Longshore drift

Definition

Longshore drift is the process by which sediment is transported along the coastline, parallel to the shore, by the action of waves approaching at an angle. This movement occurs due to the combination of wave direction and the angle at which waves hit the beach, creating a zigzag pattern of sediment transport. Understanding longshore drift is crucial for grasping coastal dynamics and the formation of various coastal landforms.

5 Must Know Facts For Your Next Test

1. Longshore drift occurs primarily due to oblique wave approaches, where waves strike the shore at an angle, pushing sediment up the beach face and then pulling it back down with the current.
2. The movement of sediment due to longshore drift can lead to the formation of various coastal features such as spits, bars, and tombolos.
3. Longshore drift is affected by factors like wave energy, wind direction, and coastal topography, all of which can influence how effectively sediment is transported.
4. Coastal structures like groins and jetties can disrupt longshore drift, leading to sediment accumulation on one side and increased erosion on the other.
5. In many coastal management practices, understanding longshore drift is essential for predicting how beaches will evolve over time and for implementing effective erosion control measures.

Review Questions

• How does the angle of wave approach influence longshore drift?
  • The angle at which waves approach the shore plays a crucial role in longshore drift because it determines the direction of sediment movement. When waves strike the shore at an angle, they push sediment up the beach face in a zigzag pattern, resulting in lateral transport along the coastline. Conversely, as waves recede back into the water, gravity pulls the sediment straight down the slope, creating a continuous cycle of movement parallel to the shore.
• What impact does longshore drift have on coastal landforms, and how can human activities modify this process?
  • Longshore drift significantly shapes coastal landforms by transporting sand and sediments along the beach. This process can create features such as spits or bars where sediment accumulates. Human activities, like constructing groins or jetties, can alter natural longshore drift patterns by blocking sediment movement. This can lead to erosion on one side of the structure while promoting deposition on the other side, highlighting the need for careful management in coastal development.
• Evaluate how understanding longshore drift can inform strategies for coastal management and erosion control.
  • Understanding longshore drift is vital for developing effective coastal management strategies because it reveals how sediment moves along coastlines. Knowledge of this process enables planners to predict potential erosion hotspots and design interventions such as beach nourishment or structures that either mimic natural sediment transport or manage it more effectively. By applying this knowledge, communities can better protect their shorelines from erosion while preserving natural ecosystems and beach environments.

Related terms

Beach nourishment: A coastal management strategy that involves adding sand or sediment to a beach to combat erosion and increase beach width.

Groin: A structure built out from a beach into the water to interrupt water flow and reduce erosion caused by longshore drift.

Erosion:

The process by which natural forces remove soil and rock from one location and transport it to another, playing a significant role in shaping coastlines.