Physical mocks Flashcards
what is water stress?
if a country’s renewable freshwater supply is between 1000 and 1700mcubed per person per year
what is water insecurity?
when present and future water supplies cannot be guaranteed
what is (physical) water scarcity?
if a country’s renewable freshwater supply falls to below 1000mcubed per person per year
which areas are experiencing water scarcity?
- areas along the sub-tropical ridge are seeing water scarcity
- saudi arabia, algeria and syria are experiencing absolute scarcity (less than 500 mcubed/person/day)
- 2025 predictions show that Southern Hemisphere will see a lot of economic water scarcity whilst the north will increase most no or little water scarcity or physical water scarcity
which areas are experiencing water stress?
- much of east africa and India are experiencing water stress
explain the growing mismatch between water supply and demand
- relates to the distribution of freshwater resources (water availability) and the distribution of the demand for water
- 12% of the world’s population consumes 85% of its water
- rapid population growth in areas where supplies are limited together with an uneven distribution of global supply and a deterioration in water quality means more people are facing water shortages
what are the 4 physical causes of water insecurity?
- salt water encroachment at the coast
- climate change is changing hydrological cycle
- ENSO cycles
- blocking sub-tropical ridge
explain salt water encroachment and the Florida case study
- physical process caused by humans directly and indirectly
- more water is being abstracted from aquifers near the ocean, as more is abstracted the salt water seeps into the ground and into the aquifer, slowly contaminating the freshwater supply
- e.g. FLORIDA where water demand is increasing due to increasing affluence meaning more swimming pools and more water is being abstracted from aquifers near the ocean
what are the 2 human causes of water insecurity?
- overabstraction from rivers, lakes and groundwater aquifers
- water contamination from agriculture, industrial and domestic pollution
explain two examples of chains of reasoning for water stress and insecurity
1) increasing pop and economic growth
2) low development levels
increasing pop and economic growth - increased demand for water - overabstraction of groundwater and surface stores - salt water intrusion at the coast - water stress and scarcity
low development levels - lack of investment into making freshwater available and affordable, damage to ecosystems, decline in water availability, water stress and security
what are the 4 main factors for the rising demand of water (explained)
1) population growth
- demand for water is growing twice as fast as pop growth
- increased urbanisation puts a threat on the availability of freshwater with more than half of the world living in urban areas
- by 2030, the urban pop in Asia and africa is set to double
2) rising living standards
- increase in middle class led to sharp increase in water use, swimming pools, washing machines and dishwashers
- changing consumption patterns such as increasing meat consumption and building bigger homes
3) economic development (agriculture and industrialisation)
- the OECD predict that global water demand for manufacturing would increase by 400% from 2000-2050
- where water is not well regulated, pollution could increase dramatically with industrial spillage and poor waste management
AGRICULTURE
- in some cases up to 90% of water used by a country is for agriculture, growing demand for food
- agricultural demands for freshwater are unsustainable through increasing pesticide and fertiliser pollution, depleting aquifers and increased salinity
- 20% of the world’s irrigated land now suffers from salinity
what are the three main pressures increasing the risk of water insecurity?
1) diminishing supply
- climate change and impacts
- deteriorating quality from pollution
- impact of competing users (upstream vs downstream)
2) rising demands
- pop growth
- economic development
3) competing demands from users (within basins)
- international issues
- upstream vs downstream
- HEP vs irrigation
explain the causes and patterns of physical scarcity
- this occurs when more than 75% of a country’s or region’s blue water (accessible liquid) flows are being used
- currently applies to 25% of the population
- qualifying countries include the Middle East and North Africa
explain the causes and patterns of economic scarcity
- occurs when the use of blue water sources is limited by lack of capital, technology and good governance
- estimated that 1 billion people are restricted from accessing blue water due to poverty
- this is seen in most areas of africa and parts of continental south east Asia
why does the price of water vary globally
- whether governments own or private companies own water supplies, in Bolivia water was privatised where an American TNC took control and this led to outrage, prices soared, mass conflict
- the initial costs involved, cost of infrastructure pipes means many rely on trees vendors (can be up to 100 times the cost than if the water were to be supplied to their home), charities such as WaterAid need to offer invaluable help, their programmes help to reduce the extent of economic water security
- governments can choose to tax water supplies or subsidise, in Denmark it is most expensive as government are trying to reduce consumption, canada subsidies for consumers, canada it is heavily subsidised by the gov and so water is 80% cheaper than in Germany where it is private.
- supply and demand
- colonial governments would install limited infrastructure and the IMF restricts gov spending on water and so now water provision is often controlled by the private sector
explain the water poverty index
the WPI uses five measures to indicate levels of water insecurity:
1) resources- the physical availability of surface and groundwater and its quality
2) access- the accessibility of safe water for human use, including domestic, industrial and agricultural use
3) capacity- the effectiveness of water management to ensure affordability
4) use- the use of water for different purposes, including domestic, industrial and agricultural use
5) environment- water management strategies to ensure ecological sustainability
each of the measures are scored out of 20 to give an overall score of up to 100
explain the water poverty index for the UK, china and the USA
UK- they have a very good WPI at 71, they score the best in terms of capacity at 17.8 meaning they are very efficient in terms of the water they use
China- they have a medium WPI at 56.6 with their use scoring the highest at 18, this could be down to their growing pop and middle class, they score the best in terms of resources at 7.1
USA- they have a a medium WPI at 58.5, their use is at 1.3 as they waste a lot of water, they are not efficient
explain the importance of water supply for human well-being (two chains of reasoning)
improvements in water, reduction in illnesses from dirty water (65% reduction in deaths from diarrhoea), improved health, access to working life and therefore reduced poverty
improvements in water, lower medical costs and fewer days off work, improved school attendance, improved education and career opportunities, reduced poverty
- water, particularly that polluted by lack of sanitation, is an effective medium for the breeding and transmission of diseases such as typhoid and cholera
- safe water is vital to human health particularly in the context of washing and food preparation, also productive breeding ground for disease vector such as parasitic worms and mosquitoes
- millennium development goals aimed to halve the number of people without access to safe drinking water and sanitation by 2015
- the WHO says ‘every dollar spent on improving sanitation generates an average economic benefit of US$7
this shows that water is very important for economic development, quality of life and escaping the cycle of poverty
explain the importance of water supply for economic development (industry, energy supply, agriculture)
agriculture
- agriculture dominates water use, more than twice the total withdrawn for industrial and domestic purposes
- in some countries 90% of water used in a country is for agriculture
- 20% of the world’s irrigated and of this most is pumped directly from aquifers and is leading to massive groundwater depletion , water situation is unsustainable
industry and energy
- just over 20% of all freshwater withdrawals are for industrial and energy production
- mounting concern of the growth of biofuels as the crops are very thirsty
- water pollution is a major problems associated with much of this industrial use of water
explain Madagascar’s dirty water
- contaminated drinking water has led to the country having one of the highest rates of stunting in the world
- stunted children don’t grow properly, physically and cognitively, this can therefore affect school and employment and therefore poverty
- 160 million children under 5 are stunted, half of children in Madagascar are stunted
- WaterAid having to intervene in order to guarantee sustainability and preventing stunting and malnutrition
what has the privatisation of water systems resulted in for developing nations?
in the 1980s the world bank and IMF gave loans to developing countries to privatise their water system to reduce costs but many have cancelled these projects as the water becomes unaffordable for a lot of people
explain what is happening in Bolivia to water
- 50% average increase in water rates for SEMAPA customers (water company) led to many residents becoming opposed to privatisation
- the smaller providers are given poorly constructed and deteriorating systems which have an estimated 35% of their water being lost to leaks
- those outside the grid are forced to pay 5 to 10 times more than SEMAPA consumers
explain what is happening in Canada to water
- current water charges are about 1/4 of european rates and 3/4 of American rates
- the rates in OECD nations are often not high enough to cover basic utility operations and maintenance costs
- almost 40% of Montreal’s water is lost each year due to leaky infrastructure cost estimated to repair at $4 billion
explain what is happening in denmark to water
- the highest prices for fresh water in the world as they believe that by setting high pries it will help the environment as they will appreciate its scarcity and true value, this leads to greater water conservation, water consumption has dropped dramatically however they have seen an economic strain as a result.
explain the importance of water supply for economic sustainability
- water is essential in the production of most goods and services including food and energy, needed to ensure economic sustainability
- industrial water supply must be reliable and predictable to support financially sustainable investment in economic activities, 400% water demand increase for manufacturing between 2000 and 2050
- agriculture or family run businesses depend on water for generating an income, water is important for reducing poverty through better health, increased poverty and time savings
- most growth in water demand is being seen in BRIC nations
- by 2050 food production will require 140% more water
explain the importance of water for environmental sustainability
- wetlands reduce floods, store water and provide economic benefits through fisheries and recreation, half are lost
- forested highlands essential for recharging aquifers and ensuring clean flows for agriculture and HEP, deforestation and urbanisation
- degraded ecosystems lose resilience leading to water quality degradation, e.g. Salton Sea in California, productive ecosystem which provides a food source for over 400 birds, since 2005 water levels have been dropping as evaporation exceeds inflow, salinity levels increasing
- due to high demand water goes to agriculture and some inflow consists contaminated runoff from fields
what are technological and attitudinal fixes?
technological fixes- either involve large scale hard engineering projects (top down) or small scale innovations and appropriate technology (bottom up)
attitudinal fixes- involves people changing their behaviour towards water use to conserve water
what are the 3 examples of hard engineering techno fix mega projects?
- the 3 gorges dam, china
- the south-north water transfer project, china
- Israel’s desalination project
explain the 3 gorges dam china and the positives and negatives
- built on the Yangtze River which flows west to east through south china
- concrete and steel dam 2.3km long, made of 510k tonnes of steel
- enables surplus water to build up and be diverted to northern china via the south-north transfer project
positives:
- the power generated by the 34 generators is equivalent to burning 25 million tons of crude oil or 50 million tons of coal
- designed to control flooding on the Yangtze, improve water supply by regulating river flow, generate HEP for china’s economic growth
negatives:
- very expensive, $35 billion
- 632m squared of land flooded to form reservoir, displacing 1.3 million people from 1500 villages
- water quality affected by waste from industry, sewage and farms
- decomposing vegetation in the reservoir produces methane which is a strong greenhouse gas
explain the south-north water transfer project, china
- to provide water for Beijing region which has 35% of the population, 40% of the arable land but only 7% of water
- 3 routes will transfer 25 billion m cubed of water from the Yangtze River to northern china: western route to the yellow river, an eastern route via a series of lakes and a central route
- the cost is US$70 billion, due for completion by 2050
- Beijing has similar water scarcity to Saudi Arabia, just 100m cubed per person
positives: - will boost economic development in Beijing
- will reduce abstraction of groundwater (water tables dropped by 300m since the 70s)
negatives: - 345,000 people displaced as submerges 370km squared of land
- risks draining too much water from southern china which has also experienced water scarcity, creating conflict within china
- eastern route runs through heavy industry so is likely to become more polluted
- water supply might be too expensive for farmers to buy so they will continue to extracts groundwater
explain Israel’s desalination project and its pros and cons
- abstraction of sea water from the Mediterranean
- water is either evaporated to leave behind the salts that make seawater unusable or undergoes reverse osmosis where water is pushed through a membrane to separate it from the salts
- produces up to 600 tonnes of potable water per hour
positives:
- can provide a reliable supply for large settlements
- 5 plants opened in 2013 aiming to provide 70% of Israel’s domestic water supplies by 2030
- some plants are using solar power to run
negatives:
- each plant requires its own power station in order to boil the water, contributing to co2 emissions
- produces vast amounts of brine that needs to be released back into the sea or disposed of which can potentially harm ecosystems
explain briefly Sydney’s desalination project
- running at full capacity yet it supplies just 15% of sydney’s water needs
- only has minimal impacts on the environment
- globally there are 15,900 operational desalination plants producing about a million cubic metres of desalinated water
what are the 4 sections of the sustainability quadrant (briefly explained)
EQUITY
- does it negatively affect those downstream?
- fair accessibility and affordability for all
- not affecting everyones well-being
FUTURITY
- conservation of water supplies so they dont run out
- provides long term security
- economically viable practises
PUBLIC PARTICIPIATION
- involves communities in decision making and implementation
- appropriate technologies used so public can access
ENVIRONMENT
- protection of wetland ecosystems
- restoration of lost and damaged ecosystems
- carbon neutral, not polluting
- tipping points
what are the main aims of sustainable water management? give statistic of no. of irrigated fields in California and statistic on pipe leakage in Cairo and Israel
- minimise waste and pollution of water resources
- ensure that there is access to safe water for all people at an affordable price
- take into account the views of all water users
- guarantee an equity;e distribution of water within and between countries
- 38% of irrigated fields in California use drip
- pipe leakage in cairo is 50%
- pipe leakage in Israel is 9-10%
what are 5 sustainable water management strategies
1) smart irrigation- slow supply of constant water, no waste, gives the minimum amount of water necessary for high yield, it is highly monitored
2) virtual water- importing crops that have used water, instead of using large amounts of water to irrigate, you only use water for other uses, seen in very arid regions
3) rainwater harvesitng- where people collect the rain falling on the roof s of dwellings and store it in butts for various domestic purposes, such as flushing toilets and watering the garden
4) recycling water- recycling sewage water and purifying it to be able to drink
5) attitudinal fix, charges increase to reflect actual costs- controlling the price of water to make people waste less
explain what is happening in Uganda in terms of sustainable water management
- local builders trained in the construction of rainwater harvesting jars which are made from locally available materials and have a capacity of 1500 litres
- they collect rainfall from roofs and store water for dryer periods
- once constructed, the jars can provide a stable water source for many years
- organised by WaterAid that raises funds to improve access to safe water, sanitation and hygiene for the world’s poorest people
In Kitayita village, Uganda where 3000 people lack access to safe water
explain what is happening in Singapore to sustainable water management
- they have the cutting edge of new technologies to re-use grey water, NEWater is recycled water that is treated using disinfectant, meets 30% of the current needs
- leakages have been cut by 5%
- Singapore still need to import water, they have an agreement until 2061 to important water from Malaysia
- desalination of seawater, two plants now meet 25% of the water demand
- they have also invested into agro technology in order to diversify their water supply (water harvesting)
explain what is happening in Israel for sustainable water management
- due to their climate, natural geography and politics it has formed them to manage their water efficiently
- aim to transfer water from the sea of galilee to the centre of the country
they have done this through: - smart irrigation, water drips slowly into roots, saves 25-75% pumped water compared to food , organised by Netafim
- reducing agricultural consumption, importing water in food as visual water
- adopting stringent conservation techniques
- pricing water to discourage waste
- Netafim says their crops yield 15% more due to the few amounts of fertilisers needed and therefore lower chemical pollution, drip tech releases fewer GGs than irrigation
they acquire new supplies through: - importing 50 million tonnes fo water per year by ship from turkey (Manavgat Project)
- piping seawater from the Red Sea and mediterranean to new inland desalination plants
explain the restoring aquifers in Saudi arabia
- circular irrigation systems to grow enough wheat to feed itself and neighbours using water from its aquifers, levels fell in aquifers
- wheat farms have been abandoned to reduce demands upon aquifers supplying irrigation waters
how is Colorado’s IDBM successful?
- in 2012, the minute 139 plan helped to revive the delta and restore some normality
- beginning to improve as people make changes, e.g. people in Las Vegas use turf instead of grass
how is Colorado’s IDBM not successful?
- the rate of climate change is far greater than the IDBM’s ability to mitigate change
- irrigation still needs to be reduced and water recycling/smart irrigation should be implemented
- attitudes must change as Americans believe they have a right to water and don’t believe the views of climate change scientists should change their lifestyles
what is absolute water scarcity?
when renewable water supplies (from rivers, aquifers and lakes) become very low (less than 500mcubed per person per year). this leads to widespread restrictions.
what is economic water security?
when clean water is unaffordable even when its available
what is renewable water?
the total amount of a country’s water resources (internal and external), both surface water and groundwater, which is generated through the hydrological cycle (precipitation)
what is desalinisation?
it is the process by which dissolved solids in sea water are partially or completely removed to make it suitable for human use. recently there have been many technological advancements in the process of reverse osmosis in order to desalinise sea water
what is a drainage basin?
it is an area of land drained by a river and its tributaries
what is the jet stream?
it is a current of rapidly moving air that is usually several thousand miles long and wide but is relatively thin
what is smart irrigation?
the process of applying controlled amounts of water to plants at needed intervals, it is a highly monitored way of ensuring no waste
what does permeability mean?
a measure of the ability of soil, sediments and rock to transport water horizontally and vertically
what does pervious mean?
a surface that allows the percolation of water including the underlying soil
what does porous mean?
a surface that allows water to pass through it, such as sand
what is the sub tropical ridge?
it is a large belt of high pressure around 30º north and south and is made up of mainly calm winds, creates trade winds and the westerlies, area of descending air
what is groundwater?
also known as aquifers, it is water held underground in the soil or in pores and crevices in rock
what is beach morphology?
the shape of a beach including width and slope (profile) and other features such as berms
what are cliff profiles influenced by?
- geology, especially the resistance to erosion of the rock
- the dip of rock strata in relation to the coastline
explain joints
- (vertical cracks), these are fractures caused either by contraction as sediments dry out or by earth movements during uplift - they are fractures created without displacement and occur in most rocks, dividing rock strata up into blocks with a regular shape - jointing increases erosion rates by creating fissures which marine erosion processes such as HA can exploit example: in bantry bay, the limestone is heavily pointed, leading to more rapid fluvial and marine processes in adjacent sandstones
explain faults
- formed when he stress of pressure not which a rock is subjected, exceeds its internal strength (causing it to fracture). the faults then slip along fault planes. - it significantly increases erosion since faulted rocks are much more easily jointed - huge forces are involved in faulting and displacing them and therefore either side of the fault line, rocks are often heavily fractured example: in bantry bay in cork in the republic of Ireland there is a major fault which runs SW-NE down the centre of the bays. the limestone is weakened allowing rapid fluvial erosion
explain folds
- they are bends in rocks formed by pressure during tectonic activity which makes rocks buckle and crumple - the main two types are anticlines and synclines - folden rock is often more heavily fissured and jolted, meaning they are more easily eroded, also increases erosion by increasing angle of dip and causing joins through the stretching along anticline crests an compressed in syncline troughs
explain dips
- refers to the angle at which rock strata lie (horizontally, vertically, dipping towards the sea or dipping inland) - its a tectonic feature, sedimentary rocks deposited horizontally can be tilted by faulting and folding by tectonic forces
what is horizontal dipping?
a vertical or near-vertical profile, notches reflect weathering and small scale mass movement
what is a high angle of seaward dip
produces a sloping, low-angled profile with vulnerable rock layers, loosened by weathering
what is a low angle of seaward dip
produces a steep profile that may even exceed 90 degrees, creating areas of overhanging rock, vulnerable to rock falls
what is landward dipping strata
produces a steep profile that may even exceed 90 degrees, creating areas of overhanging rock, vulnerable to rock falls
what is a cliff profile?
the height and angle of a cliff face, plus its features such as wave cut notches or changes in slope areas
what are micro features?
- small-scale features such a scales and wave-cut notches which form part of a cliff profile - the location of these micro-features are often controlled by the location of faults and/or strata which have a high amount of joints and fissures
what is the relief of an area affected by?
the relief or height and slope of land is also affected by geology and geological structure. there is a direct relationship between rock type, lithology and cliff profiles
explain the different stages of a cliff profile
1) horizontal starat produce steep cliffs with clear bedding planes
2) rocks dip gently towards the sea with almost vertical joints, joints are opened by weathering and pressure release
3) steep drip towards the sea and rock slabs slide down the cliff along bedding planes
4) rocks dip inland producing a stable, steep cliff profile
what is lithology?
refers to the physical characteristics of the rock. igenous, metamorphic, sedimentary and unconsolidated rock each have different characteristics.
it also influences geological structure on ameso (medium scale) and micro scale (some types of rocks are more likely to have joints and bedding planes)
how does lithology affect resistance?
1) mineral composition
2) rock type
3) structure
how does mineral composition affect resistance?
- some rocks contain reactive minerals eaisly broken by chemical weathering, e.g. calcite in limestone
- other minerals are more inert that chemically weather more slowly
how does rock type affect resistance?
- sedimentary rocks are clastic (sediment particles compacted together) and these are often reactive and easily chemically weathered
- igneous rocks are crystalline with strong chemcial bonding
- rocky coasltines differ in resistance
how does structure affect resistance?
rocks with fissures or air spaces erode more easily
what are rates of recession influenced by?
it is influenced by bedrock lithology (I,S,M) and the geology
- how reactive minerals in the rock are when exposed to chemical weathering
- whether rocks are clastic (less) or crystalline (more resistant)
- the degree to which rocks have cracks, fractures and fissures
give examples of areas from the most resistantrock to the least resistant rock
most resistant: IGNEOUS- Land’s End, South Cornwall (granite)
resistant rock: METAMORPHIC- St Ives, Cornwall (slate)
resistant sedimentary rock: SEDIMENTARY- Blackers hole, south Purbeck, Dorset (Limestone)
least resistant rock: Holderness, NE Coast, (boulder clay)
explain igneous rocks
- their crystalline structure (interlocking cystals) means they are well connected and impermeable with few lines of weaknesses (resistant)
- these rock types create rocky coastlineswith steep profile cliffs
- erosion rates: 0.1-.0.3 cm/yr
- e.g. granite, basalt
- example: lands end, Cornwall (granite)
explain metamorphic rocks
- they are also well-connected and impermeable
- however they are often folded and faulted so have weaknesses
- these rock types create rocky coasltines with steep profile cliffs (depending on folding and dip) and erode slowly
- erosion rates: 0.5-1 cm/yr
- e.g. marble, slate, schist
- crystalline rocks are resistant to erosion
- example: St Ives, Cornwall (slate)
explain sedimentary rocks
- they are clastic meaning they are made up of cemented sediment particles rather than interlocking crystals
- formed in stratas (layers) with joints which provides weaknesses and makes limestone permeable along with other jointed sediemntary rocks whereas other ones are porous due to the presence of air spaces
- rocks that are younger erode faster than the others as they are softer and weaker, older sediment is buried deeper and is subject to more intense compaction with strongersedimentation- making them more resistant
- limestone erosion rates: 1-2cm/yr, chalk erosion rate: 1-100 cm/yr
- example: Old Harry, Purbeck, Dorset (chalk)
explain unconsolidated sediment
- they are the least resistant, they are not cemented together in anyway so are very vulnerable to erosion, fast recession rates
- can create slumped coastlines due to mudslides/landslides causing slumping
- the boulder clay of Holderness coast in Yorkshire retreats at a rate of 2-10 m p.a
- boulder clay erosion rates: 100-1000 cm/yr, sandstone rate: 10-100 cm/yr
what are the factors influencing the rate of recession?
- geology
- lithology
- weathering
- mass movement
what is differential erosion?
where cliffs are composed of differing lithology, leads to different sections of a cliff eroding/receding at different rates. it can also be produced when there are alternating permeable and non-permeable strata
they may form a ‘bench’ feature at the cliff base and further up overhanging sections until they collapse by mass movement.
however, the overall rate of recession is determined by the resistance of the weakest rock layer
what are the 4 different examples of differential erosion?
- a spring creating erosion and saturation leads to slumping
- poor water pressure leads to slumping
- wave-cut notches from different rates of erosion
- resistant rock creating a bench feature at the cliff base
explain a spring creating erosion and saturation leading to slumping for differential erosion
when groundwater flows through the permeable sands but cannot flow through the impermeable clay which leads to the permeable layer becoming saturated, weakening it and causing slumping
explain poor water pressure leading to slumping in differential erosion
poor water pressure (the internal force within cliffs exerted by groundwater) in the saturated layers pushes rock particles apart, reduces friction and lubricates lines of weaknesses
explain the formation of wave-cut notches in differential erosion
wave cut notches are created by erosion of the weak coal layer with more resistant siltstone overhanging the coal below
explain the importance of permeability in differential erosion
permeable rocks allow water to pass throug them. groundwater flow through permeable rock can weaken the rock by removing the cement that binds the rock sediment. slumping is a common outcome.
what are the two different types of cliff profiles?
1) steep, unvegetated cliffs
2) shallow-angled, vegetated cliffs
explain steep unvegetated cliffs
- produced where marine erosion dominates
- there is little or no debris at the base as it is broken by attrition and transported offshore or along the coast
explain shallow vegetated cliffs
- they have a convex profile (curved like the interor of a circle)
- there is debris at the base becuase sub-aerial processes slowly move sediment downslope, but marine erosion is unable to rmeove it from base
- produced where there is little active marine erosion
what is geological structure?
refers to how the rock is arranged on a macro-scale and looks at the arrangement of different rock types in relation to each other.It looks at the rock strata, deformation and presence of faulting.It looks at the rock strata, deformation and presence of faulting.
how are waves created?
waves are created through friction between the wind and water surface, transferring energy from the wind into the water. this generates ripples, which grows into waves whedn the wind is sustained.
what does wave size depend on?
- the strength of the wind
- how long has the wind been blowing for
- the length of the fetch
what is the fetch
this is the uninterrupted distance across water over which the wind blows and therefore the distance waves have to grow in size
which area suffers the greatest waves?
the southwest due to the long fetch along the atlantic
explain wave formation and the breaking of waves
1) waves move across open ocean in circular motion as ocean swell
2) as the waves reach shallower water, when their wave height is less than half the wavelength then friction increases slowing the wave down for the circular oscillations to become more so elliptical
3) as the wavelength decreases due to the shallower water, wave height increases and eventually the wave breaks as the top of the wave is moving faster than the base
4) the waves then lose enrgy and gravity pulls the water back as backwash
what are destructive waves like?
- they degrade a beach
- high waveheight, low wavelength
- backwash > swash
- drags sediment back to sea
- scours beach
- 13-15 break/minute
- high energy
- causes cliff retreat
- plunging breaker
- steep beach
what are constructive waves like?
- they aggrede a beach
- low waveheight, long wavelength
- swash > backwash
- brings sediment back to the sea
- builds beach up
- 6-8 break/minute
- low energy
- spilling breaker
- flat beach
what are swell waves like?
- waves formed by winds blowing over larger distances, they travel out of windy and stormy areas
- swell waves originate in mid-ocean and maintain their energy for thousands of miles
- is an ocean wave system not raised by the local wind blowing
- as swell waves advance, its crest becomes flattened and rounded and its surface smooth
using cliff profiles explain how recession rates can differ
- recession rate increases if dip is towards so as weathering opens joints and gravity speeds mass movement
- steep dip to the sea increases erosion rate as gravity makes bedding planes unstable and slabs slide downslope. this increases recession rates
- a cliff with landward dipping bedding planes are relatively steep and stable whcih decreases recession rates
- landward dip with well-developed joints will increase recession rates as joints acts as slide planes
what are the 4 erosional processes explained
abrasion- the rubbbing together of hard load, sand paper effect
attrition- rocks bashing into one another breaking them down
hydraulic action- air trapped in cracks and fissures is compressed by the force of the waves crashing against the cliff face. when the wave retreats, pressure is released explosively which can widen cracks and dislodge blocks friom the cliff face
solution- where water in waves dissolves rock minerals
how are erosional processes influenced by wave type, size and lithology?
- most effective during high energy storm events with large destructive waves
- most effective in winter, in high energy storms
- faster when the tide is high
explain the cave-arch-stack-stump sequence
- the headland protrudes out into the sea as it is more resistant which means wave energy is concentrated on it due to wave refraction
- wave action attacks weaknesses in the headland due to abrasion and hydraulic action leading to cavitation
- this widens cracks into crevices and into caves
- caves can be eroded to form blowholes as the ceiling collapses
- marine erosion deepens the caves until they connect up andan arch is created and erosion continues and the roofof the arch becomes unstable from the widening of the arch due to weathering and other sub-aerial processes
- the arch eventually collapses by blockfallto form a stack
- continual undercutting and HA in the joints at the base of the stack creating a stump like Old Harry’s wife
explain the formation of old harry rocks
- wave refraction concentrates wave action on the headlnad, hydraulic action and abrasion slowly erodes the headland to form a series of landforms
1) chalk headland leads to wave refraction
2) deposited sand from nearby waters deposit to form beaches
3) waves carved into rock to form chalk cliffs, undercut to form hollow until it becomes so unstable that it collapses
4) pockets of air are compressed into the cracks with the water that it becomes unstable and falls
5) wave quarrying forms arches
what are blowholes?
- caves can partially collapse to produce a hole in the cliff
- waves hitting the base of the cliff can be forced through and sprout water at the top
how do cliffs vary in morphology?
they vary in their morphology depending on lithology and weathering are actively eroded by wave action or they are affected by sub-aerial processes
explain the formation of a wave-cut platform
1) wave action at the base of the cliff between high and low tidemeans that hydraulic action and abrasion undercuts the clif to form a wave cut notch
2) this continues and the cliff above the notch is left unsupported and eventually collapses
3) the cliff retreats leaving a wave cut platform which is the base of the cliff that is left
4) this process maintains a steep cliff profile
what is a wave cut platform
it is a flat rock surface exposed at low tide, extending out to sea from the base of a cliff
what is a wave cut notch
a curved indentation of about 1-2m high extending along the base of a cliff. it forms between the high and low tide marks, where destructive waves impact against the cliff.
what are beach profiles like in summer?
- they are steeper in summer, where constructive waves are more common than destructive. wave energy dissipates and deposits over a wide area.
- as the berm builds up, the backwash becomes weaker and only has enough energy to move smaller material, so the beach material becomes smaller towards the shoreline
what are beach profiles like in winter?
- destructive waves occur at a hgiher frequency
- berms are eroded by plunging waves and high-energy swash
- strong backwash transports sediment offshore (offshore bars are made)
- destructive, high-energy waves dominate in the winter, lowering angle of beach profile and spreading shingle over the whole beach
how does the size of sediment vary along a beach
as constructive waves have a weaker backwash can only transport smaller particles down the beach. this leads to the sorting of material with larger, heavier shingle at the back of the beach and the sand drawn back closer to the sea.the backwash onlyhas enough energy to transport down smaller sediment.they also become more angular at the back of the beach and rounder at the front of the beach.
what influences beach morphology?
1) sediment supply- if the supply is reduced from rivers, for example, due to the construction of dams on rivers that traps sediment upstream
2) human interference- often a result of coastal management in one place having an effect on processes further along the coast
3) climate change- if global warming made the UK climate on average stprmier, then destructive waves and ‘winter’ beach profiles would become more common
explain morphology along cliff profiles
- storm beaches result from high-energy deposition of very coarse sediment during the most severe storms
- berms typically of shingle/graves, result from summer swell wave deposition
- the middle area of the ebach is mainly sand, but the sand is coarser where berms/ridges have been deposited than in chsnnels and runnels
- offshore ridges formed by destructive wave erosion and subsequent deposition of sand and shingle offshore.
what are the 4 methods of transportation?
traction- where large, heavy load items are rolled along the sea bed
saltation- where lighter sediment bounces along
suspension- where very light sediment is carried within a body of water or air
solution- where seidment is carried dissolved within the water
explain the process of longshore drift
- the prevailing winds (in this case SW) mean that the waves approach the coastline at an angle
- this means the swash moves sediment up the beach at the same angle but backwash moves sediment straight down the beach under gravity
- waves carry large pebbles by rolling them (traction) and small pebbles by bouncing them (saltation) and sand, silt and clay is suspension
- as the process continues, sediment is moved east and over time, a drift aligned beach will form.
what are swash aligned beaches
waves approach the coasltine perpendicular to the beach. the swash and backwash move sediments up and down the beach = stable and straight beach
what are drift aligned beaches and give an example
waves approach at an angle and sediment is moved along by longshore drift = wide beaches but uneven in sediment
e.g. porlock bay, Somerset
what are examples of sources of sediment?
- rivers
- constructive waves (from seabed)
- cliffs
- LSD
why does deposition happen?
- deposition due to gravity settling occurs in low energy coastal environments, course dropped first, finer further away
- flocculation helps depositon of fine clay particles that are very llight. they clump together in salt water, making them heavier.
explain the formation of a spit and give an example
1) sediment is moved along the coast by a process called LSD
2) when there is a change in the direction of the coastline (river mouth), longshore drift continues
3) the waves lose energy in the slacker water behind the headlandand the largest sediments are deposited here first in the same direction (gravity settling)
4) as deposition continues, a spit is formed. finer material is carried along futher along the spit before being deposited as it is lighter (course dropped first, finer, further away). flocculation helps to settle fine clay
5) the spit grows and may form a hook if the wind direction changes
6) in the slacker water behind the spit, more deposition takes place and a saltmarsh may develop with halophytic plants helping to trap sediment (links to salt marsh succession). new land is eventually created. e.g. spurn head
e. g. hurst castle spit, Hampshire
how does a bar form and give an example
where there are no river currents, it prevents longshore drift depositing in a straight line across and so evenutally the spit joins with land to form a bar, e.g. chesil beach
it is when a beach or spit extends across a bay to connect two headlands
e.g. slapton ley, devon
what is a tombolo and give an example
- this is an island joined to the mainland. it develops when deposition occurs behind an island due to the low energy environment. eventually, the island becomes connected to the mainland.
- occur on drift aligned coastlines, when longshore drift builds a spit out from land until it contacts with an offshore island.
- they are linear ridges (bars) of sand and shingle connecting an offshore islandto the coastline of the mainland.
e. g. chesil beach
what are double spits and give an example
- Double spits are where two spits extend out in opposite directions from both sides of the bay, towards the middle.
- They form where longshore drift is operating in different directions on opposite sides of the bay
- They can also form when rising sea levels drive ridges of material onshore from the offshore zone.
-Or, a barrier beach driven across a bay forms a bar (e.g. Haff coastlines) but a strong exiting river current may breach the bar toform a double spit.
e.g. sandbanks and purbeck, Dorset
what are cuspate forelands and give an example
- low-lying triangular shaped headlands, extending out from a dhoreline, formed from deposited sediment
- forms when longshore drift current from opposing directions converge at the boundary of two sediment cells
- The sediment is deposited out into the sea by both currents creating a triangular shaped area of deposited material.
- They can extend from a few metres to several kilometres
e. g. Dungeness, kent
what are barrier islands?
- a ridge of material emerging just offshore to form a chain of beaches parallel to the coast
- these are offshore sand bars thought to have formed when a plentiful supply of sediment was deposited in sand dunes along the eastern seaboard of the USA by waves and winds
- as sea level has risen, land behind was flooded to create a lagoon but the sand dunes themselves became elongated islands running parallel to the coast (USA Atlantic coast)
- as sea level continues to rise, they migrate inland
- they provide protection to the coastline during storms as they absorb wave energy
what are offshore bars?
- Offshore bars are ridges of sand or shingle running parallel to the coast in an offshore zone.
- forms in shallow water offshore where the slope is gentle
- following large erosion events during a storm
- beach and dunes can be scoured heavily by destructive waves and carried seawards by backwash
- They are also called breakpoint bars because the offshore/nearshore boundary is where waves first begin to break.
- They can sometimes be exposed by neap tide.
- LSD can add to them or change their shape and they can be temporary
what is weathering?
the decay and disintegration of rock in situ (where they are) by mechanical, biological or chemical agents.
what is mass movement?
the movement of material downslope as the result of gravity. water commonly acts a lubricant in mass movement.
how is weathering and erosion different?
erosion also involves the transport of sediment away from the cliffs, the erosion occurs by an external agent
what might influence how vulnerable a cliff is to mass movement?
- lithology and structure of a cliff can determine mass movements it is vulnerable to
- weathering processes cancontribute to the loosening of cliff faces so that mass movements are more likely
- water from rainfall is often a key cause of mass movements
- angle of the slope will also affect vulnerability
what are the 5 different types of mass movement?
landslide
slumping
mudflow
rockfall
soil creep
what is a landslide?
rocks that have jointed or having bedding planes parallel to the slope are susceptible to landslides. increased water leads to less friction, leading to sliding
what is rotational slumping?
common where softer rock overlies harder rock, it causes rotational scars, repeated slumping creates a terraced cliff profile
- A rotational scar is a fresh, curved, unweathered and unvegetated rock surface on the cliff face.
- The detached slope section, often with vegetation intact on top of the slump, forms a beach or terraced cliff profile.
- Slumping is facilitated by the presence of water, which adds weight (increasing the gravitational force) as well as lubricating it, reducing friction.
what is mudflow?
Flows occur when unconsolidated fine grained sediment, e.g. silts and clays, mix with large volumes of water. They’re common in weak rocks such as clay or unconsolidated sands. They become saturated, lose their cohesion, and flow downslope.
- difference between a slide and a flow is that in a slide the material remains intact but in a flow the material becomes jumbled up
what is rockfall/blockfall?
- most likely to occur when strong, jointed and steep rock faces/cliffs are exposed to mechanical weathering or marine erosion,happens on slopes over 40 degres
- once broken away, it can form scree at the bottom of the cliff
blockfalls- similar to rock falls but here a large block of rock falls away from the cliff as a single piece.
what is soil creep?
the slowest form of mass movement, an almost continuous process, it is a very slow downhill movement of individual soil particles
what are the different types of biological weathering
plant roots
rock boring
seaweed acids
what are the different types of mechanical weathering?
freeze thaw
salt crystallisation
wetting and drying
what are the different types of chemical weathering
carbonation
oxidation
explain freeze thaw
- water gets into the cracks and freezes and expands up to 9%. this exerts pressure on the cracks which loosens and breaks apart rock. most vulnerable are well jointed rocks, only happens when daily temperatures fluctuate around zero degrees.
- effects: creates angular rock fragments at the base of the cliffs called scree and a jagged cliff face. also can contribute tolarge rock falls.
explain salt crystallisation
- salt spray or waves hitting cliffs makes them wet with seawater. this evaporates and leaves salt in cracks on the cliff. overtime, salt crystals form and grow, exerting pressure on the crakcs and pores which loosens and breaks apart rocks. most vulnerable are well jointed rocks (limestone) and porous rocks (sandstone). happens most in hotter climates
- effects: creates angular rock fragments at the base of cliffs called scree. some rock faces crumble away.
explain wetting and drying
- rocks rich in clay expand when they get wet and contract when they dry. this repeated process causes them to crack and break apart
- effects: cracks form in cliffs so they become vulnerable to slumping.
explain carbonation
- limestone slowly dissolves as it reacts with weak carbonic acid
- This attacks calcium carbonate in limestones, other carbonate rocks and sedimentary rocks with calcite sediment.
- effects: joints and cracks get wider on cliffs and wave cut platforms. this makes them more vulnerable to other weathering and mass movement processes
explain oxidation
- oxygen combines with iron based minerals in a rock causing a chemical breakdown of the minerals shown by red rusty colour on the rock face. it produces iron oxides and increases in volume, leading to mechanical breakdown.sandstones and shales often contain iron so are vulnerable.
- effects: leads to crumbling of the cliff as sections are no longer bonded together
explain the effects of plant roots
- tree and plant roots growing into cracks can slowly widen them and causethem to break apart. important process on vegetated cliff faces.
- seeds falling into cracks in rocks can germinate, nourished by rainwater and nutrients from wind-blown sediment.as the plant grows its roots expand and thicken,tree roots exert sufficient tensional force to widen the crack
- effects: eventually angular fragments of rock break away as cobble or boulder-sized sediment, rock falls
explain rock boring
clams and molluscs bore (dig) into rock to make their homes. they can also secrete acids that dissolves rocks. sedimentary rocks in the intertidal zone are vulnerable.
- piddocks drill depressions into sock rocks by rotating their shell equipped with sharp edges
- effects: holes and weaknesses created are vulnerable to erosion and further weathering
explain seaweed acids
- some seaweed species like kelp contain pockets of sulphuic acid that can burst on rocks and dissolve them
- when the cells break sulphuric acid attacks rock minerals like calcium carbonate leading to a chemical reaction similar to carbonation
effects: leads to crumbling of the cliff as sections are no longer bonded together
what is a talus scree slope?
The angular blockfall debris accumulates at the cliff foot to form atalus scree slope, a fan shaped mound of material.
formed from a blockfall
how can geological structure influence cliff profiles
Geological structure largely influences cliff profiles in terms of the landforms that form as a result. If it is a discordant coastline then they are to see headlands and bays but if it is a concordant coastline they will see haffs and coves. Geological structure closely relates to the resistance of the rock and so it determines the rate of coastal recession in the different areas also.
what are submergent coastlines?
they are produced by eustatic sea level rise. they produce fjords, rias, dalmatian coasts and barrier islands
- an example is the sognadjord, norway
what are emergent coastlines?
they are produced mainly by isostatic readjustment (rebound)
they produce relcit/fossil cliffs and raised beaches
example: Vik, South Iceland
explain the formation of rias
- submerged river valleys
- the lowest part of the rivers course and its floodplain may be completely drowned, but the higher land becomes exposed
- in plan view they tend to be winding, reflecting the original route of the river and valley
- before the end of the last ice age, a small river with its tributaries met the sea, creating an estuary at the mouth that is larger than the original river valley
- e.g. kingsbridge estuary, devon
explain the formation of fjords
- submerged glacial valleys
- they have steep, cleiff-like valleu sides and the water is uniformly deep
- these were formed when glaciers eroded below sea-level. when the ice melted the valleys were flodoed to form the fjords
- in plan view, fjords tend to have much straigther routes than rias due to the erosive power of the glacier
- they often have a submerged lip at the seaward end where the glacier ended and left a terminal moraine.
- example: milford sound fjord, new zealand
explain the formation of raised beaches
- areas of former wave-cut platforms and their beaches which are left at a higher level than the present coastline
- a flat surface covered by sand or rounded pebbles/boulders
- usually vegeatted by palnt succession
explain the formation of fossil cliffs
- a steep slope found at the back of a raised beach exhibiting evdience of formation through amrine erosion but now above hgih tide level
- they may contain wave-cut notches, caves and arches providing evidence of formation by marine erosion
- episodic nature of isostatic recovery allows marine processes to erode cliffs and deposit beaches when sea levels are stable. relatively rapid drop in sea level then elaves relict coastline abandoned above high tide and some distance inland
what are the micro features of a cliff and how are they formed?
These are small-scale features such as wave-cut notches, caves, stacks or blow holes. They are normally formed through the presence of faults and strata which have a high amount of joints and fissures.
describe how the differential erosion of alternating and contrasting rocks affects the coastline
This leads to a series of different landforms forming along the coastline and differing rates of recession. Higher rates of erosions will lead to the formation of bays whilst areas with more resistant rock will simply see faults and joints. It produces complex cliff profiles through the variety of different rock types. Headlands are likely to coincide with resistant rocks and will be characterised by relatively slow rates of recession.
what are the social impacts of flooding and recession
HARD TO QUANTIFY
- loss of livelihoods
- health and well-being (stress, worry)
- relocation (break up community)
- property insurance does not cover losses from coastal erosion. so there are high costs of relocation (no compensation) and breaks up community
- environmental refugees created
- the Environment Agency estimates that 800 properties will be lost by 2035
what are the economic impacts of flooding and recession
EASY TO QUANTIFY
- loss of property, business
- damage to infrastructure
- loss of farmland
- falling property values
- fall in amenity value
- south devon railway line at Dawlish was destroyed in Feb 2014 by storms (£35 million)
- homeowners on the norfolk coastline have properties now worth £1
- collapse of Holberk Hall Hotel in Scarborough 1993 after 2 months of heavy rainfall. no compensation
what are the environmental impacts of recession and flooding
DIFFICULT TO QUANTIFY
- loss of coastal ecosystems and habitats
- loss of farmland?
- as sea levels rise, salt water will be pushed higher up estuaries and damage fragile ecosystems
what are the social, economic and environmental impacts happening to australia due to coastal flood risk and recession?
social:
- 250,000 homes will be at risk leading to some relocation, breaking up communities
- 75 hospitals and health services are within 200m of the coasline
economic:
- a 1m SLR will expose more than US$162 billion of industrial, commercial, transport and housing infrastructure to flooding and erosion
- a 0.2m SLR would cause US$1.4 billion for SE Queensland
- tourism industrycontributes US$30 billion to GDP, employs 8% of workforce
- expenditure on beach nourishment increase by US$39 a year
- AUS$72 billion of homes at risk
environmental:
- groundwater supplies may be affected by salt intrusion
- great barrier reef and ecosystems like mangrove forests and salt marshes trapped between rising SL and coastal protection measures
- SLR will push salt water further up estuaries, affecting freshwater habitats in Kakadu national park
- coral reefs may not be able to grow fast enough to keep up with SLR, those more than 50m deep will die
what are the social, economic and environmental impacts of coastal flood risk and recession to the Philippines?
social
- in san fernando it is estimated that by 2100, the city will lose 300 buildings , over 283,000 m squared of land and over 123,000 m squared of beach
- social amenity losses of schools, churches and beaches
- up to 2.3 million people could be affected, 63% in manila
economic
- the costs of damage due to SLR expected to be $6.5 billion a year without adaptation costs
- high poverty means they are economically vulnerable (90% of wealth held by 15% of pop)
- in San Fernando property losses to be $2.5 million and land loss of $2.1 million
- loss of fishing jobs, hard to find alternative jobs, estimated welfare lost to the local community of $168,000 a year
environmental
- in manila bay the natural ecosystem of mangroves, corals and seagrass have been damaged by pollution, over-exploitation and siltation, which greatly reduces their ability to protect the backshore from SLR
- rate of SLR is higher than global average because the pacific ocean currents and trade winds move water towards the islands
what are the social, economic and environmental impacts of coastal flood risk and recession on the maldives
social:
- their population of 400,000 is difficult to relocate to mainland countries, they are trying to relocate the residents
- growing amount of environmental refugees having to flee their area due to environmental risks
economic:
- as it is a small country, no one has homeowners insurance and so when their homes are destroyed they will have nothing
- a new artificial island called Hulhumalé has been built from dredging coral and sediment from the seabed between 1997 and 2002 at a cost of US$32 million
- economy based on toursim and fishing and so many jobs are to dissapear
environmental:
- a SLR of 50cm by 2100 would mean the maldives losing 77% of its land area
- very small changes in sea level translate into major losses of land because of the country’s unusual topography
explain environmental refugees
- they are people and communities forced to abandon their homes due to natural processes. these processes may be sudden as with landslides or volcanic eruptions, or gradual such as rising sea levels
- between 2008 and 2013, the philippines had the 3rd largest number of internally displaced people due to natural hazards with 94% of these displacements in 2013- due to ‘storms’
- in 2005, over 1 million people evacuated from New Orleans due to hurricane katrina and went to other places across the USA, 30% did not return and became environmental refugees
- the UK does not include fleeing from climate change as being a refugee but most are to be those fleeing from sea level rise
explain what is happening to the Maldives due to SLR
- in the maldives there is conflict over adaptation to SLR. CUrrently the gov have prioritised protecting the capital city of Malé and its tourismindustrybut is not prioritising smaller communities that rely on traditional industries (farming,fishing)
- mangroves for the future is an organisation that promotes sustainable development and is helping the maldives to become more sustainably managed for the future by:
1) educating communities on the importance of maintaining coastal mangrove swamps as a natural defence against coastal erosion and flooding - the Global Environment Facility (GEF) has provided small grants to islanders to help them develop sustainable and organic farming as an alternative food and income source to coral reef fish (threatened by both overfishing and global warming)
- the Japanese gov have funded mangrove nurseries on the maldives so that damaged mangrove areas can be replanted
explain the shoreline management plan in chittagong, bangladesh and why they are so vulnerable
a coastal climate resilient infrastructure project (2012) supported by the Asian Development Bank (ADB) aims to ‘climate-proof’ the area
this involves:
- improving road connection for farmers and markets whilst raising embankments to 60cm above normal flood levels and making them resilient to CE
- creating new market areas with sheds raised on platforms above the expected 2050 sea level
- constructing, improving or extending 25 tropical cyclone shelters, taking account of SLR and higher wind speeds
- training in climate resilience and adaptation measures
- it was loaned US$60 million by the IFAD and project was rated as satisfactory
- 1.5m rise in sea level would flood 22,000km sqaured and displace 15 million people
- 40% of farmland will be lost (salt water intrusion and directly)
- mangroves dissapearing, reducing protection from surges
- funnelling bay of bengal
what are the positives and negatives and winners and losers of the SMP in chittagong, bangladesh
positives:
- helped alleviate poverty by 10% by generating income opportunities
- reduced disaster risk, road flooding 5 days a year rather than 20
- environmental enhancement through growing trees
negatives:
- disturbance of people and habitats especially during construction
- permanent removal of natural vegetation
- relocation of 200 people by road realignment
- slow progress on road embankments
winners:
farmers, local community seeking jobs
losers:
environmentalists to some extent, community who are relocated, market sellers
explain the problem of coastal flood risk in kiribati
- composed of 33 atolls, low-lying pacific island nation
- most of their 112,000 peole live on tarawa which is only 3m above sea level
- they have already seen some islands sinking
- rising sea surface temps also affetcing coral reegs, these are critical to sustaining atolls and their islands, coral bleaching
- projections that by 2080, the risk of flooding here is likely to be 200x greater than at the start of the century
- without adaptation, kiribati coud lose 34% of its 1998 GDP by 2050 due to SLR and climate change
explain the North Sea storm surges of 1953 and 2013
- 1953 storm and high tides caused a 3m surge at night killing 307 people along the east coast (2100 in the netherlands)
- 20,000 homes flooded and damage estimated at £1.2 billion (our prices), farmland destroyed
- no flood warning or forecasts, basic technology
- 2013 similar event with 5.8m storm surge on Lincolnshire
- only 1400 homes flooded and no deaths, better monitoring to warn people for evacuation, sea defences protected 800,000 homes
- thames barrier protected london
explain the impact of the storm surge of typhoon Haiyan in the Philippines
- cat 5 2013, waves of up to 7m
- economic impact estimated at $5.8 billion
- fishing communities severly affected, sotrm destorying 30k boats and equipment
- 7000 people died, 4 million displaced
- 71,000 hectares of farmland affected
- damage to oil barge led to over 1 million tonnes of oil leaking into the sea
management:
- PAGASA gave warnings two days before, evacuation of 750k people
- emergency shelters put up but not high enough to escape 5m surge
- storm protection shelters destroyed due to poor construction
- rebuilding efforts very slow, not much progress after one year
- gov criticised for poor management (corruption)
explain contemporary sea level rise
- sea levels have fluctuated and since 1850 they have been rising
- the IPCC prediction models suggest that mean sea levels will rise by between 0.45m and 0.74m by 2100 and will continue rising for centuries
- the low emission estimate for sea level change by 2100 is 28-61cm and the high emission estimate is 52-98cm
- global sea levels have risen about 7cm over the past 22 years
why is there debate and how much sea levels will rise?
- unclear about how much temps will rise and so how much thermal expansion there will be
- unclear as to how rapidly the ice sheets will melt. greenland ice sheet is more vulnerbale than antarctic as it is smaller and not as close to the pole
- sea level rise is not equal all over the world
- if greenland was to completely melt, sea level would rise by up to 7m, global warming melts the glaciers, ice caps and ice sheets and thaws permafrost, more water is then added leading to sea level rise
what is thermal expansion?
as seawater heats up by absorbing heat from the atmosphere, its volume expands. the ocean has stored 90% of the increased heat energy of the climate system in recent decades.
what are two things that the IPCC predicts to happen to the seadue to global warming
- wave heights will increase in the arctic ocean as sea ice melts, increasing wave erosion will happen on Arctic coasts
- there will be stormier seas, leading to more destructive waves. this combined with higher sea levels will make it easier to predict that erosion rates and coastal change will increase in the future
why is coastal flood risk becoming an increasingly large problem?
becuase many people have settled at the coast. By 2060, 12% of the world’s population will live in low elevation coastal zones.
flood risk increases in coastal zones thar are experiencing isostatic sinking
what is coastal flood risk?
the likelihood of flooding taking place at the coast
what are the three global factors that influence flood risk
1) eustatic sea level rise- caused by global warming, predicted by IPCC to be between 28 and 98cm by 2100
2) some evidence that global warming will increase wind speeds, wave heights, frequency of storm surges and the magnitude of tropical storms
3) population increase at the coast- by 2060, 12% will live in low elevation coastal zones. this increases demand for water extraction and means more is at risk.
what are the 6 local factors that increase flood risk?
1) dams- they block sediment getting to deltas to replace what is lost by erosion
2) groundwater extraction- can cause subsidience of land at the coast, reduces sediment volume,this is the sudden sinking or gradual downward settling of the ground’s surface
3) isostaticsinking- is causing south eastern Britain to sink
4) shape of the coast (topography)- in the case of the North Sea and the Bay of Bengal, the coast narrowing, acting as a funnel for weather systems, increasing storm surge heights, funnelling effect
5) height- low lying land especially islands (like the Maldives) and deltas are most at risk from sea level rise, temporary flood risk from storm surges and permanent flooding from SLR, archipelagos
6) vegetation removal- the destruction of mangrove forests food wood and charcoal exposes the coast to erosion. mangroves can reduce wave heights by 40%, stabilise sediment
what are depressions?
depressions are areas of low air pressure generating surface winds that spiral into the centre of low pressure in anti-clockwise directions. they occur in mid-latitudes, like the UK.
what is a storm surge?
it is a temporary rise in local sea level produced when a depression, storm or tropical cyclone reaches the coast
explain the formation of a storm surge
1) low pressure weather event (depression) creates a bulge in the sea
2) strong winds drive bluge towards the coast
3) land topography can funnel sea, increasing the height further
4) high tides can also increase height
5) sea rushes onto land as a surge
what is a rotational scar?
A rotational scar is a fresh, curved, unweathered and unvegetated rock surface on the cliff
what is succession?
the changing structure of a plant community overtimes as an intially bare surface is colonised by pioneer species and continues to develop
explain the role of vegetation in stabilising sediment
- vegetation can stabilise unconsolidated sediment and protect it from erosion
1) plant roots bind together, making it harder to erode
2) plant stems and leaves covering the ground surface protect sediment from wave erosion and from tides and currents when exposed at high tide
3) prevent sediment from wind erosion at low tide
4) plant stems interrput the flow of water and wind, encouraging deposition and when the vegetation dies it adds its organic matter (humus) into the soil
what are pioneer plants?
- these are the first plants to colonise freshly deposited sediment
- they being the process of plant succession, during which other species and take over until a balance is reached, the changes allow other species to colonise
- they modify the environment by: stabilising sediment, adding organic matter that retains moisture and reduces evaporation in sand
explain the pioneer plant present in sand dunes: marram grass
- xerophyte
- has extremely long roots which binds the dunetogether, up to 3m long
- it has rhizomes which helps it keep anchored into the ground
- holds the beach together, allows the dune to develop as it builds up dense vegetation
- leaves roll inwards to kepp in moisture
- when it dies out, it adds lots of organic matter in the soil, leading to further plant growth
explain the pioneeer specie in salt marshes: glasswort
- when submerged, plants provide a protective layer so the sediment is not directly exposed to erosion by the tide
- succulent stems to store water, continues to grow
- dead organic matter is added to the sediment and helps to create soil which is less vulenrable than loose sediment
- halophyte as it may be on higher levels, lack water
what are halophytes and xerophytes?
halophytes- salt-tolerant species
xerophytes- drought-resistant species
what is each stage in plant succession called and what si the end stage called?
a seral stage
the end result is called a climax community
what is a sand dune?
an accumulation of sand grains shaped into mounds and ridges by the wind in coastal areas
what is plant succession on a sand dune called?
psammosere
what are the sections of a sand dune called?
embryo dunes
fore dunes
yellow dunes
grey dune
dune slac
mature dunes (climax community)
explain plant succession on a sand dune and given a example of a sand dune
1) there is a plentiful supply of sand, a large area for sand to dry out and onshore winds to that blow sand landwards. sand accumulates to form an embryo dune.
2) pioneer species like marram grass colonise the dune, stabilising it and helps to trap more sand
3) a fore dune develops when enough sand has bee ntrapped an the dune starts to become more stable
4) now an established dune will become more vegetated by marram grass which provides organic matter to the sand and soil to devleop, improving the conditions
5) with soil now developed on the dune, it becomems a grey dune. this is permanent and conditions ar suited to a greater variety of species including heather and gorse
6) between dunes, dune slack develops. wind erosion can deepen them and they may be waterlogged in high tide conditions.
7) furthest inalnd is the climax community. there the soil is fully developed and the dune is fully stabilised and biodiversity is at its highest, trees can grow (birch)
e. g. Studland bay, Dorset
how do the types of plants change during psammosere
at first, the succession starts with halophytic plants capable of growing in salty, bare sand. as they trap more sand it develops into an embryo dune that alters the environmental conditions to one where xerophytic plants can flourish
what is plant succession called on salt marshes
halosere
what are the 4 things that influence sediment transportation?
- the angle of wave attack
- the process of longshore drift
- tides
- currents
how does the angle of wave attack affect sediment transportation ?
This is the main determinant of the direction of sediment transport (in the foreshore zone).
Where the wind is blowing directly onshore, the incoming swash transports the material direction up the beach at 90’ to the coastline.
Backwash then transports sediment perpendicularly back down to the beach to its original starting position.
Sediment is moved up and down the beach, but there is no net lateral movement.
A wave angle30’to the coastline produces the strongest longshore drift movement.
On most coastlines there is a dominant prevailing wind, so over time there is a dominant direction of longshore drift.
how do currents influence sediment transportation?
This is the flow of water in a particular direction, and they can transport sediment in the nearshore and offshore zones.
They can be driven by winds, or initiated by differences in water density, temperature or salinity.
Currents transport sediment over a variety of spatial and temporal scales:
The global thermohaline circulation connects four oceans and takes 500 years for one complete circuit.
Rip currents on the beach transport sediment a few metres out to sea for a few hours when the wind is blowing direcly onshore with the right strength.
how do tides influence sediment transportation?
Tides are changes in sea level produced by the gravitational pull of the moon and the Sun.
The incoming and ebbing tide can create tidal currents in the nearshore and offshore zones that transport sediment.
how do tides work
The Earth’s rotation combined with the gravitational pull of the Moon and Sun causes bulges in the water surface to shift position within each ocean or sea basin.
The tidal bulge in the water surface rotates around a location called a amphidromic point, which is determined by the morphology of the sea bed.
The sea may contain several separate amphidromic points.
Tidal range is the distance between high tide and low tide.
Tidal range is determined by the distance from an amphidromic point (range decreases with distance) and the shape of the coastline.
