AQA Geography

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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)

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

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

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

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

• 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

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

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

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

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

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