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Are houses on ‘stilts’ a good solution to more frequent flooding?

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During the flooding in Wellington final weekend, water got here up onto Guy Marriage’s path. But his residence stayed dry.

The Victoria University School of Architecture lecturer constructed an ode to the traditional Kiwi bach on piles, a mere 5m above sea stage north of Wellington.

The spot is famend for ferocious northwesterly storms and a surging ocean that is endlessly altering the shoreline. Oh, and it is a tsunami zone in an space inclined to earthquakes. But the home has solely had water beneath it as soon as, thanks to a cyclone in 2018.

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Will this bach on stilts be secure from storm surges, king tides and local weather change?

‘One in 100 year’ floods seem to now be an annual occurrence. More than 60 homes in Wesport were red-stickered as uninhabitable by Thursday morning due to flooding. Many owners of baches, cribs and beach houses around New Zealand’s coast are probably to discover their houses uninsurable inside 20 years. So might constructing more houses on “stilts” be a good solution for New Zealand’s flood-prone areas?

READ MORE:
* Award-winning bach 20m from high-tide mark defies local weather change
* NZ’s first ‘local weather secure’ residence affords secure housing on flood-prone land
* What to do in regards to the fixed menace – and actuality – of flooded houses in coastal communities
* Pitched as a solution for sea stage rise, questions stay over floating houses’ affordability

“There is certainly a logic to piles,” said Marriage. “A raised timber floor has to have a crawl space, normally about two feet. That means if you’re in an area which gets wet, you don’t have to worry about the first two feet of water.

“One of the things New Zealand always used to do was build timber floors and piles and raise houses off the ground,” he added, however by the 80s we’d began doing a lot of concrete slabs.

Marriage teamed up with his cousin Briony Ellis and her husband Roger Wood to build a classic family bach from their savings, for just $165,000. It featured on TV’s Grand Designs.

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“We wished a easy house by the seaside – protecting the supplies easy, paring it again, nothing fancy. You do not want huge houses to have a bach, you want simplicity by the ocean, and sunshine,” stated Marriage of the bach.

It has two distinct kinds, the taller being paying homage to a lighthouse. And after all there are giant home windows to maximise the views.

During the 2018 cyclone, “the waves pushed the drift wood and seaweed right underneath the house, but we were sitting comfortably without worry,” stated Marriage.

Jacking up an current home with wood flooring onto greater piles may cost about $20,000, he estimates, which is likely to be cheaper in the long term than flood clean-up.

Flood-proofing is situationally particular, he stated. “But if you live somewhere there could be water going through your house, then the logical thing to me would be to put it on piles and raise it up.”

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Architect Guy Marriage, left, with Briony Ellis and Roger Wood, who pooled their assets to construct a traditional Kiwi bach.

Retired architect George Higleholt and spouse Yvonne name their relocatable residence on a steep, slender part overlooking Nelson’s estuary a “modern-day ark”.

During the latest tropical storm Fabian, “the water basically came through the estuary and ended up halfway under the house. Are we okay? Yes. That is why we built to the conditions,” he said.

“Our house can sit on water up to 1.5m, so we’re probably safe for the next 150 years. After that, well it won’t be our problem,” he joked.

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The Higleholts spent $572,000 on the 300 square-metre house, but a lot of labour costs were saved by Higleholt working on site.

The Higleholts’ affordable, energy-efficient house, another featured on Grand Designs, features two gabled pavilions that reference the local apple-packing sheds. Their land by the estuary is a flood plain, but the home on wooden piles is relocatable, able to be “cast off”.

The piles the Higleholts used will not be the piles of the 50s and 60s. There is an engineering part, however they continue to be a “simple and affordable” solution. “I would say they cost less than two per cent of the house. On a half-million-dollar house, the piles may cost $10,000,” he said.

But while we can lift up our houses, he points out, “we can’t overlook roads and infrastructure”.

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Grand Designs host Chris Moller, pictured outside George and Yvonne Higleholt’s ‘modern ark’ house in Nelson.

Can we learn from overseas?

There is no ‘one size fits all’ approach to building more flood-resilient houses, according to Engineering New Zealand chief executive, Dr Richard Templer.

“With climate change, we know some areas of New Zealand, including the western sides of both islands from Taranaki to Westland, will be at greater risk of severe flooding events,” he said.

The professional body warns we can’t just “build our way out of things” with large-scale infrastructure like pipes, stopbanks and floodways – it is too costly.

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Tyler Croft and Amy Axford-Hooker at their Westport rental. They have misplaced all the things within the latest flooding and can want to discover elsewhere to live. Amy is due to give beginning in two weeks.

Instead, it’s calling for housebuilders to make houses more resilient, for instance by including dual-purpose areas like garages that may retailer giant quantities of water, elevating houses, designing efficient roof and drainage methods, and making houses relocatable.

Natural hazards researcher Bruce Glavovic from Massey University stated elevating houses up on stilts is frequent in elements of the world with frequent storms and floods, like low-lying areas of the Mississippi delta and elements of Asia.

“They can certainly reduce the immediate impact of flooding. Some people even live on elevated homes located below high watermark along some coasts,” he stated.

But with a altering local weather rising the depth and frequency of some climate occasions in some elements of the world, many of those measures will grow to be more and more precarious, he stated.

Researcher Belinda Storey of Climate Sigma stated whereas there are lots of unknowns in figuring out the consequences of local weather change, scientists are “very confident” that the ocean stage round New Zealand can be up by a minimal 10cm in 20 years. NIWA predicts double that sea stage rise.

“We will see some very innovative design responses in years to come,” Glavovic stated. “But none of these will overcome the ravages of rising sea level for large populations.”

Ideas like ‘floating towns’ – one thing being thought of in elements of the Netherlands – wouldn’t be a lifelike possibility for New Zealand, he stated.

Avoiding improvement in hazard-prone areas stays “the most compelling and only feasible long-term solution”.

‘Human arrogance’

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The entry to the home is tall and slender, similar to a boat shed.

When Richard Naish and his household purchased a “scary” little bit of Tāwharanui Peninsula shoreline north of Auckland, they questioned: Does it even make sense to construct a seaside home simply 20m from the high-tide mark?

The storm water drains constructed for the small seaside group 50 years in the past are undersized, and when it rains, it pours into “a small lake” on his World Architecture award-nominated property.

The director of RTA studio’s solution was an “experimental” holiday house sitting on piles that extend 12m into the ground, designed to resist coastal erosion, sea-level rise and flooding from storms.

“That is phenomenally deep, about three to four stories down,” Naish explained. Water can flow underneath the stilts, and away across recontoured land. “We created a concrete channel. When the water flows across, it sinks into the rocks, flows below the rock level and out the other side,” Naish said.

The lowest part of Naish’s house is still 4m above high tide, so even in a big weather event the water will flow up onto the section, but not indoors. It means the home should cope with 1m or more of sea level rise.

Patrick Reynolds

The interior is lined with pale timber contrasted by dark structural portals and joinery.

PATRICK REYNOLDS

Cut-out windows in the raw-finished wall beside the kitchen reference the traditional boat sheds on the coast.

Could this grow to be a regular a part of New Zealand constructing?

“The courageous architect side of me says yes, let’s do it. Let’s build climate-change-proof houses on the coast,” said Naish. “My community voice says let’s not – let’s respect mother nature and what is happening and retreat inland.”

To suppose we are able to carry on dwelling this manner is “human arrogance” in our climate-changing world, he stated.

PATRICK REYNOLDS

The view from the bach is framed by this magnificent pohutukawa tree.

Naish believes that in the end, new improvement in flood-prone areas could have to be restricted. If we have now a alternative about constructing new, then we must always construct elsewhere.

In areas that may’t be purple stickered as a result of they’re “living, breathing communities”, what we are able to do is create minimal ground ranges, he stated.

That is already taking place. “All of these flood-prone areas have regulations for them and require engineered foundations lifted to a safe height.That is the only way forward.”

But placing houses above the ocean will not be a lot use if all of the infrastructure, roads and airports are underneath it, Naish factors out.

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