Longshore drift

Definition

Longshore drift is the process by which sediment is transported along a coastline parallel to the shore, primarily driven by the action of waves and currents. This movement plays a crucial role in shaping coastal landscapes, affecting beach formation, erosion, and the creation of various depositional features such as spits and bars.

5 Must Know Facts For Your Next Test

1. Longshore drift occurs when waves hit the shore at an angle, creating a current that moves sediment along the coastline.
2. The direction of longshore drift can vary depending on wave direction and local currents, which can lead to asymmetrical beach shapes.
3. As sediment is moved along the coast, it can accumulate in certain areas, leading to the formation of features like spits and barrier islands.
4. Longshore drift is a continuous process that contributes to beach erosion in some areas while simultaneously depositing sediment in others.
5. Human activities such as the construction of jetties and groins can disrupt longshore drift, leading to unintended consequences for coastal ecosystems.

Review Questions

• How does longshore drift contribute to the formation of coastal features?
  • Longshore drift plays a significant role in shaping various coastal features by transporting sediment along the shore. As waves approach the beach at an angle, they move sand and gravel in a zigzag pattern down the coastline. Over time, this process leads to the accumulation of sediment in specific areas, resulting in the formation of features like spits and barrier islands. These features not only alter the coastline but also impact local ecosystems and human activities.
• What impact does wave refraction have on longshore drift and coastal sediment transport?
  • Wave refraction affects longshore drift by changing how waves approach the shore. When waves encounter underwater topography or variations in coastline shape, they bend, causing differences in wave energy along different parts of the beach. This variation influences sediment movement; areas where waves are stronger will erode more sediment, while calmer areas may see deposition. The result is a complex interplay between erosion and deposition along coastlines influenced by longshore drift.
• Evaluate how human interventions like jetties and groins affect longshore drift and coastal management strategies.
  • Human interventions such as jetties and groins are designed to control coastal erosion and manage sediment flow. However, these structures can significantly disrupt natural longshore drift by blocking sediment transport. As a result, areas upstream may experience increased erosion due to lack of sediment supply, while downstream regions may become overly accretive. Understanding these impacts is crucial for effective coastal management strategies that aim to balance human needs with natural processes.

Related terms

Wave Refraction: The bending of waves as they approach the shoreline at an angle, causing variations in wave energy along the coast.

Beach Nourishment: A coastal management technique that involves adding sand or sediment to a beach to combat erosion and enhance its width.

Sediment Transport: The movement of solid particles, including sand and gravel, due to water, wind, or ice, playing a vital role in shaping landforms.