FEATURE ARTICLE 3: UNDERSTANDING NATURAL HAZARD IMPACTS ON AUSTRALIA

The article was contributed by Miriam Middelmann, Research Scientist, Australian Government Agency Geoscience Australia.

Natural hazards are a global phenomenon that can strike without warning throughout the world, and impact on every Australian state and territory.

Rapid onset natural hazards including bushfires, tropical cyclones, earthquakes, floods, landslides, severe storms, and tsunami threaten lives and damage private and public assets as well as disrupt water, power, transport, and communication services. These hazards and their associated impacts can also seriously affect employment and incomes to industry, agriculture, commerce and public administration.

The impact of natural hazards on both the natural and human environments has been recorded since European arrival through diary entries, newspaper articles and anecdotal accounts. Oral history, Aboriginal Dreaming stories and the geological record also provide some evidence of natural hazards and their impacts in Australia.

In Australia, natural hazards are estimated to cost an average of $1.14 billion (b) annually (BTE 2001) but the cost of individual hazards can be much greater. For example, in 1989 an earthquake cost the community in the New South Wales city of Newcastle an estimated $4.5b.

Australia experiences a range of meteorological and geological hazards. Some natural hazards occur only in certain climatic, geological or topographic regions, while others have a high potential of occurring anywhere on the Australian continent.

Natural hazards have impacted on people since humans first walked on the Earth. They have influenced, shaped and modified human behaviour, changing the way people live with and respond to the environment. In Australia alone, billions of dollars have been spent in trying to mitigate or prevent, prepare for, respond to and recover from natural disasters. Moreover, natural disasters have resulted in enormous intangible losses, causing grief through the loss of life and personal possessions.

Natural disasters have helped to shape Australia’s history. Notable examples include Cyclone Mahina (1899), Cyclone Tracy (1974), the Sydney hailstorm (1999) and the floods in New South Wales (1955) and south-east Queensland (1974). Other examples include the Newcastle earthquake (1989) and the Thredbo landslide (1997) in New South Wales, and bushfires such as Black Friday (1939), Black Tuesday (1967), Ash Wednesday (1983) or the Canberra bushfires (2003). The article Natural disasters in Australia outlines the impact of each of these and other natural disasters that have occurred since the late-19th century.

Smaller events which affect fewer people or are less severe, but occur more frequently, emphasise that the risk posed to the Australian community by natural hazards is real. Two recent smaller events declared natural disasters were Cyclone Larry (2006) and the storms and floods in the Hunter and central coast regions of New South Wales (2007).

Australians have a long history of responding to disasters and can be proud of their successes in managing natural hazards through mitigation. However, recent natural disasters serve as a reminder that there is much more to be done to reduce the risk to communities and minimise losses.

As Australia’s population and living density continue to grow, so does the potential impact of a natural disaster upon the Australian community. Increasing numbers of people, buildings and infrastructure assets are being exposed to natural hazards as the pressures for urban development extend into hazardous areas.

Accurately modelling the likely impacts of natural hazards on communities provides decision makers with the tools to make more informed decisions aimed at reducing the impact of natural hazards. Natural hazards cannot be averted, but their consequences can be minimised by implementing mitigation strategies and reducing the potential impact to areas which are most vulnerable.

Natural hazards and their impacts are briefly described in the following paragraphs and further information may be found in a recent publication on natural hazards (Middelmann 2007), on which this article is based.


Tropical cyclones

Tropical cyclones can cause major impacts over a significantly large area and have affected Australians since the earliest days of settlement. Tropical cyclones develop over the warm oceans to Australia’s north and can produce destructive winds, torrential rains, storm tides, and phenomenal seas. As they move inland and to the south, tropical cyclones lose contact with the warm tropical oceans necessary to sustain them and weaken. Weakening storms can still cause major impacts and may adversely affect southern regions as they interact with other weather systems. Some of the rainfall can be beneficial to agricultural communities, who rely on rain from decaying tropical systems.

Tropical cyclones have caused over 2,100 deaths in Australia since 1839 (Blong 2005). The average annual cost of tropical cyclones is estimated at $266 million (m), accounting for a quarter of the cost of natural disasters (BTE 2001). As tropical cyclones occur seasonally, with the majority occurring between December and April, this enables media advertising campaigns aimed at raising the community’s awareness to target the lead-up of each tropical cyclone season.


Floods

Australia has long been called the land of droughts and flooding rains (MacKellar 1911), with La Niña periods experiencing more floods on average than El Niño years. Heavy rainfall in Australia can cause both riverine floods and flash floods. While floods are estimated to be the most costly natural disasters in Australia, their impact is not always negative as floods are a part of a natural cycle and can have significant environmental and social benefits particularly in areas which have suffered a long drought.

Records of flood impacts extend back further than those for many other hazards, with the first recorded death in 1790 (Blong 2005). Since then, there have been over 2,300 recorded fatalities in Australia. The estimated average annual cost of floods in Australia is $314m (BTE 2001). While vulnerability is increased through the development of floodplains, the potential to reduce the impact by effective management of this risk is higher than for any other hazard, as floods are restricted to definable areas.


Severe storms

Severe storms occur more frequently than any other natural hazard and have the potential to occur anywhere in Australia. They can range from isolated thunderstorms that affect only a few square kilometres, to intense low pressure systems that may affect thousands of square kilometres. They can be associated with tropical cyclones and be a substantial contributor to flooding. Severe storms produce storm tides, lightning and thunder, hail, tornadoes, water spouts, damaging winds and flash floods.

Severe storms have been estimated to cost Australia about $284m per annum (BTE 2001), representing just over a quarter of the average annual cost of natural disasters in Australia. Storm damage is a significant issue for the insurance industry with payouts for severe storm damage being greater than payouts for tropical cyclones, earthquakes, floods or bushfires. Thunderstorms have killed over 770 people since 1824 (Blong 2005), while large-scale storms often cause deaths through flooding or shipwrecks. Severe weather warnings play a vital role in reducing the risk of this hazard.


Bushfires

Bushfires are an intrinsic part of Australia’s environment. Natural ecosystems have evolved with fire, and the landscapes and their biological diversity have been shaped by and rely on patterns of fire. This has led to the concept that there are both good and bad bushfires. Bushfires originate from both natural sources such as lightning and from human activity (prescribed, accidental or arson).

Bushfires pose a threat in nearly all parts of the country at different times of the year. They pose an estimated annual average cost of about $77m (BTE 2001), and have claimed nearly 700 lives since 1850 (Blong 2005). Indigenous Australians have long used fire as a land management tool. Since European settlement, fire has been both feared and harnessed. It remains one of the most iconic natural disasters in Australia while also being harnessed to clear land for agriculture and, more recently, as a means of reducing risk to property from intense, uncontrolled fires.


Landslides

Landslides regularly impact localised areas such as buildings, and transport and communications infrastructure across Australia. They pose a serious threat to people and property, particularly when they occur suddenly and without warning. Common types of landslides include rockfalls, debris flows and deep seated landslides. Landslides in Australia are predominantly triggered by an increase in pore water pressure from intense short duration or prolonged rainfall, with about half being influenced by human activity.

The average annual damage reported is significantly lower than many other hazards, at $1.2m (BTE 2001). Indeed, only one landslide event, the Thredbo landslide in 1999, made the minimum threshold of $10,000 to be included in the Bureau of Transport Economics Report (BTE) (2001) report. Since 1842 there have been at least 95 reported deaths from landslides (Blong 2005).


Earthquakes

Australia is a tectonically stable region with few earthquakes of any consequence in any given year. The relative rarity of large earthquakes ensures that earthquakes are not prominent in the public consciousness. However, the 1989 Newcastle, the 1968 Meckering and 1954 Adelaide earthquakes clearly demonstrated that moderate sized earthquakes have the potential to tragically affect Australian communities.

The average annual loss due to moderate sized earthquakes is estimated to be around $145m (BTE 2001). However, most of this damage can be attributed to a single event - the 1989 Newcastle earthquake which left 13 people dead and 160 injured. Since 1902, there have been 16 earthquake-related deaths (Blong 2005).


Tsunami

The risk posed by tsunami to Australia was brought to the forefront following the devastation from an earthquake of magnitude 9.2 that occurred off the west coast of northern Sumatra (Indonesia) on 26 December 2004 causing a tsunami that tragically inundated much of the Indian Ocean coastline. While the overall risk from tsunami to the Australian population is lower than it is for many parts of the world, tsunami have affected Australia (PMSEIC 2005) but fortunately without any loss to life. The article Tsunami risk to Australia in the Water, land and air chapter provides more information.

To date the average annual cost of tsunami to the Australian community has not been calculated, but anecdotal evidence suggests that the cost so far has been small, with minor damage to ports, beach-side campsites and the loss of small boats.


Role of warnings in reducing loss of life

Some natural hazards, such as tropical cyclones, floods and tsunami, can often be detected hours or days before they impact upon a community. Other hazards, such as earthquake, can impact suddenly and without warning. The opportunity for emergency services to activate an emergency response plan and for residents to react to a warning is important, because it influences disaster losses. The Australian Tsunami Warning System provides approximately 90 minutes warning prior to a tsunami reaching the Australian coastline. Although short, this warning time provides emergency services with an opportunity to reduce the loss of life and damage caused by the event.

It is believed that the decrease in natural disaster fatalities in Australia (relative to population) is testament to successful disaster mitigation strategies during the 1800s that focused on reducing loss of life. Because of this early success, the focus of disaster mitigation has expanded to now include the reduction of economic loss. More recently adopted strategies include improvements in warning systems, emergency services, land use planning, communication, education and the development of building codes, and a greater understanding of the characteristics and impacts of natural hazards.


Conclusion

Natural disasters have a significant economic, social, environmental and political impact on the community. While some of the impacts of natural disasters can be mitigated, the risk cannot be completely eliminated. Therefore, decisions regarding what risks are acceptable need to be made by those involved in managing natural hazard impacts.

Tropical cyclones, floods, severe storms and bushfires and the phenomena that they produce have had by far the greatest impact historically in Australia. However, a single event, such as a moderate earthquake in Sydney, could change the historical picture of natural hazards. It is for this reason modelling potential impacts for a full range of small through to extreme events, and considering the potential impacts of climate change, is important.

Risk reduction strategies are generally confined to three areas of activity: emergency management, land use planning and construction standards. In order for these to be successful, it is vital that those who play a role in the management of natural hazards work closely with the wider community, as well as with each other.


References

Blong, R (2005) ‘Natural hazards risk assessment - An Australian perspective’. Issues in Risk Science 4, Benfield Hazard Research Centre, London, p. 28
BTE (2001) Economic Costs of Natural Disasters in Australia, Bureau of Transport Economics Report 103, Canberra
COAG (2004) Natural Disasters in Australia: Reforming mitigation, relief and recovery arrangements. A report to the Council of Australian Governments by a high level officials' group, August 2002, Department of Transport and Regional Services, Canberra
EMA (2004) Emergency Risk Management Applications Guide, Manual 5, Emergency Management Australia, Canberra
Mackellar, D (1911) 'My country', The Closed Door and Other Verses, Australasian Authors' Agency, Melbourne, pp. 9-11
Middelmann, M H (Editor) (2007) Natural Hazards in Australia. Identifying Risk Analysis Requirements, Geoscience Australia, Canberra
PMSEIC report: Tsunamis: Does Anyone Have to Die? Report of the Working Group on Tsunamis to the Prime Minister’s Science, Engineering and Innovation Council, 2 December 2005, <http://www.dest.gov.au/ sectors/science_innovation/science_agencies_committees/prime_ministers_science_ engineering_innovation_council/meetings/ fourteenth.htm>

03/04/2008 Note: This page has been amended to ensure the correct spelling of the contributing author's surname.