MELBOURNE (Reuters) – Heavy rains on Australia’s south-east coast have left thousands of people homeless due to the risk of flooding and landslides in an area affected by four major floods in the past 18 months.
Some parts of the state of New South Wales have received a month of rain in the past two days, rivers have swelled and Sydney’s main dam, the Warragamba Dam, has been forced to overflow over the weekend.
Floods in March and April in the states of New South Wales and south-east Queensland caused an insured loss of A $ 4.8 billion ($ 3.3 billion), the Insurance Council of Australia estimated.
What is the cause of incessant rain?
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Australia has been experiencing La Nina weather events in the Pacific Ocean for two consecutive years, which usually brings average rainfall to the east coast. The La Nina event ended in June, but there is a 50-50 chance of it reconstituting later this year, the weather bureau said.
Sea surface temperatures in the warm ocean and another phenomenon, the dipole in the Indian Ocean, are bringing in more humidity than normal weather. The Indian Ocean dipole index turned negative in May, raising the possibility of average winter and spring rainfall in most parts of Australia, the Meteorological Bureau said in June. Winters in Australia last from June to August.
“All of this has led to a high risk of rain at least in the next few months,” said Tom Mortlock, a senior disaster analyst at insurance company Aon.
During negative Indian Ocean dipoles, the eastern Indian Ocean is warmer than usual and the western Indian Ocean near Africa is cooler, causing more humid air to flow to Australia.
Although it is difficult to blame any single flood for climate change, Mortlock said the increased frequency of heavy rainfall is consistent with what can be expected from climate change, as warm air keeps more moisture in the atmosphere.
“Most climate models suggest an increase in rainfall in Australia,” he said.
Development in flood prone areas
The New South Wales State Emergency Service says the Hawksbury-Napier Valley in Western Sydney is a floodplain, prone to dangerous flooding “under the influence of bathtubs”. The valley is fed by five tributaries and has chokepoints limiting the flow to the sea, so the water returns during heavy rains.
Heavy rains driven by La Nina over the past two years have flooded the land and filled dams, creating flash flood conditions.
“There is virtually no penetration capacity left in any of the East Coast’s catchments,” Mortlock said.
Over the past few decades, Sydney’s rapid population growth has pushed development into the floodplain.
Prior to the recent floods, there had been no major floods for nearly three decades, which meant that officials approving land development applications may have believed that the risk of flooding was low.
“When you don’t have it for a long time, there’s a lot of complacency,” said Ian Wright, an environmental scientist at Western Sydney University.
“Our bridges aren’t high enough,” he said. “The path to flood relief is short and distant and inadequate.”
Pressure on disaster management
Residents and emergency workers are still recovering from the bushfire in 2019-2020 and the floods last year and this year, coming to the top of the COVID-19 epidemic.
Lack of building materials and labor means thousands of people are waiting for repairs from previous disasters, Wright said.
Adding to the vulnerability, many low-income residents in West Sydney cannot afford flood insurance.
The new Labor government wants to be more proactive in dealing with disaster risk, said Emergency Management Minister Murray Watt.
“Mostly, it’s not the rich people living on cheap land in the floodplain, it’s the people who can’t live on top of the hills,” Watt said last week.
The government plans to set up a disaster preparedness fund to provide up to A $ 200 million a year for disaster prevention and resilience programs.
(1 = 1.4665 Australian dollars)
(Reporting by Sonali Paul; Editing by Robert Bircel)
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