By Andrew Burke, James Ferguson and Chris Silins

Located on Dorset/Devon border on South coast

Lies on a sequence of rocks through geological time: Triassic, Jurassic and Cretaceous periods

Older rocks in the west, younger in the east

Located on Dorset/Devon border on South coast

Lies on a sequence of rocks through geological time: Triassic, Jurassic and Cretaceous periods

Older rocks in the west, younger in the east

At Lyme Regis: Triassic rock disappears below see level Jurassic rocks form the cliffs (Blue Lias) – 200m years old

Formation: Deposits from deep tropical sea with marine life – fossils

Due to weak properties of Lias Clay and coastal erosion, multiple landslides have occurred.

Strong bedrock overlaid by unstable slippery clays The angle of the layers - makes sliding easier Sea erodes bottom of slide & undermines old defences Beach eroded reducing protection Buildings damaged Landslides expand inland

Predictions for the likelihood of ground movement in the East of the town over the next 20 years

The area was split into five sections Prioritised due to potential risks and cost

BEFORE AFTER

Phase I: a new sea wall and a rock armour revetment

Four main parts:1. Foreshore works – extra sand and shingle – Extending rock

armour/renovating existing rockery2. Land stabilisation – piling of soil – new drainage – slope re-grading and some

buttress building3. Road improvements4. Landscaping

Problem:Monmouth Beach is changing shape such that the crest height is reducing in the west.

Consequences: Property on the beach will become more vulnerable to flooding and

erosion.Solution:

Decided to leave and monitorCost vs. risk

Problems

High probability there will be a major landslide within the next 1 to 5 years.

The sea wall is under threat from large-scale cliff failure.

The drainage system has defects and its outfall is under threat from continuing ground movements.

The sea wall is being outflanked at its eastern end.

The shore platform is deteriorating leaving little beach material to protect the sea wall

Problems

The lower parts of the High Wall are deteriorating and are difficult to maintain.

The Low Walkway is vulnerable to scouring by seawater and shingle overtopping the High Wall during storms.

Large areas of Lyme Regis are at risk from coastal erosion and landsliding including:

Solution split into five stages.

The schemes are being implemented over a period of time

The total cost of implementing all the schemes is estimated to be £33M

There would also be considerable secondary benefits to the environment and society of implementing the schemes.