Hard Engineering Flashcards
What are advantages of hard engineering?
Obvious to at-risk people that something is being done to protect them.
A one-off solution that could protect a stretch of coast for decades.
What are disadvantages of hard engineering?
Costs are usually very high, and there are on going maintenance costs.
Prone to failure
Coastlines made visually unattractive and needs of coastal ecosystems are overlooked.
Defences built in one place frequently have adverse effects further along the coast.
How much do groynes cost per metre?
£150 - £250
How much do sea walls cost?
£3000 - £10,000
How much does rip rap cost?
£1300 - £6000
What are construction and materials for Rip-Rap?
Large ingeous or metamorphic rock boulders, weighing several tonnes.
What is the purpose of Rip-rap?
Break up and dissipate wave energy.
Often used at the base of sea walls to protect them from undercutting.
What is the impact on physical processes of Rip-rap?
Reduces wave energy.
Sediment deposition between rocks.
May become vegetated over time.
What is construction and materials for Offshore rock breakwater?
Large ingeous or metamorphic rock boulders, weighing several tonnes.
What is the purpose of offshore rock breakwater?
Forces waves to break offshore, rather than at the coast, reducing wave energy and erosive force.
What is the impact on physical processes of offshore breakwaters?
Deposition encouraged between breakwater and the beach.
Can interfere with longshore drift.
What is the construction and materials of sea walls?
Concrete with steel reinforcement and deep piled foundations; can be stepped or vertical.
What is the purpose of a sea wall?
A physical barrier against erosion.
They often also act as flood barriers.
Modern sea walls are designed to dissipate, not reflect, wave energy.
What is the impact on physical processes of sea walls?
Destruction of the natural cliff face and foreshore environment.
If reflective, can reduce beach volume.
What are the construction and materials of revetments?
Stone, timber or interlocking concrete sloping structures, which are permeable.
What is the purpose of revetments?
To absorb wave energy and reduce swash distance by encouraging infiltration.
Reduce erosion on dune faces and mud banks.
What is the impact on physical processes of revetments?
Reduced wave power.
Can encourage deposition and may become vegetated.
What is the construction and material of groynes?
Vertical stone or timber fences built at 90 degrees to the coast, spaced along the beach.
What is the purpose of groynes?
To prevent longshore movement of sediment, and encourage deposition building a wider, higher beach.
What is the impact on physical processes of groynes?
Deposition and beach accretion.
Prevention of longshore drift, sediment starvation and increased erosion downdrift.
