Coastal Zone Flashcards
Abrasion?
The sea hurls pebbles and sands against the cliff, chipping and grinding it down
Solution/corrosion
When salts and other acids in the sea water slowly dissolve a cliff
Hydraulic action?
Powerful waves lash the cliff forcing air into tiny holes. This air expands so pressure weakens the rock breaking it down
5 types of transportation carried out by waves?
Traction Saltation Solution Suspension Longshore drift
Traction?
Large stones roll along the seabed
Saltation?
Stones bounce along the sea bed
Suspension?
Particles carried within the water
Solution?
Chemicals dissolved within the sea
Longshore drift?
Movement of material along the sea due to wave action
Explain process of lsd
Happens when swash carries material up the coast at angle of prevailing wind direction (normally 45 degrees)
Backwash carries material back down the beach at 90 due to gravity
This eventually moves material across the sea
3 types of weathering
Chemical
Mechanical
Biological
Mechanical
Decay of rock without chemical change (eg freezethaw)
Results in scree
Chemical
Decay of rock caused by a chemical reaction within rock (eg calcium carbonate and acid rain)
Biological
Decay of rocks due to flora and fauna actions (eg plant roots expanding cracks in rocks)
What is a mass movement?
The downhill movement of material under the influence of gravity
Factors affecting slope
Geology
Precipitation
Human activity
Previous weather conditions
Types of mass movement
Fall
Slide
Slip/slump
Flow
Fall?
Material falls from the scree slow, often caused by freeze thaw weathering
Slide?
Blocks of consolidated earth downhill over a straight plain
Flow?
Loose material behaving like a liquid (very saturated)
Slip/slump
Slumping of unsaturated soil and weak rock along a weak surface
How are headlands formed
What is the process called
When sea attacks a discordant coastline : Soft rock (eg clay) erodes more quickly than resistant rock leaving a section of land jutting out to sea called a headland (known as differential erosion)
What is a concordance coastline
Coastlines made of the same type of rock
Example of discordant coastline
durlston head
What is weathering?
The decay of rocks in situ or at closest to the ground surface
Attrition?
Rocks and stones that the sea erodes from the cliffs are round and broken down as they bump against each other as they’re thrown against the cliff
3 types of weathering
Chemical
Mechanical
Biological
Mechanical
Decay of rock without chemical change (eg freezethaw)
Results in scree
Chemical
Decay of rock caused by a chemical reaction within rock (eg calcium carbonate and acid rain)
Biological
Decay of rocks due to flora and fauna actions (eg plant roots expanding cracks in rocks)
What is a mass movement?
The downhill movement of material under the influence of gravity
Factors affecting slope
Geology
Precipitation
Human activity
Previous weather conditions
Types of mass movement
Fall
Slide
Slip/slump
Flow
Fall?
Material falls from the scree slow, often caused by freeze thaw weathering
Slide?
Blocks of consolidated earth downhill over a straight plain
Flow?
Loose material behaving like a liquid (very saturated)
Slip/slump
Slumping of unsaturated soil and weak rock along a weak surface
How are headlands formed
What is the process called
When sea attacks a discordant coastline : Soft rock (eg clay) erodes more quickly than resistant rock leaving a section of land jutting out to sea called a headland (known as differential erosion)
What is a concordance coastline
Coastlines made of the same type of rock
Example of discordant coastline
durlston head
What is wave cut platform?
The flat slope left after the cliff has retreated backwards, exposed especially at low tides
How do caves, arch, stack, stump form?
Hydraulic action affects headlands by eroding weak faults in the rocks
Firstly a wave cut notch is created (abrasion)
Overtime this becomes a cave
All erosion processes makes cave an arch
Eventually the top of arch collapses over own weight
This leaves a lonely stack
Weathering and erosion undercut stack and so it collapses to form a stump
How are wave cut platforms form?
1 between high and low tides abrasion takes place
2 creates a wave cut notch, exposed at a low tide- the cliff has been undercut
3 the top of the cliff is unstable and overhang collapses into the sea providing more material for abrasion and attrition
(Meanwhile simultaneously the cliff has retreated landwards)
4 a wave cut notch and a wave cut platform is left
Where does deposition occur?
Little energy environments (can’t transport materials)
Sheltered areas
Where groynes protect the beach
Where erosion provides abundant supply of material
What is a spit
A long narrow piece of land joined to mainland and juts out to sea/estuary composed of sand/shingle
How do spit forms?
Prevailing wind and maximum fetch will carry material via lsd
Change in direction of coastline so sand/shingle are deposited in the more sheltered water
(storms will build up more material)
the end of spit begins to round due to wave refraction and second dominant wind direction( it carries material to more sheltered water)
What is a tombolo? Eg?
A spit that joins island to mainland
Eg Chesel beach -30km and links Isle of Portland to mainland
What is a bar?
If a spit develops across a bay where there is no strong flow of water from the landward side, sediment can reach the other side
3 types of beaches
Sandy
Stormy
Shingle
Features of sandy beaches
V flat and wide
Most swash returns as backwash, little energy lost to friction so material is carried back down the beach
Leads to development of ridges and runnels in low water mark
Features of shingle beach
More energy needed to transport shingle so more destructive waves
Backwash isn’t able to carry shingle back out
Steep gradient of 10-20 degrees
Constructive wave ?
Strong swash and weak backwash
Created in calm weather
1m high
Long wavelength, low amplitude
Destructive wave
Stormy conditions
Weak swash strong backwash
Short wavelength, high amplitude
Hard engineering strategies
Sea walls
Groynes
Rock armour
What do groynes do?
Placed vertically along beaches
Barrier for longshore drift and keeps a wide beach
What do rock amour do
Absorb wave energy
Soft engineering beach strategies?
Beach nourishment
Managed retreat
Marsh creation
What is beach nourishment
Replaces erodes sand
What is marsh creation
Changes land use of an area so it absorbs wave energy
What is managed retreat?
Allowing controlled flooding of low lying areas/cliff collaps
Pros and cons of soft engineering
Pro
Cheap easy to maintain
Blends in with beach
Creates habitat for wildlife
Cons
Constant maintained
Land’s lost
Easily damaged by storms
What are salt marshes/ what are they found?
Found in low energy environments (eg enclosed bays/shelter of soils)
Formed when silt and mud are deposited by tides to form intertidal mudflats
What is a vegetation succession called
Halosere
What plant types develop fast
Halophytic (don’t mind salt)
How has Essex sat marsh been conserved still allowing sustainable use of the area?
- Largest scheme in Europe to create ancient wetland from 2012-19
- Turn 746 hectares of land into 360 of mudflat, 160 of salt marsh, 46 of saline lagoons, 64 of grazing marshland and 129 of pasture
- £12 to carry out
- Sustainable way of protecting the coast
- Land was taken from areas in London in which roads were built
- It was a managed realignment of the coast
Formation of salt marsh?
Exposed at low tide, thin layers of mud only contain algae
Mud deepens so pioneer plants establish (eg spartina and glasswort)
There are more plants higher up the marsh so more sediment is trapped there, therefore the marsh rises and channel deepens (marinagrass and seaspurlane)
The mud deepens so only the highest plants cover the marsh now (more plants colonise inc sea rush and red fescue come)
The channel deepens due to run off (sea thrift and lavender)
How have fauna adapted to salt marshes?
Yellow legs have reduced webbing between toes so it’s easier to walk
Curlew and egrets have long curved beak to dig into mud
Redshanks have long legs to keep body dry
Oystercatcher’s bill is perfect shape to prise muscles open
How has glasswort specifically adapted?
Glasswort has air channels in leaves for oxygen plus has concentrated salt so more water goes into the plant via osmosis
Causing for rising sea level?
Melting of ice sheets (Antarctica and Greenland) increases mass of sea
Sinking land
Near surface thermal expansion increases volume of sea (warming oceans expand)
Facts about Maldives
Airport runway just 1.2m above sea level
Sea level is predicted to rise by 86cm before 2100 - 77% of land will be lost
Economic impacts of rising sea level in the Maldives
Malé International Airport runway is just 1.2 m above sea level = would cripple economy: can’t import / export and tourist industry would plummet (which atm is 28% of country’s gdp)
Higher sea level = more beach erosion = less tourism
Money has to be invested in sea defences
Property loss
Social impacts of rising sea level in the Maldives
Loss of jobs due to loss of tourism and fishing (2nd biggest industry) industries
Loss of food (fish = food for a lot of people)
Water gets contaminated in Malé
…as a result people will migrate
Area of recent cliff collapse? When?
Jurassic Coast 2012
Erosion rate of Jurassic coast?
67m in next 100 years
Why is Jurassic coat vulnerable to cliff collapse?
Soft sedimentary rock (eg limestone) more susceptible to sea erosion and mass movement
High precipitation rates: in 2012 Dorset received 147% of national rainfall between May - December
30% of rocks is made of pores which hold water making it heavier
Impacts on lives in the Jurassic coast
Property loss in Devon
Houses decreased in value
Mass movement at Monmouth Beach caused £200 000 of damage on high quality beach huts
Closing of beach meant nearby businesses lost trade
22 year old Charlotte Blackman killed
Impact on environment in Jurassic coast?
Loss of iconic beauty sites eg Durdle Door
400 tonnes of rock fell (obviously altered shape of landscape)
But fossils have been uncovered :)
How people worsened the situation at Jurassic coast?
Tourists went hiking to out of bounds area which caused more (smaller) mass movements
Fossil hunting at base of cliff collapse our lives in danger (eg at Llyme Regis)
Case study for coastal management
Cuckmere estuary
What’s gonna happen in cuckmere? Whose decision?
Grazing land will become a salt marsh via managed retreat: farmers supported by environment stewardship scheme
National trust want this as well as salt marsh habitats are rare in England
Why is a salt marsh a good option for cuckmere?
Cheap
Dissipates the waves energy
Encourages biodiversity
Why is salt marsh formation a bad idea for cuckmere?
Will flood valuable land
Might lower tourism to area as less footpaths etc
Residents think beauty will be destroyed as there’ll be mudflats by meandering rivers which means they’ll be submerged by monthly tides as they connect to the main channel
How would salt marsh creation be compromised for residents?
Loss of footpath compensated by new footpath higher up the valley side
Enhanced recreation in east valley : walking, cycling, birdwatching
Environmental impacts of rising sea level in the Maldives?
Damage of coral reef = no habitat for fish = less fish
Pollution water = dead fish
Loss of wildlife on the land
What do environmental agency want in cuckmere? Why?
They want shingle to be moved from river to form a spit as a blockade
They believe we should work with natural processes as sea levels will continue to rise which would increase cost of coastal defence
Pros and cons of environmental agency cuckmere idea?
Cheap
Nice landscape
Homes saved
Spit could be easily damaged by storms
What do residents and businesses want in cuckmere? Why? Cons?
They want the sea valley maintained because businesses would lose tourists (45000 visitors annually)
Would cost £18 mil
What do East Sussex county council want to do? Evaluate?
Maintain current conditions to improve and enhance biodiversity
This is cheap
Short term solution = unsustainable approach
what industry isn’t possible in the Maldives and why?
Farming due to low lying land
How has the spartina adapted?
Has a double root system which binds mud and anchors
