How does a longshore drift happen?

Hello, I'm an expert in coastal geomorphology, and I'd be happy to explain how longshore drift occurs. Longshore drift, also known as littoral drift, is the process by which sediments are transported along a coastline in the direction of the shoreline. This movement is primarily driven by the action of waves and currents, particularly those that are oblique (at an angle) to the shoreline. Here's a step-by-step explanation of how longshore drift happens: 1. Wave Approach: Waves approach the shore at an angle, which is common in most coastal areas. 2. Swash and Backwash: As the wave breaks, it releases its energy in a rush of water known as the swash, which moves sediment up the beach. The backwash, the return flow of water back to the ocean, tends to carry the sediment back down the beach but at a lesser rate. 3. Net Drift: The difference between the amount of sediment moved up the beach by the swash and the amount returned by the backwash results in a net movement of sediment along the shore, parallel to the shoreline. 4. Wave Refraction: As waves approach the shore, they may refract (bend) around a headland (a point of land projecting into the sea), which can cause the wave energy to be concentrated on certain parts of the beach, enhancing the longshore drift in those areas. 5. Longshore Currents: The net movement of sediment along the shore creates a longshore current, which is a narrow, powerful current that flows parallel to the beach and is a significant agent in the transport of sediment. 6. Coastal Features: The presence of coastal features like headlands, bays, and jetties can influence the pattern and intensity of longshore drift. Longshore drift is a critical process in shaping coastal landscapes, contributing to the formation of features like spits, barrier islands, and beach cusps.

The swash 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��. ... Continual swash and backwash transports material sideways along the coast. This movement of material is called longshore drift and occurs in a zigzag.