TROPICAL CYCLONES

AUSTRALIAN NATURAL HAZARD TASK FORCE – INFORMATION KIT
CASE STUDY - TROPICAL CYCLONE LARRY (17th – 21st March 2006)


Approximately ten tropical cyclones form in the Australian region each year. Of these, six are likely to cross the coastline. Tropical cyclones can be very destructive. The intensity (category) of the cyclone can have disastrous effects, both socially and economically on the community and the environment. Being informed is the first step to formulating and implementing management strategies. This is the purpose of our information kit.

Our specific area of study is Tropical Cyclone Larry, affecting 12, 500 sq.km in North Queensland with regions including Cairns, Innisfail, Tully, Cardwell, Babinda and the Atherton Tableland.


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LOCATION MAP.


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NATURAL HAZARD: TROPICAL CYCLONE.

When the forces of nature combine to become destructive, this is described as a natural hazard. These forces may be related to movements of the Earth’s surface (landslides, earth tremors, earthquakes, tsunamis) or relate to weather and climatic factors (drought, flood, heat waves, bushfire, strong winds, storms, tornadoes) - tropical cyclones belong in this climate / weather category.

Tropical cyclones are intense low-pressure systems that form in the band between 5° and 22° N and S of the Equator, over oceans with a water temperature greater than 26.5°C.

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Global distribution of tropical cyclones and the months in which they are most likely to occur.


The warm, moist air over these oceans is heated by the sun and rises into the atmosphere. As the air rises, a LOW pressure system forms and condensation occurs, which releases latent heat, causing the air to rise further into the atmosphere. If the air pressure in the atmosphere is high, then the rising column of warm air will spiral outwards into the upper atmosphere and air will rush from the surface to replace it, forming a tropical cyclone, whose path is often erratic and unpredictable. Australia classifies tropical cyclones into five categories, according to their intensity. (i.e maximum wind gusts and the damage that may incur).

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CASE STUDY: TROPICAL CYCLONE LARRY.

The normal climatic conditions (summer months) for North Queensland coastal regions (and surrounding islands) are:

  • Temperature: 24°C – 33°C
  • Humidity: 70% - 75%
  • Rainfall: 176mm – 434mm
  • Water Temperature: 27.3°C - 29°C
(i.e warm moist conditions that are favorable for the development of tropical storms or cyclones). The Queensland region averages four to five tropical cyclones per year (mostly category 3 or less and most not reaching the coast line).

On the 16th of March 2006 a tropical LOW developed in the northeastern Coral Sea to the south of the Solomon Islands. This intense LOW Pressure system formed an erratic path (south westerly, south easterly, south west and south easterly again). The LOW consolidated and deepened to 995 hpa, and centred approximately 960nm east of Cairns. At this stage this system was officially named Tropical Cyclone Larry by the Brisbane Meteorology Department and a Tropical Cyclone Watch was issued for coastal and island communities between Cape Tirbulation and Proserpine (18th March 2006).

The cyclone continued to intensify as it approached the Queensland coast, fueled by warm ocean temperatures and humid conditions. ‘Larry’ formed a ‘well-defined eye’ that passed Flinders Reef at 79kts. The cyclone eventually crossed the coastline at Innisfail. (17.6 S / 146.2 E) at 6:30am 19/3/2006). The Bureau of Meteorology estimated a peak strength of 915 hpa and winds averaging 115kts. This is category 5 on the Australian scale. On satellite and radar imagery there was a significant increase in the northern ‘eye wall’ as the cyclone reached land at Innisfail, where some of the most severe damage was observed.

The ‘eye wall’ weakened slightly (80 kts) losing moisture and temperature as it moved over land towards the Atherton Tableland and finally losing cyclone status at Iffley Station (19.0 S/141.2 E) inland, south of the Gulf of Carpentaria. The Bureau of Meteorology continued to issue severe weather warnings as the remnant system moved westward causing widespread flooding.

FLOODING AFTER CYCLONE LARRY:
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DROUGHT RIVER SYSTEMS, BEFORE CYCLONE LARRY.


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THE IMPACT OF CYCLONE LARRY:

When a natural hazard hits a community, it is referred to as a natural disaster because of the social, environmental and economic impact it has on the community. The Australian Government declared a natural disaster following the destruction caused by Cyclone Larry, that affected many communities in Queensland’s north east and west. The impact Cyclone Larry had on the community can be divided into the following categories:

  1. Social Impact – Despite the severity of the cyclone and the destruction caused, there were only 30 injuries and no fatalities. The worst affected communities, in terms of damage to property, were those closest to the eye wall of the cyclone as it crossed the coast line (Innisfail, Babinda, Silkwood). More than 1000 buildings were damaged, many of which were beyond repair. Homes and many community structures were damaged (schools, hospitals, supermarkets). Contemporary buildings withstood the impact while older buildings sustained the most damage.
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The remains of Innisfail High School after it was hit by Cyclone Larry.

Many people were left homeless and psychologically traumatized. Safety, shelter, food and clothing became the first priority. Water supplies were disrupted and more than 120,000 homes lost power during the cyclone. Many areas were without electricity for several days. (This also interrupted banking and therefore people could not access money to buy food and clothing). Flooding, as a result of the torrential rain, left many communities isolated. Road and rail transport was also disrupted. Many livelihoods were lost (farming, local business) placing more stress on families. Counselling facilities were organized. Some farmers / growers decided to “walk off the land”. Forecasts of another cyclone in the region (Cyclone Monica) added to the community’s anxiety.

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CHART 1


2. Economic Impact – Initial estimates of the financial losses from Cyclone Larry were $350 million and included 'clean up' costs ($ 10 million), rebuilding houses, business and infrastructure, and disaster relief funding. However lost agricultural production ($300 million) as well as insured costs ($250 million) increased this figure closer to $1.5 billion. Loss of agricultural production and an increase in insurance payouts led to an increase in costs for all Australians.

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The region’s agricultural and horticultural industry was devastated – 90% of banana production was wiped out in the Tully area (near Innisfail), the centre of Australian banana production (Australian Banana Growers Council). Australia’s banana crop is disease free and imports are not allowed. Banana prices in Australia rose 300% !

Sugar cane plantations were also devastated. Australia is the third largest exporter of raw sugar in the world and harvests were reduced by 50%. North Queensland is one of Australia’s largest avocado production areas (80% of fruit in the market). Cyclone Larry hit the Queensland coast in the middle of harvest and an estimated $15 million of the crop was lost (North Queensland Agricultural Council). Macadamia plantations were uprooted (10yrs per tree for fruiting maturity) and tropical fruit plantations (mango, paw paw) were devastated and many livelihoods destroyed.

Including the destruction of crops, many farmers reported damage to farm machinery, sheds, fences, and loss of live stock. State forests were also uprooted and timber production severely affected. Economic estimation is difficult as it does not take into account the value of the trees or crops and the loss of future production, employment.

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CHART 2


3. Environmental Impact
– The impact of Cyclone Larry was significant on the human environment (buildings, infrastructure, and livelihood) and created many hazardous safety issues (risk of fatality, injury, disease). Cyclone Larry also impacted greatly on the natural environment, affecting many ecosystems and resulting in a significant loss of biodiversity:-

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CHART 3


a) Signs of ‘Larry’s’ impact on the Great Barrier Reef (World Heritage) included damage to underlying reef structure, broken and dislodged corals and movement of coral rubble and debris. Most reefs showed breakage in approximately 20% of the corals present (Great Barrier Reef Marine Park Authority). It was predicted that the affected reef would recover when the water quality improved and with management of Crown of Thorns Starfish outbreaks on renewing coral.

b) Coastal vegetation suffered severe damage with trees broken and stripped of leaves, and erosion of sand dunes. Coastal urbanisation has affected the density of natural vegetation and its resilience to cyclones.

c) It was fortunate that Cyclone Larry hit the North Queensland coast on a “neap” tide (a less than average tide occurring at the first and third quarters of the moon) therefore reducing some of the impact of the cyclone’s storm surge i.e coastal erosion, flooding and salt inundation.

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COASTAL STORM DAMAGE


d) The storm surge and associated rain from Cyclone Larry did not result in unmanageable flooding in coastal regions. HHHowever, torrential rains as ‘Larry’ moved inland flooded rivers and surrounding areas. These areas had previously been in drought and the vegetation along the rivers and streams (riparian vegetation) was washed away. Following Cyclone Larry there was evidence of deep soil erosion. Water quality was poor and many fish were found dead along the river banks their gills filled with mud. Reports of increased numbers of snakes, crocodiles and cane toads were reported further inland.

e) In the North Queensland Wet Tropic region, topography plays an important role in the impact of cyclones on native and tropical rainforests. Cyclone Larry’s destructive winds caused most regional damage on the windward side. The lee-side provided some refuge for fauna while nearby areas recovered. In areas affected by the eye-wall of the cyclone, spiraling winds destroyed forests on the lee and windward sides.

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CYCLONE LARRY - QLD COAST (PINK LINE) SATELLITE IMAGE


f) Thirty per cent of North Queensland’s Wet Tropic Heritage area was destroyed by Cyclone Larry. There was wide spread defoliation of rainforest canopy trees, removal of vines and epiphytes, and tree falls. This mainly occurred where rainforests were “fragmented” by urban and agricultural development. These areas were particularly vulnerable to ‘Larry’s’ destructive winds due to their high forest edge to area ratio. Forest microclimates in the understory were now exposed to an increase in light, temperature and lower humidity. These conditions allow the intrusion of pervasive weeds and non-native plants.

g) Following Cyclone Larry, leaf-eating marsupial numbers were stable due to the rich amount of vegetation from fallen trees. The numbers then declined as the native forests, grasslands and rainforests adjusted to regenerating. Fruit-eating bird numbers declined as a result of the devastation of fruiting tropical trees. Seed dispersal rate also declined. There was a significant decline in the Cassowary population (35%) due to displacement and then direct deaths (road kill).

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CASSOWARY


h) The “fragmented’ rainforests of the Queensland coast and Atherton Tablelands provided natural habitats for rare and endangered species such as Cassowaries, Mahogany Gliders and tree-kangaroos. A lack of effective corridors between areas of larger rainforests and the destroyed rainforests ‘fragments’ gave these animals fewer recovery options.

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MANAGEMENT OF CYCLONE LARRY / SUSTAINABLE STRATEGIES.

In hazard prone areas individuals, community groups and governments need to prepare for cyclone events. Much has been learnt form previous cyclone experiences. (eg Cyclone Tracy 1974, Darwin, category 4, Cyclone Winifred 1986, North Queensland, category 3). Accurate reporting, management and planning of each event helps educate us to deal more effectively with future events and limit their impact.

Education is the first step to formulating and implementing management strategies. Groups such as Emergency Management Australia (E.M.A), The Queensland Government State Disaster Group and the State Emergency Services (S.E.S) produce brochures and run community work shops to ensure that people are well prepared in the event of a cyclone. Active citizenship (eg joining local disaster management groups) is a positive step to raising awareness in cyclone prone communities. The social impact of a cyclone can be significantly reduced if each household takes on the responsibility of having a “cyclone plan”. Such a plan should include preparing your home (particularly between the months of November and April), checking insurance policies, having an emergency kit, an evacuation plan, knowing where the evacuation centres are and staying informed of all cyclone warnings and evacuations orders.

Geographers study natural hazards so that they can predict when and where they are likely to occur, in the hope that communities can be better prepared to deal with extreme natural forces such as cyclones. Early prediction can significantly reduce the impact of a cyclone on a community. Meteorologists tracked Cyclone Larry’s erratic path using satellite imagery and the application of Geographic Information Systems (G.I.S) at cyclone warning centres (Brisbane, Darwin, and Perth).

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The Queensland Government acted on this information from the Bureau of Meteorology and initiated cyclone warning systems in advance to prepare the community for the onslaught of tropical cyclone Larry. The community heeded these warnings (learning from Cyclone Tracy, where many individuals did not take the warnings seriously – possibly because it was Christmas day). The airports and ports were closed and boats secured and evacuation centres were established (eg. Innisfail TAFE, Silkwood School, Mission Beach Primary). Farmers were advised to move stock to higher ground. and the community advised to implement their cyclone plan.

Early emergency response and relief is also a sustainable strategy that can reduce the impact of a natural hazard. The Federal Minister for Emergency Services activated the Commonwealth Natural Disaster Relief Arrangements (N.D.R.A) and the Emergency Management Australia (E.M.A) Co-ordination Centre to assist the Queensland Government to respond and recover from cyclone Larry.

Short term relief, (3,800 personnel - Emergency Support Units, Australian Defence Force, Red Cross) and long term response efforts (Australian Government Disaster relief for families, business and industry) were co-ordination by General Peter Cosgrove.

Well supervised ‘clean up’ program strategies (S.E.S) reduce the chance of further injury or fatality (eg electrocution from submerged power lines, asbestos contamination from building debris).

To reduce the severity of impact of future cyclones, future buildings and homes should comply to ‘cyclone proof’ specifications. Programs to educate designers, builders and building certifiers should be implemented. Existing infrastructure should be inspected regularly. Sustainable urban planning, protecting the coastline and associated vegetation, would lessen the impact of a storm surge and associated flooding, by providing a natural buffer.

The evaluation of natural disasters, (eg: Cyclone Larry) helps better prepare communities for future events. Recommendations from reports (eg CSIRO and James Cook University on far North Queensland Natural Resource Management) allow us to develop strategies to better manage a cyclone’s impact: ‘cyclone resilient’ agricultural techniques (eg: grassed inter-rows in banana plantations) would limit the number of crops destroyed.

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DEVIATATED BANANA PLANTATION


Restoring healthy, native vegetation along the river regions would reduce erosion and help act as natural barrier to flooding.


Investing in natural resource management would limit the fragmentation of tropical rainforests by monitoring / restricting urban and agricultural development. Weed control programs, while rainforests recover, post Cyclone Larry, would help restore the region’s natural habitat.

Climate change has a direct effect on the occurrence and severity of cyclones. Each individual, each business and industry should adopt strategies to limit their greenhouse gas emissions.


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REFERENCES:

Van Zuylen, Sue , Glyn Trethewy, and Helen McIlsaac. Geography Focus Stage Five. 2. Pearson Education Australia, 2008. Prin
Bureau of Meteorology www.bom.gov.au/cyclone/index.shtml
Emergency Management Australia www.ema.gove.au/

Queensland Department of Emergency Services –open recovery www.operationrecovery.qld.au/
Queensland Government State Disaster Management Group www.didaster.qld.gov.au/
Australian Government Disaster Assist www.didasterassist.gov.au
Department of Primary Industries and fisheries www.dip.qld.gov.au
Great Barrier Reef Marine Park Authority - www.gbrmpa.gov.au

Atlas Updates - www.hi.com.au/atlasNet/updates