coasts revision cards Flashcards
what are the three stages in a sediment cycle?
Inputs (where sediment comes from)
transfers (the processes)
outputs eg spits and beaches
name the four parts of the littoral zone in order
backshore
foreshore
nearshore
offshore
what are the short term factors effecting the Littoral zone?
tides and storm surges
what are the long term factors affecting the Littoral zone?
changes in sea level
climate change
what are the three tides
low
high
spring tides
what is abrasion
sediment moving along the shoreline causing it to be worn down over time
what is attrition?
wave action causes rocks and pebbles to hit against each other, causing rocks to be smaller and more round. Attrition does not cause coastal erosion
what is hydraulic action?
A wave crashing into a rock or cliff face forcing air into the cracks, the high air pressure causes the cracks to force apart and widen
when are erosion rates highest?
when waves are high and have a long fetch.
waves are perpendicular to the cliff.
heavy rainfall occurs.
Winter waves are more destructive.
rate of erosion by rock type
sedimentary highest
metamorphic second
igneous slowest
describe longshore drift.
waves hit at an angle determined by the direction of the prevailing wind. The waves push sediment in the direction of the wind in the swash. Due to gravity, the wave then carries sediment back down the beach in the backwash. This moves sediment along the beach over time.
what is traction?
large, heavy sediment rolls along the sea bed, being pushed by currents.
what is saltation?
smaller sediment bounces along the sea bed, being pushed by currents
what is suspension?
small sediment is carried within the water column (a body of water)
what is solution?
Dissolved material is carried within the water
what is a swash aligned beach?
waves break with no angle so no LSD
what is drift aligned?
waves break at an angle so there is LSD
what is deposition?
deposition occurs when a wave loses energy meaning the sediment becomes too heavy to carry, deposition is gradual.
what is gravity settling?
the waves energy becomes very low and so heavy rocks and boulders are deposited followed by the next heaviest sediment
what is Flocculation?
clay particles clamp together due to chemical attraction and then sink due to their high density
name 6 depositional landforms
Tombolo cuspate forelands offshore bars spits bars sand dunes
name the processes of transportation
traction
saltation
suspension
solution
name two depositional processes
Flocculation
gravity settling
how is a tombolo formed?
formed due to wave refraction off the coastal islands reducing wave velocity
how are cuspate forelands formed?
only occurs with triangular shaped headlands. Longshore drift along each side of the headland will create beaches, which where they meet, will form a cuspate foreland
how are offshore bars formed?
They can be formed as the wave breaks early, scouring the sea bed and instantly depositing its sediment as a loose-sediment offshore bar
how are sand dunes formed?
sand dunes occur when prevailing winds blow sediment to the back of the beach and therefore the formation of dunes requires large quantities of sand and a large tidal range
name the steps of how sand dunes are formed in order?
embryo dunes yellow dunes grey dunes dune slack heath and woodland
what happens at the embryo phase?
sand starts to accumulate around a small obstacle
what happens at the yellow dune phase?
more sand accumulates. vegetation may develop which stabilises the dune
what happens at the grey dune phase?
sand develops into soil with lots of moisture and nutrients, as vegetation dies, enabling more varied plant growth
what happens at the dune slack phase?
the water table rises closer to the surface, or water is trapped between hollows between dunes during storms, allowing the development of moisture- loving plants
what happens at the heath and woodland phase?
greater nutrients develop allowing less brackish plants to thrive. Trees grow and act as a natural windbreak
name 3 weathering processes
freeze thaw
salt Crystallisation
wetting and drying
what is freeze thaw?
water enters the cracks in the rocks and when it freezes it expands which increases the pressure acting on the rock causing it to eventually break
what is salt Crystallisation?
as sea water evaporates, salt is left behind. Salt crystals expand overtime causing more pressure on the rocks, which forces cracks to widen
what is wetting and drying?
some rocks expand when wet and contract when dry. This causes rocks to break
examples of chemical weathering?
carbonation
oxidation
solution
examples of biological weathering
plant roots
birds
rock boring
what does the type of mass movement depend on?
The angle of the slope/cliff
The rocks lithology/geology
The vegetation cover on the cliff face
The saturation of the ground/previous weather patterns
What is soil creep?
The slowest but continuous form of mass movement involving the movement of soil particles downhill
What is rock fall?
Rocks falling
What is slumping?
Occur when soil is saturated with water, causing a rotation movement of soft materials (such as clay and sand) forming rotational scars and terraced cliff profiles
What is rock slide?
Water between joints and bedding planes (which are parallel to the surface) can reduce friction and lead to more sliding
What is a concordant coast?
Rock strata runs parallel to the coast. Concordant coasts can lead to the formation of the Dalmatian coas.
How are Dalmatian coasts formed?
Formed where the geology creates valleys parallel to the coast so that when sea levels rise, a series of elongated islands remain offshore
What is a discordant coast?
This is when the rock strata runs perpendicular to the sea
How are headlands and bays formed?
Headlands and bays are formed by the less resistant rock being eroded away faster than the more resistant rock
How does vegetation stabilise soil?
Roots of plants bind soil together which helps reduce erosion
What is a xerophyte?
Plants that are tolerant to dry conditions
What are halophytes
Plants that are tolerant to salty conditions in water
What waves does a high energy coastline have?
Powerful destructive waves and a long fetch
What does a low energy coast have
Weak constructive waves with a short fetch
What type of waves is more common in the summer?
Constructive waves
What type of wave is more common in the winter?
Destructive
What do storms usually lead to?
Storms lead to more destructive waves causing lots of erosion
What factors affect sea level change short term?
High/low tide
Wind strength and direction
Atmospheric pressure
What is isostatic change?
The land moving, either subsides or uplifts. Many reasons as to why.
Reasons for isostatic change
Glaciers
Tectonic activity
What is eustatic change?
The water changing volume compared to the land.
What are things that make storm surges worse?
Subsidence of the land due to tectonic activity
Removing natural vegetation eg mangroves
Global warming
What are the 4 coastal management strategies?
Hold the line
Managed retreat
Advance the line
Do nothing
Explain hold the line
Defences are built to try and keep the shore where it is
Explain managed realignment
Coastline moves in land naturally but managed
Explain advance the line
Defences are built to try and move the shore seawards
Explain do nothing
No defences are put in place and the coast is allowed to erode
What are the factors looked at when deciding which coastal management strategy to use?
Value of the land
The technical feasibility of engineering solution
The cultural and ecological value of the land
Pressure from communities
The social value
Explain why the value of the land influences the decision
Economic assets are protected because they have a higher benefit in the cost benefit analysis
Explain why technical feasibility influences the decision
It may not be possible to use certain methods at certain locations eg a sea wall might not be possible
Explain why the ecological and cultural value of the land influences the decision
May be a historical site or a site used for SSSI
Explain how pressure from the communities influences the decision
Vocal local political campaigning go get an area protected
What is cost benefit analysis?
A check that uses the pros and cons to weigh up wether/how a site needs to be managed
What does the costs in a cost benefit analysis include?
Includes construction, demolition maintenance etc. It could weigh up the price too
What does the benefits of the cost benefit analysis include?
Value of the land, homes and businesses etc
What does a place require to be given the all clear in cost benefit analysis?
For a project to be given the go ahead the expected benefits have to outweigh the costs
What does ICZM stand for?
Integrated Coastal Management
What must the ICZM involve?
The IZCM must involve all stakeholders, plan for the long term and try to work with natural processes not against them
How is a sediment cell managed?
A sediment cell is managed as a whole and often involves multiple councils
What does the ICZM recognise?
The ICZM recognises that coastal management must be sustainable whereby economic development is important but this should come at a cost for the environment
What does the ICZM do for the people?
It recognises their livelihoods
What does sustainable coastal management involve?
Managing natural resources
Creating alternative livelihoods before people lose existing jobs
Educating communities about the need and how to adapt
Monitoring coastal changes
What does policy decisions create?
Winners and losers
What are winners in coastal management?
Winners are the people that benefit economically, socially or environmentally
What do coastal managers produce?
An SMP (shoreline management plan) for an entire area to see what kind of impacts it may have
What is hard engineering?
Physical management of the coast attempts to control natural processes such as erosion and longshore drift
What is soft engineering?
Working with the natural processes and protections to defend areas of the coastline
What is cliff regrading?
A cliff may be prone to sudden collapses so engineers calculate a stable slope angle based on rock characteristics. They then artificially cut back to the stable angle
What are the advantages of cliff regrading?
Creates a natural looking slope
Should remain stable if slope is protected from marine erosion
What are the disadvantages of cliff regrading?
Costs about £1milliom
Property and land could be lost during construction
They could get calculations wrong
They need to also do stabilisation methods
When would cliff drainage be used?
Where the cliff lithology consists of a permeable layer above an impermeable layer, it may be unstable after rainfall, due to pore pressure
How does cliff drainage work?
To reduce pore pressure and reduce mass movement, drainage with gravel can be inserted into the cliff to drain water out quickly
Advantages of cliff drainage
Looks natural once completed
Reduces mass movement
Disadvantages to cliff drainage
Will not completely prevent mass moving only to some extent
Difficult to implement
What is dune stabilisation?
Monitoring the sand dunes condition and repairing them with a geofabric or replanting of grasses (marram grass), together with infilling of slacks, will help keep them in place
Advantages of dune stabilisation
Looks natural
Is an effective barrier to higher sea levels and tides
Provides a natural ecosystem
What is managed retreat?
Where it is accepted that there is little that can be done to stop high sea levels changing the coast, areas can be set aside to flood or erode
Advantages of managed retreat?
Allows natural processes to take place
Can extend current ecosystems
Disadvantages to managed retreat
Needs agreement from land and property owners.
Does not prevent land from being lost.
No compensation for land owners.
What is beach nourishment?
Replaces beach sediments that may have been eroded or transported by longshore drift. A large beach will absorb wave energy and protect the back shore from erosion
Advantages to beach nourishment
Looks natural
Supports local tourist industry
Disadvantages to beach nourishment
Cost about £10 per m3
Doesn’t last long
Could cause imbalances to the sediment cell
What are groynes?
Wooden walls on a beach at right angles to the coast, to slow down longshore drift
What are the advantages of groynes?
Maintain the size of the beach, protects the coast at that point
Assists local tourism
Less expensive than sea walls
What are the disadvantages to groynes?
£1000 per linear m
Maybe be an obstacle to people moving on the beach
Don’t look natural
Reduce sediment supply upsetting the sediment cell
What are sea walls?
Recurved sea walls use the shape of the wave to direct the water into the following wave, so reducing wave energy
What are the advantages to sea walls?
Long lasting
Give people confidence
Prevent high water levels from moving inland
Disadvantages to sea walls?
Most expensive cost of coastal defences
Don’t look natural
Makes accessing the beach difficult
Reduce supply of sediment
What is rip rap?
Boulders placed to break and absorb wave energy. They can also hold back mass movement on an unstable cliff
Advantages to using rip rap?
Long lasting
Can be used to aid other defences
Disadvantages to rip rap?
Cost £50 per m3
Don’t look natural
Dangerous to climb on
Weathering and erosion might still occur
What are revetments?
Sloped walls made of wood, placed parallel to the backshore but a short distance infront of it. They take the force of waves and let sediment pass through
Advantages to revetments?
Absorb wave energy Trap sediments behind them Longshore drift can continue Allow linear access along a beach Cheaper than sea walls
What are the disadvantages to revetments?
Cost £1500 per linear m
Reduce access along the beach
Look unnatural
May need constant maintenance
What are offshore breakwaters?
Rock boulders may be dropped and aligned in short lengths in shallow nearshore waters parallel to the shore
Advantages of offshore breakwaters?
Effective in protecting vulnerable coastal areas
Create sheltered water behind them for tourism
Can be used to protect entrances of harbours
Disadvantages of offshore breakwaters?
Cost £1-2 million
Don’t look natural
May need other coastal engineering to compliment them
May create increased deposition
What are gabions?
Pebbles in wire baskets, which when tied together can make a wall where the great surface area absorbs wave energy and breaks up waves
Advantages of gabions?
Flexible in terms of placement
Relatively cheap and easy to maintain
Disadvantages to gabions?
Not very strong, not suitable for high energy coasts
Need frequent repair
Don’t look natural
