Shingle bank extending 18 mi/29 km along the coast of Dorset, England, from Bridport in the west to the Isle of Portland in the east.
Chesil Beach connects Portland with the mainland and encloses a tidal lagoon known as the Fleet. At the Portland end the bank is about 13 m/43 ft above high water mark, and 183 m/600 ft broad. The pebbles gradually decrease in size from east to west; they are 2.5– 7.5 cm/1–3 in in diameter at Portland and reach the size of peas at Bridport. At the western end of the Fleet is the Abbotsbury swannery, a wetland reserve for a breeding herd of mute swans.
The bank was formed 10,000 years ago at the end of the last glacial period, when the rise in sea level and large waves from the southwest pushed vast quantities of rock debris and sediments inshore.
The lateral gradation of Chesil Beach's pebbles is caused by downdrift attrition (the grinding of pebbles and rocks together) and longshore drift (the zig-zag movement of pebbles along the beach, carried by waves ascending the bank at an angle and then returning in a straight descent). Strong waves from the southwest throw all material, large and small, to the east, but there is a counter-current moving along the coast working the increasingly smaller material from east to west.
The whole area of Chesil Beach and the Fleet is proposed for designation as a protected site under the European Union's habitats directive.
Chesil Beach: an Example of a Tombolo