioned correctly
     • Advantages
       • Lasts long
       • Visible: residents feel safe
       • Reflects and absorbs wave energy
   • Offshore reef
     • Concrete blocks sunk offshore
     • They alter wave direction and dissipate the energy
     • Cost: 1950 GBP/m
     • Advantages
       • Waves break further offshore
         • Less power
       • They allow the build up of sand
     • Disadvantages
       • Could be removed by storms
       • Difficult to install
   • Groynes
     • Stretches from coastline to the sea
     • Made of wood or rocks
     • Cost: 5000 GBP each
     • Advantages
       • Prevents longshore drift
       • Keeps beach in place: tourist industry
       • Lasts long
     • Disadvantages
       • Unattractive
         • Difficult to walk along the beach
       • Disrupt natural processes working on the sea
   • Gabions
     • Wire cages filled with stone
       • Used to reduce erosion
     • Cost: 11 GBP/m
     • Advantages
       • Cheap
       • Absorb wave energy
     • Disadvantages
       • They can break
       • Need to be securely tied down
       • Not very effective

2. Soft

   • Beach replenishment
     • Placing sand and pebbles on the beach
       • COST: 5,000 GPB/ 100 m
     • Advantages
       • Looks natural
       • Provides beach : tourists
         • Natural defence: dissipates wave energy
       • Cheap
     • Disadvantages
       • Affect animal and plant life
       • Requires constant maintenance
       • Noisy lorries
         • Disturbs home-owners
   • Cliff regrading
     • Cliff is cut back and given a new gentle slope to stop it slumping
     • Advantages
       • If covered in eco-matting -> encourages vegetation growth
       • Natural -> wildlife
     • Disadvantages
       • Needs other defences at the bottom
       • Homes are demolished
   • Managed retreat
     • Allowing sea to erode slowly
     • Advantages
       • Cheap
       • Creates new habitats
     • Disadvantages
       • Land is lost
       • Difficult to manage