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Coastal Management - Hard Engineering solutions
Minehead, Somerset
Background
The tides of the Bristol Channel are a mixed blessing for Minehead. They helped the town become a prosperous port, and until recently, a thriving tourist resort. But their potential for causing devastating floods has caused misery. The powerful currents of the Bristol Channel have removed much of Minehead's beach and caused floods. In a town that depends on over half a million holidaymakers to create £90 million of tourist income and jobs, something had to be done. After much consideration, a flood defence scheme was approved in 1996.
What were the options?
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Scheme
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Approved
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Rejected
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Increase the height of the sea wall by over two metres to stop the waves overtopping during a storm
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This was ruled out because of the unacceptable impact on the visual amenity of the bay and acces to the beach
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Increase the level of the beach to the promenade level by importing large quantities of sand and cobbles. Waves would then break further off-shore, away from the sea wall.
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This was considered to be unsatisfactory because of the time and cost to maintain this and because very large, long extra groynes would be needed.
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To combine elements of the first two options above. It raises the sea wall by 0.6 metres and adds a moderate volume of extra sand and cobbles which will raise the beach by 2 metres
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This solution will cause waves to break further offshore. Consequently, they will have a longer distance to use up their energy. The waves will also be less powerful so should not overtop the wall or wash the beach away. Four new rock groynes will prevent the beach material drifting eastwards.
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Do nothing
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The sea wall would not withstand another severe storm. Damage to houses, businesses and Somerwest World could cost £21 million. Although the chance of such a storm is a once in a hundred year chance, doing nothing was considered too risky.
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What did the approved scheme involve?
•· Length of defence: 1.8 km
•· Quantity of rock armour: 90,000 tonnes. Cost of rock armour (Phase 2): £3.5 million
•· Quantity of sand and shingle: 300,000 tonnes. Cost of sand and shingle (Phase 3): £2.4 million
•· Cost of sea wall construction (Phase 1): £9.2 million
•· Cost of enhancing the sea front (Phase 4): £2 million
•· Total cost of construction: £16.1 million
Advantages and disadvantages of the scheme
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Advantages
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Disadvantages
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Raised pavement levels adjacent to the sea wall will retain sea views for pedestrians. Includes new seating areas and raised shelters.
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High cost of initial construction work.
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Rock armour will prevent beach material drifting out to sea.
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Periodic maintenance required to recover and replace shifted beach material to maintain the sea defence.
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New improved access to the beach will provide safe ramped access for wheelchair and pushchair users.
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May alter the natural movement of beach material along the coast (longshore drift).
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Will help sustain tourism in Minehead, by providing a beach and protecting facilities such as Somerwest World.
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D. Drake 2010
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