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The grounds of Queen's High School, King's High School and Tonga Park are inundated during the June 2015, South Dunedin floods. PHOTO: STEPHEN JAQUIERY

As sea levels rise and severe storms intensify, warnings mount about the future that coastal Dunedin faces.

But a University of Otago researcher cautions against the urge to "retreat" from an incoming sea.

Prof Lisa Ellis University of Otago philosophy, politics and economics programme director: "There are lots of important decisions we should be making collectively about how to deal with a coastal future — none of them is to maintain status quo, because we don’t have that option." PHOTO: GRAHAM WARMAN

Reports from the Beehive address a managed retreat from coastal areas threatened with inundation; researchers describe a cascading series of insurance-driven financial and infrastructure retreats that will occur before storm surges regularly inundate coastal land.

However, University of Otago philosophy, politics and economics programme director Lisa Ellis said the concept of a retreat could be harmful when communities looked for equitable solutions.

The word retreat unnecessarily scared people and made them think they were out of options.

A retreat sounded like some distant authority was making the decisions that affected local communities, Prof Ellis said.

"There are lots of important decisions we should be making collectively about how to deal with a coastal future — none of them is to maintain status quo, because we don’t have that option," she said.

There might have to be a change in the way coastal areas were used over the rest of the next century, she said, but there were alternatives other than simply abandoning the land.

For example, in some places wetlands, or athletic fields, could provide a community with benefits, and could also withstand increased flooding better than built structures.

In Dunedin there was pressure to increase the housing supply and pressure to be responsible about future flooding expected in coastal areas not yet developed.

But cities needed to address the problem of adapting existing communities such as South Dunedin that had dense networks of valuable social and community ties — institutions like schools and also clubs and neighbourhoods.

"If you’re looking at things from an insurance perspective you’re looking at market value and that doesn’t come close to the actual value of an existing densely networked neighbourhood," she said.

Globally, flooding had already made decisions for communities before the questions had been adequately raised.

Hurricane Katrina slammed into the American city of New Orleans in 2005.

The storm surge caused 53 levee breaches and left a reported 80% of the city flooded.

Eight weeks later, 700 bodies were recovered.

The city’s neighbourhoods were "just blasted", she said.

And people were scattered.

Not only did they lose their homes, they lost their communities, and those communities were not put back together, she said.

"And New Orleans was smaller, and richer, and whiter," Prof Ellis said. "It was a different city and nobody made that decision deliberately.

Associate Prof Janet Stephenson University of Otago Centre for Sustainability director: "It is increasingly important that something is put in place, because these people are blameless, and could be suffering hugely." PHOTO: LINDA ROBERTSON

"I think New Zealand has a real shot to make these decisions deliberately and to think about what the values are, and so, get ahead of the game."

University of Otago Centre for Sustainability director Janet Stephenson said a recent rough estimate by LGNZ showed, nationally, council infrastructure exposed to foreseeable damage due to rising sea levels increased sharply at each increment of sea-level rise. Across New Zealand, $7.1billion worth of council-owned infrastructure was exposed to flood damage at 1.5m of sea-level rise.

But those assets did not include community assets such as schools, parks, or libraries, Prof Stephenson said.

Further, while there were some people who continued to invest in parts of Dunedin in coastal flood zones, despite a growing body of evidence, those who bought there a long time ago, before the science was clear, should not be held responsible for investing in an area at a time when the exposure to sea-level rise had not been known.

And yet there were no arrangements at present that made it clear whether there was any assistance for people in those situations, she said.

"It is increasingly important that something is put in place, because these people are blameless, and could be suffering hugely," she said.

University of Otago PhD candidate Benjamin Tombs said New Zealand had a history of collective responses that offered insight into the issue.

Both the Earthquake Commission, and New Zealand’s Covid-19 response emphasised a collective response, he said.

Benjamin Tombs, University of Otago PhD candidate: "New Zealand is a very unique landscape when it comes to natural hazards and a sense of collective responsibility." PHOTO: CHRISTINE O’CONNOR

There were lessons learned, both good and bad, from both.

"New Zealand is a very unique landscape when it comes to natural hazards and a sense of collective responsibility," Mr Tombs said.

"How can we, team of 5million, get over this series of losses that are foreseeable and are going to happen due to sea-level rise?"

But nevertheless, the 1-in-100 year events that happened in South Dunedin in 2015 were expected to now happen much more frequently.

In 2050, due to sea-level rise, the 1% chance of a storm that severe happening in any given year, could climb as high as 50%.

People living in those flood zones were in a "property purgatory".

They could feel stuck in coastal properties they did not necessarily have much choice or ability to get out of.

And how New Zealand responded to the future inundation of its coasts remained unknown.

"It’s all just very ambiguous at the moment and that’s very immobilising," he said.

Climate economist Belinda Storey wrote a government-funded report for the Deep South National Science Challenge on insurance retreat last year.

Ms Storey’s research predicted a relatively small increase in sea-level rise would cause at least partial insurance retreat for the vast majority of properties in coastal flood zones within just 15 years.

She said there was reluctance from some parts for her work to be undertaken, on the assumption that when it was published, house prices would fall.

But even after a disaster property prices bounced back very quickly.

South Dunedin, she said, presented a very difficult problem because it was not a strip of coastal homes but almost an entire suburb.

And though a typical response to the increased exposure to flooding was to "harden the coasts", she said, it would not work.

Engineering solutions like sea walls, stopbanks and levees would only delay damage at best.

At times, hard solution were even counterproductive, as they aggravated the effects elsewhere.

She said she firmly believed New Zealand needed to talk about how to move out of hazardous locations rather than how to mitigate the exposure to a rising sea.

"Measures taken to defend property are only short-term solutions," she said. "They don’t eliminate the risk; the reckoning will come."