There are flash holiday homes on one side and big retirement homes on the other. Each side of the Coromandel Peninsula is threatened by the coming tide of climate change. National Correspondent Charlie Mitchell reports.

On a sunny and cloudless spring afternoon, John Leenan was surprised to find himself standing on a flooded street.

It looked like a wave had washed through the northern suburbs of Thames, on the Coromandel peninsula. Water was flowing up through the drains and pooling on the road, beneath parked cars and on grassy berms.

Leenan found at least three streets partly underwater. He stopped and put his finger in the water; it was salty. The sea was at least 200 metres away.

A bit of basic hydrology solved the mystery. The groundwater beneath Thames is connected to the sea, meaning it rises and falls with the tides.

The effect is usually invisible, hidden beneath buildings and roads and soil, but a particularly high spring tide had crept up through grates that would usually be closed and spilled onto the road.

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It was fixed the next day and the streets quickly dried. But it demonstrated how precariously the town is placed - not merely on the edge of the rising sea, but on top of it.

"When you see the level of the tide showing in the street, you realise just how low lying some of these residential spaces are in Thames," Leenan says.

"We're a bit of a sitting duck when it comes to climate change. Low-lying areas like parts of Thames and the Coromandel coast ... we're a bit of a disaster that just hasn't happened yet."

DOMINICO ZAPATA/STUFF The sea-wall is the only thing protecting Moanataiari, a suburb of Thames, from a rising sea.

On the other side of the peninsula, near the resort town of Whitianga, there's a beach with particular significance for New Zealand's colonial history.

Around 250 years ago, Captain James Cook stepped ashore to study a rare astronomical event, the transit of Mercury across the sun, which he hoped would allow him to calculate the longitude of New Zealand.

The experiment inspired the area's name, Mercury Bay. The beach where he disembarked is today called Cooks Beach, and the road that runs parallel is called Captain Cook Road.

A long time ago, a cairn was placed on the approximate spot where Cook undertook his experiments.

Much like Thames in the west, sea-level rise is posing a significant problem in the east, albeit in a different way. Instead of rising groundwater, it comes in the form of coastal erosion, a natural process made quicker and more consequential by climate change.

The coastline is moving inland in jagged bursts, getting closer to the roads and the houses that were built to enjoy the proximity to sea. Several dozen houses are in the area deemed most at risk, where there is "potential for complete loss of most properties" by 2100, according to the Waikato Regional Council's coastal erosion management strategy.

The shape of Cooks Beach has changed since Cook anchored the Endeavour to watch the planets. The sea has stripped away land, moving the coastline closer to the beachfront houses that now line the beach along Captain Cook Road, defended by seawalls jutting over the sand.

After a storm in July, the cairn marking Cook's experiment fell onto the beach, after the land underneath it eroded. It's now being held in storage until it can be placed elsewhere.

SUPPLIED A memorial to James Cook near Whitianga which fell onto the beach as a result of severe erosion.

The Thames-Coromandel District is relatively small - an estimated population of around 30,000 - but because it entirely comprises a peninsula, it has a sprawling coastline.

Its coastline is similar in length to Christchurch city (which includes Banks Peninsula), but it surrounds a population base 13 times smaller. And, unlike Christchurch, there is little space inland for people to move.

Some researchers have seen the Coromandel coast as emblematic of the issues facing small councils around the country.

It is already battling two common threats posed by sea-level rise – coastal flooding and erosion – on opposite sides of its coastal boundary. And due to its small rating base, it is having to make tough decisions about what should and shouldn't be allowed near the coastline, which is the district's greatest asset.

DOMINICO ZAPATA/STUFF Coastal housing north of Thames.

Although they share a peninsula, Thames and Whitianga are markedly different in character, which presents a social challenge.

The district as a whole has the oldest population in the country – one in three residents is retirement-aged – and many of these residents are concentrated in Thames, which has two large retirement villages on the coast. Most people in Thames live there permanently, and have for some time.

Whitianga used to be a sleepy beach community, but has since become a tourist destination. The majority of houses are now holiday homes, sitting empty until the summer months when the town's population can swell up to four-fold. Its popularity has come with significant investment, with new hotels and subdivisions and marinas popping up on the beach, and a revamp of the town centre, at a cost of more than $6m.

On one side you have tourists, marinas, and sandy beaches. On the other, you have retirees, anglers, and historic buildings.

CHRISTEL YARDLEY/STUFF The beachfront town of Whitianga.

Navigating the threat posed by sea-level rise is the responsibility of the district's coastal engineer, Jan van der Liet.

On his first day on the job, he already had a crisis on his hands - a storm had struck over the weekend, leaving a broken and damaged coastline when he turned up for work on Monday.

"Mother nature gave me plenty of work immediately," he says.

The storm that had struck in the first week of January was, on its face, unextraordinary. But it had arrived at precisely the wrong time, conspiring with a king tide and westerly winds to fuel high waves that hit the coast at speed, crashing over seawalls and into coastal streets around Thames.

Parts of the road north of Thames fell into the sea, and houses in Kaiaua and Tararu, small communities on the firth, were inundated with saltwater.

DOMINICO ZAPATA/STUFF Damage to State Highway 25 between Thames and Coromandel.

The enormous clean-up cost tens of millions of dollars. But among the storm's most enduring impacts was the long-term questions it raised. Chief among them: How should the peninsula prepare for storms in the future - which are certain to be more frequent and more damaging - as the sea rises?

Van der Liet is one of the few coastal engineers in the country solely dedicated to managing the coastline of a particular district.

A major challenge, as he sees it, is the different drivers on each side of the peninsula. It means there is no one size fits all approach: Different responses will be needed from bay to bay.

"The main challenges we have on our beautiful yet fragile coastline is that there are distinctive differences between our east coast and west coast," he says.

SIMON STEPHENS/SUPPLIED Flooding in Te Puru, on the Thames coast.

The erosion issue has been known about for a long time in Whitianga. Erosion setbacks on the district plan show how the coast is expected to move closer to the town centre, which itself is increasingly flood-prone.

It hasn't stopped development on the coast, despite the obvious sign of seawalls popping up along the beachfront and public land falling into the sea.

The community as a whole is stuck, says Dr Paul Schneider, a research fellow at Massey University who studies adaptation to climate change.

Schneider lives in the Coromandel, and has been researching the community's attitudes towards climate change for nearly a decade.

Through interviews with locals, authorities, developers, and others with a stake in the district, he has found a common thread: Sea-level rise, even now, is not seen as a major problem.

"If you talk to folks on the ground, here in the Coromandel especially, there's a laid back attitude to all of this," he says.

"Development-wise, there's almost a collective obsession with being in the here and now - do it while you can. People want to be on the coast, but they don't really want to see that it's not a good place to be."

There are already beaches where you can no longer walk from one end to the other at high tide due to the sea-walls, he says. But people are still in what he calls the "understanding phase" - a lack of agreement about the extent of the problem, and how it will affect them personally.

"I've found the level of understanding is really low, and there is little consensus in the public on the Coromandel for what it will mean and bring in the future," he says.

"But people's plates are all so full - it's not just single mums with busy lives, this is across the board, from infrastructure providers to council representatives, politicians and beachfront property owners.

"I've always been surprised, and continue to be surprised, by the level of acceptance, or even surrender. What I heard a lot is that 'when it happens, it happens, there's not a lot I can do about it.'"

One of the concerns is that those on the beach-front - who, in Whitianga, are typically wealthy - could have an outsized influence on the response to coastal hazards.

This type of conflict has yet to happen in Whitianga, Schneider says, although the "voices are beginning to get a bit louder."

"If you have assets tied up on the coast, what matters most is the protection of your property, and that's understandable," he says.

"What makes it more difficult is that private coastal property owners tend to be wealthy and have political power. If you then ask the general public what matters most to them, it's public amenity values, which boils down to the natural coast ... It becomes problematic when private property owners and local authorities interfere with the coastal processes in order to protect private property, because it stands in direct conflict with the public values."

It's a concern several researchers have raised about the social impact of sea-level rise: That it could risk privileging people who live on the coast, at the expense of those who do not.

The ongoing development in Whitianga means the community could be a prime example of this in the future.

At the moment, it's like a game of chicken, says University of Otago's Dr Lisa Ellis, who recently published research on the ethical implications of sea-level rise.

Because it is unclear who will pay for property that becomes uninsurable in coastal areas, the incentive is to push for others - namely, fellow ratepayers and taxpayers - to cover any damage.

"Generally speaking, people who make risky coastal investments are relatively advantaged, and the average ratepayer or taxpayer is relatively socially disadvantaged compared to those investors," Ellis told Stuff last month.

"It's not as if people are saying I want to take advantage of my fellow citizens. The problem is we don't have a predictable, legal framework outlying where those risks should lie."

WAIKATO REGIONAL COUNCIL Potential coastal inundation in Thames after a strong storm surge and 1m of sea-level rise.

On the other side of the peninsula, there is less private pressure to allow expensive coastal development.

But unlike Whitianga, Thames's geography - a narrow strip of land bounded by the sea and steep, forested hills - makes it difficult for the town to grow in the same way.

It has put the council in a difficult position. The easiest land to build on in Thames has already been developed, leaving only trickier, marginal land for future development.

Sea-level rise experts say councils should be wary of allowing continued development on the coast, given the inevitability of sea-level rise.

It's an argument which has been made directly to local authorities by the co-lead authors of central government guidance for councils on sea-level rise, Dr Judy Lawrence and Dr Rob Bell.

"[The guidance] should be the motivator for local government to really start being much more careful about what it's consenting in low-lying areas," Lawrence told Stuff last month.

While the Thames-Coromandel District Council has adopted the guidance, it remains to be seen how closely it will be followed, particularly in relation to much-needed public facilities.

SUPPLIED A proposed resort hotel in Whitianga.

It looks set to be tested on a long-desired project for Thames: A proposed pool and sports ground that would serve as a drawcard for families to the aging town.

Thames already has a swimming pool, on land it leases from the iwi. The pool, however, was built on an urupa. The council and the iwi have agreed to not renew the lease when it expires in 2027 so the urupa can be returned.

The town's existing sportsground is in a flood control area, effectively acting as a spillway. When it rains, water is released over the State Highway, flooding the sports grounds and seeping out to sea.

One proposed version of the facility includes swimming pools, hydro slides, spas, a cafe, and sports fields, costing upwards of $20 million. The question is where such a large building can go.

After narrowing down three possible sites, all close to the foreshore, the council is moving forward with a site on a low-lying paddock near the airfield, at the town's southern entrance.

The paddock already floods with saltwater after storms, and the regional council's inundation map shows it is among the areas most prone to even modest sea-level rise in the district.

DOMINICO ZAPATA/STUFF A coastal paddock in the area where a new sports ground and swimming pool are proposed to be built.

Although it has yet to undertake public consultation, the council recently spent $1m buying land for the proposed facility. Some in the community have already raised concerns about building an expensive public facility on a floodplain.

Among them is local property lawyer Denis Tegg, who thinks there's a critical flaw with the council's reasoning. He says that under current planning laws, it's unlikely to get resource consent.

In a lengthy legal opinion, he argues that planning laws require development be "avoided" in coastal hazard areas - and a recent court decision determined that "avoid", in simple terms, means 'not allow'.

"It is highly improbable that the proposal will be consented under the RMA," his opinion concludes.

He strongly urges the council to find a new location for the proposed facility.

The council is insistent it has done its due diligence, and says it's reviewing what it needs to do to get resource consent. The area is already protected by seawalls, it says, so no new protective infrastructure would be needed.

Its due diligence includes a feasibility report commissioned from Tonkin & Taylor which found there were no "fatal flaws" in putting the facility there. They were not, however, asked to look at groundwater flooding, despite its own testing showing the groundwater is 1m below the surface. (The council says this will be taken into account when applying for resource consent, and in the building's design).

The testing done by Tonkin & Taylor also appears to fall short of the new central government guidance (it was completed before the guidance was released), by considering the effects of 1.3m of sea-level rise. Under the guidance, sea-level rise of around 1.9m should be considered.

The council, however, says any facility's design would take flooding risks into account.

"Risk from flooding and inundation will be factored into the design of any facility that is eventually built at this site," a spokeswoman said in a statement.

"Keep in mind, the site is already protected from coastal flooding by stopbanks, which also protect the airfield, the wastewater treatment facility and the Totara Palms subdivision."

DOMINICO ZAPATA/STUFF Parts of Thames's main urban area are on the edge of the firth, including a supermarket and a mall.

While the council has been praised for its recent work towards addressing coastal hazards, there is still lingering scepticism about how far it is willing to go.

The council was not among the more than 40 councils that signed the Local Government Leaders' Climate Change Declaration, a pledge to take strong action against climate change, despite the fact that Thames-Coromandel is among the districts most exposed to sea-level rise.

In the public section of a council meeting earlier this month , Thames resident Sheena Beaton read out the long list of names of the councils which had signed the declaration, asking why the Thames-Coromandel district had not.

There are lingering questions about the new pool project, too. After deciding to pursue a facility at the site by the airfield, the council told its regional counterpart, the Waikato Regional Council, what it was thinking.

Through a no surprises policy, staff from both councils drafted the regional council's response, which would effectively support the district council's plans.

The emails, obtained by Stuff, include a telling exchange: A draft of the letter was edited to remove references to climate change, at the behest of the district council.

One management-level district council staffer, responding to a draft version of the letter, wrote: "I don't think [name redacted] will like the reference to 'climate change strategy'," they wrote.

"Is there a term 'we' would prefer they use?"

The name, redacted by the district council but released on request by the regional council, was "Rob" - presumably the district council's chief executive, Rob Williams, the intended recipient of the letter. (The council, in a statement, confirmed it was referring to Williams).

There was further discussion about requested changes, before the letter was finalised and sent, largely untouched from its draft version except in two significant ways: The reference to "climate change strategy" was removed, as requested, and replaced with the term "adaptation strategy"; and a second reference to "climate change" risk was removed and replaced with "inundation" risk. A third reference to "impacts of projected climate change" remained in the final version.

The council says the references to "climate change" were removed because the term was too broad, and encompassed issues like mitigation and increased bush fire risk, alongside sea level rise.

"We preferred to be specific in our correspondence with Waikato Regional Council and so deleted the references to climate change in preference of more specific terminology about the issues at hand," a spokeswoman said.

DOMINICO ZAPATA/STUFF Locals in Moanataiari, a suburb of Thames, walk along the sea-wall that protects the community from the sea.

While the council's public facing position on climate change is progressing, like other coastal councils, its willingness to take a stand remains unclear. Coastal development drives short-term economic activity, but may become a burden in the long-term, if retreat is required.

"The investment they allow generates revenue, and no one really likes biting the hand that feeds them," says Schneider, the researcher.

After nearly a decade speaking to people in the Coromandel about climate change, attitudes are changing, he says. Early on, he would avoid using the term "climate change," because some people treated it with resistance.

The storm in January was a "game-changer", he says, and made the issue starkly apparent. Now that climate change was widely accepted, the barrier was one of understanding how it would affect people - which, in the Coromandel, remains a significant issue.

"I think this coastal conundrum can actually be turned into an opportunity," Schneider says.

"I still believe that the Coromandel has the potential to actually lead the way in this space, with the right kind of people on board."

WAIKATO REGIONAL COUNCIL Potential coastal flooding in Whitianga after a strong storm surge and 1m of sea-level rise.

The council recently approved spending of $2.6m over three years for coastal hazard issues. It's using a model recently piloted in Hawke's Bay, in which the coastline is divided into pieces to be managed individually.

Each area will have a community-led plan with timeframes of 10, 50 and 100 years, which can be changed as the situation develops. Some may choose to stay and hold the line, others might look to slowly move away.

"You're looking at all the options, from the sublime to the ridiculous," says van der Liet, the coastal engineer.

"That includes managed retreat, doing nothing, fantastic schemes... The question is always how much is the public willing to pay, and how much the council will contribute."

With that work likely to take years, it could be some time before a long term climate change strategy is in place for the Coromandel communities.

DOMINICO ZAPATA/STUFF A new subdivision recently built on the Thames foreshore, which has raised flooding concerns.

At least one is already taking matters into its own hands. A small community called Tararu, north of Thames, has had its own community flood protection scheme for 20 years, which was damaged during the January storm.

The community is fundraising to rebuild it, through a process run by a community elected committee: "It's a little community that's becoming quite resilient," van der Liet says.

Mirroring that kind of effort across the district would be a challenge, but it has to be done.

"The fact is climate change is happening, sea-level rise is happening, so how are we going to deal with it and make it a resilient community?

"It's tricky and there are challenges. But I like challenges."