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A Century of Natural Disasters – What are the Costs?

Australian folklore from the last two centuries is full of tales of natural disasters. But Australia has changed drastically. The population has vastly grown and our built environment is more complex and dispersed across the landscape. Can we accurately compare the impacts of disasters from more than 100 years ago with more recent events? Bushfire and Natural Hazards CRC research will enable comparisons of natural hazard events, even if they are many years apart.

The research
This article is based on a paper that is a first pass at quantifying the impacts of natural hazards on fatalities and building losses in Australia over the past century. The emphasis is on developing a methodology that allows the effects of societal changes (population and wealth) across time to be taken into consideration. This process, termed ‘normalisation’, effectively estimates the building losses or fatalities from an event as if the event were to impact present-day society, allowing a comparison of the most damaging natural hazard events, even if they occurred decades apart.

The Bushfire and Natural Hazards CRC project, An analysis of building losses and human fatalities from natural disasters, aims to measure and understand the impacts of natural hazards in terms of the toll on human life and the built environment. This examination is a fundamental first step to providing an evidence base for future emergency management policy, practice and resource allocation and to enable efficient and strategic risk-reduction strategies. The analysis underpinning the project will be based on an examination of the historical record of losses caused by natural hazards in Australia since 1900. There are two distinct focuses of the research:

  1. an analysis of building damage, by hazard, across time and by state or territory due to natural hazards
  2. a longitudinal analysis of the social and environmental circumstances in respect of fatalities, injuries and near-misses.

This second aspect will include an examination of trends over time in terms of exposure and vulnerability. It is envisaged these trends will be interpreted in the context of emerging issues (e.g. an ageing population, spatial population shifts and climate change) and how these issues might influence vulnerability and exposure trends in the future.

Key to this project will be the collection of data relating to losses (human and building) from natural disasters, in particular flood, cyclone, bushfire, severe storm, heatwave and earthquake. Some data already exists in the Risk Frontiers PerilAUS database; the objective is to make this dataset as complete as possible.

Image courtesy of Bushfire and Natural Hazards CRC

Image courtesy of Bushfire and Natural Hazards CRC

Database of natural hazards in Australia
The study will use Risk Frontier’s unique database of natural hazard impacts, PerilAUS, which has been compiled over the past 30 years. It is a comprehensive database of natural hazard events in Australia that have caused natural hazards fatalities and/or damage to buildings, agriculture, infrastructure and lifelines. Hazards covered are bushfire, earthquake, flood, windstorm, hailstorm, heatwave, landslide, lightning strike, severe rain, tornado, cyclone and tsunami. All major disasters since 1900 to the end of 2013 are covered, resulting in almost 14,500 individual events.

Where available, data has also been collected on the economic, social and environmental impacts of the event and on the number of people injured, evacuated and/or rendered homeless.

Building losses from natural disasters
Globally, insured losses caused by natural disaster events have increased rapidly in recent years. While the insured real losses are rising, the losses are seen to fluctuate wildly from year to year. Australia is not immune to this. Data from the Insurance Council of Australia’s Historical Disaster Statistics list, see Figure 1, is composed of insurance industry losses from weather-related natural hazards (e.g. hail, floods and cyclones) in Australia since 1967.

The data shows an increasing trend over time – the trend is statistically very significant, and increasing at an annual average rate of $32 million per year.

What might be causing this increase in losses? Over recent years there have been societal changes, for example significant population growth and movements of some of this population to areas susceptible to natural hazards (such as river floodplains and coastal or bushland fringes). Furthermore, with this increase in population has come an increase in wealth in hazard-prone areas – homes are costing more in dollar terms and are getting bigger. The Gold Coast in Queensland is a great example – today’s version is vastly different from the Gold Coast of the 1950s.

These societal changes offer a clue to the increase in insured losses from natural hazards.

But to accurately compare disasters that occurred many decades apart, sometimes more, data must be normalised. This is the process of adjusting historical losses for known societal changes (i.e. numbers of homes, the value of these homes and improvements in building codes and construction).

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After normalisation the loss data shows a different picture (see figure 1). While there is substantial variability across time, there is now no statistically significant upward trend. This result implies that no signal has yet been detected to indicate that insured losses from causes other than societal changes (such as population changes and wealth growth) are increasing.

Major Australian disaster losses in dollar terms
Normalisation allows a comparison of the most damaging natural hazard events, even if they occurred many years apart. After removal of the impact of population and wealth, no single peril dominates or is responsible for most insured building losses – hailstorms (Sydney, 1999), cyclones (Tracy, 1974), earthquakes (Newcastle, 1989), floods (Queensland, 2011) and bushfires (Ash Wednesday, 1983) all feature as the most damaging events in Australia. This means mitigation against natural hazards cannot be limited to one disaster type alone.

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Fatalities from natural hazards
A glimpse at human fatalities caused by natural hazards is revealing.

In a similar vein to building-loss data, an analysis of the number of human fatalities per year should be normalised to take into account population growth. Figure 2 shows fatalities from bushfires, earthquakes, floods, wind gust, hail, landslides, lightning, rain, tornadoes and cyclones in Australia from 1900 to 2010. A line through the raw data on this figure would show no significant trend, i.e. the fatality rate has been constant across time, while a line through the normalised data, Figure 3, shows a highly significant decreasing trend, amounting to around 0.7 deaths per year over the past 110 years. This finding is in line with research on global natural disasters, which indicates human fatalities are either constant or decreasing.

Natural hazard fatalities from 1900 to 2011 are recorded in PerilAUS, and show that more people in Australia have died as a result of extreme heat (4,555, or 55.2%) than from the effects of all other natural hazards combined.

For further information, go to www.bnhcrc.com.au

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Rob Van den Honert is a Bushfire and Natural Hazards CRC researcher from Risk Frontiers.