Coastal Flood Defences: Groynes

What is the primary purpose of the groynes built along Walney Island's coastline?

What is the approximate width of the narrowest section of Walney Island?

Which body of water exposes the west coast of Walney Island?

What effect have flood events had on Walney Island?

How long is Walney Island approximately?

What is the primary purpose of groynes in coastal flood defence?

What are the two types of groynes based on their permeability?

Which of the following is a disadvantage of using groynes?

What is the alignment of groynes in relation to the shoreline?

How do groynes impact coastal maintenance?

Which of the following describes the durability of wooden groynes compared to rock groynes?

What is a consequence of groynes being intrusive on the landscape?

What is longshore drift?

Coastal Flood Defences: Groynes

Coastal flood defences are crucial for protecting low-lying land from sea water.
Groynes are a type of hard engineering, easy to construct and have long-term durability, requiring low maintenance.
Groynes are designed at a 90-degree angle to the shore to trap sediment and prevent longshore drift.
They are immediately effective but can be intrusive and cause problems elsewhere.

What are Groynes?

Groynes are low-lying wooden or concrete structures placed offshore to trap sediment.
They dissipate wave energy and restrict sediment transfer during longshore drift.
Longshore drift is the movement of sediment along the shore due to waves at an angle.
Groynes slow down erosion by preventing sediment from being transported further down the coast.
Permeable groynes permit some sediment movement, while impermeable groynes prevent all sediment movement.

Advantages and Disadvantages

Advantages:
- Easy to construct and maintain
- Long-term durability
- Reduce need for beach nourishment
Disadvantages:
- Wooden groynes are less durable than rock
- May visually impact the landscape
- Can cause erosion downstream, necessitating further maintenance.

Case Study: Walney Island, Cumbria

Walney Island is a narrow island in the west of England.
The island has approximately 13,000 residents and is 11 miles long with 5 sq miles of area.
Low-lying parts of West coast are vulnerable & exposed to high tides and storm surges.
Groynes have been built to lessen the impact of flooding & coastal erosion.
This coastal protection measure aims to prevent the island from splitting.

This quiz covers the concept of groynes as coastal flood defences. Learn about their construction, functionality, and the advantages and disadvantages they present in managing coastal erosion and sediment transport. Explore how groynes play a crucial role in protecting low-lying areas from sea water.