Coastal Defences - Rock Armour

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Coastal Defences - Rock Armour

Advantages

  • It is relatively cheap
  • Quick to built, easy to maintain
  • Much quicker and cheaper than a sea wall
  • Can last a long time if well maintained
  • Versatile, as it can be placed in front of a sea wall to lengthen lifespan or used to stabilise slopes on sand dunes
  • Norwegian rocks are highly resistant, so they will last a long while

Disadvantages

  • Rock armour makes access to the beach difficult, as people have to clamber over it or make long detours
  • People may have accidents when clambering over it as rocks may be unstable, and, if the rocks are regularly covered by the tide, they may collect seaweed which accentuates the hazard.
  • Highly resistant rocks from Norway / Sweden are commonly used in preference to local stone. This inflates the cost considerably
  • Heavy storm waves move the rocks so the armour needs regular maintenance
  • Ugly, do not blend with local geology
  • Covers vast areas of the beach
  • Driftwood & litter get trapped in the structure

Evaluation

Rock armour is also known as rip-rap. It is made of hundreds of huge boulders of hard rock such as granite, and acts as a barrier between land and sea. Their downward slope arrangement deflects and absorbs the wave energy. Water flows through the gaps and pressure is released, so wave scouring does not occur at the base, making them very effective. However, the danger to humans is significant, and for this reason I personally would recommend that they are used mainly in less tourist-y areas. 

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