Ch 2.6 How do humans influence and manage coastal environments? Flashcards
What is the general coastal environment in Hong Kong?
Western part of Hong Kong: low-lying and depositional coastline.
Eastern part of Hong Kong: more rugged and erosional in nature as it opens the open sea and with well-joined rocks.
Coastlines of urban area: modified and reclaimed land
What are the hard strategies?
- Sea walls.
- Breakwaters.
- Rock armour.
- Gabions.
- Groynes.
How does sea wall work?
They are concrete walls placed parallel to the shoreline and can deflect and reflect waves.
What are the benefits of the sea wall?
- Strong and durable.
- Efficient and effective in parallel and defect and reflect wave energy.
- Provides recreational areas, such as a promenade.
- Helps protect coastal structures from coastal flooding.
What are the limitations of the sea walls?
- Expensive to build and maintain.
- Undercutting by waves makes the wall less durable. The wall may eventually collapse if maintenance is not carried out.
- Visual pollution can be an eyesore.
How do breakwaters work?
They are partly submerged rock barriers placed offshore. They can break incoming waves out at sea.
What are the benefits of breakwaters?
- Efficient and effective in reflecting and dissipating wave energy.
- Provides safe anchorage for ships in typhoon shelter.
What are the limitations of breakwaters?
- Expensive to build and maintain.
- Visually unattractive.
- May be easily destroyed by a storm.
- Weakens water currents behind the structure, which makes pollutants difficult to disperse and causes water pollution.
- Waves deflected will cause erosion elsewhere.
How do rock armours work?
Large boulders/ concrete piled up along a coastlines. It can force waves to break and absorb their energy.
What are the benefits of rock armour?
- It is easy to build.
- Relatively cheap if local boulders are used.
- Easy to maintain.
- Have good permeability.
- Local boulders may blend with local geology.
- Provides a place for fishing.
What are the disadvantages of rock armour?
Looks ugly and awkward.
Expensive for construction and maintenance.
Needs maintenance.
Restrict access to beaches.
How do gabions work?
Wire cages filled with rocks placed at the foot of a cliff or the top of a beach.They can absorb energy of waves.
What are the advantages of gabions?
- Relatively cheaper and flexible.
- Blends with the local geology and reduces the cost if local rocks are used.
- May eventually blend with the environment as soil is collected between rocks in the cage, which allows vegetation to grow.
What are the limitations of the gabions?
- Not as effective as sea walls.
- Looks unnatural.
- Cages are easily corroded by seawater. Therefore, they require regular maintenance.
- If the cage breaks, it poses a risk of injury.
- Compared with other measure, it has a shorter life-span.
What are groynes?
- Barriers built at right angle to the coastline to reduce the effect of longshore drift.
- Can trap sand and stabilise beach deposition.
