by Heath Fitzsimmons
BUSHFIRE MANAGEMENT OFFICER
When considering the bush fire risk faced by a home it is most important to consider three major methods of bush fire attack; flame contact, radiant heat and ember attack. Direct ignition from radiant heat or flame contact accounts for less than 15% of the houses lost to bush fire, while the overwhelming majority (approximately 85%) of losses are due primarily to ember attack. The three bush fire attack methods also have a cumulative effect, with houses exposed simultaneously to ember attack and radiant heat or flame contact at greatest risk.
The threat posed by radiant heat and flame contact is very effectively reduced by establishing an Asset Protection Zone (APZ), i.e. increasing the separation distance between buildings and bush fire prone vegetation. The separation distance required ranges from 10m-100m depending on slope, vegetation type, and the nature of the asset. Where appropriate separation distances can be accommodated within private property boundaries it is the responsibility of private property owners to manage these areas. Councils, NSW National Parks & Wildlife Service and other public land managers maintain APZs on public land in some locations.
It is important to note that even the largest APZ provides a negligible reduction in the risk posed by ember attack and the only effective way to increase a home’s resilience to ember attack is through upgrading and effectively maintaining the building and immediate surrounding area. It is also critical that people living in bush fire prone areas recognise that there can be no guarantee that even buildings constructed to the absolute highest standards will be defendable or able to provide a safe refuge during a bush fire, and often the only safe option is to leave early, before a fire even starts. No buildings are designed to withstand a bush fire during Catastrophic Fire Danger Rating conditions, and many older buildings and subdivisions were not designed to withstand bush fire at even the lower Fire Danger Ratings.
Hazard reduction burning is an important aspect of an effective bush fire risk management plan, but does not provide long term protection from the threat of bush fire on its own. Rather, it is intended to complement other bush fire protection measures such as ember protection and APZs. More specifically, the purpose of hazard reduction burning is to:
A range of environmental considerations must be taken into account when planning hazard reduction activities, and for information on this see Guidelines for Ecologically Sustainable Fire Management and Bush Fire Environmental Assessment Code. A key concept of these guidelines is that of an appropriate fire interval – the minimum and maximum length of time between fires that is necessary to maintain ecosystem functions. Recommended fire intervals vary depending on vegetation type, with the minimum intervals ranging from 2 years for grassland to 25 or 30 years for wet eucalypt forests, depending on the location.
The final critical component of an effective bush fire risk management plan is community engagement; land managers and fire agencies actively engaging with individuals and communities to assist in increasing the resilience of their homes and neighbourhoods to extreme weather events including bush fire.
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