The heavy rain that has battered Wollongong and caused repeated flash flooding in recent weeks will become more severe and frequent, potentially displacing people from their homes and public infrastructure.
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That is the message contained within a new plan, due to be adopted by Wollongong City Council next week, which sets out how the city must adapt to climate change.
The plan says "managed retreat" away from flood prone land may be necessary in parts of the city.
The suburbs of Thirroul, Bulli, Figtree, Wollongong, Dapto, Unanderra and Warrawong are identified as being most at risk from flooding, now and into the next decade.
The council's Climate Change Adaptation Plan clearly states that the naturally variable rainfall pattern of the Illawarra will be exacerbated as the world heats up.
Based on "compelling science" that shows the world has warmed by 1.44 degrees since 1910 and, on its current trajectory, will warm by 3.4 degrees by the end of the century, the council report also sets out how bushfires, drought, storms and sea level rise will affect the city.
"Wollongong has a history of significant flooding that has led to a high level of floodplain management planning incorporating climate change predictions. We must plan for the likelihood of more floods and increased severity of flooding."
- Wollongong City Council's Climate Change Adaptation Plab
Lord Mayor Gordon Bradbery said flooding was particularly relevant given recent weather events.
"Whether you believe it's associated with climate change or not, this is impacting on our lifestyle and our residents now," he said.
He said the city had "done well" in this summer's deluges compared to some areas, crediting the council's actions over the 20-odd years since the destructive 1998 flood.
"1998 was like a warning shot, it put us on notice and we've had to act accordingly. This weather we are seeing now reinforces our approach," he said.
The adaptation plan states that there will continue to be a decrease of rain in winter and increased deluge events over summer.
"This means that we must prepare for more floods, which are likely to impact private property, council assets and cause danger to residents and visitors and disruption," it says.
"Wollongong has a history of significant flooding that has led to a high level of floodplain management planning incorporating climate change predictions. We must plan for the likelihood of more floods and increased severity of flooding."
In the medium term, the council may consider "managed retreat" if it can't defend properties against flood risk.
Cr Bradbery said this could include looking at properties that are very vulnerable to flooding and coming up with a plan to buy them back, or simply notifying people that their property was at risk.
"I don't want to cause alarm, but it is our task to identify the impact of climate change on any property in our city and bring it to the front of consideration," he said.
"People might be told their properties are prone to flooding, inundation or bushfires - these things will all need to be revisited as we adapt."
Northern suburbs Greens councillor Mithra Cox said a managed retreat might include not repairing infrastructure which was inundated or damaged during storm surges or floods.
"This is going to be a fraught space, because the council only manages public land - so a road, footpath, sporting field or surf club - but when we're talking about people's private houses, people are going to be really stressed and really upset," she said.
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"We need to be transparent early about what these climate impacts are going to be so it doesn't come as any kind of shock."
She said Lismore might provide an early example of managed retreat, "from places where people have lived for generations that are suddenly no longer inhabitable due to the changing climate - and there a lots of impacts Wollongong can expect to face that are similar and terrifying".
"I feel that the debate has changed, when there has been previous weather related disasters there has been a sense that you're not allowed to talk about climate change," Cr Cox said.
"But now lots of people who are personally affected this time are saying, this is what climate change looks like."
Like Cr Bradbery, she said the work the council had already done has really made a difference, and that the city "could have been much harder hit in these past few week".
"The difficult thing about climate change is that the expected rainfall is not part of a pattern that we have ever seen before," she said.
"It will be much cheaper and easier to prevent this problem happening in the first place."
Read more: Wollongong gets serious about climate change
The council has already adopted a Climate Change Mitigation Plan, which looks at actions the council and city can take to limit global warming.
The adaptation plan is another step in the council's commitment to the Global Covenant of Mayors, which it made in 2017. Under the covenant, the city committed to a series of activities to achieve a resilient and low-emission society.
Councillors will debate the adaptation plan, with staff recommending it be adopted at next Monday's meeting.
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