Article author:
Melbourne —Torrential Rain Thousands of people have been displaced due to the risk of floods and landslides in areas that have hit the southeastern coast of Australia and have been hit by four floods in the last 18 months.
In some parts of New South Wales, a month of rain has fallen over the past two days, rivers have swollen, and Sydney's main dam, the Waragamba Dam, has spilled over the weekend.
The Australian Insurance Council estimates that the March and April floods in New South Wales and southeast Queensland caused insurance losses of A $ 4.8 billion ($ 3.3 billion). I am.
What is causing the constant rain?
Australia has been exposed to the La Niña phenomenon in the Pacific Ocean for the second consecutive year. This usually results in above average rainfall on the east coast. The La Niña phenomenon ended in June, but the Meteorological Bureau says it has a 50-50 chance of being reshaped later this year.
Due to the Indian Ocean Dipole phenomenon, which is a different phenomenon from the warm sea surface temperature, it rains more than normal weather. The Indian Ocean Dipole Index turned negative in May, increasing the likelihood of above-average winter and spring rainfall in most parts of Australia, the Meteorological Bureau said in June. Winter in Australia lasts from June to August.
"For all these conditions, the dice will be loaded for rain events that are likely to occur at least in the coming months," said senior disaster analyst at insurance company Aon. Tom Mortlock says.
During the negative Indian Ocean Dipole mode, the East Indian Ocean is warmer than usual, the West Indian Ocean near Africa is colder, and more moist air is in Australia. It flows toward.
Climate change
It is difficult to attribute a single flood to climate change, but Mortlock said the increased frequency of heavy rainfall is due to the retention of warmer air. , Said that it is consistent with what is expected from climate change, more humidity in the atmosphere.
"Most climate models suggest an increase in the frequency of rainfall in Australia," he said.
Flood Area
Hawkesbury-Nepian Valley in western Sydney is a floodplain and is prone to dangerous floods due to the "bathtub effect" New South Wales emergency Service states. There are five tributaries in the valley, with chokepoints that limit the flow to the sea, allowing water to flow backwards during heavy rains.
Heavy rains caused by La Niña over the last two years have saturated the ground, filled dams and created flash flood conditions.
"There is virtually no osmotic capacity left in any of the catchments on the east coast," said Motlock.
Sydney's rapid population growth over the past few decades has boosted its development into floodplains.
Before the recent floods, there were no major floods for about 30 years. In other words, the authorities approving the land development application may have considered the risk of flooding to be low.
"I was quite complacent when I didn't have it for a long time," said Ian Wright, an environmental scientist at Western Sydney University.
"Our bridge is not high enough," he said. "There are few and inadequate flood evacuation routes."
Disaster management constraints
Residents and rescuers are on a wildfire 2019-2020 And still recovering from last year's and this year's floods, in addition to COVID-19 pandemics.
A shortage of building materials and labor means that thousands of people are waiting for repairs from previous disasters, Wright said.
In addition to the vulnerability, many low-income people in western Sydney cannot afford flood insurance.
The New Labor Party government wants to be more proactive in tackling disaster risk, said Murray Watt, Minister of Emergency Management.
"Often not the wealthy people who live in the cheap lands of the floodplain, but the people who can't afford to live on the hills," Watt said last week.
The government plans to establish a disaster preparedness fund that will provide up to A $ 200 million annually in disaster prevention and resilience programs. ($ 1 = AUD 1.4665) (Reported by Sonali Paul, edited by Robert Birsel)