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Transcript
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
The Geology of Lyme Regis

Greensand
 Clay
 Shale
 Blue Lias
Steep slope
The Beginnings of a Landslip

Charmouth Road Car
Park
 Asphalt is contributing
to landslip
 Work underway to
improve drainage
system
The Black Venn

Between Lyme Regis
and Charmouth
 Mostly Clay and
Shales with Beef
 Prone to landslides
 Rich source of fossils
The Blue Lias

West of Lyme Regis at
Monmouth Bay
 Greensand
 Clay
 Limestone
Landslides

1962 Langmoor
Gardens
 Caused by
construction activities
 The area was regraded and Langmoor
gardens were
established
The Spittles

East of Lyme Regis
 The whole system was
reactivated in 1986
Long-shore drift interrupted

Beach buildup
 Monmouth beach
 Increased protection

Beach depletion
 Shingle supply
interrupted
 This results in depletion
The depleted beach(1960’s) and
breached seawall (1974)
Coastal Defenses - The Cobb
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
Beacon Rocks

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
Rock Armor at Cobb Gate Jetty
Finishing up at Cobb Gate Jetty
Reinforcements at Cobb Gate
Lyme Harbor beach restored
Work continues at Langmoor
Gardens
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

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
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