Hazards case studies Flashcards
Black Saturday (dates, location)
- NW Australia
- Feb 2009
- Australias worst bushfire disaster
Impacts of Black Saturday
- 173 deaths
- 3,500 properties destroyed
- 450 ha burnt (forest loss)
- 7,000 displaced people from homes
- Losses of agriculture inc. cattle, sheep and horses, loss of standing crops
- large areas of natural parks along with the wildlife (RSPCA estimated over 1 million perished during fires)
- Electricity supplies disrupted
- Looting of empty properties reported
- Cost= $4.4 billion- largest component was insurance
Causes of the wildfires of black Saturday
- Eucalyptus forests cover Victoria which have an oil rich foliage which easily burns
- The summer climate often features periods where the temperates are over 40c with low humidity and the state also suffers from period droughts (produces tinder try vegetation and it will only take a spark to set off a major fire.
- Area is also susceptible to huge winds blowing out of Australias interior which can fan and spread fires
- Power cables into rural areas (they can produce the spark that starts a fire)
- rural depopulation (less rural services meaning it is more difficult to fight the fires when they occur)
Responses to the wildfire of black Saturday
- In Oct 2009 it was announced that a new fire hazard system would replace the one existing before the fires.. A new fire system would replace the one existing before the fire.
- Everyday during the fire system the Bureau of meteoroligy would forecast an outlook for the fire danger index by considering the predicted weather inc. temperature, humidity, wind speeds and dry mass of vegetation. On the highest risk days residents would be advised to leave the potentially affected areas
- New building regulations for bushfire- prone areas were fast tracked by the government. As part of an on-going debate, the government also urged by experts to ban housing in the highest risk areas. (the gov. recieved criticism for allowing rebuilding in Maryville which had been 90% destroyed by the event.
Background to the fires (black saturday)
- Late Jan 2009 an exceptional heatwave affected he south-eastern parts of Australia. The configuration of the pressure systems also meant that the hot tropical air was directed towards that area.
- On 7th Feb, hot, north westerly winds of over 100km hit the state causing a low hurricane
- sources: lightening strikes, sparks from falling power cables, sparks from power tools and machinery (in some cases the fires being deliberately started with arson
Earthquakes- Christchurch summary
- 22nd Februrary 2011
- There was no deaths after an earthquake of 7.1 on the 4th September 2010.
- Chrustchurch in the Canterbury region of South Island experienced an aftershock from an earthquake that had happened several months earlier. After short-term emergency action the New Zealand government launched a a plan called blueprint to help the city recover from the catastrophe
- Most deaths were caused by the collapse of 2 office blocks.
What were the impacts of the earthquake in Christchurch?
- The old city centre core was made virtually unstable, with 40% of the buildings damaged beyond repair. Some of them including the Canterbury TV building collapsing completely
- 185 people were killed and 6,000 injured
- Economic damage was estimated to be over $20 billion. $10 billion was set aside to completely redevelop the city
- Secondary impacts: landslides, particularly around Lyttelton. Further away a large chunk of the Tasman Glacier calved into the sea
- The Rugby world cup was moving to other locations further affecting the future economic influence of the city.
What was the cost of damage in Christchurch equal to?
20% of New Zealands GDP.
Explain a secondary effect of Christchurch
Liquefaction of soil- producing around 400,000 tonnes of silt. This was a massive natural disaster
What were the short term responses to Christchurch’s aftershock?
- Army treated the injured, retrieved the dead and provided food, water and electricity,
- Companies sent generators and tankers of water
- Power and water supplies were restored to most house holds within two weeks
- Sewerage systems were so damaged that households put up emergency latrines
- Community laundries and portable shower units were set up.
What was ‘the blueprint’?
- run by New Zealand’s central government.
- consists of a number of projects lasting 20 years forming a compact CBD.
Describe the features Blueprint comprises of
- A frame for the CBD made up of two strips of open space, east and south, combined with a corridor along the River avon
- anchor projects including a conference centre, hospitals, libraries, and a redeveloped Cathedral square
- a light rail network, walkways and cycle lanes providing links
- precincts for health, arts and entertainment, retail and the justice and emergency centre.
4 years after the earthquake in Christchurch what were the conditions like?
Still signs of rebuilding:
- cranes on the skyline
- landmarks like the cathedral were slowly decaying because its future was undecided
- empty houses
- road diversions
- wasteland
- demolition sites
What were the immediate consequences of the blueprint?
- commercial areas developing outside the CBD
- wealth being transferred
- heritage buildings being demolished
- population declining
- inequality increasing
What is a tropical storm?
a localized, very intense low-pressure wind system, forming over tropical oceans and with winds of hurricane force.
What are the characteristics of a tropical storm?
- known as a cyclone (India)
- hurricane (North Atlantic)
- typhoon (south-east Asia)
- they can extent 500km in diameter
What are the average winds caused by a tropical storm?
-in excess of 120km/h
What is the eye wall?
-the bank of cloud that rings the central eye
How are oceans important in affecting the distribution of tropical storms?
1.) Oceans-tropical storms derive their moisture (through the transfer process of evaporation) and energy (in the form of latent heat) from the oceans: there are clear links with the water cycle. This explains why tropical storms form and continue to develop over ocean areas and then peter out on reaching land
How are high temperatures important in affecting the distribution of tropical storms?
- a sea surface temperature in excess of 26 degrees is required for formation of tropical storms
- this is why they are formed in low lattitudes during the summer, when temperatures are at their highest
How is atmospheric instability important in affecting the distribution of tropical storms?
-tropical storms are most likely to form in regions of intense atmospheric instability, where warm air is being forced to rise. The ITCZ where two limbs of the Hadley cell converge to form low pressure on the ground, is perfect for spawning ground for Tropical storms.
How is rotation of the earth important in affecting the distribution of tropical storms?
- a certain amount of ‘spin’ is needed to initiate the rotating motion of a tropical storm
- the influence of the Earths rotation on surface phenomena is called the Coriolis effect. This increases with distance away from the Equator and expplains why tropical storms do not usually form in the region between 5 degrees n and 5 degrees s (close to the equator)
How does uniform wind direction at all levels affect the distribution of tropical storms?
-winds from different directions at altitude prevent a tropical storm from attaining height and intensity. The vertical development is effectively ‘sheared off’ by the multi directional winds.
How does a tropical storm form?
- warm moist air rises rapidly in its centre to be replaced by air drawn in at the surface
- a central vortex will develop as more and more air is drawn in and rises.
- the very centre of the storm (the eye) is often characterised by a column of dry, sinking air.
- as the air rises, it rapidly cools. This leads to condensation and the formation of towering cumulonimbus clouds.
- sometimes a number of isolated thunderstorms will coalesce to form a single giant storm
- when condensation occurs latent heat is released which effectively powers the storm
- a tropical storm will continue to grow and develop as it is driven by the prevailing winds across the oceans. Only when it reaches land and the supply of energy and moisture is cut off the storm will start to decay, it it moves back over the ocean it will become reinvigorated
What are the hazards associated with tropical storms?
- strong winds
- storm surges
- coastal and river flooding
- landslides
How do strong winds caused by a tropical storm cause a hazard?
- average speeds in excess of 120km/h, although gusts of over 250 km/h have been recorded at eye wall
- tearing off roofs, breaking windows and damaging communication networks
- debris forms flying missiles
- damaged power lines often lead to widespread electricity cuts and occasionally fires
- debris on the road can cause transport disruption