AQA Geography

Rivers, Glaciation, Population, Health

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  • Created by: alex
  • Created on: 23-05-12 19:43

Rivers

Drainage Basin Cycle:

  • open system - inputs and outputs
  • inputs - energy from sun, precipitation
  • outputs - evapotranspiration, percolation, runoff
  • stores - glaciers, rivers, lakes, vegetation, soil and permeable rocks
  • transfers - throughfall, stemflow, infiltration, groundwater flow

Factors affecting a hydrograph:

  • slope angle
  • temperature
  • land use - urbanisation
  • vegetation
  • intensity and duration of the storm
  • geology - impermeable/permeable
  • size and shape of drainage basin
  • antecedant rainfall
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Rivers

drainage basin discharge = precipitation-evapotranspiration+/- storage change

A hydrograph is a means of showing the discharge of a river at a given point over a short period of time

Factors affecting discharge:

  • Basin size, shape and relief - small reach river quicker
  • Types of precip - prolongued and snowfall
  • Temp - restrict infiltration and increase surface runoff and evapotranspiration
  • Land use - vegetation, urbanisation
  • Rock type
  • Soil type - sandy allows infiltration, clays increase runoff
  • Drainage density - surface streams and flash floods
  • Tides and storm surges
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Rivers

Channel processes:

  • Hydraulic action - force of water
  • Abrasion - rubbing action of rocks
  • Attrition - rocks/boulders colliding
  • Corrosion - acids dissolve rocks

Total energy for erosion depends on:

  • mass (weight) of water- more mass more energy
  • height of river above base level - potential energy
  • steepness of channel - speed and kinetic energy

Influence of velocity on turbulence:

  • higher speed - higher turbulence
  • where there is a lot of turbulence, eddies form turbulent flow
  • where there is little turbulence there is laminar flow
  • highest velocity is lower course of the river
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Rivers

Velocity is influenced by:

1. Channel shape

  • Hydraulic radius = cross sectional area/ wetted perimeter
  • greater hydraulic radius the more efficient - greater velocity

2. Roughness of the channel bed

  • angular rocks increase friction and reduces velocity

3. Channel slope

Hjulstrom found:

  • clays are more cohesive so are entrained at higher velocities than sands
  • particles are carried at lower velocities required to entrain
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Rivers

Influences on spatial variations in load:

  • drainage density
  • relief - high altitudes lots of erosional energy
  • rock type - e.g. limestone carried in solution
  • precipitation - low = low loads
  • human activity - dams trap sediment, fertilisers

Drainage density:

  • densities are generally high in Cornwall - reflection of impermeable granite of area, more liable to 'flashy' response to rainfall

Processes of river transportation:

  • traction - boulders rolled along river bed
  • saltation - particles bounced along bed
  • suspension - carried in the water even at low discharge
  • solution - minerals dissolved in the water
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Rivers

Capacity - total volume of load, when velocity doubles increases by 8X

Competance - diameter of largest particle, if velocity doubles increases by 64X

River Landforms:

  • Potholes - eddying when energy high, not strong enough traction, water forms hollow
  • Rapids - sudden increase in slope of channel or gently dipping harder bands of rock, as water becomes more turbulent erosive power increases
  • Floodplain - fine silts deposited during periods of high discharge
  • Levees - sediment built up on banks, thickest and coarsest deposited first
  • Terraces - former floodplain, vertical erosion
  • Bluffs - edges of floodplain
  • Riffles - low flows deposit sediments, water flows inefficiently around it
  • Pools - at times of high flow, areas between riffles are eroded
  • Meanders - water around riffle, helicoidal flows material deposited on inside (point bar) centripetal force outer concave bank created (cut bank)
  • Deltas - as hits standing body of water, topset, forset, bottomset
  • Braided streams - fluctuations in discharge, high channel gradient abundant sediment
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Rivers

Rejuvination:

  • attempting to reach dynamic equilibrium
  • due to isostatic (land) and eustatic (sea) change
  • water has further to fall and more erosive power,
  • begins nearest sea and erodes back upstream - knickpoints
  • slope, waterfalls, steps, incised meanders, terraces

Rejuvination:

  • near Hartland point, Cornwall-Devon border, Strawberry water
  • River Greta, Lake District, Breezley Falls knickpoint

Incised meanders:

  • Entrenched - symmetrical cross-section, very rapid incision by river
  • Ingrown - less rapid incision by river, allowing lateral erosion assymetrical
  • entrenched, Durham, River Wear
  • ingrown, River Wye
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River

Lynmouth 1952:

  • antecedent rainfall on exmoor causing saturation
  • tributaries of East and West Lyn rivers - flood surge to town at mouth
  • flood prevention walls made worse, bridges
  • 34 deaths
  • large pebble delta at mouth of River Lyn

Causes of flooding (exceeding bankfull discharge):

  • snowmelt
  • little vegetation
  • heavy, prolongued or antecedant rainfall
  • steep valley sides
  • small river basin
  • low evapotranspiration
  • impermeable rock
  • coastal storms
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Rivers

Impacts of flooding depends on:

  • level of precipitation at location
  • amount of warning
  • level of economic development
  • size and scale of flood
  • resources available

Flood management attempts to reduce:

  • frequency of flooding
  • magnitude of flooding

Hard engineering

  • Dams and weirs, reservoirs, retention basins and temporary storage
  • channel improvements,
  • diversion channels, sluice gates, dredging
  • offering protection through engineering
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Rivers

River basin management:

  • naturalisation, wetlands,
  • flood abatement - afforestation, contour ploughing
  • flood proofing
  • flood plain zoning
  • flood prediction and warning

Soft engineering:

  • the somerset levels, series of flood plans conflict in 60s and 70s, six SSSI

Hard engineering:

  • River Tone, Japan - levees, concrete walls, tetrapods, did not work
  • Aswan dam - river levels remain steady, navigable, allows double cropping, 20% lost through seepage and evaporation, no more silt, fertilisers needed, declining fishing at mouth
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Rivers

Bangladesh 1998:

  • 3/4 underwater
  • 1000 died, 1 million refugees
  • 30 million affected
  • due to 3 rivers, Brahmaputra, Ganges confluence, monsoons, 1 metre above sea level, 80% on river floodplain
  • response - 7 dams, improve forecasts and afforestation in Nepal

Carlisle 2005:

  • confluence of river eden and 73% runoff
  • 3 died, communications affected, urbanisation had increased, geology
  • response - river management, upstream storage, flood defences, levees

Dam projects have displaced up to 80 million people worldwide

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Glaciers

Theories of climate change:

  • milankovitch cycles - orbital theory
  • eruption theory
  • sunspot theory
  • trapping of CO2 by oceans
  • changes to oceans currents

Ice ages get colder due to reflectivity (albedo) of ice

From snow to glacier ice:

  • Snow -> fim (one winter and one summer) -> ice

Sequence of conversion stages:

  • settling of snow
  • nivation - annual and diurnal temp causes repeated freeze thaw
  • sintering - fusion and squeezing of air from ice as a result of compression
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Glaciers

Distant past:

  • Pleistocene period ended 10,000 years ago
  • we are in Holocene epoch of quaternary period

Finding out about the distant past:

  • dendrology (trees)
  • glacial landforms
  • ice cone samples
  • fossils

Glaciers, an open system:

  • inputs - snowfall, avalanches, wind blowing snow
  • outputs - calving ice burgs, sublimination, ablation, moraine deposits
  • storage - glacier itself
  • transfers - ice moving, meltwater

Ice budget - fastest velocity/movement of ice is at equilibrium line

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Glaciers

Movement of ice:

  • Internal deformation - realigning orientating ice crystals
  • Regelation - (refreezing) under pressure melting and refreezing
  • Creep - pressure causes ice to be more plastic in behaviour
  • Extensional - pulling away from up valley ice
  • Compressional - upper valley ice pushing against down valley ice
  • Rotational flow

Crevasse - a deep v-shaped cleft formed in the upper brittle part of a glacier due to ice undergoing extension

Serac - a tower of unstable ice that forms between crevasses commonly in ice falls or other regions of accellerated glacier flow

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Glaciers

Erosional landforms:

  • cirques
  • aretes
  • pyramidal peaks
  • glacial troughs
  • rock steps - caused by extensional flow and more resistant rock
  • fjords
  • truncated spurs - from interglacial periods
  • roche moutonnees - formed by plucking from regelation
  • rock drumlins - more streamlined bedrock
  • crag and tail - larger mass of resistant and less resistant rock
  • striations - angular debris may cause scratches and grooves
  • hanging valleys

Lambert glacier, Antarctica is the worlds largest glacier

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Glaciers

Examples:

  • Snowdonia, snowdon (pyramidal), Crib Goch arete, Glaslyn corrie, cwm dyli hanging valley, nant froncon valley roche,
  • ribbon lake - wastwater, Lake district
  • arete - striding edge, lake district
  • Chiles fjords - pantagonia,

Glacial depositional landforms:

  • Till - unsorted
  • fluvioglacial material - sorted by meltwater
  • erratics - different geology to bedrock, Big Rock, Alberta, Canada, different strata
  • moraines - lateral, medial, ground (sub glacial), recessional, terminal
  • drumlins - deposits which are then smoothed over
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Glaciers

Fluvioglacial landforms:

  • outwash plains
  • braided streams
  • kettle holes - ice covered by outwash and kames, distinctive topography
  • kames - d shaped delta like deposits
  • kame terraces - walls of glacier
  • varves - winter finer darker calibre sediments
  • proglacial lakes
  • eskers - subglacial streams sorted material

Periglacial:

  • permafrost - ground permanetly frozen, can be up to 600 m deep
  • frost heave - formation of ice lenses, heave stones upwards, causes patterned ground, stone polygons, stone stripes
  • pingo - open system free water pushed up by hydraulic pressure and refreezes, closed system groundwater trapped by freezing from above and permafrost beneath from talik.
  • ice wedge polygons
  • solifluction and solifluction lobes -  due to active layer
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Glaciers

Old Crow flats:

  • Tundra, once proglacial lake
  • continous permafrost
  • limited ecosystem, low biodiversity
  • lichen only grow at 1-2mm per year, takes 40 years to recover from caribou
  • 'people of the lakes' - Vintut Gwitchin
  • the people rely on caribou - traditional hunting methods
  • 1002 lands for oil propesition
  • pipeline built on stilts as compromise, support pylons in active layer, sliding shoes, suspension bridges, crosses mountain ranges, major oil spill likely, crosses earthquake belt.

Antartica/Southern Ocean:

  • limited species, keystone species disrupted, takes up to 50 years to return to original state if disrupted, contains minerals
  • Antarctic treaty - 12 nations, protects world UNESCO site
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Population

TFR - replacement level is 2.1

51 MEDC's have fewer than 2.1

47 LEDC's have 5 children or more

Niger has highest TFR in world (8)

Irans TFR went from 6.7, 1986 to 2.4 in 2004

Why do birth rates decline?

  • education
  • later marriage
  • availablility of contraception
  • reduction in maternal, infant and child mortality
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Population

Indicators of changes in population:

  • infant mortality
  • GDP per capita
  • Life expectancy

Russia - pro natalist policies

  • collapse of soviet union, standard of living fell, recovery from stalinist russia
  • low life expectancy, excessive alcohol and smoking
  • demographic policy 2008-2025, increase life expectancy and health, migration policy

TFR - total fertility rate varies due to:

  • death rates
  • traditional demands and cultural expectations
  • education of women
  • social class
  • political influences (population policies)
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Population

Mortality rate varies due to:

  • infant mortality
  • medical infrastructure and economic development
  • spread of disease

Advantages of DTM

  • shows change through time, identifies processes of population change
  • many countries went through stages
  • new industrialise North Korea, detailed structure of how countries developed

Disadvantages of DTM

  • not relevant for non industrialised
  • stage 2 skipped as healthcare imported into colonised countries
  • stage 3 held back by attitudes to family size etc
  • doesn't take into account policies
  • HIV/AIDS - south Africa - stage 1
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Population

DTM:

  • stage 1 - high fluctuating - e.g. rainforest tribes, Ethiopia
  • stage 2 - early expanding - e.g. Kenya
  • stage 3 - late expanding - e.g. cuba
  • stage 4 - low fluctuating - e.g. Japan

Ghana and TFR:

  • 1994 - TFR 5.5, govt. plan to reduce to 3.0 by 2020
  • 2008 - TFR 4
  • rural areas - birth control and family planning low
  • high fertility - misinformation about contraception
  • not many legal abortions - sexual violence not treated as an offence
  • modern contraceptives and medical facilities often treated with mistrust
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Population

Ageing population:

  • soon 1 in 3 will be over 60
  • social impact - health, housing
  • economic - pensions/retirement, taxes
  • political - 'grey vote'
  • solutions - incomes of retired fall/workers incomes pay to pensions/people retire later

Cost of migration on host country:

  • educating migrants children
  • segregation
  • calls for control on immigration
  • over dependance of some industries on migrant labour e.g. construction, UK
  • dominance of male workers reinforced
  • pressure on resources
  • aspects of cultural identity lost
  • remittance payments
  • discrimination and fundamentalism
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Population

Benefits of migration on host countries:

  • gains skilled cheap labour
  • take up less desirable jobs
  • 'skills gap' filled
  • creation of multi-ethnic society
  • influx of new local services
  • growth of ethnic retailing and areas associated with ethnic food outlets e.g. 'curry mile' manchester
  • new languages, cultures introduced
  • boost local economy e.g. housing

Migration - slough

  • local economy booming, property prices rising, schools and hospitals working well
  • O2 and celltech would go outside the UK if it could not get staff needed
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Population

  • Thomas Malthus  - 'an essay on the principle of population' 1798
  • population grows exponentially
  • food supply increases arithemetically
  • said there would be a Malthusian catastrophe, Malthus checks
  • positive checks and preventative checks
  • evidence -population explosion, 800 million are chronically malnourished
  • critics - development of technology, 'green revolution'

Esther Boserup - 'conditions of Agricultural Growth' 1910-1999

  • people have resources of knowledge and technology to increase food supply as neccessary
  • evidence - move from 'slash and burn'

China one child policy

  • infanticide,
  • little emperor syndrome
  • elderly dependant population but did reduce population
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Population

The effect of urban growth:

  • slums
  • illegal squatter settlements
  • favelas
  • shanty towns
  • transport issue
  • pollution
  • unemployment
  • crime

Sao Paulo:

  • developed without planning
  • 5% of population live in favelas
  • PCC terrorist attacks in 2006
  • underground limited, 2007 crater killed 7
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Population

Lognor rural decline and regeneration:

  • Integrated rural development (IRD) projects - intorduced business and tourism (grants for young farmers)
  • rural development comission (RDC) grants - for single shops in isolated villages

The census:

  • taken every ten years
  • first taken in 1801
  • who doesn't get counted - students, those on holiday, homeless, soldiers, illegal immigrants, prisoneers, shippers, travellers
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Health

Types of indicators:

  • mortality (deaths)
  • morbidity (illness)
  • general well being

Top three causes of death:

  • MEDC - CHD, stroke, lung cancer
  • LEDC - lower respiratory infections, CHD, diarrhoeal diseases

Factors affecting health:

  • sanitation, sewage
  • availability of food and diet
  • healthcare
  • poverty
  • education (female)
  • state and society/civil breakdown
  • gender
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Health

Malaria:

  • kills about 3 million each year
  • 300 million affected worldwide
  • 90% of those with Malaria live in Sub Saharan Africa

Distribution of HIV is uneven:

  • cost of treatment and availability
  • contraception and awareness
  • status of women
  • religion
  • female genital mutilation
  • nutrition and poor sanitation
  • prevention programmes
  • denial
  • education
  • stigma
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Health

Diseases of affluence:

  • type 2 diabetes
  • depression
  • CHD
  • obesity
  • some forms of cancer
  • alcholism

Factors associated with the increase:

  • use of car
  • less excercise
  • accessability to large amounts of low cost foods
  • more high fat and high sugar foods in diet
  • processed foods
  • increased leisure time
  • spare income
  • greater consumption of alcohol and tabacco
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Comments

AlekWalsh22

hey girls....

Michael Warranger speaking

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