Coasts Flashcards
Four zones of coast
offshore
nearshore
foreshore
backshore
How do waves affect coastal environments?
Wave action
When wind blows across the surface of seas and oceans, energy from moving air is transferred to water surface to generate waves
What are tides?
Daily alternate rising and falling of sea level along coasts caused mainly by gravitational pull of moon & sun on earth
What are crest and trough?
Crest: highest part of wave
Trough: lowest part of wave
What are currents?
large scale and persistent movements of water in seas and oceans driven by prevailing winds which generally blow in one direction
How do currents affect coastal environments?
Distribute sediments as they carry large amounts of energy and shape coasts through the processes of coastal erosion, sediment transport and deposition
How does current produce milder climate in coastal areas?
They regulate temperatures by transporting cool water away from the north and south poles towards equator, and move warm water to the poles.
What happens to wave height and wavelength when wave breaks on shore?
Wave height: increase
Wavelength: decrease
What is swash?
When wave breaks and runs up on the beach
What is backwash?
When a wave retreats back to the seas
Constructive waves have…
- low energy, deposit materials
- strong swash, weak backwash
- creates sandy beaches with gentle slopes
Destructive waves
- high energy, break violently on shore
- strong backwash, weak swash
- coasts are eroded away
HEADLANDS OR BAYS?
Where do waves bend to?
BAYS
HEADLANDS OR BAYS
Where does waves diverge?
HEADLANDS
Name the 4 ways of coastal erosion
- Hydraulic action
- Abrasion
- Attrition
- Solution
Describe Hydraulic action.
Air may be trapped in cracks when waves crash
Trapped air is compressed repeatedly by oncoming waves
this weakens the cliff
Describe abrasion
Small rocks are hurled towards cliff by waves
They grind down the surfaces and weaken them
Describe Attrition
Waves smash rock and pebbles on shore into each other
They break up and become smooth and rounder
Describe Solution
Chemicals in seawater react and dissolves certain rock
Describe longshore drift
Currents flowing parallel to coast
Combined effect of sediment transport by beach drift and longshore current
Describe beach drift
zig zag movement along the beach due to swash and backwash
What is a cliff and how is it produced?
Steep and near vertical rock face along coasts
Produced by action of waves undercutting a steep rock coast
What are headlands?
Extensions of bedrock jutting out into the sea usually with a cliff
Define Bays
Bodies of water connected to the seas due to surrounding land blocking off some waves
Describe formation of headlands and bays
Waves move towards coast made of alternate strips of more and less resistant rocks
Softer rocks erode to form bays and harder rocks remain to form headlands
What is a spit?
sand that sticks out into the sea but is joined to the land at one end
What is the difference between tombolo and spit?
Tombolo connects 2 islands together
How is spit formed?
Longshore drift carry material along coast
When there is a abrupt bend in coastline, longshore drift continues to transport materials the original direction
When material enter sea, deposition occur and accumulate and appear above water surface.
How are caves formed?
Within headlands, there are some less resistant rocks, eroded faster.
Waves force their way into line of weakness such as joints/fault and undercut it
How is arch formed?
Formation of caves then hollowed out by wave action some more
How is stack formed?
When roof of arch collapse
3 MAIN ways people use coastal area
- fisheries
- housing
- tourism
Give example of how people use coastal areas for fisheries
Vietnam, Ca Mau
shrimp production centre, mangrove areas cleared
grown rapidly to US$800M in 2010
Give example on how people use coastal areas for housing
Kukup, Malaysia
stilt house community, floating fish farms
sell fresh fish and other marine products and use boats as transport
Give example on how people use coastal areas for tourism
Sentosa singapore
resort island with many recreational facilities
e.g. OneMarina club is a harbour with whafts providing maintenance for yachts and boats, recreational boating facilities
Describe coral reef ecosystems
structure found at or slightly below sea level on seabed built by tiny animals aka coral polyps
Describe the distribution of coral reefs
Mainly between Tropic of Cancer and Capricorn
Conditions for coral reef growth
Sea surface temp: not lower than 17-18 DEGREES
Sunlight received: clear saline water required for algae photosynthesis
No sedimentation
moderate water motion for corals to receive oxygen
Why are coral reefs important?
maintain natural ecosystem, supports more than 25% of earth marine species for breeding and growing
source of food and habitat
absorb wave energy
5 ways corals are threatened
Overcollection of corals
Fishing methods
Climate change
Recreational use of coast
Coastal development
Where are mangroves distributed?
Between tropic of cancer and capricorn
What are some features of mangroves?
Aerial roots to take in air when they are not submerged
Prop roots to anchor them firmly in the soft mud
Javelin shape and buoyant fruit that is easy to germinate
Value of mangrove in environments
Dense network of roots, stabilise shorelines, slow down water flow, build up sediments to protect coastal areas
4 pressure ways that threaten mangroves
Coastal development
Conversion to other land use
Rising sea level
Increased demand for wood and charcoal
5 hard engineering measures for coastal protection
Seawall
Groyne
Gabion
Breakwater
Tetrapods
3 laws and regulation methods to manage coastal areas
Limit damaging activities
Protect coastal resource
Restrict development in areas prone to natural hazards
3 Soft engineering measures
Planting vegetation and stabilising dunes
Beach nourishment
Encouraging coral reef growth
Pros and Cons of beach nourishment
pros: transform coast into wide sandy beach, provides immediate protection to inland area
cons: time consuming & costly
Pros and Cons of encouraging coral reef growth:
Pros: weaken wave energy & provide breeding ground for fish
Cons: rate of coral growth may be very slow
Pros and Cons of planting vegetation and stabilising dunes
pros: roots hold sand firmly to the ground and prevent erosion
cons: takes time, costly to maintain dunes, non-resistant to natural elements and human elements e.g. vandalism&storms
Pros and Cons of limiting damaging activities to manage coast areas sustainably
Pros: balance needs and demands of people to access or develop the coastal areas
EX building fences
Cons: beach becomes less attractive and prevent local people and visitors from accessing to all parts of the beach
Pros and Cons of Seawall
Pros: absorb wave energy
Cons: require constant repair and is costly to build and maintain
Pros and Cons of gabions
Pros: absorb wave energy better than seawalls , more effective in defending against high energy waves
Cons: unsightly, costly, corroded by seawater easily
Pros and Cons of Groynes
Pros: absorb energy of waves so materials can be deposited on updrift side of groynes facing longshore drift
Cons:
Pros and Cons of Breakwaters
Pros: break force of incoming waves, allows deposition and accumulation of materials to form beaches
Cons: unsightly costly, protect coast unevenly
Pros and Cons of Tetrapods
Pros: can be used quickly to protect coast from wave attack, less likely to be damaged by waves
Cons: unappealing, costly, dangerous to beach users
