Understanding the environmental circumstances that lead to loss of life in bushfires
The safety of people in communities exposed to bushfires is influenced by their awareness, preparedness, responses and decision making, and by warning systems. In Australia, the existing Fire Danger Rating System is based on the McArthur Forest Fire Danger Index (FFDI).
The FFDI relates the expected fire behaviour and rate of spread in common fuel types in eastern Australia to the large-scale weather conditions. It was originally developed to inform fire suppression activities, but its use has been extended to include a much broader range of applications including community warnings.
The 2009 Victorian Bushfire Royal Commission recommended significant improvements to risk communication, education and warnings. The recommendations resulted in a review of the fire danger rating system and the development of the National Framework for Scaled Advice and Warnings to the Community.
The implementation of this new warning framework also triggered a review process to undertake a major evaluation of the current National Fire Danger Rating system. While there have been studies on fatalities behaviour during bushfire, this review process identified the need to improve our understanding of the environmental circumstances that lead to life loss in bushfires.
A comprehensive bushfire fatality database
Between 1901 and 2011 there have been 260 bushfires in Australia associated with a total of 825 known civilian and firefighter fatalities. We used data on bushfire-related life loss over this period to develop the Life Loss database. This database is the most comprehensive data set of its kind, linking information about loss of life in bushfires with environmental factors including:
- Location – was the person sheltering in a building, sheltering in a vehicle, or out in the open?
- Fire weather – what was the forest fire danger index (FFDI)?
- Proximity to fuel – how far away was the nearest forested land?
- Activity and decision making – were the victims sheltering, defending their properties or attempting to leave?
Fuel and fire weather
Our analysis of the database suggests that fire weather (as represented by the FFDI) and proximity to fuel are strongly related to loss of life in a bushfire: over three-quarters of all fatalities occurred within 30 m of the forest and half of all fatalities occurred on days with an FFDI greater than 100 (the current threshold for declaring a day as ‘catastrophic’).
Civilian fatalities were dominated by several iconic bushfires that have occurred under very severe weather conditions. The fatalities from Australia's 10 worst bushfire days accounted for 64 per cent of all civilian fatalities.
Location, activity and decision making
We also found that 58 per cent of fatal bushfire exposures occurred out in the open while leaving early or defending a property and 28 per cent inside buildings.
When bushfires occurred in weather conditions with an FFDI value greater than 100, over 75 per cent of all fatalities occurred within buildings. These are associated with people dying while attempting to shelter, mainly in their place of residence. When the FFDI is lower, more people are caught outside while defending their properties. The number of fatalities where people sheltered inside a building rose from 6 per cent for the time period 1901–1965, to 40 per cent for 1965–2011.
Male and female civilian fatalities within structures were evenly represented, while male fatalities out in the open were approximately three times greater.
Most civilian fatalities (82 per cent) occurred close to or within their homes, with 82 per cent of the ‘in structure’ fatalities being in their place of residence, and 61 per cent of other fatalities were with 100m of their residence. Of the fatalities which occurred inside structure in a location that was specifically known, 41 per cent occurred in rooms with reduced visibility to the outside conditions (mainly bathroom).
The better understanding of the location of fatalities within structures raises several questions in relation to egress, sheltering and the rate of loss of tenability of houses.
Safer bushfire strategies
The national ‘Prepare. Act. Survive.’ strategy, adopted after the 2009 Victorian bushfires, stresses the safer option of leaving early, and the dangers and significant level of preparation needed for successful defence.
The message highlights the importance of preparation well ahead of the fire, the need to take action on the forecast daily fire danger rating, and stresses the importance of contingency planning and alternative options if the fire or personal circumstances prevent planned preparations and actions.
This strategy asks residents to evaluate the risk in the event of a bushfire and decide on the appropriate response, but it is only effective if residents fully understand the risks they are facing and the implications of their decisions and actions.
Our findings will help the responsible agencies to provide better warnings and information to the public, and to develop policies, programs and advice that will increase community safety during bushfires.