Investigate a coastline experiencing rapid retreat - Dorset Coast



1. Rapid erosion at the base of the cliffs  - this leaves the cliff behind unsupported and more likley to collapse.

There is little beach material to absorb the energy of the waves so the waves erode the foot of the cliff. The waves that hit Lyme Regis from the south-west are particularly powerful, having travelled across 7000km of open sea (this distance is called the FETCH of the waves).

2. Weathering of the cliff face loosens cliff material. Here is particular biological weathering from plants and animals that live on the gently sloping cliff-face.

3. Rainfall and runoff add a conserable weight of water to the permeable sand and  clay layers on the top of the cliff.

4. This water infiltrates the top of cliff making it heavier and slippery, but cannot pass into the impermeable layer beneath. This creates a very slippery layer between the two layers.

5. Buildings built on top of the cliff add further weight to the cliff.

Cliff collapse happens here because the heavy and slippery upper layers of sand and clay eventually cascade downwards due to mass movement (caused by gravity).

What damage has been done at Lyme Regis?

 * Before the new coastal management scheme 170 properties in Lyme Regis were under threat from either landslides or coastal erosion.
 * Subsidence was continually damaging property as well as roads and car parks.
 * Houses along Marine Parade were regularly flooded and hammered with stones from the beach during storms.