Article author:
Associated Press
Rod Mcguirk
Canberra, Australia (AP) — Some of Australia's largest cities have been tired of four floods since March last year. I'm wondering how many victims there are. The number of times they can be rebuilt.
Recent disasters follow Sydney's rainiest year. An unprecedented year begins, with dams overflowing, unable to absorb rain, and instead raining, which should swell the waterways.
The climatic, geographic and demographic factors behind the scale of Sydney's recent flood emergencies are:
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Leader's blame Climate change
Prime Minister Dominique Perotet of New South Wales said government and community flooded He said he needed to adapt. Australia's most populous state as a whole.
"There is no doubt that these events are becoming more common to see what we are seeing throughout Sydney," Perotet said on Monday.
Prime Minister Anthony Albanese said that the fourth largest flood in Sydney after a catastrophic wildfire in the same region in the summer of 2019-2020 in the Southern Hemisphere is climate change countermeasures. Said that it is proof of the need for.
"We know that Australia has always been affected by floods and bushfires, but it is extreme if we do not take global action against climate change. I know science has taught me when it comes to weather, events will be more frequent and more intense, "Albanese said Wednesday.
"Unfortunately, what we're seeing is that it works," Albanese added.
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La Niña and other weather patterns
Two La Niña phenomena caused above-average rainfall on the east coast of Australia in 2021 and this year. The second was declared last month, but the Bureau of Meteorology predicts that it will rain more than normal winters in Sydney's Southern Hemisphere and that La Niña will return with a 50-50 chance this year. The
agency says the two climatic factors have led to the floods in Sydney since Saturday.
Floods were affected by the Indian Ocean Dipole, which represents the difference in sea surface temperature between the western and eastern Indian Oceans. In the negative phase, warmer water is concentrated near Australia and more water is available to the transcontinental meteorological system, leading to above-average winter-spring rainfall in the Southern Hemisphere. IOD has repeatedly sunk into the negative stages of rain over the past month and is expected to remain negative within a few months.
The second effect was the positive Antarctic ring mode. SAM refers to the non-seasonal north-south movement of strong westerlies that blow almost continuously from mid-latitudes to high latitudes in the Southern Hemisphere. In the positive phase, SAM sends more moisture-filled air to eastern Australia, promoting above-average rainfall and east coast cyclones in winter.
In a recent rainfall event, the very warm waters of the Australian coast, 21-23 degrees Celsius (70-73 degrees Fahrenheit), provide extra energy and water to deep valleys and lowlands on the east coast. And concentrated the heavy rain. During the 24-hour period starting at 9am on Saturday.
Several rain gauges in and around Sydney set a record for July or a record high.
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Geography and Demography
Most of Sydney's rains flow into spillable river systems, but due to economic gains, The movement is greatly hindered. To mitigate floods.
The Hawkesbury-Nepian River system is partly centered on a 22,000-square-kilometer (8,500-square-mile) rain catchment area that covers Blue Mountain at the western end of Sydney and 5 million western suburban cities. It flows into. Of the worst flood.
Australia faces extreme flood risk as the river system faces extreme flood risks as the canyon restricts the flow of the river to the sea side and after heavy rains water rapidly flows back and spills over the floodplain. Jamie Pitok, an environmental professor at the National University, said. society.
Hawkesbury-The Nepean Valley is home to 134,000 people, who were projected to double by 2050 as Sydney's population and real estate prices rise, he said.
"Potential economic benefits from real estate development are a major driver of the lack of effective action to reduce flood risk," said Pitok.
The state government wants to raise the walls of Sydney's main reservoir, Warragambadam, to reduce flooding in the valley.
However, some argue that raising the wall can only control half of the floods and cannot prevent the massive floods caused by other rivers in the area, says the University of Sydney. Dale Dominy Howes, a professor of hazard and disaster risk science, said.
