Overstrand To Cley
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Transcript of Overstrand To Cley
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• Coastal Processes
• Management Strategies
• Sustainability Issues
Coastal Study
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The North Norfolk Coast
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Study Sites
Sheringham
West Runton
Cley-next-the-Sea
OverstrandCromer
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Factors Affecting Erosion
•Geology
•Sub-aerial Processes.
•Human Influence
•The Sea
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Distance over which waves have to build up
NE 600km Denmark
N 4100km Arctic
Fetch
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Cross-section of a typical cliff in North Norfolk
Glacial Till250 - 450 Ka
West Runton Freshwater Peat Bed650 Ka
Chalk60 - 70 Ma
Weybourne Crag1 - 2 Ma
Geology
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Sub-aerial Processes Saturation
UndercuttingSlumping
Transportation
S.U.S.T.S.U.S.T.
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Erosion Consequences
Loss of 1 metre of cliff annually• Not Uniform
• Coastal Variations
Effects• Destruction of Property
• Loss of Livelihood
• Habitat LossOverstrand Hotel
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Coastal Defences
Angled Sea Wall
Groynes
Flat Sea Wall
Rock Armour GroynesRip-Rap
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Beach Nourishment
Revetments
Bore Pipes
GabionsShingle Ridge
Coastal Defences
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SustainabilityBruntland (1987)“meeting the needs of the present without
compromising the ability of future generations to meet their own needs”
• Example :Groynes are made of wood from rainforests.Therefore we chop down forests to make groynes.Eventually this deforestation leads to global warming and higher sea levels.Consequently there is an increased need for groynes.
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Costs and Payments
• Norfolk coastline is 74km long (Hunstanton to Lowestoft)
• 34km of it is being protected by sea defences
• If all defences were taken out and re-built today cost would be £70m
• Annual maintenance budget of £280,000
• Sheringham spent £5.25m on defences between 1995 and 2000
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So Who Pays?DEFRA (Department for the Environment,
Food and Rural Affairs)
• Can pay up to 75% of cost for sea defences
• Only contribute 55% in North Norfolk
Local District Councils • Pay the rest, but can get a
‘supplementary credit agreement’ loan
As they pay the majority, DEFRA decide where the defenses will go
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DEFRA Criteria For Funding
Urgency
Is the cliff likely to fail again in the next 5 years
Economics
Cost benefit analysis
Priority
Is the area urban or rural in location?
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Shoreline Management Plans
“Management of one area of coast may have an adverse
impact on other areas”
• The UK coastline is divided into management cells and sub-cells corresponding to changes in longshore drift
• Norfolk is divided into sub-cells 3a and 3b, with the division roughly at Sheringham
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Advance The Line
Managed Retreat Do Nothing
Hold The Line
S.M.Ps. Four Strategies
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Tomorrow• Meeting time . . .
• Structure of the day
• Weather
• What you need to bring . . .
1. Weather dependent: waterproofs, warm clothing, extra drink, sun cream
2. Essentials: work stuff, comfortable shoes
• Citizenship –
“take nothing but pictures, leave nothing but footprints”
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Cley-next-the-Sea
• Population 600
• Fishing industry
• Freshwater marsh (SSSI), owned by NWT, prone to flooding
• Starting point of shingle spit
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Sheringham
• Population: 7,500
• 2nd biggest tourist resort in North Norfolk after Cromer
• Steam railway is a major attraction (125,000 per year)
• Heavy sea defences
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West Runton
• Population: 800
• Built up around fishing industry
• Fantastic geology (SSSI)
• Locally important as a Rocky Shore
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Cromer
• Population: 8,000
• “Gem of the North Norfolk coast”
• Many sea defences because of weak geology
• Cliff-top settlement
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Overstrand
• Population: 1,100
• Highly exclusive tourist resort
• Site of Clifton Way project - experimental sea defences
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Flat Sea Wall
• Reinforced concrete
• Maximum life span 100 years
• £3,000 per linear metre
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Angled Sea Wall
• Reinforced concrete
• Maximum life span 100 years
• £5,000 per linear metre
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• Granite from Norway
• £1-3,000 per boulder (depending on size)
• 100 + years life span
Rip-Rap
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• Tropical Greenhart wood
• 30-40yr life span
• £1,000 per linear metre
Groynes
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Rock Armour Groynes
• Made from Rip-Rap
• More effective at stopping longshore drift than wooden groynes
• £1,250 per linear metre
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• Were made from iron, now flexible plastic
• £ 120 per metre
Bore Pipes
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Beach Nourishment
• Movement of beach material from one beach to another
• Longshore Drift transports it along shore
• Replenished each year
• £10 per m3
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Shingle Ridge
• Beach material bulldozed into a barrier
• 6 Month lifespan
• £40,000 maintenance each year
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• Tropical Greenhart wood
• 30-40yr life span
• £1,500 per linear metre
Revetment
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• Cages filled with beach material
• 5-10 year life span
• £50 per cage
Gabions