Chesil Beach is a 29km long bank. Pebbles vary from around pea size at Burton Bradstock to tennis ball size at Portland. The grading of particles is due to longshore drift. Waves in the prevailing wind’s direction are strong enough to carry any sediment, regardless of size, while when waves travel in the other direction they are weaker so can only take smaller sediment. The main direction of the wind at Chesil beach is from the South West.
At its tallest, the beach is up to 15m high. Chesil Beach started as an offshore bar 10,000 years ago which gradually rolled onshore as sea levels rose.
(Image Sources: https://en.wikipedia.org/wiki/Chesil_Beach http://travel.aol.co.uk/2012/10/05/womans-body-found-in-sea-off-dorset-beach/ )