What is longshore drift?

Longshore drift is the process by which sediment is transported along a coastline by wave action.

When waves approach the shore at an angle, they carry sediment such as sand and pebbles up the beach in the direction of the wave (this is called the swash). Gravity then pulls the water and sediment back down the beach at a right angle to the shore (this is called the backwash). This zigzag movement of sediment along the coast is what we call longshore drift.

The direction of longshore drift is determined by the prevailing wind and wave direction. For example, if the prevailing wind is from the southwest, the waves will generally approach the coast from that direction, causing sediment to move northeast along the shore. Over time, this can lead to significant changes in the shape and size of beaches.

Longshore drift plays a crucial role in the formation of various coastal features. For instance, it can lead to the creation of spits, which are narrow stretches of sand or shingle that extend out into the sea from the coast. It can also contribute to the formation of bars and tombolos, which are landforms that connect an island to the mainland or another island.

However, longshore drift can also cause problems. It can lead to the erosion of beaches in some areas, while causing sediment to build up in others, potentially leading to issues such as harbour blockages. Coastal management strategies, such as groynes and breakwaters, are often used to control longshore drift and protect coastal areas from erosion.

Understanding longshore drift is essential for managing and protecting our coastlines, making it a key topic in GCSE Geography.