Moving people and homes permanently out of the path of climate change hazards may sound like an extreme response, but experts say "preemptive" managed retreat will be essential for some areas in future.
The Cyclone Recovery Taskforce is wrestling with whether the areas devastated by the January floods and Cyclone Gabrielle should be rebuilt or the residents bought out to move elsewhere.
And, simultaneously, the Government is tackling a longer-term plan for what managed retreat might look like for Aotearoa as a whole.
"Where you have no viable or cost-effective way of protecting people who are clearly at risk, or in increasing risk, then managed retreat is going to be the only realistic option," says Jonathan Boston, emeritus professor of public policy at Victoria University of Wellington.
Boston is part of an expert group coming up with recommendations for the Climate Change Adaptation Bill heading to Parliament this year.
He describes managed retreat as being a purposeful and planned movement of people and assets out of harm's way. It has to be publicly authorised and involve some kind of assistance to enable people to move, he says.
The Ministry for the Environment similarly says it's a process of identifying areas at "intolerable risk" and then enabling people to move their houses, activities, and sites of cultural significance away within a planned period of time.
Scenes of the extraordinary rooftop rescues in Hawke's Bay hammered home the reality of the deadly impacts of flooding caused by climate change fuelled extreme weather events. But Boston says while in the short term river flooding is likely to be the most serious risk, in the long run sea level rise will be the most significant issue for New Zealanders.
With the ninth longest coastline in the world, land subsidence in 40% of coastal areas, and most of our major cities located on the coast, we're looking particularly vulnerable in the face of sea level rise.
Globally, sea levels are expected to rise by about half a metre by 2100, but projections released last year show that for some parts of New Zealand it could exceed one metre because of the double whammy of land subsidence.
A NIWA study found that with half a metre of sea level rise around 36,000 buildings and close to 50,000 people will be at risk.
Rob Bell, environmental engineer and expert in climate change adaptation and coastal risk assessment, says we should expect to see a significant increase in the frequency of coastal flooding in the next two to three decades, affecting hundreds of thousands of homes in low lying areas around the country. Managed retreat is not only feasible, but essential, in his view.
"We need to bite the bullet preemptively in a number of these locations and say 'let's in the longer time frame plan towards managed retreat', because we know it's going to be inevitable in a number of low-lying areas."
Seawalls might only be a temporary fix
Managed retreat is only one of a range of possible climate adaptation responses, alongside protective measures such as seawalls and dykes, accommodating for the threats by raising buildings onto stilts or lifting floor levels, and avoiding building in the problem areas in the first place.
In deciding which response is the most cost-effective and appropriate many factors will need to be weighed up, such as the level and frequency of the threat, the density and value of the housing and infrastructure at risk, and environmental downsides to the protection measure.
Seawalls may be a cheaper option in the outset (and a fit-for-purpose option in some situations), but Bell emphasises the need to consider the longer-term outlook, with walls needing to be built up incrementally as the sea level rises, increasing maintenance costs, and the risk of the seawall being breached and a wall of water tearing through.
There are also environmental impacts, with waves bouncing off the walls carrying away sediment and damaging the beach.
"The wall is going to finish somewhere. You can get some pretty severe erosion," says Bell.
The 'accommodation' response also has limitations. While buildings may be raised relatively easily – roads not so much, which can leave a community isolated.
"Access to roads I think is going to be one of the crucial issues… some areas may need to be retreated even if they're not directly impacted, because the one or two roads into that area are constantly flooded," says Bell.
The different approaches don't exist in isolation, and with a managed retreat process potentially taking decades, an interim solution might see protection or accommodation options used to buy time.
Making the funding fair
Amongst the many critical issues that will need to be tackled by a national managed retreat framework, one of the most crucial is who will foot the bill.
In considering potential answers to this question, Boston suggests distinguishing between 'preemptive' retreats, moving people before they suffer serious and repeated inundations, and 'post-disaster' retreats.
In post-disaster situations, in many cases people will have insurance and be eligible for some compensation, whereas for a planned retreat it's unlikely insurance will cover the losses.
Boston's opinion is that our track record of solidarity in the face of disaster suggests we will have some form of public compensation when dealing with losses due to a managed retreat.
"Given the history of this country, where we have taken the view that natural disasters are things that should be significantly addressed by the community as a whole, and that there should be some kind of collective risk sharing."
There are some big questions to be worked through around eligibility (e.g. how holiday homes are treated), possible caps on the total level of assistance, and how to ensure that the funding arrangements do not intensify disadvantage.
"There's the question of whether it would be fair to provide full compensation in the event of preemptive retreat to those who owned mansions on the coast, which might be worth millions of dollars," Boston says.
"People with significant resources aside from their family home are going to be better able to move out of harm's way and protect their interests to those who have very limited assets, or indeed no assets at all."
Boston addresses funding issues in detail in a recent report in which he recommends a few features that "merit consideration" for a compensation scheme: a single funder; multiple sources of revenue (like ACC); an element of pre-funding (like EQC and Super); tailored compensatory arrangements for the loss of Māori land and other assets; a new Crown entity to manage the scheme.
Empathetic process needed to get community on board
Paula Blackett is the Principal Environmental Social Scientist at NIWA, with experience working with communities around climate change adaptation.
She says mature discussions about managed retreat are essential, but it's a conversation people are reluctant to have.
"The word 'retreat', it feels like we're losing a battle. But in some situations, the hazards resulting from climate change are a battle we can't win in the long term… and moving out of the way is probably one of the key long term solutions."
Although the social impacts of relocating people through managed retreat are vast, Blackett says it's important to consider that against the risks to life, health and happiness if people stay put, and the emotional toll that repeatedly fixing things and waiting for the next inundation or flood event will take.
"You don't just walk in and say 'all right guys, we're moving, you're done here!' It's a carefully thought out, empathetic process that happens over a period of time, which allows people to express their emotions and their hopes for the future, and works through some of these fears of fragmentation and loss."
In her view, moving people as a group, such as through land swaps, as they did in Grantham in Queensland after devastating floods in 2011, can help maintain community cohesion and connections to place.
She cautions against social impact assessments of adaptation options that only look at a five or 10 year time frame.
"Protection of what we have today dominates the thinking. But our future selves and future communities will not thank us if we don't think very carefully about what we do," Blackett says.
What if people don't want to go?
For various reasons it is inevitable that some people will not want to commit to a managed retreat process. Bell has come across this stoic attitude already while working with communities on their adaptation plans.
"Sometimes people will say to me 'we're fine here, we'll just tough it out and take the risk on ourselves'," Bell says. But it could present future issues for councils needing to provide infrastructure such as wastewater and drinking water for those staying put.
Boston acknowledges that in some situations, a "degree of coercion" might have to be applied, if people chose to remain in high risk areas because of the dangers it presents to human health, vulnerable people and ultimately to the lives of first responders who might have to rescue them.
"We won't be able to tolerate multiple situations in which the police are literally dragging homeowners off their properties or out of their businesses – I just don't see that as being viable in the kind of democracy we are."
Avoiding this scenario is one of the many reasons Boston thinks we need a comprehensive public compensation scheme to encourage people to move voluntarily – and he says any such scheme will need enduring cross-party support for success.
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