Longshore drift

Definition

Longshore drift is the process by which sediment is transported along a coast by wave action and currents. This movement occurs at an angle to the shoreline, primarily driven by waves hitting the shore at an angle and creating a zigzag pattern of sediment movement. It plays a crucial role in shaping coastal landforms, impacting beach stability and influencing the ecosystems found in these areas.

5 Must Know Facts For Your Next Test

1. Longshore drift is crucial for maintaining beach profiles and can lead to the formation of features like spits and bars as sediment accumulates in certain areas.
2. The angle at which waves approach the shore can significantly affect the direction and efficiency of longshore drift.
3. Human interventions, such as jetties and groins, can disrupt longshore drift, leading to increased erosion in some areas and sediment buildup in others.
4. Longshore drift operates continuously, transporting sand and gravel along coastlines, which can influence local ecosystems by altering habitats.
5. Seasonal changes in wave patterns can affect the intensity of longshore drift, with stronger winter storms often leading to increased sediment movement.

Review Questions

• How does wave direction influence the process of longshore drift?
  • Wave direction plays a vital role in longshore drift because waves hitting the shore at an angle create a lateral movement of sediment along the coastline. This angled approach generates a current that carries sand and other materials down the shore in a zigzag pattern. As waves break, they push sediment onto the beach at an angle, while backwash pulls it straight back into the water, resulting in a continuous transport of materials along the coast.
• Discuss how human activities can impact longshore drift and subsequent coastal features.
  • Human activities such as constructing jetties, groins, and seawalls can significantly alter longshore drift. These structures are designed to protect beaches but often interfere with natural sediment movement. For example, they can trap sand on one side while causing erosion on the opposite side. As a result, such interventions can lead to changes in coastal features like beach widths and shapes, disrupting ecosystems that depend on stable shorelines.
• Evaluate the environmental implications of disrupted longshore drift on coastal ecosystems.
  • Disrupted longshore drift can have significant environmental implications for coastal ecosystems. When natural sediment transport is altered due to human structures or changes in wave patterns, it can lead to habitat loss for various marine and coastal species. For example, beaches may erode faster than new sediments are deposited, affecting nesting sites for sea turtles and shorebirds. Furthermore, changes in sediment composition can impact vegetation growth along coastlines, ultimately altering food webs and biodiversity in these sensitive areas.

Related terms

Littoral Zone: The part of the shoreline that is affected by wave action, extending from the high-water mark to the low-water mark, where longshore drift primarily occurs.

Beach Erosion: The process whereby beach material is worn away due to wave action, currents, and human activities, often influenced by longshore drift that redistributes sediment.

Coastal Management: Strategies and practices aimed at preserving and protecting coastal areas from erosion and other forms of degradation, often involving measures to manage longshore drift.