Longshore drift and landforms created

Longshore drift

Longshore drift is the gradual movement of material further along the beach as a result of the waves approaching the beach at an angle. The waves break at this angle as a result of the prevailing wind. This is a wind that is not necessarily the strongest but most common. This only occurs if the waves are destructive.

When this happens, beaches lose their sediment and begin to retreat. In order to prevent this, groynes are often installed to trap the sediment instead of it being transported to the end of the shore.

The sediment transported by longshore drift is either transported as part of:

1. Solution
2. Suspension
3. Saltation
4. Traction

1. Solution is when material has dissolved in the water making it invisible.

2. Suspension is when small particles of rock/ material are carried along in the water, making it appear cloudy.

3. Saltation is when small fragments of material are bounced along the sea bed and are propelled by the force of the water.

4. Traction is when large pieces of sediment are rolled along the sea bed. The current cannot suspend this therefore it is rolled at a slow pace.

Longshore drift can produce various coastal landforms:

1. Spits
2. Tombolos
3. Bars
4. Bayhead beaches

1. A spit is formed when longshore drift extends the shoreline beyond the land. The sediment being transported is deposited in calm, shallow water. The spit may form a curve at the end when the wind direction changes. Where the spit is curved it can shelter an ecosystem such as a salt marsh. The salt marsh would not be ruptured by the sea here.

2. A tombolo is essentially a spit joined to an island. The spit is formed by longshore drift and the sediment is deposited next to the island where there is calm, shallow water as a result of the shelter of the island. Like the curved ends of the spits, tombolos can provide a sheltered space for salt marshes to form.

3. A bar is formed by longshore drift. It is created across a bay and links two headlands. When there is a storm and a river may flood, the bar would be destroyed by the force of the water.

4. Bayhead beaches are spits joining two headlands across a cove.