Chesil beach in Dorset, UK. Chesil beach is a depositional pebble landform known as a tombolo. It stretches from West Bay at Bridport to Chiswell Bay on the north side of the Isle of Portland. This view is looking west along its 29km arc. The beach is up to 200m wide and reaches a maximum height of 14m above the mean sea level at the Portland end. The size of pebbles on the beach increases from west to east. This graduation in size indicates that longshore drift was the likely cause of the beach's formation. Chesil beach is the longest tombolo in England.