Key Points:

  • New Zealand doesn't have a 'nationally co-ordinated plan' to adapt to climate change
  • Councils given four best case to worst case scenarios to consider when planning
  • More than $200b in public assets and infrastructure at risk

A Government-commissioned report has acknowledged New Zealand doesn't have a co-ordinated plan to deal with future climate change, which threatens to damage hundreds of billions of dollars of property and infrastructure.

The Climate Change Adaptation Technical Working Group's stocktake report, released this morning, forms a first step toward putting New Zealand on track with other countries which have already begun adapting to more frequent extreme weather and sea levels which could be up to a metre higher by 2100.

It revealed a range of weak spots and knowledge gaps - notably that there was no nationally co-ordinated strategy, and that New Zealand tended to react to events instead of preparing for them.

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It found inconsistencies in timeframes across legislation affecting adaptation, and some "competing objectives" across legislation and policies, meaning roles could be confused and investing in resources was made challenging.

Without investment in building capability, capacity to adapt was "limited", the working group reported.

The Government also today released new guidance setting out a 10-step process for councils and communities based on the latest science.

The Niwa-produced Coastal Hazards and Climate Change recommended a planning approach that involved mapping out a series of possible actions over time based on several scenarios for local conditions.

It offered four scenarios, ranging from a best-case scenario where the world was successful in ceasing carbon emissions by 2100, through to a scenario where emissions increased, climate change continued unabated, and the polar ice sheets melted faster than currently expected.

Surface flooding along Auckland's Tamaki Drive in January 2011. With just 30cm events of sea level rise, such events could happen as often as once every four years. Photo / File
Surface flooding along Auckland's Tamaki Drive in January 2011. With just 30cm events of sea level rise, such events could happen as often as once every four years. Photo / File

But it stopped short of making firm predictions of sea level rise as there remained too many unknowns.

Further work on adaptation was under way, and another working group report on how New Zealand could adapt to climate change was due in March.

"It's important that New Zealanders have a clear picture of the potential impacts of climate change so that communities, local and central government, business and other sectors of our economy can make well-informed decisions about how we build resilience and adapt," Climate Change Minister James Shaw said.

READ MORE: The Big Read: Our slow moving disaster as sea level rises

Most of New Zealand's major urban centres and most of our population were located on the coast or floodplains of major rivers.

Communities, homes, commercial assets and infrastructure were exposed to flooding, sea-level rise, storm surge and inundation from rising ground water levels.

The mid-range projected sea-level rise over the next 50 years was 30cm - enough to effect all coastal areas to varying extents.

Flooding in South Dunedin in June 2015. 30cm of sea level rise would make flooding in Dunedin a one-in-two-year event. Photo / File
Flooding in South Dunedin in June 2015. 30cm of sea level rise would make flooding in Dunedin a one-in-two-year event. Photo / File

Under this scenario, in Wellington a one in 100-year flood would become an annual event, in Dunedin this would become a one in two-year event, and in Auckland a one in four-year event.

That meant the once-in-a-century January 2011 storm that put much of the Northwestern Motorway underwater would happen once every four years, and 40cm would make it a two-year occurrence.

A 70cm rise would make it a monthly event.

It's important that New Zealanders have a clear picture of the potential impacts of climate change

Damage and disruption to assets and critical infrastructure - including more than $200 billion in government and council-owned infrastructure assets - was expected.

The most recent national assessment found nearly 170,000 buildings sat within 3m of the mean high water spring, exposing them not just to sea level rise, but also storm-tide and wave flooding that could reach 1-2m in exposed places.

Nick Gant from Kohimarama unsuccessfully tries to paddle through a king tide-flooded Tamaki Drive in 2014. Photo / File
Nick Gant from Kohimarama unsuccessfully tries to paddle through a king tide-flooded Tamaki Drive in 2014. Photo / File

If all of those buildings were lost, they would cost $52 billion to replace.

About 68,000 buildings are below the 1m mark, carrying a replacement value of about $19b.

By the end of the century, the uncertainty range of the expected rise would likely widen to between 50cm and 1m, depending on how global emissions track.

The reports come after calls from the local government and insurance sectors for more clarity and consistent guidelines.

READ MORE: Q&A: What we don't know about sea level rise

Last year, the Insurance Council of New Zealand released a report that included 15 recommendations to address risks from natural hazards, demanding more information, more funding and a nationally co-ordinated strategy.

For insurers, which have chalked up a record $242m in weather related losses this year, climate change could mean hiking up excesses or premiums, or both, and, further down the track, putting exclusions in place, or withdrawing coverage for some properties altogether.

A wave crashes over a house in Haumoana, Hawkes Bay. Two thirds of New Zealanders live in areas threatened by flooding or storm surges. Photo / File
A wave crashes over a house in Haumoana, Hawkes Bay. Two thirds of New Zealanders live in areas threatened by flooding or storm surges. Photo / File

More than 50 mayors and chairpeople have also signed a declaration singling out climate change as a serious issue facing communities.

Local Government New Zealand president Dave Cull has suggested a new climate-focused mandate could be built into the Local Government Act, along with a clear statement on responsibilities for adaptation actions that included fiscal responsibility and legal liability.

The new reports have been published on the Ministry for the Environment's website.