Coastal Environments Case Studies

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The North Sea Storm Surge 1953

  • Most serious in twetieth century 
  • deep atlantic depression moving across Scotland and deepening, pressure fell to 970mb
  • rapid fall in pressure could haved caused rise in sea level (0.5M)
  • anticyclonbe lying to wesr of British Isles
  • large fetch from north and stong wind - waves over 6M
  • high spring tides, rivers discharging into sea
  • sea defences breached 
  • England - thousands of hectares of land flooded
  • England - damage to property
  • England - comunication and agriculture disrupted
  • England - loss of livestock
  • England - over 250 people drowned
  • Netherlands - dyke system breatched 
  • Netherlands - over 1,800 lives lost
  • Netherlands - 10% of agricultural land flooded
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North Sea Tidal Surge 2007

  • England east coast, 9th November 2007
  • wind exceeding 50mph and high tides
  • Great Yarmouth - 7,500 advised to leave homes
  • London - safe due to barrier
  • Lincolnshire, Norfolk, Suffolk, Essex and Kent left underwater 
  • UK Environment Agency "extreme danger to life and property"
  • 500 people spent night at refugee centres
  • Netherlands - Maeslant surge barrier closed 
  • Netherlands - Rotterdam's port closed
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North Sea Storm Surge 2013

  • 5th/6th December 2013
  • warm air from Atlantic met cool air from Arctic to form low pressure weather system
  • Moved eastwards, low pressure deepened rapidly gales of 80mph across Scotland 
  • Great Yarmouth homes evacuated 
  • Man killed on a mobility scooter in Retford Nottinghamshire when hit by a falling tree
  • 230 flood alerts 
  • 380 square miles submerged under water 
  • eastern England - 10,000 homes evacuated 
  • Thames barrier closed 
  • flights cancelled 
  • flood defences evaluated afterwards
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The collapse of Holbeck Hall Scarborough 1993

  • Holbeck Hall was built on top of cliffs behind South Bay in Scarbrouogh 
  • not thought to be in danger but collapsed into sea
  • dry weather cracked clay on cliff top followed by heavy rain, lubricated lines of slipping
  • hotel collapsed bit by bit - rest demolished by contractors 
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Barton-on-sea, Hampshire

  • cliffs of Barton and highcliffe in Christchurch bay known for rapid coastal erosion
  • parts of the cliff are soft (Barton Clay) water bearing sand above, capped by pourous and permeable gravel
  • water drains into gravel - cliffs vunerable to landslides
  • houses are close to edge of cliff - property in Barton could have been destroyed 
  • debates about sea defences to protect vunerable property
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Lulworth Cove and Stair Hole

  • South-west of Southampton, east of Bournemouth, south coast of England
  • Rock type - chalk, upper greensand, gault clay, wealden clay, purbeck limestone, portland stone
  • coastal lanforms - wave-cut platforms, arches, caves
  • highest point on chalk cliffs - 90M
  • highest point on Purbeck  limestone cliff - 30M
  • widest point of Lulworth Cove - 350M
  • width of entrance to Lulworth Cove - 100M
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Towyn Floods, Wales - February 1990

  • 10m waves through 140 year old sea wall
  • Towyn lies on Chester to Holyhead railway - where it crosses low-lying area - Morfa Rhuddlan
  • It was protected by an embankment 3km long 
  • effects - 5000 people affected, £30 million to restore area
  • 2,800 properties evacuated, 1,880 in Towyn, 4,512 in Kinmel Bay, Pensarn 
  • 6,000 caravans damaged 
  • 40% had no contents insurance, 15% no building insurance 
  • £1.4 million spent on immediate work on property
  • Further £3 million on structural damage to road etc.
  • 3,000 people in temporary accomodation a few weeks after 
  • 3 months after, 1,000 people still not able to return
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Storm Surge in Bangladesh

  • In a strom surge high winds due to tropical cyclones form the south and push northwards into the narrowing Bay of Bengal
  • Water then hits coast of Bangladesh (Ganges Delta)
  • Water levels can rise by over 10m 
  • Storm surges travel many km inland destroying farmland, villages and infrastructure, ruining crops and drowning livestock and people
  • 1970 estimated death toll - 300,000 
  • Salt water - long term problems e.g. salinisation of soils 
  • Bangladesh now starting to fight back e.g. allowing the delta to be inundated but protecting Dhaka (capital city)
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Coastal Management Pevensey Bay, East Sussex

Organised and maintained as countries first public-private partnership (PPP) coastal managment scheme.

  • Begun 1st June 2000, 25 year contract and £30 million
  • Involves the Environment Agency, HM Treasury and Pevensey Coastal Defence Ltd (PCDL) - work within DEFRA guidelines 
  • The sea defences
    • stretch 9km east from Sovereign Harbour frontage
    • protect 50km2 of low-lying land, 15,000 properties, holiday caravan sites, the A259 coast road, the railway line from Hastings to Eastborne, Brighton and Portsmouth, two nature reserves, a wetland SSSI site and many arable farms and livestock
    • shingle beach strenches length of Pevensey Bay coast 6m high and extends 45m inland
    • 150 groynes - poor quality
    • beach no longer self-sustaining - needs regular replenishment, LSD caused a loss of sediment 
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Coastal Management Pevensey Bay, East Sussex (2)

  • What has been done?
    • Beach reprofiling - The use of bulldozers to move sediment where it is needed
    • Beach replenishment - A barge/dredger is used to bring shingle from offshore Hastings bank to Pevensey Bay shore at high tide. Up to 700m3 can be brought each trip
    • Beach monitoring - Monitoring areas of loss using quad bikes, GPS and computers
    • Key Groynes - most 150 old groynes taken down, only useful ones will be replaced
    • Wooden retaing wall wall - Herbrand walk, a two-tier timber retaining wall 250m long built landward face of beach, preventing inland migration 
    • Use of new materials - non-traditional materials, compressed tyres and steel plates
    • Crown Estate research project - Pevensey Team working with crown esate to evaluate rate at which sediment is disappearing  
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Flamborough Head - Selwicks Bay (NM Video)

  • Hard chalk, bedding planes joints, wave-cut platform, geo, arch, caves
  • Mass movement - vegetation on cliff top
  • Vertical - hard - not easily eroded 
  • Horizontal bedding planes
  • Chalk - warm seas quiet, calcium carbonate 
  • Change in climate causes faults 
  • Hydraulic action - compresses air in cracks 
  • Open to attack
  • Arch wider at high tide
  • Sub-aerial processes attack cliff-top causing arch
  • Porous - sponge, permiable - passes through joints and bedding planes 
  • Refraction on headland 
  • White areas - rockfall
  • Beach closed for safety - rockfall
  • Basalt brought by sea 'erratics' 
  • Wave-cut notch 
  • Biological weathering 
  • Cross fault 
  • Abrasion/corrasion - sand paper affect 
  • Major fault causing bay
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Barmston - Holderness Coast (NM Video)

  • Caravan owner trys to prevent erosion with boulders - sea eroded around the back - although has worked 
  • Shallow narrow beach - waves comes right up to the cliff face 
  • Wet boulder clay, dry above squashing below
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The Holderness Coast, Yorkshire

  • Weather contributing to coast erosion 
    • Winter storms produce stronger waves and higher sea level
    • Rain intensifies land-based (sub-aerial) processes 
    • Saturated clay cliffs suffer increased run off - slumping and other mass movement
  • Waves contributing to erosion 
    • Dominant waves from NE - direction of longest fetch 
    • Destructive waves to erode beach, attack cliffs
    • Tides and low energy on Humer estuary allow sediments to collect forming a spit, mudflats and sand dunes near Spur Head
  • Geology contributing to erosion 
    • Two main types of rock - chalk, boulder clay
    • Chalk more ressistant - survive large scale erosion - Flamborough Head
    • Boulder clay cliffs to the south are easily eroded - retreat formed sweaping bay of Holderness 
  • Distinctive features of this coastline 
    • Chalk headland - Flamborough 
    • Retreating clay cliffs - Holderness Bay 
    • 6km spit - Spurn point
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The Holderness Coast, Yorkshire - Flamborough Head

  • Features at Flamborough Head 
    • Notch, arches, sea stacks, stumps, rock falls 
  • Processes
    • Hydraulic pressure (action) - weight of waves striking the cliffs or air being trapped in faults
    • Wave refraction - concentrates waves on headland - development of caves into arches, stacks and stumps 
    • Sub-aerial processes - rock falls
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The Holderness Coast, Yorkshire - Holderness Coast

  • Holderness cliffs - why are they there?
    • Boulder clay cliffs formed from material left by ice sheets 
  • They are retreating at a rate of 1.8m per year because of effect of land (cliff-face) processes and sea (cliff-foot) erosion
  • Affects on the cliffs 
    • Rainwater - enters the clay causing it to slip sewards on natural slip planes in cliff or it may slump
    • Removing vegitation and increasing urbanisation - makes these effects quicker, cliff top properties make this worse 
    • Longshore drift 
      • carries half a million tonnes of sediment southwards each year
      • little material left for beaches to protects cliffs
      • placed along this coast strong rip currents may excavate ords or deep hollows, lead to fast rates of cliff erosion 
      • examples - Great Cowden and Easington, cliff retreating at over 10m per year
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The Holderness Coast, Yorkshire - Littoral Cells

  • A litterol cell is a small section of the coastline (eg. Flamborough to the Humber estuary) they are open systems with inpuuts transfers and outputs of water and sediment 
  • Inputs - sediment from cliffs, offshore bar
  • Transfers - waves, LSD
  • Outputs - sedminet forms a spit, offshore bar 
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The Holderness Coast, Yorkshire - Sea Defences

  • Sea wall - Hornsea, Withernsea
  • Revetment - Easington gas terminal
  • Gabions - Skipsea
  • Groynes - Hornsea, Withersea, Mappleton
  • Offshore Bars - Only used as small scale pilot study so far
  • Rip-rap - Withernsea, Easington
  • Cliff Drainage - Small scale project at Easington
  • Cliff regrading - Mappleton
  • Beach nourishment - Hornsea, Mappleton
  • 'Do nothing' - Neck of spurn head
  • 'Managed retreat' - Suggested 1994 Hornsea but not implemented
  • Coastal resiliance - Flood sunk island, plant sand dunes south of hornsea 
  • Shoreline managment plans - Applied to coast further norrth in the Scarborough and Whitby areas
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The Holderness Coast, Yorkshire - Protection of th

  • Little protection needed north of the Holderness coast - much of the beach material is relatively stable 
  • Coastal protection at Barmston - dumping of rock waste 
  • Hornsea 
    •  Groynes have been repaired and new ones built (£5.2 million), steel doors guard entrace to beach
    • Advantages - Groynes locally effective and relatively low cost
    • Disadvantages - Groynes require maintainance 
  •  Withernsea 
    • Groynes, sea wall, rip-rap, beach nourishment 
    • Advantages - Will hold the line, calm concerns of local residents and hotel owners
    • Disadvantages - Coasts limit length of sea wall, rocks reduce access to the beach
  • Easington 
    • Rock armour replaced at foot of the cliff to protect gas terminal
  • Spurn Head
    • Managment strategy abandoned, enable the sea to wash over the spit 
    • Advantages - costs of protection saved
    • Disadvantages - community of lifeboat men and coast guards have to move their families elsewear
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The Holderness Coast, Yorkshire - Mappleton

  • Issues 
    • Erosion rates recorded. Retreated 3.5 km from 1786 - 1988
    • Access to the beach impossible 
    • Houses on cliff falling into sea
    • Threat to coast road 
    • Scheme included two rock groynes 
    • Cliffs regraded to reduce slumping 
    • Some beach nourishment
  • Problems in Mappleton 
    • Regraded cliffs are showing early signs of slumping 
    • Rapid erosion of beaches and cliffs
  • Coastal Managment schemes 
    • Regraded cliff, groynes, rock revetment
  • Problems 
    • Reccent slumping, cliff collapse, scour
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