Coastal change is a natural, ongoing process that has always happened.
As sea water meets cliffs and shores, it causes sediment or rocks to be broken down and washed out to sea. In some instances, this material may be moved to a different part of the coast and deposited in large quantities, causing ‘accretion’ – the opposite of erosion, where shorelines may advance or build up with sediment over time. In fact, the sand and shingle that makes our beaches is a product of erosion, and to remain in place they need a continual supply of material.
Erosion can happen under any conditions, but its rate tends to increase when waves are powerful and water levels are high – for instance during storms or in high winds.
How waves cause erosion
Waves cause erosion to happen in four main ways:
- Waves bring with them particles of rocks and sand that grind the cliff down.
- The constant force of water against the shore wears it away.
- The action of powerful waves causes rocks and pebbles from the shore to smash into each other and break up.
- Acids in the sea also slowly dissolve certain types of rocks.
How erosion affects our coast
The way erosion changes different parts of our coast depends largely on the type of rock – in other words, its geology.
Erosion of coasts with hard rocks tends to be slower, and can form dramatic rock formations over time, including tunnels, bridges, columns or pillars such as at Lulworth Cove in Dorset.
Where coastal geology is formed out of sedimentary deposits, such as on the soft cliffs around parts of the east coast, erosion can pose more of a risk for human settlements. Sedimentary rocks, such as sandstone and chalk, naturally erode more easily than hard rocks, so the coast recedes at a faster rate.
Coastal erosion and coastal flooding are often linked. One may lead to another, especially where shorelines separating the sea from flat, low-lying land are eroding.