Agencies rethink faster impact of climate change on major new projects

Terrible weather and stark new sea level rise data this year has led to a rise in public concern about the impacts of climate change in the capital.

Both factors have also prompted Wellington authorities to take another look at some large infrastructure projects just getting underway.

May saw the release of chilling new sea level rise data, which showed swathes of coast in and around the harbour sinking - effectively doubling the rate of sea level rise.

It means in just 18 years parts of the capital will see 30cm of sea level rise, causing once-in-a-century flood damage every year.

Construction has just started on the new walking and cycling path linking Wellington and Lower Hutt.

Waka Kotahi's Robyn Elston said it previously thought the project might need an upgrade in 50 years, but it may have to happen five or 10 years sooner.

"It would be additional walls or raising of the path. The actual design does allow for adaptation."

Over the other side of the harbour, work on Eastbourne's new $30 million cycleway has begun.

Hutt City Council head of transport Jon Kingsbury said, given the storms this year, he has asked the builders to check if there was anything that could be done within its resource consent - but over and above the planned work - to future proof it.

"Discussions that might have been a few years down the track are now just coming forward so that we can start looking at these options for increasing resilience a little quicker than we might have otherwise."

The path won't be any higher than the current road - meaning in large storms waves could still break onto the road, requiring ongoing repairs.

But Kingsbury said the new path was designed to repel waves, and could be more easily upgraded when needed.

He said blocks could be dropped into place in the wall - similar to Lego - but for now it was a solid foundation to build from.

Long term the council might look at other protection options including a possible offshore breakwater to take some force out of the waves smashing into the sea wall.

'The water's got nowhere to go'

Greater Wellington Regional Council senior natural hazards analyst Dr Iain Dawe said an increasing climate risk, which flew under the radar for many people, was how sea level rise would affect places away from the shoreline.

"A lot of our stormwater is gravity fed, you've probably seen the pipes coming out of sea wall or flowing across the beach.

"If you've got a storm surge running or you've got flood waters blocking that pipe ... the water's got nowhere to go so it literally just [backs up]."

For example Miramar, Kilbirnie and parts of Hutt Valley like Petone, and areas of the Kāpiti Coast and Wairarapa could require pumping stations at a cost of tens of millions of dollars.

Wellington and Hutt Valley already face spending billions of dollars to upgrade failing water infrastructure.

Wellington City Council climate change response manager Alison Howard said the major question hanging over all climate resilience decisions was: who will pay for what among ratepayers, taxpayers, councils, and central government.

The answer to that was yet to be revealed, it is part of resource management act reform still underway.

Robyn Elston from Waka Kotahi said the money it spends fixing highways and other infrastructure from storms increases every year, and the agency is more and more thinking about how the transport system may need to change.

Meanwhile, Dawe said the council used to get significant pushback from homeowners and politicians about the need to take action on climate change.

But he, Waka Kotahi and the councils all said the extreme weather and increased damage in the past year have prompted a sea change in the public's interest and appetite to start to deal with it.

Dawe also said the launch of the Sea Rise map showing in a fine grained way which places were going to be worst affected has been a game changer for public awareness.