Transport
There are various sources of the material in the sea. The material has been:
- eroded from cliffs
- transported by longshore drift along the coastline
- brought inland from offshore by constructive waves
- carried to the coastline by rivers
Waves can approach the coast at an angle because of the direction of the prevailing wind. The swashswash: The water flowing towards a beach when a wave breaks. of the waves carries material up the beach at an angle. The backwash then flows back to the sea in a straight line at 90°. This movement of material is called transportation.
Continual swash and backwash transports material sideways along the coast. This movement of material is called longshore drift and occurs in a zigzag.
Coastal transport
There are four ways that waves and tidal currents transport sediment. These can then contribute to the movement of sediment by longshore drift.
| Process | Description |
|---|---|
| Solution | Minerals are dissolved in sea water and carried in solution. The load is not visible. Load can come from cliffs made from chalk or limestone, and calcium carbonate is carried along in solution. |
| Suspension | Small particles are carried in water, eg silts and clays, which can make the water look cloudy. Currents pick up large amounts of sediment in suspension during a storm, when strong winds generate high energy waves. |
| Saltation | Load is bounced along the sea bed, eg small pieces of shingle or large sand grains. Currents cannot keep the larger and heavier sediment afloat for long periods. |
| Traction | Pebbles and larger sediment are rolled along the sea bed. |
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