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ASSESS THE EFFECTIVENESS OF HOLISTIC MANAGEMENT STRATEGIES USED TO PROTECT…
ASSESS THE EFFECTIVENESS OF HOLISTIC MANAGEMENT STRATEGIES USED TO PROTECT A STRETCH OF COAST FROM EROSION
BARTON ON SEA
a combination of unresistant geology and high energy processes has led to coastal recession rates averaging 1m per year
the geology of Christchurch Bay is dominated by relatively unresistant sedimentary tertiary sands and gravels and at Barton on Sea underlying clay is exposed. the juxtaposition of strata with permeable sands on top of impermeable clays leads to mass movement in the form of rotational slumps. Groundwater flows towards the sea from about 400 m inland which increased cliff face erosion and instability
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hard engineering
sea walls, groins and revetments
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Christchurch Bay in Hampshire extends 17km from Hengistbury Head in the west to Hurst Castle Spit in the east and is a sub cell of Dorset-Hampshire sediment littoral cell
COASTAL MANAGEMENT
what is costal erosion?
coastal erosion can be defined as the loss of land and the encroachment of the sea. it is a complex process involving considerable interactions between components such as: wind, wave action, tides, types of sediment, transport, storms
coastal erosion is a significant problem to land use. It results in cliff face slumping, loss of coastal land which may have been developed for human activities, erosion of beaches and flooding. For example, studies of the Kent coastline have indicated retreat of cliff areas by 27m between 1872 and 1970
coastal management has two fundamental aims: to provide defence against water inundation and to provide protection against coastal erosion
soft coastal defences
this is the use of natural systems in coastal defence, for example, salt marshes and beaches, which can absorb and adjust to wave and tide energy. soft coastal defence involves manipulating and maintaining these systems without changing their structure
hard coastal defences
these are rigid engineering solutions made principally of concrete such as sea walls and groynes. Hard engineering resists the energy of waves and tides by a fixed structure.
POSITIVES
effective on a local scale through both absorbing and reducing wave energy and retraining local structures
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DISADVANTAGES
localised or coastal protection can be counter-productive on a larger scale. Defence work in one area has consequences for neighbouring regions
hard coastal defences such as sea walls require expensive maintenance around £3000 to £5000 per metre
sea walls directly behind natural ecosystems, such as saltmarshes, prevent the ecosystems responding to sea level change and increased erosion
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HOLDERNESS COAST
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Coastal management
Hard engineering:
The coast at Skips has a series of Gabion cages (wire cages holding smaller rocks) built by the local landowner.
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Hornsea (holiday resort) has groynes (repaired for over 5.2 million pounds) and a sea wall which was recently raised to reduce erosion further. Groynes seem locally effective, they are relatively low cost, acceptable visually and development of low-lying land has now been possible. However this trapping of sand may have caused scour at further down the cost, the groynes also require regular maintenance.
Withernsea (resort in the south) consists of groynes and a sea wall. To prevent wave erosion a new wave return wall has been built. The wall is further protected by rip-raps. Costs have limited the length of the sea wall, the rocks have reduced access to the beach and views are restricted, there is a problem with wave noise: starting a tourism issue. However, it will hold the line, calm concerns of local residents and hoteliers and save seasonal jobs in the resort.
Easington received help of revetment rock armour placed at the foot of cliffs to protect their natural gas terminal which handles 25% of North Sea production.
Soft engineering:
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Withernsea's natural beach has all but disappeared leaving more erosion (lowering local house prices). Some beach nourishment has taken place here.
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LYME REGIS
Background
- lies at the heart of the World Heritage site known as 'The Jurassic Coast' (one of the most beautiful stretches of coastline in Britain)
- The scenery that surrounds the town was formed as a result of constant erosion by the sea and the slipping of cliffs and hills
- the costal zone that Lyme Regis is located on is one of the most unstable and rapidly eroding in Europe
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Final options
- inc intensity of storms made it necessary to consider a theme that will give long-term protection and reduce annual maintenance costs
- costing £30 million
- managed retreat was not possible as there was no where to retreat to, prevent and discourage was unrealistic as town relies too much on tourism
- a proactive approach, occurring as before events
- stabilising the land behind the beach by fixing unusable slipped land to firmer rocks
- protecting the foreshore from the sea with a new sea wall and extended offshore barrier
- replenishing the two areas of the beach with sand and shingle
RESULTS
Tourists
- 80% improved access to the beach
- 80% inc shelter for boats in the harbour
- 80% inc in noise pollution
- 50% inc in parking problems
Local people -
- 30% improved access to the beach
- 80% inc parking problems
- 60% loss of income to local businesses