Dead Man Zone
The Dead Man Zone is defined as the area directly around a bushfire that is likely to burn within five minutes given the current wind conditions or an anticipated change in wind direction. The distance this zone extends from the firefront is highly dependent on terrain, windspeed, fuel type and composition, relative humidity and ambient temperature, and can range from under 100 m to well over 1 km.
The term "Dead Man Zone" was coined by members of the CSIRO research team in Australia who were investigating the spread of bushfires (Project Vesta). Project Vesta, headed by scientist Phil Cheney, found that when the wind changes direction, the line of fire will move out at its maximum rate of spread almost immediately, and that that speed was nearly 3 times what was previously thought. Project Vesta's research into bushfire behaviour makes up the majority of what we know about bushfire today.
The initial results are of critical practical importance. They include:
- Traditional tables of forest fire behaviour, which have been in use for guiding fire management decisions since the mid 1960, were found to under-predict the potential rate of fire spread in dry forests at higher wind speeds by a factor of up to 3-fold. This information is critical to decision-making during situations of high fire danger.
- Lines of fire longer than 100 m and aligned perpendicular to the prevailing wind, while taking time to build up flame dimensions, reach the potential rate of spread immediately. This finding has important implications for fire-fighter safety (inasmuch as the so-called Dead Man Zone then manifests), and has already been incorporated into national training programs.
- A new relationship between the wind speed and the rate of fire spread has been described and this will provide more reliable extrapolation to the very high wind speeds experienced during extreme weather.
- A method has been developed for describing fuel structure that is robust and easy for field operators to apply to a range of different fuel types, and which is effective for predicting fire behaviour and relative suppression difficulty.
- The temperature structure of a flame front, an important variable for fire prediction purposes, has been analysed and described.
- A statistical measure of the variation of the wind structure within a forest, describing the error associated with a prediction of fire spread that is caused by wind variability alone, has been developed. Such error determinations are crucial for risk assessment during decision-making.
Quoted from the CSIRO website: http://www.ffp.csiro.au/RC-BushfireBehaviour.asp
Outcomes from project Vesta have been integrated into fire fighter training in Australia, and are beginning to appear in the U.S.A. as well.
Firefighters will try to stay out of the dead man zone at all times, working from safe points such as burnt ground or a large area of non-burnable ground, i.e. an oval or large car park. This is achieved by attacking the fire from the flanks, or the rear, so that burnt ground is always nearby, and the fire is always in front of the firefighters. (Were they to attack fires at the head of the fire, they risk having spot fires start behind them. They would also risk changes in wind behaviour accelerating the spread of the fire.)
The result of several inquiries into firefighter death in Australian Bushfires found that fire fighters should stay out of the Dead Man Zone, and that they should always keep 250 litres of water in their truck for personal safety. This is now a standard operating procedure in the Country Fire Service and Country Fire Authority.
- Country Fire Service (South Australia)
- Country Fire Authority (Victoria, Australia)
- New South Wales Rural Fire Service (Australia)
- Ash Wednesday fires
- List of disasters in Australia by death toll
|This article does not cite any references or sources. (September 2007)|