Knowledge is power

Unlike a scrub or forest fire that liberates burning leaves and bark to be carried ahead of the main fire front to start new fires known as spot fires, grass fires generally don’t have the spotting problem, except where they involve trees or shrubs in their path.

Photographs taken after a fire on the side of the Calder Freeway near Sunbury earlier this year show shrubs close to the side of the Melbourne-bound lane that had been involved in fire.

Under the influence of a strong northerly wind the fire quickly “spotted” across the two lane carriageway and into the centre medium strip. The grass having earlier been slashed, the flame height was not high enough to reach across the north-bound two lane carriageway and continue on towards Melton. With no shrubs or trees in the median strip, there were no wind-borne embers to cross the carriageway. The short grass assisted brigades to contain the fire to the centre median strip.

The western side of the north-bound carriageway with stock in the paddock beyond. The fire brigades did fine work under severe conditions to keep the fire to the centre median strip.

The message here is that if grass is cut low or eaten out by animals the flame height will be low, with a consequent reduction in fire intensity and duration of the fire front.

A wind driven grass fire moves quickly across the landscape, often too fast to ignite well-constructed buildings and other forms of vegetation in its path. The real damage is done when the grass is left uncut up to the edge of a building, as around this house on the western side of Wallan when photographed early in January 2003 (one of my before/after series to use for instructional purposes and I’m looking forward to learning if that house is still there) or the fire burns under nearby trees or shrubs and the building is showered with embers. When photographed there was an LP gas cylinder alongside the barbecue on the timber veranda

With the grass left uncut, no ember protection and someone in attendance to extinguish small fires around the building it may eventually be lost if the fire brigade does not come to its rescue. Most of the film and photos I’ve seen show houses burning down from the inside, clearly the effect of ember attack.

Click on a very informative video clip available on "The Age" web site that shows the effect of the Mickleham fire travelling north towards Darraweit Guim after the wind change.

Look closely at the condition of the vegetation around the houses lost, it's very informative. Having viewed it several times I'm of the opinion that many of those houses could have survived. Ember-proofing the houses, cutting the grass short for at least 30 metres around them and removing rubbish from under plantations is important.

In the video look at the condition of shrubs and trees around the lost houses, and some motor vehicles that the fire seems to have gone under or around without igniting them and a large LP gas storage cylinder that seems not to even have its paint damaged. Grass fires are relatively easy to protect against and wind-driven grassfires go past very quickly

Knowledge of fire behaviour is a critical factor to consider when contemplating evacuation — ‘knowledge is power’ and we should never consider ourselves powerless when dealing with bushfire. When fire does threaten, to understand what is really happening we need to disregard the awesome smoke column and the dramatics of the media and make our own assessment of the threat. And be aware of our own emotional and physical limitations

In my next posting I will go into a little more detail on what to expect as a grassfire approaches and explain the Fire Danger Index and the CFA fire danger warning messages.