Coastal transportation and deposition Learning Intentions
In this section, you will learn: • how material is transported along the coastline by longshore drift
• how landforms along the coastline are formed by coastal deposition
• how to identify landforms of coastal deposition • how to recognise landforms of coastal deposition on an OS map.
Longshore drift
The material transported by waves, such as sand, shingle, mud and eroded material, is called the load. The movement of the load along the coastline is called longshore drift. Longshore drift involves two steps:
1. Waves approach and move up the shore at an angle (matching the direction of the prevailing wind). When a wave breaks, the swash moves the load up the shore at an angle and deposits some material there, and so the material is moved along the shore.
2. The backwash carries material back down the shore. This movement follows the slope of the beach, and is usually in a straight line.
The process is repeated over and over, resulting in the gradual movement of material along the shore in a zigzag fashion.
DID YOU KNOW? Winds are named after the direction from which they come. The most common winds that blow over an area are the ‘prevailing winds’. In Ireland the prevailing winds are south- westerly.
