Coasts Flashcards
how are waves created?
the action of the wind blowing over the water, it creates friction and causes a swell. The energy of the wind causes the swell to grow and move forwards as a wave.
what is fetch?
how far the wind had travelled uninterrupted (larger fetch = larger wave)
why do waves break?
as they approach the coast, the friction between them and the ocean floor causes them to break. the sea floor slows down the base of the wave but the top keeps moving and eventually falls over due to gravity.
what is the energy of a wave determined by?
-how long the wind has been blowing
-the strength of the wind
-how far the wind has blown (fetch)
name 4 characteristics of a destructive wave
-higher
-shorter wave length
-weak swash
-strong backwash
name 4 characteristics of a constructive wave
-low
-long wavelengths
-strong swash
-weak backwash
what kind of beach does a destructive wave create?
a steep beach
what kind of beach does a constructive wave create?
a gentle, sloping beach
give two examples of mechanical weathering and what they are
-salt weathering - crystals of salt grow in cracks and cause fragments to break off
-freeze-thaw weathering - repeated cycles of freezing and thawing of water trapped between the rocks causes fragments of the rock to break off
name three types of chemical weathering and what they are
- hydrolysis - acid rainwater reacts with granite causing it to crumble
-oxidation - oxygen dissolved in water reacts with iron rich minerals and makes them crumble
-carbonation - carbon dioxide dissolved in rainwater forms weak carbonic acid. this reacts with calcium carbonate to form calcium bicarbonate which is carried away by water.
name the one type of biological weathering and what it is
living organisms like nesting birds, burrowing rabbits or plant roots break bits of the rock away
what are the four types of mass movement?
-rockfall
-landslide
-mudflow
-rotational slip/slump
what is a rockfall?
individual fragments or chunks of rock fall off a cliff face often as a result of freeze-thaw weathering
what is a landslide?
sliding blocks of rock moving rapidly downslope along a linear shear-plane usually lubricated by water.
what is a mudflow?
saturated mineral (usually clay) flowing downhill which may also involve elements of sliding or slumping
what is a rotational slip/slum?
slumping of loose material often along a curved surface lubricated by water
name the 4 types of coastal erosion
-hydraulic action
-abrasion
-solution
-attrition
what is hydraulic action?
the power of the waves forcing air into cracks in the cliffside
what is abrasion?
the waves throwing material at the cliffside and acting like sandpaper
what is solution?
the dissolving of soluble rocks such as chalk
what is attrition?
pebbles in the waves collide with each other making them rounder
name 4 types of coastal transportation
-traction
-saltation
-suspension
-solution
what is traction?
large particles rolling along the sea bed
what is saltation?
a bouncing or hopping motion along the sea bed by pebbles too heavy to suspend
what is suspension?
particles suspended and carried in the water
what is solution? (transportation)
chemicals travelling dissolved in the water
what is coastal deposition?
where sediment carried by the sea is dropped and left behind.
give 4 places where deposition often takes place
-in bays
-areas shetered by bars and spits
-places with constructive waves
-near rapidly eroding cliffs
give examples of both resistant and less resistant rocks
resistant:
-granite
-limestone
less resistant rocks:
-clays
-sands
what do resistant rocks/less resistant rocks form?
resistant = headlands
less resistant = bays
what is a concordant coastline?
where the rocks are parallel to the coast forming more or less a straight line
what is a discordant coastline?
where the rocks reach the coast at right angle creating headlands and bays.
headlands are exposed to ….. ….. … so are likely to exhibit signs of ……. like …. …. ……. and …..
exposed to high energy waves so are more likely to exhibit signs of erosion like wave cut platforms and stacks.
bays are …… by headlands so tend to experience ….. ……. ….. resulting in ….. and the formation of …..
are sheltered by headlands so tend to experience low energy waves resulting in deposition and the formation of beeches.
headlands and bays are characteristics of a…
discordant coastline
give the 4 steps in the creation of headlands and bays
- abrasion and hydraulic action wear away the softer rock faster
2.the leaves the harder rock jutting out
3.as the coastline becomes more indented, the headlands take the brunt of the incoming waves - this means erosion no longer takes place in the bay
what are the 3 steps in the formation of a wave cut platform?
- when waves break at the foot of the cliff, they erode a wave cut notch due to hydraudlic action and abrasion
- this undercuts the cliff face which eventually collapses through mass movement (eg landslide)
- the cliff retreats inland leaving a wave cut platform which is made smooth overtime by abrasion
where are caves, arches and stacks formed
at headlands
give the 2 steps which create caves and then arches
- a large crack in the cliff is enlarged by hydrualic action
- overtime the cave becomes larger until it is completely hollowed out and becomes an arch
give the 3 steps that create stacks and then stumps
- eventually the top of the arch collapses due to freeze-thaw weathering which leaves behind a stack
- notches form at the base of the stack which make it unstable
- the stack then topples over leaving a stump
where would you find sandy beaches?
in an area with low energy waves, in a bay
where would you find a pebbly beach?
a place destructive waves (as their strong backwash removes all the finer sands) so are therefore often narrow and steep
what is wave refraction?
the bending of waves due to frictional drag. friction with the sea bed as waves approach the shore causes the wave to be distorted or refracted
shallower water causes ……. ……. and …… ……
shallower water causes low velocity and shorter wavelengths
deeper water allows for …….. ……. and …….. ……
steeper waves and greater velocities
where would you find sand dunes?
- on broad sandy beaches
give the steps involved in the formation of sand dunes
- sand accumulates against obstacles on the beach such as drift wood or seaweed
- the sand builds up and forms embryo dunes due to wind being blown up the beach
- hardy plants (like marram grass) grow on and stabilise the dune so they form fore dunes
- dead organic matter add nutrients to the sand enabling more plants to grow on it and forming yellow and grey dunes
- dune slacks may form where wind hollows out a depression and exposes the water table
- trees and shrubs grow on the mature dunes that are the furthest away from the sea
what is a spit?
a shingle ridge that extends out from the coast into the sea. it tends to hook at the end
give the 5 steps on the formation of spits?
- longshore drift transports sand along the coast
- the spit grows out into the sea
3.the end of the spit can become curved due to short changes in wind and wave directions - salt marshes form by the accumulation of mud in the sheltered environ behind the spits.
- plants grow here
what is a bar?
a ridge of sand or shingle that extends across a bay creating a lagoon
how is a bar formed?
by longshore drift transporting sediment from one side of the bay to the other.
how do bars form offshore (in the middle of the sea)
sediment may be dragged back out by destructive waves forming a ridge that may be visible at low tide.
what is Old Harry’s Rocks an example of?
a stack and a stump
give four examples of hard engineering
-sea wall
-groynes
-riprap/rock armour
-gabions
what does a sea wall do?
reflect the energy of the waves back into the sea
what are the advantages and disadvantages of a sea wall?
advantages:
-successful in protecting the coast
-oppourtunities for developing a walkway on the top = social benefits
disadvantages
-very expensive to build and maintain
-looks unattractive and ruins the natural landscape
-interference with waves can lead to higher energy waves breaking elsewhere along the coast
what does a groyne do?
stops longshore drift
advantages and disadvantages of groynes
advantages
-very effective at stopping longshore drift
-it creates a wider beach = tourism
disadvantages
-ugly
-could starve beaches further down the coast increasing the risk of flooding and erosion down there
-several groynes are needed to be effective
-regular maintinence is needed as they could get damaged or overflow
what is riprap/rock armour?
large rocks that act as protection
advantages and disadvantages of riprap/rock armour
advantages
-relatively cheap to build and maintain (boulders arrive by barge)
-can be used for things like fishing
disadvantages
-the boulders are imported from other countries so are not native
-ugly/obtrusive
-potentially dangerous
what are gabions?
wire cages filled with rocks built up against a cliff to prevent erosion
advantages and disadvantages of gabions
advantages
-flexible construction options (like lego blocks)
-relatively cheap to build and maintain
-quick to build
-plants quickly colonise the area
disadvantages
-unattractive
-cages may break and make them dangerous
-they begin to rust very quickly
name three soft engineering methods
-beach nourishment/beach reprofiling
-dune regeneration
-managed retreat
what is beach nourishment/beach reprofiling?
the feeding of sand or pebbles to a beach to increase its height or width so that it absorbs the wave energy
advntages and disadvantages or beach nourishment
advantages
-looks natural
-increases tourism
-cheap and easy to maintain (sand comes on barges)
disadvantages
-constant maintinance is required especially after storms
-people are prevented from using the beach during maintinance
what is dune regeneration?
plants like marram grass can be sown in the dunes to encourage them to develop. fences are placed around dunes to protect them from humans
advantages and disadvantages to dune regeneration
advantages
-considered very natural
-produce tourism (picnics, walks ect)
-increase habitats and biodiversity
disadvantages
-time consuming to plant and keep people off
-easily damaged by storms
what is managed retreat
allowing the sea to erode or flood an area but in a controlled way
advantages and disadvantages of managed retreat
advantages
-low costs
-creating of a salt marsh which is natural protection and a great habitat
-increased tourism
-more attractive
disadvantages
-farmland could be lost
-local people may have to relocate
-footpaths may be blocked
-ecosystems may be effected
why was coastal management needed in Eastbourne?
-erosion was threatning beaches and coastal settlements.
-people rely on tourism for income so damage may be detrimental
-danger of flooding for 743 homes if sea levels rose
what was the problems with Easbourne’s coastal protection before it was updated.
-sea defences had been damaged by more frequent storms and rising sea levels caused by climate change.
-groynes damaged by the waves and overflowed with sand so were no longer effective.
-sea walls had been destroyed
what did they do to Eastbourne from 1994-1999?
received £30m funding to:
-construct 94 timber groynes
-construct rock revetments
-repair the sea wall
-add 1million tonnes of shingle
what are the positive and negative social impacts of coastal management in Eastbourne?
positive
-properties protected
-new coastal promenades
negatives
-conflicts between people concerned about habitat destruction
what are the positive and negative economic impacts of coastal management in Eastbourne?
positive
-the renourishment of the beaches means that the groynes wont need to be replaced as often
negative
-some people from outside the area felt it was an expensive scheme for a low, ageing population
what are the positive and negative environmental impacts of coastal management in Eastbourne?
positive
-the use of recycled material promotes Eastbourne as a Site of Special Scientific Intrest
negative
-disturbances to habitats during the process
Give an example of a bar?
Chesil beach, Dorset
Give an example of an arch?
Durdle door, Dorset
Give an example of a bay?
Lulworth Cove
Bay = clay
Headlands = limestone
What new sea defences have been build in Eastbourne?
-94 timber Groynes (larger than previous ones)
-rock armour
-repair and encased old sea wall
-1 million tonnes of shingle
How much funding did Eastbourne receive and how much did they spend in total?
-£30 million funding
-spent £300 million
What challenges are Eastbourne still facing?
-rising sea levels due to climate change
-95% of all new homes are built on flood planes
What were Eastbourne’s challenges before they started the coastal management project?
-seawall damaged
-Groynes destroyed in storms
-beach doesn’t have enough shingle
What is the shoreline management plan for Eastbourne?
-maintain and improve exsisting sea defenses
-annual council budget of £100k
-maintain current position of coastline
Why did Eastbourne cause conflict?
-Groynes made of hardwood - deforestation in tropical places
-sea wall increased erosion rates down at Pevensey Bay
-issues over money spent on an ageing population
