- Define and explain Managing Coasts in your own words
- Use key terms such as managed retreat accurately
- Apply what you have learned to new examples and questions
- Avoid the common mistakes learners make with this topic
This lesson focuses on Managing Coasts: evaluate hard and soft engineering strategies and their trade-offs.
Evaluate hard and soft engineering strategies and their trade-offs.
Key ideas
Hard versus soft engineering
Hard engineering — sea walls, rock armour, groynes — is expensive but immediately effective and popular with residents. Soft engineering — beach nourishment, dune regeneration, managed retreat — works with natural processes and is cheaper and more sustainable, but may mean sacrificing land. Every scheme needs a cost–benefit analysis weighing economic, social and environmental impacts.
Coasts work as systems
A coastal system has inputs (weathered cliff material, river sediment), transfers (longshore drift), stores (beaches, dunes) and outputs (sediment lost offshore or to another cell). Building a groyne or sea wall interrupts the transfers, which is why protecting one stretch of coast can starve beaches further along the sediment cell.
Key term — managed retreat: A soft-engineering strategy that allows the sea to flood low-value land, creating natural defences like salt marsh further inland.
Why might managed retreat be chosen over a sea wall for farmland?
Farmland is low value, so an expensive wall is hard to justify; managed retreat is cheaper, creates natural habitats like salt marsh, and works with coastal processes.
Answer: Farmland is low value, so an expensive wall is hard to justify; managed retreat is cheaper, creates natural habitats like salt marsh, and works with coastal processes.
- Assuming hard engineering has no downsides Groynes trap sediment but starve beaches downdrift, often shifting the erosion problem along the coast — this knock-on effect is called terminal groyne syndrome.
- Saying longshore drift moves sediment straight along the beach The movement is a zigzag: swash up at an angle, backwash straight down. The net result is alongshore, but the path is not straight.
Practice
Destructive: tall, steep, frequent, strong backwash — erode. Constructive: low, long, less frequent, strong swash — deposit.
The distance wind blows over water; longer fetch allows bigger, more powerful waves to develop.
Cave → arch → stack → stump.
Waves erode the cliff base by hydraulic action and abrasion, undercutting it until the overhang collapses; as the cliff retreats, a rocky platform is left behind at the high-tide level.
Quick check
Which of these best defines "managed retreat"?
Give one advantage and one disadvantage of groynes.
- Managing Coasts: evaluate hard and soft engineering strategies and their trade-offs.
- Hard versus soft engineering: Hard engineering — sea walls, rock armour, groynes — is expensive but immediately effective and popular with residents.
- sediment cell: A stretch of coastline within which sediment is eroded, transported and deposited as a largely closed system.
- Watch out for: assuming hard engineering has no downsides