Coasts part 4

• Why is hard engineering needed for coastal protection

  The main idea of hard engineering is to stop the waves eroding the coast or stop coastal flooding. However these structures can be very costly especially when an entire coastline requires protection
• What are the hard engineering strategies used to protect coasts

  sea wall

  groynes

  rock armour

  gabions
• Describe a sea wall

  concrete or rock barrier against the sea placed at the foot of cliffs at the top of the beach. Has a curved face to reflect waves back into the sea
• What is the cost of a sea wall

  £5000-10,000 per metre
• What are the advantages and disadvantages of building a sea wall

  advantages:

  -effective at stopping the sea-reflects wave energy

  -often has a walkway or promenade for people to walk along

  disadvantages:

  -very expensive and high maintenance

  -can look obtrusive and unnatural
• Describe a Groyne


  Timber or rock structures built out to sea from the coast. They trap sediment being moved by longshore drift and enlarge the beach. The wider beach acts as a buffer to reduce wave damage
• What is the cost of Groynes

  timber groynes £150,000 each (at every 200m)
• What are the advantages and disadvantages of Groynes

  Advantages:

  -create a wider beach, which can be popular with tourists

  -provide useful structures for people interested in fishing

  -not to expensive

  disadvantages:

  -can loom unnatural and unattractive

  -by interrupting longshore drift they starve beaches further along the coast often leading to increased rates of erosion elsewhere
• Describe rock armour


  Large boulders dumped at the foot of a cliff. The rocks force waves to break absorbing their energy and protecting the cliffs. The rocks are usually brought by barge to the coast
• What is the cost of rock armour

  £200,000 per 100m
• What are the advantages and disadvantages of rock armour

  advantages:

  -relatively cheap and easy to maintain

  -often used for fishing

  -can provide interest to the coast

  -can provide some habitats

  disadvantages:

  -can be very obtrusive

  -expensive to transport

  -doesn't fit in with local geology

  -rocks are usually from other parts of coastline or even from abroad
• Describe gabions


  Wire cages filled with rocks that can be built up to support a cliff or provide a buffer against the sea in a similar way to rock armour
• What is the cost of gabions?

  Up to £50,000 per 100m
• What are the advantages and disadvantages of gabions

  advantages:

  -cheap to produce and flexible in the final design

  -can improve drainage of cliffs

  -will eventually become regenerated and merge into the landscape

  disadvantages:

  -cage only lasts 5-10yrs before they rust

  -look unattractive until vegetation starts to grow over them
• What are soft engineering strategies?

  -managed retreat

  -beach nourishment

  -sand dune regeneration

  -beach reprofiling

  -dune fencing
• What is managed retreat?

  Managed retreat is a deliberate policy of allowing the sea to flood or erode an area of relatively low-value land

  It is a form of soft engineering because it allows natural processes to take place
• Benefits of managed retreat

  -in the long term it is a more sustainable option than spending large sums of money on groynes or sea walls. As sea levels continue to rise, managed retreat seems likely to become an increasingly popular choice for managing the coastline
• Case study for managed retreat

  Medmerry managed retreat, West Sussex
• Describe Medmerry Managed retreat

  - flat, low lying coastline (so more likely to flood)

  -used for farming and caravan parks (brings in money)

  -previous defences is a low sea wall which needed repair so decided to use managed retreat because a new sea wall is an expensive option for a low- value area

  -embankments have been constructed inland to protect farms, roads and humans
• How much did the Medmerry scheme cost?

  £28 million