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Lyme Regis No longer Slip-sliding Away

Lyme Regis No longer Slip-sliding Away. September 1, 2006. Introduction. Location. England Southwest Coast Dorset Jurassic Coast World Heritage Site Exposed to severe winter storms. West, 2006. Stormy Weather. Undated, 1970’s storm Source: West, 2006. Calm Weather.

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Lyme Regis No longer Slip-sliding Away

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  1. Lyme Regis No longer Slip-sliding Away September 1, 2006

  2. Introduction

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

  4. West, 2006

  5. Stormy Weather Undated, 1970’s storm Source: West, 2006

  6. Calm Weather

  7. The Geology of Lyme Regis • Greensand • Clay • Shale • Blue Lias

  8. Steep slope

  9. The Beginnings of a Landslip • Charmouth Road Car Park • Asphalt is contributing to landslip • Work underway to improve drainage system

  10. The Black Venn • Between Lyme Regis and Charmouth • Mostly Clay and Shales with Beef • Prone to landslides • Rich source of fossils

  11. The Blue Lias • West of Lyme Regis at Monmouth Bay • Greensand • Clay • Limestone

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

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

  14. Long-shore drift interrupted • Beach buildup • Monmouth beach • Increased protection • Beach depletion • Shingle supply interrupted • This results in depletion

  15. The depleted beach(1960’s) and breached seawall (1974)

  16. Coastal Defenses - The Cobb

  17. 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

  18. Beacon Rocks

  19. 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

  20. Rock Armor at Cobb Gate Jetty

  21. Finishing up at Cobb Gate Jetty

  22. Reinforcements at Cobb Gate

  23. Lyme Harbor beach restored

  24. Work continues at Langmoor Gardens

  25. 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

  26. 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

  27. 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

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