2B.11A Flashcards
Give examples of hard engineering approaches
groynes, sea walls, rip rap, revetments, offshore breakwaters
What are the two main effects of hard engineering
economically costly and directly alter physical processes and systems
Pros of sea wall/groynes/recurved sea wall
- Effective – land protected, land stable
- Income will be possible , e.g. From tourism
Cons of sea wall/groynes/recurved sea wall
- Expensive, millions of pounds
- Need maintenance continually
- Visual impact is poor – can harm tourism
- Interfere with natural processes, e.g. LSD can prevent beach formation downdrift (terminal groyne syndrome)
Pros of beach nourishment/managed retreat
- Works with nature – allows natural processes to work
- Replicates natural environment where possible – means tourism can continue etc.
- Doesn’t damage natural processes
Cons of beach nourishment/managed retreat
- Can be ineffective, or need continued resupply of materials
- People can lose homes and land value sharply declines (e.g. With managed retreat)
How many people live on the cuaseway coast of portballintrae
734
Describe the historic fishing village of portballintrae
- Small fishing pier since 1760
- Damaged by storms in 1830
- Replaced in 1895 and enlarged in 1970
Describe fetch right now at portballintrae
Wave fetch from Atlantic, refracted around Ireland
Describe growth at portballintrae
Rapid growth since the 1970s
- Mainly 2nd homes
- 3db bungalow = £300,000
- Potentially a Trump Golf Course
One bad thing at portballintrae
huge amount of beach removal
Describe basic geology at portballintrae
- Reworked glacial sands
- Rocky headlands
- High energy waves (2k km fetch)
Main changes over time at portballintrae
- Alterations since 1800s
- Lost 1,000m2/yr
- Sand beaches now very boulder orientated
Why hasn’t hard engineering worked:
what processes have been disrupted at portballintrae
- Leslie’s Pier – built in 1760, rebuilt 1895
- by diffracting incoming waves, it’s created a low-energy zone in the shadow
- Therefore, waves attack centre of the bay
- Longshore drift from centre to East, removing sand
- Rip current takes sediment out into deeper water
- Beach is deprived of sandy sediment
When should you use hard engineering
- As part of Hold the Line / Advanced the Line
- When the cost of the defences < economic benefits
E.g. infrastructure – (Easington Gas Terminal / Dawlish railways line - If there’s political advantage, e.g. not cutting off a community
- If there are coastal habitats / environments worth protecting
BUT: if engineering would damage a sensitive coastal habitats?
OR: if erosion / mass movement rates are very very high?