Flooding in South Dunedin, in 2024.
A new report shows that it is feasible to lower the flood risk in South Dunedin but it will take a sustained effort and investment over decades
South Dunedin Future - a joint Otago Regional and Dunedin City councils initiative - has presented three possible futures ranging from raising land and pumping water, creating wetlands and canals, and shifting out of harm's way
The costs range from $1.6 billion to $2.4b for the different futures, but modelling indicates they will be lower than the status quo
A large managed retreat is off the cards, but property acquisition will likely be needed to support infrastructure upgrades, land raising or new green spaces
A Dunedin councillor says residents are shocked they identified their homes in possible acquisition zones during a briefing rather than be told earlier.
South Dunedin can significantly reduce its flood risks without resorting to wholesale managed retreat , but it will not be cheap and there will be trade-offs and tough decisions ahead.
That was the latest finding from the South Dunedin Future programme which has presented three proposals for how the low-lying community can adapt to the effects of climate change .
While a major relocation was not on the cards, up to 1700 properties might need to be bought to carry out specific public works.
But Dunedin councillor Jo Galer said residents were blindsided after discovering their homes were in areas where acquisition could be on the cards .
Dunedin councillor Jo Galer.
Future management of the area has now been narrowed to three possibilities with total costs mapped out over 100 years:
Protect - raising land and pumping water - $2.1b
Restore - making space for water with wetlands and canals - $1.63b
Reshape - raising land and using infrastructure to shift out of harm's way - $2.45b
Jonathan Rowe, who leads the South Dunedin Future programme, said each also included a mix of pipes and pumps, coastal protection and green spaces along with developing hundreds of new homes.
"Really good news is that it looks like it is feasible to manage flood risk in South Dunedin - that would be a key message - and to do that over the next 100 years," he said.
"The costs of doing so are lower than we had anticipated in earlier stages so the costs are coming down."
They were also better value than the status quo, he said.
Total damages were expected to cost $1.45b over the same timeframe with hundreds of home impacted by rising groundwater, he said.
But he encouraged people to prepare for trade offs - there would be less flooding, but it would take significant investment, disruption and change to get there.
Focus would not be on formal managed retreat, rather buying properties for specific purposes like pump stations, Rowe said.
"There is property acquisition for the purpose of public works so we only need to buy property in order to build a pump station or a water detention basin or a canal that then provides a broader community benefit in terms of risk reduction," he said.
That could see between 1100 to 1700 properties bought up out of roughly 6500 in the area - mostly in the next 25 years.
He was keen for acquisitions to be a voluntary process with willing sellers.
Flooding on Surrey Street.
Dunedin councillor Jo Galer said residents were shocked when they could identify their homes during a briefing on Tuesday.
"That's very disturbing if your life savings are tied up in that one property and I don't think that's fair. In fact, I think that's downright cruel that they should come away from that meeting distressed, upset and unable to contemplate what their future might look like," she said.
They had already had to deal with years of floods and stormwater frustrations, she said.
"They've also now had to endure the humiliation of having their homes identified publicly without them first being told about it. Just imagine if that was your home," she said.
On Tuesday morning, Jonathan Rowe confirmed the areas were identifiable and residents had not been informed yet.
"The locations shown in the technical reports are based on current information and are indicative only. Specific properties would be confirmed later, after detailed project design," he said.
"Any final decisions would be made by councils, after considering community feedback and further technical advice"
They would be able to tell residents about what the different futures might mean for their property during drop-in sessions, he said.
Rowe confirmed Bayfield High School might need to be relocated if plans for a sea wall to protect the community from inundation from the harbour did not cover Andersons Bay Inlet.
Bayfield High School might need to be relocated if plans for a sea wall did not cover Andersons Bay Inlet.
If the community did not adapt, the modelling suggested roughly $200 million worth of damage each year from flooding in 100 years' time - that was from the combination of high groundwate…
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