ABC Science
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James Purtill
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Floods account for the greatest property damage of any natural
disaster in Australia.
(ABC North Coast: Samantha Turnbull)
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The ongoing floods in Queensland and New South Wales are on track to be one of
Australia's worst-ever natural disasters.
And if this news isn't bleak enough, we can expect more extensive and more
frequent flooding as climate change intensifies.
These are the conclusions of a Climate Council report summarising the latest
data on the scale of the disaster and underlining the link to global warming
caused by human activity.
The Brisbane "rain bomb", for instance, dropped more water on the city than
typically falls in London over an entire year, and the volume flowing through
the Brisbane River far exceeded the 2010-11 floods.
Insurance claims along the eastern seaboard may be as great as the 2019-20 Black
Summer bushfires.
So how bad is the property damage?
Insurance claims will exceed 2010-11 Queensland floods
The scale of the 2022 floods is emerging as reports filter out of the disaster
zones, insurance claims are made, and statistics compiled.
The Climate Council report, published today, provides a snapshot of what we know
so far — and it appears this natural disaster is going to rank highly.
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The cost of weather-related disasters in Australia has risen since
the 1970s.
(Supplied: Climate Council)
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The total value of the insurance claims will exceed those of previous major
floods, including the last time Brisbane flooded in 2010-11, said Nicki Hutley,
economics spokesperson for the Climate Council.
"Obviously we're still counting the costs and don't know the full extent," said
Ms Hutley, a former Deloitte economist.
"The Queensland floods of 2010-11 had property damage of $1.5 billion, and we're
certainly probably already at that level, if not exceeding it."
Insurance claims could even exceed the 2019-20 Black Summer bushfires, which
totalled about $2.5 billion.
"Certainly the property damage may be higher — the fires burnt through millions
of hectares, but a lot was uninhabited," she said.
"In terms of the total number of people affected and total costs, I imagine this
will be, if not the worst natural disaster, then certainly right up there."
Flood level records broken
Local records for rainfall, flood levels and flood rescues have been broken.
The "rain bomb" that broke over Brisbane on Friday, February 25, deposited 80
per cent of the region's
annual rainfall within three days.
The downpour was greater than the 2010-11 floods: about 50 per cent more water
poured into the Brisbane River's Wivenhoe Dam in half the time.
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Brisbane's "rain bomb" dumped more than one metre of water on most
of the city.
(Supplied: Climate Council)
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Wilsons River in the Northern Rivers district of NSW broke the 1954 flood level
record by more than two metres.
The Richmond River at Woodburn topped 7.18 metres, nearly 50 per cent high than
its previous record.
NSW SES carried out more flood rescues in 24 hours thanit had ever done before.
The mass of water in this flood is "quite remarkable", says Will Steffen from
Australian National University's Climate Change Institute.
"It will certainly rank up with one of the biggest natural disasters around the
country," he said.
Extreme events are becoming 'ordinary'
When Brisbane flooded in 2010-11, the disaster was reported in the media as a
one-in-100-year event.
The same happened when Townsville flooded in 2019, Professor Steffen said.
"And now we've heard that term applies to the latest bout of flooding," he said.
"The point is we're having extreme events more often. 'Ordinary' extreme
events are occurring now in rapid succession."
Extreme rainfall can occur for a variety of reasons and directly linking a
single event, like a flood, to climate change requires a formal attribution
study, which can take years to produce.
However, it is possible to
say whether climate change
contributed to the floods.
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Parts of Brisbane were still recovering from the 2010-11 floods
when the latest flood hit.
(ABC Radio Brisbane: Antonia O'Flaherty)
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This is a complicated question and some experts say there's
a risk of overstating the effect of climate change
on the multi-day heavy rainfall that has led to the 2022 floods.
But Professor Steffen says there's no doubt that a "climate system on steroids"
contributed to the floods.
A warmer atmosphere is both more energetic and can hold more water, which
"stacks the odds" in favour of extreme rainfall, he said.
"For every one degree of temperature rise, the atmosphere can hold 7 per
cent more water.
"The intensity of rainfall will continue to increase on that ratio of 7 per cent
for every degree of temperature rise."
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Floods cause the greatest damage of any natural disaster in
Australia.
(Supplied: Climate Council)
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This change is already being observed, he said.
The
2020 CSIRO and Bureau of Meteorology State of the Climate report
found the intensity of short-duration extreme rainfall (i.e. flash flooding) had
increased by around 10 per cent in some regions.
The recent
Intergovernmental Panel on Climate Change (IPCC) report
predicted the world was on track to warm by 1.5C in the early 2030s, and by 2C
this century.
As the temperature of the atmosphere continues to rise, destructive floods are
likely to happen more regularly, Professor Steffen says.
"They would happen at a regularity that would make it difficult to recover
in between events — that's almost happening now.
"The economics of this is going to make a lot of places unviable."
Should every house be rebuilt?
On Wednesday, Prime Minister Scott Morrison
declared a national floods emergency, which gives the federal government power to deploy money and resources
faster.
Communities impacted by the floods will receive public funds to rebuild.
But some areas should not be rebuilt, Professor Steffen says.
"We need to have a very good look at zoning laws and where people are allowed to
build."
Insurers are already refusing to cover flood damage in some areas, because
climate change has made the risk so high, Ms Hutley said.
One solution to this is for the government to step in as the insurer, but this
is risky and could eat up public funds.
"It's a never-ending bottomless liability and it becomes extremely dangerous
from a financial security point of view," Ms Hutley said.
"We've been absolutely negligent on where people can build for a decade or
more."
Politicians will have to make difficult and unpopular decisions about where
people can rebuild — and where new housing developments can be located.
And these decisions will need to be made quickly, she said.
"People who want to rebuild now need an answer sooner rather than later."
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