Coastal Environments Flashcards
How many employed in north sea oil and gas?
450,000
What needed protecting at Medmerry?
348 properties and a sewage plant
Corrasion is what?
Sediment thrown at cliff
What is traction?
Large material rolls along seafloor
Common weathering in humid tropical (e.g. Brazil)
Chemical - high temps and rainfall
Geology of Happisburgh
Glacial tills seperated by beds of silt, sand, and clay
What lyme regis phase was scrapped?
Phase 3
How much would it cost to close gaps in costal defences at Happisburgh?
£15 million
What is a neap tide?
Sun and moon at right angles to Earth. Sun cancels out some effects of the moon. Lower tides.
Term for sea retreating
Marine regression
Tombolo explanation and example
Spit joins an island to a mainland.
Chesil Beach, Isle of Purbeck, Dorset
Isostatic sea level change
Local
What is oxidation as a type of chemical weathering?
Oxygen and iron in rock react. Rusts, which weakens and breaks down rocks.
How much sand in Sand Motor?
21.5 million m3
Where is Happisburgh?
Northeast Norfolk
What is a sediment cell?
A length of coastline self-contained in terms of matter.
How much of Europe’s wind energy flows through Scotland?
25%
Place being rapidly eroded due to GY dredging
Winterton
Common weathering in glacial (e.g. Norway)
Mechanical - too cold for much chemical
How did Dalmation Coast form?
African + Eurasian plate collide and compress limestone. Creates anticlines and synclines. Sea level rise floods the synclines.
Where needs beach nourishment due to lack of sediment supply from GY dredging?
Sea Palling
Where is line being held instead of Happisburgh?
Sea Palling
How fast is rotational slumping?
Slow
What causes variation in wave energy? (3)
Wind - velocity, duration, fetch
Onshore flow hurricane explanation.
NE side of storm produces winds out of the SE to S that force ocean water towards the coast.
Example of wavecut platform
Kimmeridge Bay
What is a spring tide?
Sun and moon aligned with Earth. Higher tides due to exacerbated tidal pull.
Sea breeze explanation
Onshore flow. during afternoon air over land is warmer than air over water causing air to rise vertically over the land and ocean air to move to shore to fill empty space along the coast. Means storms 5-10 miles on shore (t-storms).
When did sea levels reach today’s levels?
6000 years ago
What is attrition?
Waves cause pebbles/stones to bump into each other and break up.
What year was the Sand Motor built?
2011
Sussex sand dune site
Camber Sands
Netherlands longterm responses to 1953 storm surge.
Expansion of dikes (embankments) and storm surge barriers.
When did Happisburgh policy change to MR?
2012
Concordant coasts
Rock strata runs parallel to coastline
Smoo cave annual visitors
40,000
1990 Happisburgh
300m sea wall destroyed in storm
What is a tidal bore?
High tide funnelled into a narrow bay or estuary. Creates a wall of water that travels against the current.
Happisburgh population
1400
Medmerry storm example and costs
2008, damages of £5 million
How many accepted Happisburgh buyback offer?
9 out of the 12 offered
What is the foreshore?
The area between the high tide and the low tide mark.
What type of cliff does rockfall often occur?
Ones with many joints, faults, and BPs
What happens to low lying regions on an emergent coastline?
Fall in base level causes river gradient to steepen. Potential energy increases, which cuts into river plane, rivers enlarge.
What type of waves is corrosion more effective with?
Constructive, spilling swash on a less steep beach means longer time for the water to remain on the rock.
How fast is rockfall?
Very rapid
Scotland - place with some of the fastest tidal currents in the world
Pentland firth
What used to be between Happisburgh and the sea?
Another village
Example of a fjord
Sognefjord, Norway
2021 Jurassic Coast cliff failure
largest in 60 years
4000 tonnes of rock slump
300m cliff affected
What coastline is Lyme Regis on?
The Jurassic coast - world heritage site
‘Other’ longterm responses to 1953 storm surge.
Improvements to: weather forecasting, flood warning systems, broadcast technology, multi-agency plans, training of responders.
What is the nearshore?
The area of shallow water beyond the low tide mark, within which friction between the seabed and waves distorts the wave sufficiently to cause it to break. (breaker zone) There may be a breakpoint bar between the offshore and nearshore zones.
Tidal energy project
MyGen Tidal Energy Project
Term for large scale vertical tectonic motions of continents (depression/uplift)
Epeirogenic Movements
How far offshore is Great Yarmouth dredging?
9km
Common weathering in temperate (e.g. France)
Variation in temperature and precipitation.
Chemical and mechanical.
Detail Severn Tidal Bore.
Range up to 15m, bore up to 2m high, travels ~25 miles at up to 20mph.
Define wave frequency.
The number of wave crests passing a point each second.
Term for uplift or subsidence of land due to filling and emptying of magma chambers
Bradyseismic change
When was the most famous North Sea Storm Surge?
31st January 1953
Mangroves and salt marshes on emergent coastlines
Increase their extent
Lyme regis phase 1
Sea wall and promenade. Stablilised cliffs.
Orientation of flip plane for landslide
Diagonal slip plane
Lyme regis phase 4
390m sea wall. 480 homes protected. Cliffs stablilised again (draining and nails).
Term for movements in relation to mountain-building
Orogenic movements
Lulworth cove formation
Sea breaks through hard rock (portland limestone) to soft wealden clay that is rapidly eroded.
4 possible SMP approaches
Hold the line, advance the line, managed realignment, no active intervention.
Characteristics of destructive waves.
Short wavelength, steep and tall wave height, high frequency, backwash > swash.
What is abrasion?
Sand paper effect. Sand and fragments hitting cliff, not so much thrown at it.
Subsidence of UK east coast each year.
2mm
When did Holbeck Hall collapse?
1993
2 parts of hydraulic action
1 - direct impact of water has pressure
2 - Air compressed into cracks, as it withdraws the air ‘explodes’ outwards, expanding cracks
Stacks at John O’Groats
Duncansby Stacks
Smoo cave distance from John O’ Groats
50 miles
What type of beach formed by LSD
Drift aligned
How much sediment dredged at Great Yarmouth?
7.7 million tonnes
What is the backshore?
The area above the high tide mark, affected by wave action only during major storm events.
1600-1850 Happisburgh erosion
250m
Lyme regis phase 2
Sea wall and promenades. Creation of wide beach. Rock armour.
Discordant coasts
Different rock strata aligned at angle to coastline. Forms headlands and bays.
When did lyme regis phase 2 occur?
2005-07
What type of beach formed by LSD
Drift aligned
What is a Psammosere?
Another name for a sand dune ecosystem
How did Holbeck Hall cliffs collapse?
1 - hot and dry early summer caused clay to crack
2 - heavy May rainfall infiltrates cracks and saturates cliffs
3 - major slump then series of landslides
Eustatic sea level change
Global
Lyme Regis population change in summer due to tourism
4000 but increases to 14,000 in summer
How much land made infertile in UK due to 1953 storm surge?
1000 square kilometres
How many viewing points at Medmerry?
4
How many died in north sea storm surge?
> 2100
Sources of sediment for cells.
Erosion, transport (fluvial or aeolian), LSD/deposition, and biogenic (e.g. cells).
Name for pattern of ria
Dendritic, meaning tree like - branches out
How far away from cliffs was Holbeck Hall built?
75 metres
Lyme regis phase 4 cost
£20 million
What is weathering?
The breakdown of rock in situ, and may be a mechanical, biological or chemical process.
How many houses damaged in UK by 1953 storm surge?
24,500
South Dorset erosion
Very slowly. Straight coast. Mostly due to undercutting.
What measures have been taken at Camber Sands?
Marram planting, paths, boardwalks
How many sediment cells do England and Wales have?
Eleven
What is suspension?
Small material suspended and carried
Example of rockfall
St. Oswalds Bay, Dorset
2013
80m section of cliff detached
How much did Bacton sandscaping cost?
£20 million
What Lyme Regis erosion affects tourism?
Erosion of the foreshore
Characteristics of constructive waves.
Long wavelength, low wave height, low frequency, swash > backwash.
Constructive waves average frequency,
6 to 8 per minute
When did lyme regis phase 4 take place?
2015-17
What is saltation?
Material bounces along seafloor
Volcanic islands and sea level change
Displace water, sea level rise. Weight can also depress oceanic crust, opposite effect.
Rock geology of South Dorset Coast
Hard portland limestone parallel to sea amd purbeck limsetone + wealden clay (soft) behind.
Cliff steepness for rockfall
Steep, vertical
What is lyme regis famous for?
Fossils
Where is Medmerry?
West Sussex
What did the UK build in response to 1953 storm surge?
The thames barrier
2 examples of a Ria
Milford Haven, Wales.
Fal Estuary, Cornwall.
What caused UK emergent coastlines?
Isostatic rebound following end of Pleistocene 10,000 years ago
Example of raised beach
King’s Cave on Isle of Arran, Scotland. 5m above current sea level.
What does Bacton Terminal supply?
1/3 of the UK’s gas supply
How many evacuated in England due to 1953 storm surge?
30,000
What type of coastline are rias more common on?
Discordant
What is solution?
Very small material dissolves and is carried
Village lost in Devon after dredging
Hallsands
How much land in Netherlands was flooded in 1953 storm surge?
150,000 hectares
What is the actual Sand Motor life now?
40 years
What do epierogenic movements do to ocean basins?
Alter size. Bigger = sea level fall. Smaller = sea level rise.
Spit examples
Spurn Head, Yorkshire
Hurst Castle Spit, The Solent
What % does water expand when it freezes?
9%
Term for sea advancing
Marine trangression
How much did the Sand Motor cost?
£60 million
Destructive waves average frequency.
10 to 14 per minute.
What countries were impacted by North Sea storm surge?
Netherlands, England, Belgium, Germany
Annual profits from GY dredging
£14 million
Why does the Mediterranean coast have lower tides?
Only outlet is straits of Gibraltar. Limits flow of water as it is a small neck of land.
NE scotland income from tourism
£500 million
Wetting and drying - which is which with expanding and contracting?
Expands when wet.
Contracts when dry.
What is an onshore flow?
Movement of any weather feature moving towards the shore.
What needs to be curved for rotational slumping?
The slip plane
How much did Medmerry scheme cost?
£28 million
How many barrels have been extracted from north sea?
42 billion
How many visitors does John O’ Groats get anually?
100,000
Sand Motor benefit to system
Doesn’t disrupt seabed repeatedly
Example of a UK sediment subcell.
Holderness.
2 points about definition of mass movement.
1 - Downslope movement of material
2 - under the force of GRAVITY
What is an offshore flow?
Movement of any weather feature from land to sea.
Lyme Regis geology
Clay on sandstone, risk of landslides. Unstable cliffs and one of the highest rates of erosion in Europe.
When did lyme regis phase 1 take place?
1990-95
Lyme regis phase 2 cost
£22 million
What collects at bottom of a cliff after rockfall or landslide?
Scree
How does water facilitate rotational slumping?
Lubricates material, adds weight - more gravitational force.
When did rapid erosion of Happisburgh start?
1996
How many visitors per day in Summer to Camber Sands?
20,000
How fast is Happisburgh eroding?
2 metres a year. 6/7 metres can be lost in 1 cliff collapse.
Chances of flooding for Medmerry houses.
Used to be 1 in 1 year, now 1 in 100 years
Causes of 1953 storm surge.
Spring tide. Deep, low atmospheric pressure over north sea. Northerly gale force winds. Surge travelling south.
Why are Rias dendritic?
Reflects the valley and tributaries of the drowned river valley.
Corrosion is what?
The dissolving of minerals (carbonates) like like limestone
England deaths in 1953 storm surge
> 300
What was the sand motor life expected to be?
20 years
Irish cliffs
Cliffs of Moher
Term for eustatic sea level change due to melting of ice
Glacio-eustatic change.
Where is Lyme Regis?
Dorset
What did Medmerry scheme create?
New intertidal zone, embankment. Rock armour. Salt marsh.
What is an SMP?
Shoreline management plan
What is the offshore?
The area of deeper water beyond the point at which waves begin to break. Friction between the waves and the sea bed may cause some distortion of the wave shape.
