This stretch of coastline has been described as one of the most rapidly eroding coasts in the world. Not surprisingly it presents a huge challenge to the engineers to protect West Bay and area from flooding and coastal erosion. Cliff failure and recession at West Bay are due to mass movement, such as slipping, slumping (in the clays) and rock falls (of sandstone) caused by both coastal and non-marine weathering and erosion processes. See also "Summary of Coastal Defence Problems" at figure 5. 

East Cliff sea erosion processes such as wave pounding, hydraulic action, abrasion and attrition, are clearly at work here. The base of the East Cliff is naturally protected by its deep shingle beach, and the man-made shingle ridge, built up by the Environment Agency for flood prevention.

A wave-cut platform is in evidence when not covered by shingle, and reveals the recession of the cliff. Clearly the effects of rain wind and spray are also very erosive and have created gullies in the Bridport Sands. Vertical fissures and joints in the cliffs have been picked out and eroded by wave pounding, hydraulic action abrasion and corrasion, which weaken the cliff structure. After many years of slow weathering, the harder calcite-cemented bands project and show honeycomb weathering. It is chemical weathering which gives the exposed cliff face its orangey colour (limonite) as fine-grained pyrite is oxidised. When rock falls occur the newly exposed cliff face is much flatter and blocks of fallen and shattered rocks are found at the cliff foot. There have been incidents of people narrowly escaping such rock falls as they sat on the beach and warning signs are in place (and often ignored by visitors).

East Beach This is in fact the most westerly end of the Chesil Bank. In 1986 a sea defence bank of shingle was constructed to a height of 7.5m AOD. The bank is highly mobile and provides varying degrees of protection dependant on its width. The Environment Agency is responsible for maintaining this and uses shingle from Burton Bradstock to re-profile the beach as shown at figure 6.

In recent years there has been a major loss of material from this beach with a consequent increase in flood risk. Serious flooding occurred in 1990. Periodic beach overtopping has enforced the need to build up the shingle ridge and replenish it to create a stronger flood barrier, especially for the cottages on the beach itself. Unlike the West Beach, there has been no hard engineering approach to the East beach, as it's an SSSI.

West Cliff

A comparison of old and recent photos of West Cliff (figures 7-9) gives a fascinating insight into the extent of coastal erosion over the years. The West Cliff sea wall and rock armour have effectively protected the foot of the cliff from recession since 1969, but by 2000 this defence was already under threat itself due to construction failure. The recession of the West Cliff is not only a result of coastal erosion processes; West Cliff appears to have been affected by landslips over a long time and the photographic and map evidence show several properties on the cliff top that are now protected by stabilisation work.

The photographs at figures 8 and 9 from 1929 and 2003, taken 74 years apart which is a very short period in geological time, are particularly interesting to compare.

Mass movement within the cliff's Frome Clays is caused when slipping and slumping occur, as the wet clays slide over the underlying rocks. It seems likely that the presence of the faults has weakened the overall structure of the Frome Clay, and that the flow of ground water within the fault zone will have increased its instability. The cliff was regraded in 1969 when the construction of the new sea wall and esplanade took place. Despite this and further remedial action, there has been a series of slips. Engineering attempts to stabilise the cliff in the 1990s included the insertion of drainage pipes and the use of gabions (heavy wire mesh boxes filled with stone). The coastal footpath was upgraded at this time too.

West Beach

This is a narrow sand and shingle beach which is backed by a sea wall, originally built in 1887 and replaced in 1982. As you can see in the photos, the West Beach has been steadily reducing in width and height over the years. It has suffered from lack of natural replenishment from the east, ever since the piers were constructed in 1740. Also the westerly sediment drifts have been limited by landfalls on the beaches west of West Bay, notably at Golden Cap, effectively cutting off the sediment supply from the Charmouth end. Additionally the beach has lowered by 2.5m since the construction of the additional sea wall at the western end in 1969.

This wall has itself been eroded by wave attack, especially attrition of its limestone cladding in storms, and corrosion of the steel pile toe and will need attention. Figure 10 shows evidence of past erosion of the sea wall on West Beach in November 1942.

In order to maintain its value as an amenity for holidaymakers it has been recognised that protection and enhancement/replenishment of this beach is most important. The sea wall at the eastern end is frequently overtopped during storms, which results in flooding and damage to properties from wave borne gravel.