Coastal Environments Case Studies
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- Created by: Kendal Shaw
- Created on: 10-02-14 19:05
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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