Longshore Currents

Longshore currents are ocean currents that travel parallel to the shore.
They are also known as littoral currents.
As the waves of a longshore current reach the shoreline, they carry or push water, sand, and sediment in a single direction down the length of the beach.
Longshore currents are located closest to the shoreline, compared to other types of currents.

Undertow currents carry sand and sediments near the shallow ocean floor.
Undertow currents influence the formation and activity of waves closer to the surface.
When waves from further into the ocean come toward shore, they mix with the longshore current and potentially form a rip current.
Rip currents are dangerous movements which can sweep sediments and people deeper into the ocean.
A cross-current is the location where the longshore current and rip current meet.
Strong longshore currents can be dangerous, especially in the presence of another form of current.

The largest factor that affects the direction and strength of the longshore current is the wind and angle of wave approach.
Littoral currents may also be affected by the velocity or speed of waves and contact with other ocean currents, such as rip currents.
Waves often conform to the shape of the coastline because they make contact with other waves, currents, or segments of the beach before reaching shore.
Waves that break at an acute angle or are very tall are more likely to increase the velocity of the longshore current.
Waves that break over a broader area or are not tall slow the velocity of the longshore current.
Waves typically come ashore at an angle, which allows for objects to be swept down the shoreline.
The strength of the current is largely based on many factors being present at once.
A long and straight beach with large waves increases the velocity of the longshore current.

Longshore transport refers to the movement of sand and sediment parallel to the coastline as a result of the longshore current.
The same concept can apply to any natural or synthetic item, from seashells to beach balls.
The speed of longshore transport is defined by the speed of the longshore current.

Longshore drift pertains to the progressive movement of sand and sediment along the beach caused by angled waves and the shape of the land.
Longshore drift is one of two factors that allow the process of longshore transport to take place, the other being longshore currents.
Longshore currents, longshore drift, and longshore transport have a uniquely dependent relationship.
Longshore currents run parallel to the shoreline and create angled waves as they come into contact with the shore, waves, and other forms of current.
They allow longshore drift to occur by providing a continuous parallel movement, meaning that sand and sediments can be transported as well.
Longshore transport is the process of materials being carried along the length of a shoreline in a parallel fashion by angled waves, the force of gravity, and the shape of the land.
The process is dependent on the occurrence of longshore currents and longshore drift.

When longshore currents reach the shore and waves break on land, the water carried onshore by the waves is usually referred to as swash.
The area at the water's edge where waves crash or lap up onto the beach is known more specifically as the swash zone.
Swash arrives onshore at an angle as the result of waves striking the coast in a similar fashion, thus causing sand and sediments to be carried by swash in the same direction as the waves' motion.
Due to the forces of gravity, swash is pulled back into the ocean at a perpendicular angle to the shoreline.
The receding water that moves back into the ocean becomes known as backwash.
The effect of swash coming onshore at an angle and backwash returning to the ocean in a perpendicular direction is the continuous deposit of sand, sediment, and other materials in a zigzag pattern down the beach.
The process of longshore transport is caused dominantly by beach drift.