Coastal Zone Flashcards
What are the impacts on the environment due to cliff collapse on the Jurassic Coast?
20m of South West Coastal Footpath gave way - lead to an estimated 400 tonnes of mud and rock fall onto the beach, hugely alters the shape of the landscape
There are concerns that continued erosion and cliff collapse will cause iconic arch, Durdle Door, near Lyme Regis in Dorset to collapse
What factors affect mass movement?
Geology
Precipitation
Antecedent (previous) weather conditions
Human activity
What is hard engineering?
Building artificial structures such as sea walls, aimed at controlling natural processes
What are the fauna adaptations in the Essex salt marshes?
To get food supply deep in the mud and water the Curlew bird has a long, curved bill
To keep their bodies dry Redshanks and Oystercatchers have long legs
To prise open mussels and cockles Oystercatchers have a perfectly shaped bill for this
What is weathering?
The breakdown of rocks in situ
What 3 factors affect the SIZE of waves?
Wind speed
Wind duration e.g. succession of storms
Fetch
Dune regeneration: what it is, benefits, costs
Dune regeneration is creating or restoring sand dunes by nourishment or by planting vegetation to stabilise the sand
Benefits: sand dunes are a barrier between the land and sea, absorbs wave energy, stabilisation is cheap
Costs: protection is limited to a small area, nourishment is very expensive
Describe the difference between sand and shingle beaches.
Sand beaches are flat and wide - sand particles are small and the weak backwash can move them back down the beach, creating a long, gentle slope
What are discordant coastlines?
Coastlines where the geology alternates between hard rock and soft rock
What is traction?
Heavy particles and big rocks roll along the sea floor.
What is attrition?
The knocking together of pebbles, making them gradually smaller and smoother
What are the flora adaptations in the Essex salt marshes?
To withstand the effect of wave action and water movement the Spartina plant has a double root system, attaching it to the surface and 2m deep into the sediment below
To adapt to the low oxygen content the Spartina and Glasswort plants have aerenchyma, which supply oxygen to submerged parts of the plant
To adapt to the high salt content in the water the Spartina and Glasswort plants are halophytes with special glands to excrete the salt
To tolerate the dry conditions Glasswort plants are xerophytic which concentrates salt into their roots to lower water potential, allowing osmosis to take place
Explain the formation of beaches
Beaches form when there is a build up of material so that deposition outweighs any erosion that would remove material. Often, there is a clear source of sediment nearby e.g. a soft cliff. Deposition of sand and shingle occurs in sheltered areas where waves are not powerful and where the waves are constructive with a strong swash, forming the beach
What is longshore drift
The transport of sediment along a stretch of coastline, caused by the waves approaching the beach at the same angle as the prevailing wind.
Why do waves break at the coast?
The sea becomes shallower, so friction against the sea bed slows the bottom of the wave. The top of the wave is not slowed by friction, causing the wave to become increasingly elliptical closer to the shore. It begins to appear as ‘curved’. The top of the wave is moving much faster than the bottom so the wave breaks. Water rushes up the beach as awash and back down the beach as backwash due to gravity.
How are wave cut platforms formed?
A wave-cut platform is a wide, gently sloping rocky surface at the base of a cliff.
Waves erode the base of the cliff by the processes of hydraulic power This creates a wave cut notch as the cliff has been undercut. The top of the cliff becomes unstable. This overhang will collapse into the sea providing more material for corrasion. The cliff has now retreated. This process of corrasion will continue. Because there is no corrosion below low tide a rock platform is left called a wave cut platform.
What are beaches?
Beaches are found on coasts between the high water mark and the low water mark. They are formed by constructive waves depositing material like sand and shingle.
Location of the Jurassic coast and brief sentence about why it is vulnerable to cliff collapse
The Jurassic Coast is a 95 mile stretch of the south coast from Exmouth in Devon to Studland in Dorset. It is vulnerable to cliff collapse because of its differential rates of erosion on the discordant coastline
Location of Holderness
The Holderness coastline is 61km long stretching from Flamborough Head (a headland) to Spurn Head (a spit).
What is a vegetation succession?
A sequence of vegetation species colonising an environment
Why are some areas of the Jurassic Coast susceptible to undercutting by the sea and collapse?
Differential rates of erosion due to different geology e.g. Limestone at Lyme Regis and Chalk at Studland - these are sedimentary rocks and the less resistant geology (e.g. chalk) will be susceptible to erosion and undercutting by the sea, therefore mass movements are common.
Also, these sedimentary rocks contain pore spaces (which make up almost 30% of the rock) - when it rains (esp when there is heavy rainfall like in 2012 in Devon and Dorest), these pores hold water and thus increase the mass of the cliff making it unstable and susceptible to mass movement
Rotational slip on the Jurassic Coast occurs when sandstone and/or limestone are interbedded with clay along a concave pane. Heavy rain saturates the ground and the earth slumps.
What problems have the hard engineering strategies at Holderness caused? (costs)
1) Groynes cause narrow beaches to form further down the coast - this increases erosion there e.g. Cowden Farm (south of Mapleton) is now at risk of falling into the sea
2) The material produced from the erosion of Holderness is normally transported south into the Humber Estuary and down the Lincolnshire coast - reducing this amount of material increases the risk of flooding in the Humber Estuary, because there’s less material to slow the floodwater down
3) The rate of coastal retreat along the Lincolnshire coast has increased, because less new material is being added
4) Spurn Head is at risk of being eroded away because less material is being added to it
5) Bays are forming between the protected areas and the protected areas are becoming headlands which are being eroded more heavily - this means maintaining the defences in the protected areas is becoming more expensive
When drawing a diagram of LSD what do you need to draw?
DRAW Sea Arrows representing swash and backwash A pebble showing where the sand moves LABEL direction of LSD direction of prevailing wind (same direction as swash) Sea Land/Coast
What is hydraulic action?
When waves crash against rock and compress the air in the cracks, putting pressure on the rock. Repeated compression widens the cracks and causes bits of the rock to fall off
What is a salt marsh?
A low-lying coastal wetland mostly extending between high and low tide that is periodically flooded
What is abrasion?
The ‘sandpapering’ effect of pebbles grinding over a rocky platform, often causing it to become smoother
What are the four types of mass movement?
Fall
Slide
Flow
Slip/slump
How do waves form?
Waves form as wind passes over the surface of the water
Energy from the wind is transported into the topmost layers of water (via friction and pressure)
These forces develop a disturbance (ripples) that are transported through the sea water and develop into waves
WAVES MOVE NOT WATER
Why does Holderness need coastal management?
The average rate of erosion at Holderness is about 1.8m/year
The main reasons for its rapid erosion is that most of the cliffs are made from boulder clay, it has naturally narrow beaches and has powerful waves
Groynes: what they are, benefits, costs
Groynes are wooden fences placed at right angles to the coast that trap material transported by LSD
Benefits: create wider beaches so slows the waves and is good for tourism, not too expensive (£10,000 each)
Costs: the problem is shifted, creating narrower beaches further down the coast, unattractive
What is mass movement?
The downhill movement of material under the influence of gravity
Managed retreat: what it is, benefits, costs
Managed retreat is removing an existing defence and allowing the land behind it to flood
Benefits: over time the land will become marshland - creates new habitats, flooding and erosion reduced by marshland, fairly cheap
Costs: people may disagree over what land is allowed to flood e.g. flooding farmland would affect the livelihood of the farmers
General political impacts of coastal flooding
Government has to make policies to reduce impacts of future flooding by:
building more and better flood defences
managing the use of areas that might be flooded e.g. by stopping people living there/relocating
What are the impacts on people’s lives due to cliff collapse on the Jurassic Coast?
Property loss and damage - mass movement at Monmouth beach cause damage to £200,000 beach huts
Death - threat of death due to mass movements in 2012, July 2012, Charlotte Blackman was buried by tonnes of rock following cliff collapse
Local economy - because of the threat on people’s lives, they had to shut down beaches, affect tourism and jobs§
