The information found here reflects completed USGS work. The content of this page is static and has not been updated since the mid 2000's.
Beaches: Sand on the move!
Description of longshore currents and transport
Breaking waves disintegrate into churning sheets of water called swash that carry sand and gravel up onto the beach. Each wave brings new sediment and carries some sediment back into the surf zone. If more sediment is deposited by waves than is carried away, a beach builds up. If more sediment is removed than is deposited, the beach erodes.
Waves from the Pacific Ocean breaking on the shore with bluffs.
Labels illustrating the effect of a longshore current.
Wind blows toward the shore, creating waves
Waves move sediment towards the shore at an angle (oblique)
Backwash (retreating waves) carry sediment away from beach at 90°, perpendicular to the shore
The effect of these processes is longshore transport (beach drift) of sediment parallel to shore in the general direction of the prevailing winds