Fire Management – 101. Introduction to Fire Suppression. – Victoria’s Forests & Bushfire Heritage

“Fires always look worse at night, and fires always look worse from a distance” – Alan McArthur, c 1961.

Firstly, it is important to understand that bushfire perimeter, rather than bushfire area, is the main control problem for forest firefighters on the ground. A conundrum rapidly compounded by spot fires.

In extreme cases, the perimeter to be extinguished can stretch for hundreds of kilometres through thick bush, in rough terrain and remote from any access tracks.

The principles of effective forest fire suppression have not changed over the decades. It requires –

Early detection combined with rapid and determined first attack to keep fires small.
The flames must be suppressed.
The perimeter must be surrounded by a bare-earth trail or non-combustible edge like a road or river, to ensure that smouldering fuels are physically separated from unburnt ones.
Smouldering material in the burnt area, within a certain distance of the fire edge (> 50m), and including large logs, trees alight in hollows and roots that can burn underground must be extinguished. This often requires tree-felling, digging and breaking open large material (aka – blacking out).
The fireline must be patrolled and blacked out until it is certain that it won’t relight.

Dry firefighting involves building a mineral earth trail down to bare dirt. In addition to building new hand trails, an existing road, strategic fuel break or 4WD track can be a suitable control line.

It is often the only option where there is limited access to reliable and plentiful water supplies, which characterised the prolonged campaign bushfires in remote and mountainous locations in the middle of summer.

A strong fuel moisture differential (e.g. river, heathland or swamp) is sometimes suitable as a control line but needs careful and ongoing monitoring.

Areas that have recently been burnt, with lower fuel levels, generally have milder fire behaviour and can offer safer access for crews and act as anchor points for control lines or back burning.

These operational techniques have proven effective firefighting in heavier forest fuels which, unlike grass, tend to retain heat and smoulder.

Direct attack is the normal tactic in the early phases of a bushfire when it’s still small. It requires getting a crew close to the edge, either on the flanks or at the head of the fire as quickly as possible, and building a break with hand tools like rakehoes, axes and chainsaws… or with small First Attack Dozers (FADs).

It is possible to control a small bushfire using direct attack provided the flame height is less than about a metre or so, the bushfire is accessible on foot or vehicle, the scrub isn’t too thick, and the weather remains stable.

For hand crews on foot, making sure there is a nearby safety zone that is clear, or has already been burnt, if the fire builds unexpectedly. This is often known as “keeping-one-foot-the black”. Maintaining good communication and vigilant lookouts is an essential safety strategy.

Aircraft are very effective, particularly in the early stages. Sometimes a load of retardant dropped from a small firebomber or helicopter can suppress the flames and buy enough time for ground crews to reach it, particularly if the bushfire is remote or a single tree that has been hit by lightning.

By contrast, indirect attack usually involves building a fallback control line along roads or ridges, often well away from the active fire edge , and backburning.

Indirect attack is often done in conjunction with aerial ignition to burn out the remaining fuels, but it also rapidly increases fire complexity, size and perimeter.

And while aircraft and firebombers can make a big difference, particularly in the early stages, absolutely nothing beats “boots on the ground” for blackout and patrol.

The Forests Commission, (now DEECA/FFMVic), honed these firefighting skills over many decades of hard-won experience.

And falling trees and branches remain the greatest risk to the safety of firefighters on the ground.

FCV – Blackout film