Coasts Flashcards
litoral cell
area near coastline where high and low tide occur
sediment inputs
if deposition is bigger then coats is expanding
if erosion is bigger the coast is retreating
energy inputs
tides
currents
precipitation
gravity
foreshore zone
part of shore between high and low tide marks
nearshore zone
shallow waters nearest land
backshore zone
area furthest from sea
only affected by waves in big storms or spring tides
the 5 processes
weathering
erosion
deposition
transport
mass movement
outputs
erosional landforms
depositional landforms
different types of coasts
rocky coastlines
high relief
resistant rock
high wave height
destructive waves erosion is greater than deposition
sandy coastlines
low relief areas
not resistant rock
low wave height
constructive waves
deposition is greater than erosion
esturaine coastlines
low relief
salt marshes and mudflats
low energy
soft rock
constructive waves
example of discordant coastline and concordant coastline in Britain
d - holderness
c - dorset
concordant coastline
alternating bands of hard n soft rock parallel to coast causing lower rates of erosion
discordant coastline
alternating bands of hard and soft rock at 90 degrees to coast
what forms at concordant coastline
Dalmatian coats
what forms at discordant coastline
headlands and bays
igneous rocks
formed by magma crystallization the crystals interlock , resistant to erosion, contain few joints and weaknesses (Basalt and Granite)
metamorphic rocks
formed by change in heat and pressure, resisant to erosion as crystals overlap but don’t interlock . (Slate and Marble)
sedimentary rocks
formed by build up of sediment , not resistant to erosion . Limestone and chalk
permeable rocks
poreous - contain pores that allow water
numerous joints
less resistant to erosion as surface vulnreable to chemical weathering is increased
dune order
embryo , fore , yellow, grey, mature
what dunes to sea rocket and crouch form in
embryo and fore dune
how dunes change as you get further away from coast
stronger
more vegetation
more sheltered
embryo dunes
form at coastline
have pioneer plants - these increase soil nutrients and allow other plants to grow
xerophyetes
tolerate dry conditions
halophyetes
tolerate salt
constructive waves
strong swash
weak backwash
deposition greater than erosion
destructive waves
larger height
shorter wave length
strong backwash, weak swash
create steep, narrow beach
erosional processes - hydraulic action
wave gets into cracks of cliff and widens them - force of water breaks rocks
destructive waves are more effective
erosional processes - abrasion
pieces of rock hit against the sea bed
destructive waves are more effective
erosional processes - attrition
pieces of rock hit against eachother becoming smaller and more rounded
destructive waves are more effective
erosional processes - corrosion
chemical reaction between sea water leaving minerals and a solution
susceptible rock such as limestone
constructive waves are more effective
mechanical weathering
application of force onto rock
( freeze thaw weathering , wetting and drying , salt crystal growth)
chemical weathering
a weak chemical reaction between water and rock where rainwater mixed with carbon dioxide forms carbonic acid , this reacts with carbonate in limestone to form bicarbonate which is soluble.
biological weathering
rocks broken down by living things
( plants roots widening cracks in rocks, rock boring where animals live in a rock)
inputs / sources of a sediment cell
cliff erosion
subaerial processes
onshore currents
transfer’s of sediment cell
processes that move sediment between sources and sinks
( LSD , swash , backwash , wind)
sinks of sediment cell
areas and landform where sediment is stored
( sand dunes , beaches , barriers)
eustatic change
rising of sea level due to ice age - ice melts and sea rises
isostatic change
rise in land as ice was sat on it and melts so land rebounds
tectonic change
land rises and sinks at boundaries
emergent coastlines
coast line rises relative to sea level
submergent coastlines
coast being flooded by sea due to rising sea levels
5 depositional landforms
Spits, Bars, Bayhead Beaches, Tombolos, cuspate forlands
depositional landforms- spit
long finger of sand sticking out from beach caused by LSD ( Duriston head)
depositional landforms- bar
spit grows accross a bay ( start bay devon)
depositional landforms - curved spit
spit curves inland due to prevailing winds
depositional landforms - cuspate foreland
triangle shape caused by LSD from 2 directions
depositional landforms- bayhead beach
beaches formed in bays by constructive waves
( Durdle door)
depositional landforms- tombolo
spit that has joined two landscapes ( portland bill)
Caves
weakness in a cliff widens
Arches
cave erodes whole way through
( durdle door)
stack
top of arch collapses
stump
stack erodes futher
Longshore drift
wave approaches at an angle , backwash pushes it straight, difference in angles between swash and backwash mean sediment is transported along the coast
wave cut notch and wave cut platform
sea attacks base of cliff which then collapses and creates an overhang
overhang eventually collapses
once this has collapsed the rubble watches away and creates a wave cut platform
3 soft engineering strategies
beach nourishment , cliff regrading, dune stabilisation
beach nourishment and a positive and negative ( Lyme Regis)
transporting sediment from elsewhere to beach.
Costs - £300,000 for 100 metres
positive - cheap and easy to maintain, looks natural , increases tourism
negative - needs constant maintenance because of erosion
cliff re grading and a positive and negative
reducing angle of cliff to help stabilise it
positive - works on clay or loose rock where other methods don’t work
negative - can cause cliff to retreat
marsh creation and a positive and negative
allowing low lying areas to flood so land becomes a salt marsh
positive - cheap , creates natural defence and habitat to wildlife
negative - agricultural land is lost
dune stabilisation and a positive and a negative
creation or restoration of dunes by either fencing them off or planting maram grass
positive - maintains environment for wildlife and is cheap
negative - planting marram grass is time consuming
5 hard engineering strategies
sea walls , rip rap , groynes , revtments, off shore breakwater
sea walls and a positive and negative
concrete walls that refract wave energy
positive - little maintainence
negative - expensive
rip rap and a positive and negative
pile of boulders to reduce energy
positive - cheap
negative - limit beach access
revetments and a positive and negative
angled sea wall
positive - most cost effective
negative - regular maintenance
offshore break waters and a positive and negative
pile of rocks parralell to coast
positive - calm beach conditions
negative - expensive
groynes and a positive and negative
wooden posts at 90 degree to coast which aim to trap sediment and widen the beach
positive - widen beach
negative - beach further down narrows
Cost benefit analysis
determines economic value of coastline to see if intervention is necessary
Environmental impact assessment
asses long and short impacts on enviroment
ICZM
looks for most effective management, considers social and economic factors
managed realignment ( Abbots hall farm)
allowing coastline to retreat but in a managed way such as breaching flood banks to low quality land
pros- reduces flooding in important areas
cons- difficult to sell houses that are unprotected
hold the line - pros and cons
maintaining current position of coastline ( using hard engineering)
pros - good for residents
cons- expensive and needs maintaining
advance the line
construct new defences
no active intervention - pros and cons
letting nature take it’s course and allowing sea to erode
pros- free , not affecting environment
cons- whoever uses the land loses out
Maldives - coastal flooding
removal of mangroves led to increase flooding, relys on tourism , meant fresh water supply was limited, fish farms ruined
Studland - contemporary sea level rise
sea level is rising so low lying areas such as Studland are vulnerable to flooding
Kirabati - contemporary sea level rise
sea level is rising 1cm a year
this means Kiribati is likely to disappear
Kiribati have purchased land in Fiji to use for farming and if necessary move people to
Abbots hall Farm ( Essex) - coastal management ( managed retreat)
RSPB breached parts so sea could go in which reduces pressure on coast and attracted wildlife.
Created 200 acres of mudflats, salt marshes and coastal grassland
Netherlands Delta project
a hard engineering mega project which began after 1953 floods
built an open barrier to remain tidal movement for birds benefit but could close during storm surges
cost $5 billion
morphology
shape and form of coastal landscape
lithology
physical characteristics of particular rocks
erosion
action of surface processes that removes soil, rock or dissolved material from one location and transports to another
weathering
decay and disintegration of rock
cliff profiles - relief
angle at which cliff lies to sea
affected by geology
subaerial cliff profile
curved and sloped
lower angle face
accumulated debris
marine cliff profile
steep face
limited cliff base debris
4 factors affecting rate of erosion
geology, lithology, weathering, mass movement
freeze thaw weathering
water gets into cracks of rocks and freezes making the rock expand and become brittle
mechanicalweathering - wetting and drying
clay rich rocks expand when wet and contract when dry
this results in cracks
mass movement - soil creep
continous however slowest form of mass movement where individual particles move downhill
mass movement - soliflucation
movement is 5cm to 1m per year
occurs in areas of permafrost where top layer melts in warmer temps and slides over lower frozen layer
mass movement - mudflow / landslides
downslope movement of blocks down moderately flat plain
chemical weathering causes rocks to weaken and gravity slowly pulls them down
mass movement slides - rock fall
occur on slopes over 40 degrees
rock weakens due to erosion and weathering
and drops down vertically leaving a talus scree slope
mass movement - rotational slumps
rock failure and movement along a curved slope
occurs in weak unconsolidated material
rocks fall in rotational movement
strata
layers of rocks
bedding planes
horizontal , natural breaks in strata caused by gaps in time during periods of rock formation
geological structures - joints
vertical cracks created by rock not moving
igneous it occurs during magma cooling
sedimentary it occurs due to compression of overlying rock
geological structures -folds
bends in rock caused by sedimentary rocks layering
dip
refers to the angle at which the rock strata lies
geological structures - faults
large fractures caused by tectonic plates
make the rocks easily erodable
erosion- hydraulic action
air trapped in cracks is compressed by force of waves crashing against cliff face causing cracks to open
destructive waves are most effective
erosion - abrasion
sediment is thrown against cliff face or sea bed which causes it to break down
erosion- attrition
collisions between loose sediments and makes sediment smaller and more rounded
erosion - corrasion
solution by rainwater causing rocks to break down
fetch
length of water that is uninterupted
tides
changes in water level caused by gravitational pull of the moon
Jurassic coast - how geology has effected features - Lulworth cove
a concordant coastline
soft rock is chalk which is poreous
rocks vary in resistance to erosion
sea broke through portland stone to create horseshoe shape
cuspate foreland
formed when sediment comes from 2 directions to form an accumulation of sediment creating a triangular feature
Hallsands - lost village ( South Devon)
example of village built on a source zone where they dredged the shingle to be used for buildings, the beach dropped and village got destroyed
3 causes of land rising and falling
weight of ice
tectonic movement
sediment build up
3 things that form at a submergent coastline
dalmation coasts
fjords
rias
dalmation coasts formation
concordant coastline or submergent coastline
Fjords formation
formed when glacial troughs are flooded by rise in sea level
Rias formation
when valleys in dissected uplands are flooded, providing a natural harbour with a deep mouth , due to submergent coastline
emergent coastline - raised beaches
as land rose as a result of isostatic change, former shorelines and their beaches were raised above present sea levels
what is causing contemporary sea level rise
glaciers melting
ice sheets melting ( antarctic)
thermal expansion ( hot water takes up more space)
Hard engineering Vs Soft engineering
hard engineering is contructing something new whereas soft engineering involves working with nature
depressions
intense low weather systems that occur when fast moving cold air moves into a region of warm air
5 causes of coastal flooding
land subsidence
removal of vegetation
building sea defences
storm surges
climate change
storm surge
short term change in sea level caused by low pressure and wind
2 things causing a storm surge
depression and cyclone
2 things making storm surges worse
strong winds that push waves onshore
high/spring tide occurring at the same time
1953 storm surge Canvey islands and Netherlands
winter storm over 2 day period with no planning in place
Canvey island had no defences and was mainly bungalows
killed 306 in UK
killed 1800 in Netherlands
2013 storm surge Canvey islands and Netherlands
surge combined with high winds and high tide
killed 2
flooded 1400 homes
£100 million of damage
4 local factors affecting risk of coastal flooding
low lying land
coastal topography ( narrow causes funnel affect)
subsidence ( sinking of land relative to sea level)
removal of coastal vegetation
2 global factors affecting risk of coastal flooding
eustatic sea level rise caused by global warming
thermal expansion and ice sheets melting causing rising sea levels
climate change and tropical storms
27.5 degrees is temp needed for tropical storm and climate change has resulted in more oceans being over this
3 types of vegetation that protect a coastline
mangroves
salt marshes
sand dunes
sediment is protected by plants in 2 ways
roots of plants bind sediment together
plants protect sediment from sand erosion
3 causes of coastal subsidence ( sinking land)
destruction of vegetation exposing to erosion
groundwater abstraction
river straightening causes sediment to be propelled too far offshore
where do salt marshes develop
sheltered areas where deposition occurs
where salt water meets fresh water
`human causes of coastal retreat
coastal defences
offshore dredging
physical causes of coastal retreat
destructive waves
subaerial processes
geology
UK and coastal erosion
occurs along 17% of UK coastline
2300km of UKs coastline is protected
Erosion at Holderness
Holderness is one of Europe’s fasting eroding coastlines
erodes 2m a year
29 villages have been lost
Coastal defences of Holderness
Has invested in sea walls, groynes and rock armour
They have caused problems south of coast as starved them of sediment
Key players of Holderness - Central government agencies
responsible for coastal management
Key players of Holderness- Local government
joint responsible for coastal management with Environment agency
Key players of Holderness- stakeholders in local economy
tourist industry want greater spending
farmers want protect their land
residents want to protect their homes
insurance companies won’t insure vulnerable properties
Why is erosion such a problem at Holderness - Lithology
much of coast consists of boulder clay which is structurally weak and not resistant to erosion
soft poreous rock , weak joints , they dip seawards and are heavily faulted
Why is erosion such a problem at Holderness- Fetch
fetch of about 500-800km which is small but the waves have huge power due to currents and a deep water floor
Why is erosion such a problem at Holderness- longshore drift
not enough sand to stop waves reach cliffs as tide flows south which transports material by longshore drift
Holderness - Economic Loses
owner of golden sands lost 100 sea chalets in 15 years
by 2100 predicted 200 homes will fall into sea
between 2010-2012 Yorkshire council spent £1.2million on helping people live with erosion
Holderness - social losses
homes and businesses lost
managing coastlines - engineering feasability
what’s the best method
is it achievable
is it within budget
managing coastlines - environmental sensitivity
does the coast include protected sites
( Flamborough and Spurn head are considered heritage coasts)
managing coastlines - land use and value
what is the land used for and how much is it worth
managing coastlines - impacts on coastal processes
doing nothing means sediment continues to be supplied to the right places
holding the line starves other areas of sediemnt
managing coastlines - political, social and economic reasons
agriculture and tourism are key industries
costs must be acceptable to the government
adaptation
making changes to lessen the impact
mitigation
making effort to reduce GG emission so sea level rise stops
Bangladesh - Eco engineering
working with the environment by building 4000km of embankments and planting mangroves
LIC so needed cheap protection
sustainable coastal management
designed to cope with future threats (increased storm events, rising sea levels) but its implementation can lead to local conflicts in many countries.
coastal communities face the threat of
- rising global sea levels, but there is uncertainty about the scale and timing of the rise
- increased frequency of storms and the possibility of increased erosion and flooding
4 egs of sustainable coastal management
- managing natural resources ( fish, farmland)
- managing flood and erosion risk
- creating alternative livelihoods
- educating communities to understand why change is needed
3 reasons sustainable management coastal can create conflict
- coastal natural resources may have to be used less - people use less income
- relocation may be needed
- some erosion and flooding will always occur as engineering can’t protect against all threats
Holderness - Mappleton
hold the line - a rock groyne
- This has protected the main road, homeowners can still get a mortgage, businesses can stay in the area.
- cost benefit analysis found this was viable to protect
Holderness - Withernsea
-hold the line has been selected including a sea wall and rip rap.
-Residents can stay in their homes
- but the council must cover the cost of keeping the coastal management in place.
Holderness - Easington
-hold the line has been selected including rip rap.
- British consumers and the gas industry have benefited since the gas station hasn’t needed to be relocated.
Holderness - Kilnsea
-managed retreat has been selected.
- A caravan owner was able to buy the land behind him and rollback. They get 5 pitches for every 4 lost previously.
Holderness - Bridlington and Hornsea
far up the coast
two seaside towns
hold the line
Holderness - Ringborough farm
farm land , no active intervention
farmers have had to move back and build new land
Holderness - Sprun head
managed retreat as important for shipping and SSSI
( science)
Holderness - sediment cell
spurn head is the sink as the depositional landforms form here
Flamborough head is the source - where the sediment is coming from
why understanding sediment cells is important
- if you don’t understand you put wrong protection in wrong place , increases erosion ( Sidmouth)
