AS Geography Coasts Case Studies

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Coastal Erosion

The Holderness Coast

The Holderness Coastline is 61km long – it stretches from Flamborough Head to Spurn Point. In some places, eg. Great Cowden, the rate of erosion has been over 10m per year in recent years, but the average rate of erosion at the Holderness is about 1.8m per year.

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1.  Easily eroded rock type – the cliffs are mostly made of till (or ‘boulder clay’). Not only is till easily eroded through abrasion, but it’s also prone to slumping when wet.

2.  Narrow beaches – beaches slow the waves, reducing their erosive power. Narrow beaches protect the cliff less.  Beaches along the Holderness coast are narrow for two main reasons:

  • Flamborough Head stops sediment from the north replenishing the beaches along the Holderness. It’s also made of chalk, which dissolves when eroded rather than making sand for the beaches.
  • Coastal defences, eg. at Mappleton. This is a human cause of erosion.

3.  Powerful waves – the waves are powerful because of:

  • The long fetch (all the way from the Arctic Ocean).
  • The coast faces the dominant wind and wave direction (from north-east).
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  • Property prices along the coast have fallen sharply for those houses at risk from erosion.
  • Around 30 villages have been lost since Roman times.


  • Visitor numbers in Bridlington dropped by over 30% between 1998 and 2006 (though this could have also been due to other reasons).
  • Many caravan parks are at risk from erosion, eg. Seaside Caravan Park at Ulrome is losing an average of 10 pitches a year.
  • £2 million was spent at Mappleton in 1991 to protect the coast.
  • The Gas Terminal at Easington is at risk (it’s only 25m from the cliff edge). This terminal accounts for 25% of Britain’s gas supply.
  • 80,000m squared of good quality farmland is lost each year. This has a huge effect on farmers’ livelihoods.
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  • Some SSSIs (Sites of Special Scientific Interest) are threatened – eg. The Lagoons near Easington are part of an SSSI. It has a colony of over 1% of the British breeding population of little terns. The Lagoons are separated from the sea by a narrow ***** of sand and shingle. Erosion of this would connect the lakes to the sea and ‘The Lagoons’ would be destroyed.
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Coastal Flooding

Tsunami in Southern Asia, 2004

The tsunami that devastated areas of Indonesia, Sri Lanka, Thailand and India on 26th December 2004 was caused by a submarine earthquake in the Indian Ocean. The earthquake is estimated to have measured 9.0 on the Richter scale, making it one of the strongest earthquakes ever recorded.

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Effected Areas

  • The epicentre of the earthquake was off the western coast of Sumatra in Indonesia.
  • Waves up to 30m high struck the Indonesian island of Sumatra within minutes of the earthquake.
  • The tsunami reached more than 2km inland at Trincomalee in the north east of Sri Lanka.
  • The tsunami travelled across the Bay of Bengal at speeds up to 800km per hour. The waves struck south eastern India just two hours after the earthquake.
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  • It was the deadliest tsunami ever recorded, with an estimated 230,000 people killed or missing.
  • It’s estimated that 1.7 million people were made homeless.
  • Many sources of fresh drinking water were polluted, either by sewage or by saltwater.
  • An estimated 400,000 lost their jobs in Sri Lanka alone.


  • 8 million litres of oil was released into the environment after 2 oil plants in Indonesia were destroyed. The oil caused wide spread pollution at sea and contamination of the soil, posing health risks to humans in the area.
  • Mangrove forests as far away as the East African coast were damaged by the force of the waves, or covered in layers of silt.
  • The high salt content of the floodwater destroyed the natural balance of many ecosystems, eg. the Karagan Lagoon in southern Sri Lanka.
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  • Estimates of the cost of the initial damage caused by the tsunami are between $8 billion and $15 billion.
  • Fishing is a large part of the economy for many of the areas hit by the tsunami. Boats, nets and other equipment were destroyed or lost, severely affecting the livelihood of fishermen.
  • Salinisation (increase in salt content) of land has severely reduced soil fertility. Crop production will be lower for several years to come.
  • Tourism is important to the economy of many of the countries affected. 25% of hotels in southern Thailand were closed for at least 6 months because of damage and the number of foreign visitors to the island of Phuket dropped 80% in 2005 as the areas was perceived to be less safe.
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Human Activity

Human activity increased the impact of the flooding

  • Mangrove forests protected parts of the Sri Lankan coast by absorbing wave energy. Pressure for tourist development and the creation of intensive prawn fisheries has led to the destruction of mangrove forests in other areas around the Indian Ocean. It’s estimated that Thailand has lost up to half of its mangrove forests since 1975. The lack of protection meant that waves could reach further inland and the flooding was much worse than in areas protected by mangroves.
  • It’s thought that the healthy coral reefs surrounding the Maldives acted as a breakwater (reducing the power of the tsunami waves) and prevented the complete destruction of the low-lying islands. Illegal coral mining and the use of dynamite in explosive ‘blast fishing’ has destroyed many offshore coral reefs in the Indian Ocean. This reduced the level of natural protection from the waves.
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Coastal Management - Hard Engineering

The Holderness Coast

The Holderness coast is the fastest eroding coastline in Europe. A total of 11.4km of the 61km coastline is currently protected by hard engineering:

  • Bridlington is protected by a 4.7km long sea wall as well as timber groynes.
  • There’s a concrete sea wall, timber groynes and riprap at Hornsea that protect the village.
  • Gabions just south of Hornsea help protect Hornsea Caravan Park.
  • Two rock groynes and a 500m long revetment were built at Mappleton in 1991. They cost £2 million and were built to protect the village and the B1242 coastal road.
  • There are groynes and a sea wall at Withernsea. Some riprap was also placed in front of the wall after it was damaged in severe storms in 1992.
  • Easington Gas Terminal is protected by a revetment.
  • The eastern side of Spurn Head is protected by groynes and riprap.
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The schemes are locally successful but cause problems down-drift.

  • The groynes trap sediment, increasing the width of beaches. This protects the local area but increases erosion of the cliffs down-drift (as the material eroded from the beaches there isn’t replenished), eg. the Mappleton scheme has caused increased erosion of the cliffs south of Mappleton, for example in Aldbrough. Cowden Farm, just south of Mapleton, is now at risk of falling into the sea.
  • The sediment produced from the erosion of the Holderness coastline is normally washed into the Humber Estuary (where it helps to form tidal mudflats) and down the Lincolnshire coast. Reduction in this sediment increases the risk of flooding along the Humber Estuary, and increases erosion along the Lincolnshire coast.
  • The protection of local areas is leading to the formation of bays between areas. As bays develop the wave pressure on headlands will increase and eventually the cost of maintaining the sea defences may become too highAll these problems make the existing schemes unsustainable.
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Possible Schemes

Possible schemes all pave problems:

  • The Shoreline Management Plan (SMP) for the Holderness for the next 50 years recommends ‘holding the line’ at some settlement (eg. at Bridlington, Withernsea, Hornsea, Mappleton and Easington Gas Terminal) and ‘doing nothing’ along more unpopulated stretches. However, this is unpopular with owners of land and property along these stretches where nothing is being done.
  • Coastal realignment of businesses has been suggested, eg. relocating caravan parks further inland. This would be a more sustainable scheme as it would allow the coast to be eroded as normal without endangering businesses. However, there are issues surrounding how much businesses will be compensated by for relocating. Also, relocating isn’t always possible, eg. farmland can’t be ‘relocated’, and there may be no land for sale to relocate buildings to.
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Possible Schemes

  • A sea wall has been proposed to better protect Easington Gas Terminal. This would cost £4.5 million. The problem is that it would reduce sediment flow to the south, increasing erosion at the village of Easington (with a population of 700 people). A longer sea wall could be built that would protect the village as well as the Gas Terminal, but that would cost £7 million.
  • Offshore reefs made from concrete-filled tyres have been proposed to protect the coastline. They act like breakwaters. Similar reefs have been built in the USA and have reduced erosion. Some people think that the reefs will harm the environment though (although there’s currently no evidence for this).
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Coastal Management - Soft Engineering

Blackwater Estuary

Soft Engineering has been used along Blackwater Estuary. Blackwater Estuary is part of the Essex coastline. Land in the estuary is being eroded at a rate of 0.3-1m per year. In some exposed areas (eg. Cobmarsh Island) the erosion rate is 2m per year. The area is also at risk of flooding as sea level is rising and the South of England is sinking relative to the sea.

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Soft Engineering

There are some hard engineering schemes in the estuary, but these are becoming too expensive to maintain, so soft engineering approaches are now being implemented:

  • Coastal realignment was implemented at Tollesbury Fleet in 1995. An existing sea wall was breached and 21 hectares of farmland were flooded to encourage a marshland to form. A new lower sea wall was built further back on higher ground to protect from flooding.
  • Beaches have been nourished along the estuary, eg. at Mersea Island.
  • Marsh establishment has been carried out by planting stakes and brushwood on water line to encourage sediment to build up, eg. at Ray Creek.
  • In 1991 an existing sea wall was lowered and breached flooding 0.8 hectares of land at Northey Island.
  • In 1995 a sea wall was breached and 40 hectares of farmland at Orplands were flooded as part of coastal realignment.
  • Coastal realignment has been carried out at Bradwell-on-Sea by breaching an old sea wall.
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The schemes are more sustainable than hard engineering schemes:

  • The schemes are more sustainable in the long term, eg. to repair the sea wall at Orplands would have cost more than £600,000 (and it would only last for 20 years). The 40 hecares of farmland flooded was valued at around £600,000, but the marshland created would defend the coast for longer as its self-repairing.
  • The schemes have created more marshland, which provides a larger habitat for wildlife.
  • However, some areas haven’t changed to marshland (e.g parts of the Orpland site are still bare mud, which is easily eroded). Also, grazing land has been lost.
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