Explain transportation by longshore drift.

Longshore drift is a key coastal transportation process that occurs when waves approach the shore at an angle. As waves break, they carry sand and pebbles up the beach in the direction of the wave's movement, a process known as swash. When the wave recedes, gravity pulls the sediment back down the beach at a right angle to the shoreline, known as backwash. This zigzag movement of sediment along the coast can lead to the formation of various coastal features, such as spits and bars, and plays a crucial role in shaping the coastal landscape.