What is the Difference Between Longshore Current and Longshore Drift

The main difference between longshore current and longshore drift is that longshore currents are the ocean waves that travel parallel to the beach whereas longshore drift is the transportation of sediments along a coast, parallel to the shoreline.

The terms longshore current and longshore drift are important in the field of geology as they describe the behaviour of oceanic waves and the effect of waves on beach shape. Moreover, the movement of a wave indicates the movement of sediments as well.

Key Areas Covered

1. What is Longshore Current 
     – Definition, Characteristics
2. What is Longshore Drift
     – Definition, Characteristics
3. What is the Difference Between Longshore Current and Longshore Drift
     – Comparison of Key Differences

Key Terms

Longshore Current, Longshore Drift

What is Longshore Current

Longshore current is a type of oceanic wave that travels parallel to the shore. Generally, the speed of an oceanic wave that reaches the beach depends on the seafloor, shoreline features and the depth of water. When a particular oceanic wave reaches the beach, different segments of the wave reach the beach before others. This phenomenon causes the wave segments to slow down. Here, the oceanic wave tends to bend and get the shape of the shoreline. Therefore, these waves tend to reach the beach parallel to the shoreline. However, these waves do not always reach the shoreline in a parallel way; the waves come in a slight angle. This angle is called the ‘angle of wave approach’. The current that comes with this wave and is parallel to the shoreline is named as the longshore current.

Figure 1: Longshore Current

The nature of a longshore current is affected by the velocity and the angle of a wave. If the longshore current breaks the beach in a more acute angle, then it encounters a steep beach slope. Similarly, a wide breaking angel indicates a gentle beach slope. In either case, the longshore current moves towards the beach and comes back to the ocean. During this moving forward and backward process, the longshore current can carry sediments on and off the beach. This process is called longshore drifting.

What is Longshore Drift

Longshore drift is a geological process that includes the transportation of sediment materials along a coast parallel to the shoreline. Longshore drift is a result of longshore currents that approach the beach. The movement of longshore currents towards and backwards the shoreline causes the sediments to move on and off the beach. Here, the most common sediment materials include clay, silt, pebbles, shingle, etc.

However, this geological process mainly depends on the direction of the incoming wave. The incoming wind that comes with the longshore current squeezes the water along the coast and generates a water current that is parallel to the shoreline. Here, the sediments that come with water can remain on the beach; sometimes, the sediments on the beach can move off the beach with the water current. This geological process takes place in the surf zone.

Difference Between Longshore Current and Longshore Drift

Definition

Longshore current is a type of oceanic wave that travels parallel to the shore. Longshore drift is a geological process that includes the transportation of sediments along a coast parallel to the shoreline.

Process

While longshore current involves the movement of oceanic waves parallel to the shoreline, longshore drift involves the deposition and removal of sediment material on the beach.

Factors affecting the Process

Longshore current is affected by the angle of longshore current, depth of water, and velocity of the incoming wave. In contrast, longshore drift mainly depends on the incoming wave direction.

Conclusion

In conclusion, longshore current and longshore drift are two important terms used in the field of geology. The main difference between longshore current and longshore drift is that longshore currents are the ocean waves that travel parallel to the beach whereas longshore drift is the transportation of sediment materials along a coast parallel to the shoreline.

Reference:

1. “Longshore Currents.” Currents: NOAA’s National Ocean Service Education, 1 June 2013, Available here.
2. “Beach Drift.” Physical Geology Today, Available here.
3. “Longshore Drift.” Wikipedia, Wikimedia Foundation, 29 May 2020, Available here.

Image Courtesy:

1. “Longshore drift” By Yefi – Own work, Public Domain) via Commons Wikimedia
2. “Longshore drift at work, Dungeness – geograph.org.uk – 1006936” By Simon Huguet (CC BY-SA 2.0) via Commons Wikimedia