Lyme Regis No longer Slip-sliding Away

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Lyme Regis No longer Slip-sliding Away

• September 1, 2006

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Introduction
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Location

• England
• Southwest Coast
• Dorset
• Jurassic Coast World Heritage Site
• Exposed to severe winter storms

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West, 2006
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Stormy Weather
Undated, 1970s storm Source West, 2006
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Calm Weather
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The Geology of Lyme Regis

• Greensand
• Clay
• Shale
• Blue Lias

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Steep slope
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The Beginnings of a Landslip

• Charmouth Road Car Park
• Asphalt is contributing to landslip
• Work underway to improve drainage system

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The Black Venn

• Between Lyme Regis and Charmouth
• Mostly Clay and Shales with Beef
• Prone to landslides
• Rich source of fossils

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The Blue Lias

• West of Lyme Regis at Monmouth Bay
• Greensand
• Clay
• Limestone

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Landslides

• 1962 Langmoor Gardens
• Caused by construction activities
• The area was re-graded and Langmoor gardens were
  established

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The Spittles

• East of Lyme Regis
• The whole system was reactivated in 1986

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Long-shore drift interrupted

• Beach buildup
• Monmouth beach
• Increased protection
• Beach depletion
• Shingle supply interrupted
• This results in depletion

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The depleted beach(1960s) and breached seawall
(1974)
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Coastal Defenses - The Cobb
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Coastal Reinforcements

• Beacon Rocks extended by 110 meters
• North wall rockery realigned
• Added rock armor at Cobb Gate
• New jetties at Lister Gardens and Cobb Gate
• Beach replenishments
• Sand and shingle
• Raised beach level by 2 meters

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Beacon Rocks
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• Armor rocks
• 11,000 tonnes core rock, 2 - 5 tonnes each
• 26,500 tonnes armor, 9 - 18 tonnes each
• Source Norwegian granite
• Byproduct of granite counter top industry
• Shingle (pebbles)
• 72,000 tonnes
• Source Isle of Wight
• Sand
• 37,000 tonnes
• Source northern France
• Precast concrete
• Source UK
• Limestone facing
• Source China

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Rock Armor at Cobb Gate Jetty
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Finishing up at Cobb Gate Jetty
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Reinforcements at Cobb Gate
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Lyme Harbor beach restored
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Work continues at Langmoor Gardens
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Slope stabilization

• Began in 2005, scheduled completion 2007
• Major engineering effort involved considerations
  for seismic stability
• Only small equipment allowed until slope was
  sufficiently stabilized
• Gradual increase in machinery size based on
  monitoring

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• 1,150 auger-cast piling
• Drilled holes thru clay into bedrock
• Filled with concrete and reinforcement
• Act as dowels to hold slope
• Soil nails
• Similar to piling but horizontal
• 2,300 meters drainage
• Counterforts - at base
• Drilled drains -in hill
• French drains - below car park

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Conclusion

• Phase II construction is nearly complete
• Coastal defenses
• Slope stabilization
• Increased security for town
• Increased income due to tourism
• Cost to maintain will be less than the cost of
  emergency repairs