Coasts Flashcards
What are the costs and benefits of managed retreat?
- allows natural erosion to occur
- allows build up of the beach
- expensive - building loss and compensation for people
Give an example of managed retreat
Tollesbury, Essex
What are the costs and benefits of rip rap/rock armour?
- absorbs wave energy and so protects cliffs/buildings form erosion
- unaesthetic
- cheaper - £1000-3000
Give an example of rip rap/rock armour
Slapton, Devon
What are the costs and benefits of a groyne?
- stops longshore drift - so builds up the beach and encourages tourism
- cheaper - £2000 /m
- unaesthetic
- may expose other areas of the coast
Give an example of a groyne
Bournemouth, Dorset
What are the costs and benefits of a sea wall?
- protects buildings/cliffs from erosion successfully
- durable - last 80 years
- expensive £6000 /m
- curved seawalls reflect wave energy back into the sea so they remain powerful
Give an example of a seawall
Torcross, Devon
What are the costs and benefits of beach replenishment?
- sand absorbs wave energy so protect the coast
- builds up the beach and natural looking so encourages tourism
- cheaper £2000 /m
- doesnt last long and transportation is time consuming
Give an example of beach replenishment
Bournemouth, Dorset
What is the difference between hard and soft engineering?
Hard engineering options are more expensive and have a high impact on the landscape, they are more effective but have a shorter term impact (vice versa for soft engineering)
What are the characteristics of destructive waves?
have strong backwash and weak swash - material dragged into the sea
high energy, develop in stormy conditions
usually 6-8 per minute
What are the characteristics of constructive waves?
have strong swash and weak backwash - sediment is deposited and builds up the beach
low energy, develop in calm conditions
10-15 per minute
What is the fetch?
the distance of water over which the wind travels, transferring energy
What is the amplitude of a wave?
the height
How are cave arch stack stumps formed?
- waves erode a joint and open it up (hydraulic action)
- joint/fault grows into cave which continues to grow
- cave erodes back until it meets the other side of a headland
- the arch continues to erode until the headland can no longer support itself and collapses
- this leaves a tall rock stack which is subject to erosion until the base is separated from the top and a stump is formed
Give an example of a cave arch stack stump
The Old Harry Rocks, Swanage, Dorset
What are joints and faults?
joints are smaller cracks in rock
faults are larger cracks in rock
- they both make rock more prone to erosion
Which human activities have affected the coastline?
- urbanisation
- agriculture
- industry
How has urbanisation affected the coastline?
- urbanisation raises interest in protecting coasts
- weight of buildings can harm cliffs
- leads to soil saturation
How has agriculture affected the coastline?
- habitats created e.g. by hedgerows
- causes soil erosion
- sedimentation increases
How has industry affected the coastline?
- brings wealth to an area
- air noise and visual pollution occurs
- destroys habitats to make way for new developments
What are the effects of coastal recession and flooding on the people and the environment?
(impacts of flooding and coastal recession)
- habitats destroyed
- homes destroyed
- more deposition further down the coast
- loss of business (caravan park, cafes etc) from disappearing cliffs
- property value decreases
- dangerous for walkers
- communication network disruption (e.g. roads)
How is a spit formed?
- form where there is a change in coastline direction
- prevailing wind push swash onto beach, depositing sediment
- backwash drags sediment back into sea through gravity
- this process repeats itself - longshore drift
- sediment reaches end of coastline and is deposited
- eventually so much is deposited that a ridge is formed - creating a spit
- prevailing winds curve the spit
- a salt marsh forms behind it
How is a bar formed?
- form where there is a change in coastline direction
- prevailing wind push swash onto beach, depositing sediment
- backwash drags sediment back into sea through gravity
- this process repeats itself - longshore drift
- sediment reaches end of coastline and is deposited
- eventually so much is deposited that a ridge is formed - creating a spit
- the spit then grows all the way across a bay so a stretch of water is cut off and damned to form a lagoon e.g. Slapton Ley (???)
How is a tombolo formed?
- form where there is a change in coastline direction
- prevailing wind push swash onto beach, depositing sediment
- backwash drags sediment back into sea through gravity
- this process repeats itself - longshore drift
- sediment reaches end of coastline and is deposited
- eventually so much is deposited that a ridge is formed - creating a spit
- the spit then extends outwards over time until the sediment reaches an island e.g. Chesil Beach in Dorset connects to the Isle of Portland
Give an example of a spit
Spurn Head, Yorkshire
Give an example of a bar
Slapton Ley ???
Give an example of a tombolo
Chesil Beach - connects the Isle of Portland to the mainland of Dorset coast
How is a wave-cut platform formed?
- weather weakens the top of a cliff
- the sea erodes the base of the cliff - undercutting it and coming a wave-cut notch (e.g. Holderness)
- the notch grows until the cliff collapses
- the backwash carries the old cliff towards the sea
- a wave-cut platform has occurred and continues to erode causing the cliff to retreat
Give an example of a wave-cut platform
Lyme Regis, Dorset
What are the types of sediment transportation at the coast?
- saltation
- traction
- solution
- suspension
- longshore drift
What are the types of erosion that affect the coast?
- abrasion
- attrition
- solution
- hydraulic action
What are the types of mass movement that affect the coast?
- slumping - slopes become saturated and loose rocks move downhill slowly under the force of gravity
- sliding - loosened rocks and soil suddenly slide down the slope - blocks of material may all slide at once
- rockfall - when rocks are weathered and break away from the slope
Which types of weathering affect the coastline?
- biological (e.g. plant roots breaking up rocks)
- chemical (e.g. acid rain dissolving minerals in rocks)
- physical weathering (e freeze thaw where water freezes and expands by 9-10%)
What is a discordant coastline?
where bands of more and less resistant rock run adjacent to the coastline - eroding at different rates to result in headlands and bays e.g. Swanage
What is a concordant coastline?
a coastline where bands of rock run parallel to the coastline - so it erodes at the same rate and results in straight cliffs e.g. the White Cliffs of Dover
What are the factors to do with the UK’s weather and climate that impact coastlines?
- seasonality
- storm frequency
- prevailing winds
How does seasonality impact coastlines?
e.g. cold temperatures in winter leads to more freeze-thaw weathering
How does storm frequency impact coastlines?
winds increase wave energy and so increased erosion as a result - Spurn Head at risk of being cut off, beach sediment removed from areas and sand dunes removed
How do prevailing winds impact coastlines?
winds in UK come from south-west - bringing warm moist air and frequent rainfall which contributes to mass movement
What is the difference between coastal erosion and coastal retreat?
coastal erosion - the breaking down and removal of material along a coastline
coastal retreat - when coastal erosion causes the coastline to move further inland
What is Holderness? (5 points, whole casestudy)
- 60km stretch of coastline in East Yorkshire
- 20-30m high with boulder clay geology which slumps easily
- fastest eroding coast in Europe with 2m per year
- waves have a long fetch from North sea and waves are destructive and have a lot of energy
- hard engineering e.g. groynes/rip rap at Mappleton have protected the coast from erosion and cliff collapse - but prevents transport and worsens erosion in other areas
What is the impact of climate change on the coast? (4)
- sea levels will rise 0.3m by 2100 - putting low lying areas at risk e.g. Bangladesh
- insurance companies predict flooding to be 12 times more likely by 2100
- Thames Barrier put up to prevent this
- March 2018 - A417 destroyed in storms at Slapton - shingle bastions protected the carpark at start bay and seawall at Torcross
How does longshore drift occur?
- longshore drift is the movement of sediment along the coast in the direction of prevailing winds
- the action of the swash forces sediment up the beach at a 45º angle
- the backwash brings sediment back down at 90º under the force of gravity
- this “zigzag” process continues and moves the sediment up the beach
What is deposition?
when a body of water loses energy and velocity, forcing it to drop its sediment
What are the three factors that influence deposition?
- sheltered spots
- calm conditions
- gentle gradient offshore which causes friction
What is the influence of less resistant rock on coasts?
- cliffs aren’t high or steep
- lots of borders at the base of cliffs
- lots of solution - causing discoloured sea
- bays form
What is the influence of more resistant rock on coasts?
- cliffs are high and steep
- not many boulders at the base of cliffs
- clear sea
- wave-cut platforms, headlands with cave arch stack stumps form
