Extreme Weather - Geography AS

Notes on AS Geography for Edexcel. 
Unit 2, topic 1 - Extreme Weather. 

If there is anything else you think I should include, please let me know. I haven't included much about fieldwork and research because everyone does different case studies.

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  • Created by: Laura
  • Created on: 08-05-12 17:34


Characteristics (Summer):

  • No clouds
  • High ground temperatures
  • Potential heat wave
  • High pressure
  • Dry conditions
  • Light wind

Characteristics (Winter):

  • Cloudless skies
  • Cold temperatures
  • Frost
  • Fog
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Extreme Weather and it's Impacts - 1

Warmer temperatures with more frequent hot days and nights, fewer cold days and nights.

Agriculture, Forestry, Ecosystems

Increased yield in colder areas; decreased yield in warmer areas.

Water Resources

Possible decline in water supplies

Human Health

Fewer deaths caused by cold

Industry, Settlement, Society

Energy used for cooling instead of heating; declining air quality in cities.

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Extreme Weather and It's Impacts - 2

Increase in warm spells/heat waves

Agriculture, Forestry, Ecosystems

Decreased yield in warmer regions; increased risk of forest fires

Water Resources

Increased water demand; water quality problems

Human Health

Increased risk of heat-related deaths among old, sick, very young and poor

Industry, Settlement, Society

Reduced quality of life for people without appropriate housing

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Extreme Weather and It's Impacts - 3

Heavy precipitation events; frequency increases in most areas

Agriculture, Forestry, Ecosystems

Damage to crops; soil erosion; water-logged soils can't be used

Water Resources

Adverse affects on water quality; contamination of water supply

Human Health

Increased risk of death, injury or illness

Industry, Settlement, Society

Disruption of settlements, business and transport due to flooding; loss of property

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Extreme Weather and It's Impacts - 4

Area affected by drought increases

Agriculture, Forestry, Ecosystems

Land degradation; lower crop yield/failure; increased livestock deaths; increased risk of fire

Water Resources

More widespread water stress

Human Health

Increased risk of: food and water shortage; malnutrition; water- and food-borne diseases

Industry, Settlement, Society

Water shortages for settlements, industries; reduced HEP potential; increase in migration

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Extreme Weather and It's Impacts - 5

Intense tropical cyclone (hurricane) activity increases

Agriculture, Forestry, Ecosystems

Damage to crops, trees and coral reefs

Water Resources

Power cuts cause disruption of water supply

Human Health

Increased risk of deaths, injuries, water- and food-borne diseases

Industry, Settlement, Society

Disruption by flood and high winds; loss of property; withdrawal of insurance cover; possible migration

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Boscastle 2007 - Causes

  • Heavy downpours
  • High vulnerability
  • Land already saturated
  • 300x normal amount of rain
  • 200mm rain in 24 hours
  • End of jet stream, had changed course
  • Low pressure system (depression)
  • Ulley reservoir burst
  • Steep, small catchment area
  • Flash flooding
  • Urbanisation
  • Large depression
  • Urbanisation
  • Diversion of West Lynn River
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Boscastle 2007 - Effects


  • 165 000 households affected; 58 properties flooded
  • 1 000 residents and visitors affected
  • Raw sewage contaminated flood water and raised health concerns


  • Damage to infrastructure
  • Cars swept away
  • Footbridges and stone bridge parapets washed away


  • £2 million of damage


  • Trees uprooted
  • Contaminated water
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Boscastle 2007 - Flood Management

Plans to demolish the bridge and rebuild it further downstream to reduce the risk of it becoming blocked and therefore reducing the chance of flooding in the lower part of the river.

River bed of the Valency is lowered so it's bankfull capacity is greater.Upstream of the car park, a wide braided channel was created to slow the river and encourage the deposition of sediment upstream, decreasing the risk of flooding in the river.

Height of the car park is being increased and barriers put to stop vehicles being washed into the river

A large culvert was laid that would carry excess water away after heavy rainfall. Completed in 2005 and can carry twice the amount of water as the old one.

The key players are the environment agency, local authorities, police, fire services. Outline why they are key players and what they do. Use page 147.

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Flooding Research/Fieldwork - IMPACT

  • How much money claimed from insurance companies e.g. Aviva
  • How impacted different people by interviewing/questionnaires
  • Talk to business owners about losses
  • Comparison to previous floods
  • Impact on services - talk to local council/service providers
  • Speak to registrar about deaths to see how many people died
  • Analysis of newspapers e.g. daily mail/telegraph
  • Environment agency - environmental impact
  • Flicr.com for blog analysis

Examiners like specific examples of where you could get research from so it is important to have a few in your head.

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Flood Hydrograph Labelled Diagram (http://www.google.co.uk/imgres?imgurl=http://cgz.e2bn.net/e2bn/leas/c99/schools/cgz/accounts/staff/rchambers/GeoBytes%2520GCSE%2520Blog%2520Resources/Images/Rivers/Flood_Hydrograph.gif&imgrefurl=http://geobytesgcse.blogspot.com/2006/11/hydrographs-and-river-discharge.html&h=378&w=491&sz=9&tbnid=Adzy3h0LzHgjcM:&tbnh=90&tbnw=117&zoom=1&docid=8hq0Kh14l0rNAM&hl=en&sa=X&ei=oWWpT6CSCKKR0AWuq5jtAw&sqi=2&ved=0CGwQ9QEwAA&dur=373)

Things that affect the hydrograph:

  • Precipitation type (e.g. snow/rainfall)
  • Shape of drainage basin
  • Length of rainfall
  • Deforestation
  • Urbanisation
  • Rock type
  • Steepness of basin
  • Size of drainage basin
  • Infiltration rate
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General Flood Management Techniques


  • Dams
  • Embankments
  • Flood Walls
  • Channelising the river
  • Flood storage reservoirs
  • Flood relief channels
  • Barriers
  • Weirs, sluices and pumping stations


  • Insurance
  • Land use zoning
  • Afforestation
  • Warning Systems

For each technique, outline how it prevents/lessens flooding and it's impacts.

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El Niño

What Happens

There is low pressure in South America, causing heavy rain.

There is high pressure in Australia, causing droughts.

The Humboldt current has ceased because the water has warmed so much, so no cold water is sucked up. The winds which change round divert the water so it travels from Australia to South America.

Why it Happens

The high pressure system pushes the sea water to the East due to the blocking high. This can't go west due to an Australian mountain range

Unfortunately, geographers still don't know exactly why there is El Niño and La Niña.

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Australia Drought 2007 - Agricultural Impacts

Short Term

  • Irrigation allocation to some farms was cut
  • The 2008 vintage wine year crippled with 40% of grapes picked this year.
  • Harvests were decimated
  • Farmers and small businesses receive support from Australian drought assistance programme

Mid Term

  • Annual crops were not planted as there wasn't enough water
  • Non-essential crops weren't allowed water so died.

Long Term

  • Farm incomes sank, farmers with debt for years after
  • Soil erosion
  • Took years for wine companies to invest in Australian grapes again
  • Takes 4-5 years for trees to be replanted and bear fruit.
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Australia Drought 2007 - Environmental Impacts

Short Term

  • HEP production reduced as reservoirs fell below required levels

Mid Term

  • More pollution due to less HEP production as resort to gas to create power
  • Loss of vegetation and wetland wildlife in the Murray Darling Basin
  • Bushfires and dust storms caused havoc to neighboring wildlife
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Australia Drought 2007 - Social Impacts

Short Term

  • Rural suicide rate soared
  • 4 minute showers were the max, and a ban on washing cars enforced.
  • Local services such as schools and shops closed as people weren't there to support them
  • Water restrictions in all major Australian cities

Mid Term

  • Tourism decreased and Alpine areas noticed a reduction of 80% of visitors in 2007.

Long Term

  • Declining water quality as pollutants become more concentrated
  • New South Wales became a ghost town
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Australia Drought 2007 - Economic Impacts

Short Term

  • Price of food soared as people had to buy more as food became imported at a higher cost
  • 60% of businesses in Victoria suffered a loss of earnings in 2007

Mid Term

The drought wiped 1% off the Australian economy

Long Term

Energy and water prices soared.

Using the last 4 slides on the impacts of the Australian drought, analyse whether you think this was an agricultural, environmental, social or economic disaster and explain why.

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Australia Drought 2007 - Management Ideas [1]

Farming Technologies

  • Drought tolerant plats
  • Crop and pasture management
  • Precision farming
  • GPS used for accurate sowing of seed
  • Sustainable farming

'Drysdale' yields 5% more than other varieties in dry conditions. Conservation of water and sustainable management reduces water loss and soil erosion

Independent farmers may not have the money to change crops and get new technology 

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Australia Drought 2007 - Management Ideas [2]

Large Scale Water Project

  • Construction of an embankment to divide the lake into 2 parts 
  • Deepen the outlet channel to access more water from deepest part of lake
  • Creation of 2 wetlands

Improves efficiency of existing scheme. Reduces evaporation. Improves quality of water. Keeps waterbird breeding areas.

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Australia Drought 2007 - The Plan

  • Modernising Irrigation Methods
  • Addressing over-allocation in the MDB
  • Reforming the management of the MDB
  • Upgrading water information
  • Northern Australia
  • Great Artesian Basin

For each of the above points, write everything you know about why it is needed and the action that is being taken.

You can check this on page 165 of the Edexcel textbook for AS geography with the fish on the front.

Using a named extreme weather event, evaluate the use of technology over other approaches to manage the issue. [10]

For this question, you could use the Australian drought.

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Australia Drought 2007 - The Murray Darling Basin

  • Give the Murray Darling Basin Authority (MDBA) full control of the basin
  • A new lower cap on amount of water extracted from basin
  • Provision for critical human needs. Allow South Australia to store water upstream in reservoirs
  • Continued setting of annual water allocation by states
  • National government to invest up to $1 billion to reduce water loss caused by inefficient irrigation techniques and leaks
  • The first ever direct purchase of water for the environment by the government.

For each of the points, explain what they will mean and evaluate whether you think they are a good idea.#

e.g. for the first point:
Reduces confluct and leads to intergrated management accountable to all users equally.
This is a sensible and very necessary thing to do socially, economically and environmentally.

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Locations Susceptible to Drought

Tropical High Pressure Zones
Low rainfalls since the air warms as it descends. Results in atmospheric moisture evaporating leaving few clouds and little rain. e.g. Sahara and Arabian deserts 

Mid-Continental Areas
Low rainfalls due to their distance from moist oceanic air. e.g. Gobi desert 

Lee Coast Deserts
Where the prevaling winds across a continent bring dry interior air over the coast. e.g. Kalahari desert 

Rainshadow Deserts
Found where dry air descends in the lee of a mountain range. e.g. Atacama desert 

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Conditions For a Hurricane to Form:

  • Sea temperature at 27 degrees C at a depth of up to 60m - summer and autumn
  • Between 5 and 20 degrees either side of the equator where trade winds can spiral into a storm due to the coriolis effect.
  • Low atmospheric shear.

Stages to Hurricane Development

  • Strong upward movement of air draws water vapour upwards from the ocean
  • Air spirals as it rises, cools and condenses releasing huge amounts of heat energy that powers the storm
  • Colder air sinks down through the centre of the hurricane to form the eye.
  • When the hurricane reaches land it's source of energy disappears, so it decreases in strength.
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Hurricane Katrina 2005 - Impacts on New Orleans

  • Looters. Smash and grab culture
  • At least 100 dead
  • 90% buildings destroyed
  • 80% covered in water
  • Many people trapped
  • Levees breached
  • Water polluted by sewage
  • Rich, white people left and poor, black people stayed
  • Roads destroyed
  • No phones or communication
  • Businesses destroyed
  • Insurance increased
  • Jobs lost
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Hurricane Katrina 2005 - Causes and Track

One of the reasons why hurricane Katrina was so devastating was that people didn't know it was coming. The hurricane passed across Florida where they were tracking it, but the communications between Florida and New Orleans was bad.

Some of the reasons it wasn't expected to pass over New Orleans was:

  • It goes overland twice, which is rare. This meant it was able to repower when it was oversea.
  • It had a very high wind speed so travelled quickly.
  • There were 2 days between Florida and New Orleans

2 days is enough time to warn people the hurricane is coming and get them out. Evaluate whether you think the cause could be human, and to what extent this would be.

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Former Member


really good, thanks

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