Depositional landforms
When water loses its energy, any sediment it is carrying is deposited. The build-up of deposited sediment can form different features along the coast.
Beaches
Beaches are made up from eroded material that has been transported from elsewhere and then deposited by the sea. For this to occur, waves must have limited energy, so beaches often form in sheltered areas like bayA low-lying inlet of land on the coast.. constructive waveWaves which help build up material on the beach. They tend to have a low frequency and strong swash. build up beaches as they have a strong swashThe water flowing towards a beach when a wave breaks. and a weak backwashThe movement of water down the beach..
Sandy beaches are usually found in bays where the water is shallow and the waves have less energy. Pebble beaches often form where cliffs are being erodeThe wearing away of the landscape., and where there are higher energy waves.
A cross-profile of a beach is called the beach profile. The beach profile has lots of ridges called berms. They show the lines of the high tide and the storm tides. A sandy beach typically has a gentle sloping profile, whereas a shingle beach can be much steeper. The size of the material is larger at the top of the beach, due to the high-energy storm waves carrying large sediment. The smallest material is found nearest the water as the waves break here and break down the rock through attritionThe wearing down of the load as the rocks and pebbles hit the sea bed and each other, breaking into smaller and more rounded pieces..
Spits
A spitA stretch of beach at one end of a coastline caused by waves depositing material. is an extended stretch of sand or shingle jutting out into the sea from the land. Spits occur when there is a change in the shape of the landscape or there is a river mouth.
This is how spits are formed:
- Sediment is carried by longshore drift.
- When there is a change in the shape of the coastline, depositionWhen material is deposited or left behind, eg when a river loses its energy and is unable to carry its load any further, or waves move sand onto a beach but lack the energy to carry it away. occurs. A long thin ridge of material is deposited. This is the spit.
- A hooked end can form if there is a change in wind direction.
- Waves cannot get past a spit, therefore the water behind a spit is very sheltered. siltFertile sand-sized particles found in the lower course of a river. Also known as alluvium. are deposited here to form salt marshes or mud flats.
Bars
Sometimes a spit can grow across a bay, and joins two headlands together. This landform is known as a barA spit that has grown across a bay. Also known as barrier beaches.. They can trap shallow lakes behind the bar, these are known as lagoons. Lagoons do not last forever and may be filled up with sediment.