Groyne

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Groyne

A groyne (or groin) is a rigid hydraulic structure built from an ocean shore or from a bank that interrupts water flow and limits the movement of sediment. Groynes are often used in coastal engineering to prevent beach erosion and to maintain or widen beaches that are losing sand. They are typically constructed perpendicular to the shoreline and extend into the water.

Purpose

The primary purpose of a groyne is to trap and accumulate sand that is being transported by longshore drift. By interrupting the flow of sediment, groynes help to build up the beach on the updrift side, which can protect the shore from erosion. However, this can lead to increased erosion on the downdrift side, as the supply of sediment is reduced.

Types of Groynes

Groynes can be constructed from various materials, including:

• Wood
• Concrete
• Rock
• Steel

They can also vary in design, such as:

• Permeable groynes: Allow some water and sediment to pass through.
• Impermeable groynes: Block water and sediment completely.

Construction

The construction of a groyne involves several steps: 1. Site Selection: Choosing a location where the groyne will be most effective. 2. Design: Determining the length, height, and material of the groyne. 3. Installation: Building the groyne, often using heavy machinery to place materials.

Environmental Impact

While groynes can be effective in preventing beach erosion, they can also have negative environmental impacts. These include:

• Downdrift Erosion: Increased erosion on the downdrift side of the groyne.
• Habitat Disruption: Alteration of natural habitats for marine and coastal species.
• Aesthetic Impact: Changes to the natural appearance of the coastline.

Maintenance

Groynes require regular maintenance to remain effective. This can include:

• Inspection: Regular checks for damage or wear.
• Repair: Fixing any structural issues.
• Sediment Management: Ensuring that the trapped sediment is distributed as needed.

See Also

• Breakwater (structure)
• Seawall
• Jetty
• Beach nourishment
• Coastal management