Chesil Beach is known throughout the world as an impressive shingle storm beach. The beach acts as a vast natural defence, but in very heavy storms the area behind the beach may be flooded. Huge waves pounding against the beach force water through the pebbles to the back of the beach. The biggest waves sometimes overtop the ridge, sending water and shingle onto the road behind. In recent years extensive flood alleviation schemes have been implemented by the Environment Agency and the Ministry of Agriculture Fisheries and Food to minimise the impact of such flood events, and a flood warning system alerts residents in the area if a major flood event is predicted.

Formation of Chesil Beach

Local legend says that Chesil Beach was cast up by a violent overnight storm and that even today local sailors and fisherman can tell exactly where they are on the beach by the size of the pebbles! The most acceptable scientific theory presents evidence that at the end of the last glacial period (10,000 years ago) sea level rise pushed vast quantities of rock debris and seabed material inshore by large waves from the south west.

Recently a group of geomorphologists, coastal engineers and managers with an interest in Chesil Beach met to discuss the level of present knowledge of the area and its evolution. They concluded, however, that although a lot of data has been gathered, analysed and interpreted, a lot more research need to be done before we can account for its formation and its present day change!

Formation of Fleet Lagoon

The Fleet at 13 km long is the largest lagoon in the UK and is unique for its naturalness and lack of human disturbance. It is of national and international significance for its aquatic plant and animal species, including a number of rarities. Over 150 species of seaweed and 60 species of mollusc have been recorded and it supports a rich and diverse invertebrate community. Sponges, anemones and sea squirts abound especially with the tidal rapids of the outer lagoon near its mouth into Portland Harbour. The stiller waters of the inner lagoon are home to the rare starlet sea anemone. The lagoon is protected as a nursery area for bass whilst the shy and unusual black faced blenny can sometimes be spotted.

The Fleet is recognised as a wetland of international significance under the Ramsar convention and as a Special Protection Area for its bird interest under the EU Birds Directive.

The main theories accounting for the formation of the Fleet are closely tied to those of Chesil Beach although early geomorphologists though it was a river valley running parallel to the coast. Accepting the view that Chesil advanced onshore across the floor of West Bay it met cliffs near Cogden, whilst east of Cogden the beach advanced as a great sweep around to Abbotsbury separating the area behind from the open sea and thus forming the Fleet.

The whole area of Chesil Bank and the Fleet is proposed as a candidate site for designation under the EU Habitats Directive.