Geography - coasts useful case studies

Lulworth cove - Dorset

  • concordant coastline - high energy, geology runs west to east
  • entrance to cove is narrow where waves cut through weaknesses in resistant limestone (hard rock is purbeck and chalk)
  • cove widens where softer clays (wealden clay) have been more easily eroded
  • at the back of the cove - more resistant chalk = slower rates of erosion
  • in the future Stairhole (another feature of the concordant coastline on the Dorset coast) will be like Lulworth cove
  • swash aligned feature
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Durdle Door - Dorset

  • found on the concordant coastline (west to east geology)
  • coastal arch
  • formed from a layer of hard limestone standing vertically out at sea (usually limestone runs horizontally so geology must have been altered by plate tectonics)
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Spurn Head spit -Holderness Coast (Yorkshire)

  • sand or shingle beach ridge extends beyond a turn in the coastlibe
  • longshore drift current spreads out and loses energy leading to deposition
  • length of a spit is determined by the existence of secondary currents causing erosion
  • made of soft boulder clay = quick erosion
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St Ninian's - Shetland

  • sand or shingle bar that attaches to the coastline to an offshore island
  • form due to wave refraction around an offshore island creating an area of calm water and deposition between the island and the coast
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Chesil Beach - Dorset

  • barrier beach/bar
  • sand or shingle beach conneting two areas of land with a shallow water lagoon behind
  • occur when a spit grows so long that it extends across a bay closing it off
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Hurst Castle - Hampshire

  • hooked/recurved spit
  • soit whose end is curved landward into a bay or inlet
  • seaward end of the spit naturally curves landward into shallow water
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Dungeness - Kent

  • cuspate foreland
  • roughly triangular-shaped features extending out from a shoreline
  • growth of two spits from opposing longshore drift directions
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Holderness Coast sediment cell

  • 11 sediment cells around the English and Welsh coast
  • sediment cells are areas along the coastline and in the nearshore area where the movement of material is largely self-contained - considered a closed coastal sub-system 

In each cell are:

  • sources - where sediment is eroded from cliffs (Flamborough Head's chalk, Hornsea's boulder clay) or sand dunes; sources can be offshore bars. River systems (River Humber) are also important sources.
  • transfer zones - places where sediment is moving along the coast by longshore drift and offshore currents; beaches, parts of dunes and salt marshes (Humber Estuary) perform this function. 
  • sinks - locations where the dominant process is deposition; depositional landforms are created including spits (Spurn Head) and offshore bars.
  • some coastal features may operate as both sinks and sources, depending on whether the dominant process is erosion or deposition at a given time.
  • Human intervention, in the form of coastal management, plus threats such as a sea-level rise as a result of global warming, represent risks to the longer-term dynamic equilibrium of sediment cells like Holderness.

Positive feedback that leads to disequilibrium in the coastal system: increased storminess erode beach material faster, rising sea levels could increase the erosion of spits like Spurn Head, reomving sediment faster than it can be replaced.

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Minehead (Butlins)

  • Butlins was once marshland and prone to flooding
  • low lying
  • Butlins is a major economic asset as it provides jobs and contributes to the economy through toursim
  • hard engineering: groynes 
  • soft engineering: beach replenishment so sand is not natural
  • coastal management type: HOLD THE LINE
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Porlock

  • farmland
  • flooded
  • coastal management type: MANAGED RETREAT
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Happisburgh coastline

  • Norfolk coast
  • houses fallen into sea as a result of coastal erosion
  • wind and waves eating it away 
  • glacial boulder clay = easily eroded
  • coastal management type: DO NOTHING
  • hard engineering: groynes, revetments, rock armour - costs time and money to maintain so is not sustainable
  • part where farmland is on coastline, has never been protected - not needed/worth it
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Bacton

  • coastal management type: HOLD THE LINE
  • gas terminal - cost of losing this is greater than defending it
  • ICZM (integrated coastal zone management) - players comes together to establish a shoreline management plan
  • hard engineering: groynes, rock armour
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Norfolk Broads

  • government, local councils and other players complete a shoreline management plan
  • coastal management type: HOLD THE LINE - valuable ecosystem
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Holderness

  • coastal management type: DO NOTHING
  • ice sheet expanded then melted, leaving boulder clay behind
  • Europe's fastest eroding coastline
  • unconsolidated rock (loose sediment)
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Mappleton

  • coastal management type: HOLD THE LINE
  • major link road between towns so must be protected
  • CBA (cost benefit analysis) = hold the line for road
  • hard engineering: groynes - have been successful in protecting the coast
  • by 2105, main coastal road is likely to have been destroyed by erosion south of Mappleton
  • small village of 50 properties, a church and a garage could be cut off apart from the minor road running west from the village
  • high risk location due to the possibility of outflanking (occurs when erosion gets behind coastal defences at the point where they stop, leading to rapid erosion inland and undermining of defences) its defences
  • properties would be very difficult to sell and theur value would have been significantly reduced
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Great Cowden

  • groyne from Mappleton affecting erosion rates here
  • Great Cowden farm eroded away
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Withernsea

  • CBA - worth it to HOLD THE LINE
  • tourist destination
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Highcliffe

  • CBA - worth it to HOLD THE LINE
  • hard engineering: groynes, rock armour, piping
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Easington

  • HOLD THE LINE
  • protecting gas terminal
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Naish farm holiday village

  • not being defended, not worth it
  • DO NOTHING
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Dalmation coast

  • mainly found in Croatia
  • concordant coastline
  • formed as a result of a rise in sea level
  • also known as Pacific coasts
  • when valleys flood because of sea level rise, the tops of the ridges remain above the surface of the sea
  • vallyes and ridges run parallel to each other
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Haff coast

concordant features 

  • long spits of sand and lagoons

named after the Haffs or lagoons of the southern shore of the Baltic sea

  • enclosed by sand spits or dunes
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contemporary sea level change in Kiribati

  • 2014, president of Kiribati finalised the purchase of 20 square km of land in one of the Fijian Islands
  • inhabitants of Kiribati now own a refuge somewhere else
  • nation of Kiribati consists of 33 widely spread islands - very low lying sand 
  • its been predicted that many of its own islands could disappear under the sea in the next 50 years
  • in some places the sea is rising by 1.2cm a year

Whats next?

  • rising sea levels are contaminating water resources = affecting the ability to grow crops
  • people may have to move to Fiji (where land has been purchased in case this does happen) = guarantees the nations food security
  • if islands are submerged, population will become environmental refugees and forced to migrate
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sea level change in the UK

  • land in the south and east (which the ice sheets never covered) is sinking. Rivers pour water and sediment into the Thames estuary - the weight of this sediment caused the crust to sink there and relative sea levels to rise
  • south-east England faces increased flood risks as a result of the land sinking due to isostatic change, as well as a rising sea level caused by global warming
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Sea level change due to tectonic activity

  • boxing day earthquake
  • earthquake caused Banda Aceh to sink - permanently flooded some parts of the city
  • raising of sea bed reduced the capacity of the entire Indian Ocean - permanent rise in sea level of estimated 0.1mm
  • magnitude 9.0 = tsunami in Indian Ocean
  • caused by fault line slipping about 15 metres along the subduction zone - where the Indian plate slides under Burma plate
  • 300,000 dead
  • island of Sumatra hit the worst - closest land to earthquakes epicentre
  • sea level had rose several metres - displaced a large amount of water triggering the tsunami
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South west England rias

  • ria = sheltered winding inlet with irregular shorelines
  • most distinctive features associated with a rise in sea level
  • form when valleys in a dissected uplan area are flooded
  • Kingsbridge estuary in Devon is a ria - provides a natural harbour with the deepest water at its mouth
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Norway, New Zealand, Chile - Fjords

  • formed when deep glacial troughs are flooded by a rise in sea level
  • long and steep sided with a U shaped cross section and hanging valleys
  • much deeper than rias
  • the shallower entrance marks where the glacier left the valley
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East Riding coastal change fund

  • offers limited help in terms of financial assisstance 
  • free advice to those residents affected by coastal erosion

relocation package can fund:

  • the demolation costs for a property
  • some relocation costs - max of £1000
  • expenses caused by relocating to a new home - max £200
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coastal flooding - Bangladesh

  • 46% of the country's population lives less than 10 metres above sea level
  • lies on the floodplains of 3 major rivers - Brahmapurta, Meghna and Ganges
  • almost every year huge areas of the country flood as Himalayan snowmelt adds to monsoon rains and high tides in the Bay of Bengal
  • some islands have sunk by 1.5 m in the last 50 years as a result of isostatic readjustment, clearance and drainage of more than 50 large islands which used to be forested but have been cleared and now used to grow rice
  • 1960/70s -embankments were built around islands to protect them against tidal and storm-surge inundations
  • human action prevented natural deposition of sediment used to maintain the islands height - islands are submerging = increased risk of flooding if the embankments give way
  • removing vegetation - removing mangroves = less interception of water
  • cycline sidr - 2007 - storm surge reached up to 6m high
  • storm surges are common - changes in sea level caused by intense low-pressure systems - depressions and tropical cyclones 
  • for every drop in air pressure the sea level rises
  • electricity supplies and communications knocke dout
  • 71% of Bangladesh's mangrove forested coastline is now retreating by as much as 200 m per year
  • drinking water contaminated
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coastal flooding and storm surges in developed cou

  • UK - was hit by a succession of major storms driven by a powerful jet stream bringing low-pressure weather systems
  • storm December 2013
  • cyclone xaver
  • as the storm moved over Iceland it deepened dramatically, with very low air pressure and rising storm surge potential
  • winds of over 140 mph recorded in mountainous areas of Scotland
  • gale-force northerly winds drove the storm waves on to North Sea coasts
  • surge corresponded with hide tide in many locations making flooding even worse
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Odisha's coastal zone

  • Indian's north east coast
  • rich in mineral deposits
  • huge potential for offshore wind, tidal and wave power

Coastal zone under stress from:

  • urbanisation/industrialisation
  • marine transport, fishing and aquaculture
  • tourism
  • coastal and seabed mining
  • coastal erosion
  • offshore oil and natural gas production
  • rising sea levels
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sustainable management in the Maldives

  • rising sea levels
  • money spent [rotecting the capital city and creating new artificial islands means that isolated islands are ignored
  • sustainable management of traditional income sources (e.g. fishing) and resources (e.g. mangroves) is overlooked in favour of protecting urban and tourism development from coastal threats
  • potential conflict if coastal management focuses on some areas rather than others and the needs of certain groups of people over others
  • the organisation Mangroves for the Future is working with Maldivian communities to educate them on the importance of maintaining coastal mangrove swamps as a natural defence against flooding and erosion
  • the Global Environment Facility has provided small grants to islanders to help them develop sustainable and organic farming as an alternative food and income source to coral reef fish
  • the Japanese government has funded mangrove nurseries on the Maldives so that damaged mangrove areas can be replanted
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The Blackwater Estuary

  • Essex
  • area of tidal salt marsh and low-lying farmland
  • prone to flooding and coasta erosion
  • used to be protected by hard engineering but now rising sea levels and greater rates of erosion are taking over - building higher defences is not sustainable because of coastal squeeze
  • as sea levels rise estuary salt marshes naturally respond by migrating inland
  • sea defences prevent this so the salt marsh is squeezed and would eventually disappear
  • this would remove the natural protection of the salt marsh 
  • solution:
  • managed realignment scheme implemented by creating 5 breachers in the sea wall in 2002
  • new salt marshes formed inland
  • Benefits to the scheme:
  • Abbots Hall Farm owners recieved the market price for their threatened farm
  • high costs of hold the line policy were avoided but flood risk reduced
  • water quality improved
  • new paths and waterways created
  • additional income from ecotourism
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