Hurricanes

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  • Created by: Gabzay
  • Created on: 26-04-13 16:49
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  • Hurricanes
    • HURRICANE KATRINA, AUGUST 2005
      • Impacts
        • Infrastructure
          • Communications infrastructure failed - telephones, mobiles, Internet access and local TV stations did not work
          • Most major roads into, and out of, New Orleans were damaged
          • Levees and floodwalls protecting New Orleans were breached
          • 80% of the city was under water when the levees broke
          • 1.7 million people lost electricity across Mississippi and Louisiana
          • Extensive damage to buildings
        • Economic effects
          • Many left unemployed - no one was paid, or spent any money, so  government could not collect taxes
          • Total economic impact of Hurricane Katrina was $150 billion
          • Affected importation and production of oil and natural gas
            • Oil and petrol prices rose
        • Social effects
          • 1464 people died in Louisiana; many bodies not recovered for days
          • 80% of population evacuated but 20% did not have the means to leave
          • 1 million people were made homeless
          • Lack of sanitation led to health concerns
          • 600,000 pets were killed or left without shelter
          • In the immediate aftermath of the hurricane, looting and civil disturbance became serious problems
      • Causes
        • Global warming
          • Hurricanes are becoming more intense because of rising sea temperatures
          • Global warming causes sea temperatures to rise
        • Wetlands disappearing
          • Wetlands provide a barrier which can absorb the energy of storm surges at the rate of 0.3m per 2.7 miles when hurricanes hit the coast
          • Provide protection for places inland
        • Levees and  floodwalls
          • Poor design, faulty construction and poor maintenance were all possible causes of the failures
        • Widespread building of levees, engineering works along the Mississippi and gas from below the delta has speeded up the removal of the wetlands
        • Hurricane activity fluctuates naturally
        • It is only since 1970 that observations have been taken of hurricane intensity
        • Difficult to separate human-induced climate change from natural variability
    • WHAT ARE HURRICANES
      • Very similar to typhoons and cyclones
      • Intense, destructive, low-pressure weather systems
      • Very strong sustained winds of over 120 km/h and torrential rain (250 mm can fall in one day)
      • Hurricanes tend to develop...
        • ...over warm, tropical oceans, where sea temperatures are at least 27 degrees
        • ...in late summer and early autumn when temperatures are at their highest
        • ...in the trade wind belt between latitudes 5 degrees and 20 degrees either side of the equator
        • ...where there is low atmospheric shear
      • Hurricanes are named to improve communication
      • Hurricanes are measured by using a Saffir-Simpson scale  which rates the intensity of hurricane from 1-5
      • How hurricanes form
        • A strong upward movement of air draws water vapour up from the ocean
        • As the air rises, it spirals, cools and condenses - releasing huge amounts of heat energy, which powers the storm
        • Colder air sinks down through the centre of the hurricane to form the eye
        • When the hurricane reaches land - and its source of heat energy and moisture disappears - it rapidly decreases in strength
    • MANAGING HURRICANES
      • Defending New Orleans
        • Temporary floodgates and pumps at canal entrances to prevent storm surges from breaking flood defences
        • Build a system of weirs to regulate the flow of the Mississippi River Gulf Outlet
        • Build a system of 8.5 metre high levees to the east and north of the city
      • Managing the risk
        • Hurricane watch - announce that specific coastal areas could experience hurricane conditions within 36 hours
        • Hurricane warning - warn that certain coastal areas can expect sustained winds of at least 119 km/h within 24 hours
        • Making people more aware of how vulnerable they are, and what actions they should take
          • National Hurricane Centre run a Hurricane Preparedness Week every year
          • Hurricane simulation programme in schools to help students learn how to plan, prepare for and deal with the aftermath of a hurricane
        • Evacuation
          • Difficult and expensive
          • Not everyone can afford to leave
          • Notice of a hurricane does not give enough time for proper evacuation measures

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