Bushfires were like atomic bombs: probe

The inferno that swept across Victoria killing 173 people on February 7 generated
enough energy to fuel 1,500 atomic bombs, the bushfires royal commission has been
told.
Bushfire behaviour analyst Dr Kevin Tolhurst said in a submission to the inquiry the
fires were like "1,500 atomic bombs the size of Hiroshima" that could have
potentially supplied Victoria's domestic and industrial energy needs for a year.
"It is an enormous amount of energy being produced by these fires," he said.
Dr Tolhurst said the January heatwave and underlying drought had contributed to the
dire fire conditions on February 7.
In some areas, the blaze spotted 35km ahead of the main fire, he said.
Dr Tolhurst said it was important to evaluate a fire on a three dimensional level,
taking into account not just surface winds but upper winds created by the plume of
smoke above a fire.
He showed the commission photos of trees that had been snapped off three to four
metres above ground level in the Black Saturday bushfires by these types of gusts.
"You would have needed winds of 120km/h or more to produce that," he said.
The commission also viewed graphic footage of the Black Saturday bushfires captured
by cameras at four locations around Victoria.
The cameras were controlled from Melbourne and in particular captured the
Murrindindi blaze that obliterated Marysville.
Located on a tower between Marysville and the O'Shannassy Reservoir, the footage
shows the Murrindindi fire spotting into the area for about an hour before a wind
change moves through, sweeping the fire across the ground in waves while airborne
gases spontaneous explode into fire "whirls".
Dr Tolhurst said this effect was what witnesses often referred to as fireballs.
"It's actually a horror situation when the cold front hits," he said.
"The fire then burns quite fiercely for a period of two, three, four, hours after
that."
He told the commission the footage showed how fires did not simply approach as one
firefront then pass, but could burn for lengthy periods in different areas.
Dr Tolhurst was also shown a photo of a home on Bald Spur Road in Kinglake where
36-year-old Robert Davey, his wife Natasha, 33, and their two daughters Jorja, 3 and
Alexis, eight months, perished on February 7.
Mr Davey's mother Joan gave evidence to the commission this week that she believed
the home, located at the very top of a densely-wooded ridge, was indefensible.
Asked whether there was any way the house could have been defended from an
encroaching fire by someone on the ground, Dr Tolhurst said it was unlikely.
He said flames from the inferno could have reached heights of 35 metres because of
the height of nearby trees, and anyone attempting to defend their home would need to
be at least 120m away from the radiant heat of the shooting flames.
A clearing surrounding the Davey home provided a sanctuary of just 20m from the trees.
"I would say you would have a very low probability of defending that house," he said.
Dr Tolhurst also told the commission a team of fire behaviour specialists were at
the Integrated Control Centre in Melbourne on February 7 assisting to predict the
path of fires, but the team was somewhat "disconnected" from the activity of the
IECC because they were located outside the main room.
The hearing continues on Monday.