By Gareth Vaughan
If we were building Auckland from a blank canvas with the knowledge we have today there are lots of places where you wouldn't build, says Martin Brook, Associate Professor of Applied Geology at the University of Auckland.
Speaking in the Of Interest podcast, Brook says this year's spate of extreme weather events means we are talking more about the dangers of floods, slips and landslides, but there's a lot of work to do to better prepare ourselves for future such events.
"Generally if we were planning we'd avoid slopes and flood plains and obviously that includes a lot of Auckland. In fact GNS reports in 2009 stated that most of Auckland is at moderate or high risk of landslides...That encompasses a lot of the landscape of Auckland and it would mean that we wouldn't build in a lot of Auckland," says Brook.
"If you look at the Auckland Unitary Plan it doesn't encompass the geomorphology [the study of landforms and landform evolution], if you like, which is the land forms and the earth's surface processes that are currently shaping our landscape."
"I think we build too close to slopes. We love doing that, we cut trees down, we love building mansions on slopes so we have wonderful views. We have a history in New Zealand of building on unstable land, and part of that is the 1981 Local Government Amendment Act which absolved councils of civil liability if they permitted building on unstable land," Brook says.
He says landslides have killed more people in NZ over the last 150 years than earthquakes.
In parts of Auckland Brook says there's a lack of adequate building set-back distances, being the distance between a dwelling and slope or cliff, with set-backs from the bottom of slopes also very important.
Ideally, Brook says, a house on a 30-metre high North Shore cliff should be set-back about 100 metres from the cliff edge.
Brook suggests we have a general issue of politicians not liking to make difficult decisions, but is encouraged by Finance Minister Grant Robertson recently providing risk categories and definitions for properties affected by flooding and cyclones.
"People are talking more about hazards other than earthquakes and volcanic eruptions. Storms do cause floods and landslides and we seem to get them rather often unfortunately. So people are talking about this which I think is great. So let's hope some good does come out of it," says Brook.
In the podcast Brook also talks about managed retreat, places becoming uninsurable, the idea for a national geotechnical control office perhaps within the Earthquake Commission (Toka Tū Ake EQC), warning systems and monitoring of moisture levels in slopes, and why he'd prefer "a more holistic storm based approach" than Auckland Council's Making Space for Water initiative.
*You can find all episodes of the Of Interest podcast here.
53 Comments
I think it says a lot about the current want to regulate. “We wouldn’t build in most of Auckland because of one flood”. In fact I’d argue it’s land use regulation that has caused a lot of the problem, no one builds houses on piles these days due to height to boundary restrictions, so our houses are only 100mm off the ground.
That probably contributes, but also because the concrete base is better for insulation and structural accuracy for framing or precast walls etc.
Having said that, I've seen lots of new developments that build up the soil height on sections before building to get the section flat enough for the concrete base. This can cause havoc with water then flowing onto neighbours' sections. Happened to a mate and the response was: the modelling didn't show any issues. Even as the rainwater was running through his bottom storey.
Jimbo, you often complain about planning rules, including height in relation to boundary.
I therefore presume you would be comfortable with no shading protection rules, and would also be comfortable with that equating to someone being able build in a manner that obliterates winter sun into your property?
Why would anyone build appartments etc in a suburban area like ours if they were allowed to build them closer to the city where there is better amenities? Left to it’s own devices I believe the city would grow like it should do, with density in the centre and stand alone houses in the outer. If you appreciate a back yard with sunlight then don’t buy near the centre (although I am sitting outside now with a cup of tea and sun is streaming in from a fairly good height so it would need to be a very tall building to block it). The current planing rules are doing the opposite - protecting the rich in the centre with density in the poorer burbs. You can get resource consent to build almost anywhere, in rich areas it’s always contested but in poor areas people don’t have the knowledge or money to fight it.
Having said that I think height to boundary is one of the few planing rules that has merit. But it should cascade out from the centre, with much looser rules in the centre than the outer.
AFAIK there is nothing stopping your neighbour from growing massive trees near the boundary.
Apartments cost a lot to build. Terrace houses much less.
You seem to be drinking the kool aid that if there were few planning controls then most people would be able to buy or rent homes in central locations.
It’s a load of baloney.
A terrace house in the suburbs will always represent much better value for money than a central city apartment. Both land and build costs much cheaper.
Yes.
But it’s a gross simplification to say massively liberalising planning rules will result in a lot more supply.
There’s lot of factors beyond planning rules that influence what and how much gets built, and where.
Having said that, I would like to see more liberal planning rules (eg. I think there needs to be a higher bar for ‘special character’ protection). But there needs to be a balance.
End of the day why should someone expect to live in suburbia only a short distance from a CBD anywhere.
You're either wanting to live in the heart of civilisation or not. Worst case, the use of your own property only increases in value the more dense things get and then cash out and go live in the Waitaks or something.
Am building one right now on piles and subfloor way better than concrete floor also can run future services into the house if or when that happens also alot easier to re level after an earthquake look at the old pile weatherboard houses in Christchurch stood upto the earthquake better than modern concrete floor brick and tile
Slightly off topic sorry, but I have lived both rural and urban and would choose rural every time.
Can anyone tell me according to the data how the price of rural land (both highly productive and marginal) correlate with urban when housing prices crash?
[Just out of curiosity, here is ChatGPT’s answer. Rather informative, but not necessarily specific to New Zealand’s situation:
Historically, when housing prices crash, rural land prices tend to be less affected than urban land prices. This is because when housing prices fall, demand for urban land decreases, which can lead to an oversupply of land. Conversely, demand for rural land tends to be more stable, as it is driven by agricultural and other non-residential uses. However, the specific correlation between the price of rural land (both highly productive and marginal) and urban land prices during a housing crash can vary depending on a variety of factors, including location, market conditions, and government policies.]
Hard to say definitely. A house price crash is usually accompanied by a wider economic downturn, and there's a flow on effect into funding and viability of agricultural lands. But really depends on the nature of the land, suburban houses are pretty interchangeable, but it's hard to compare a dairy farm with a kiwifruit orchard or hop plantation.
Compare it to small town prices.
They are an "overflow" aspect so rise in price after main centers rise, and fall in price after main centers fall.
You'll see after or during the boom period people looked further and further afield to afford a place.
The main problem with rural is you're on your own and councils won't look to add amenities or safety nets to protect you from flooding etc actually you'll be first in line to be made into an over land flood zone to be sacrificed in order to protect the highly populated urban areas.
I doubt they turn down loans (profit) for no reason, they must get higher defaults from those. Ideally banks wouldn’t turn down risky loans, instead they should adjust the interest rate according to the risk. I have no idea why our household that is almost no risk whatsoever pays the same interest rate as someone with much less equity for example.
I don’t think councils can deny building consent can they? If you have an engineers report saying the build is sound I don’t think they can argue against it. They can only deny building consent if the design does not meet the building code or planning rules, they can’t just say “nah looks a bit dodgy”.
They can and do review the report internally, via multiple subject matter experts, and then generate a list of questions to which they require satisfactory responses. If there's an argument between the applicant's engineer and council's after the questions have been answered, they can require a peer review from an agreed third party. I think they could still decline an application after that, but would be unlikely to and the applicant can always apply to MBIE for a determination (building consent) or to the Environment Court (resource consent).
Nothing wrong with building on a slope, depends on the gradient. Hill tops are fine, cliff tops not so much. The best building sites are always elevated, the top of a hill is the best, impossible to flood. Also comes down to soil type, some places are very sandy this provides excellent drainage where as other places are all clay which is terrible and that also suffers massive expansion and contraction from wet to dry. The problem going forward is the 1 in a 100 year floods are going to be 1in 5 year floods so a whole pile of existing builds are now in unacceptable positions.
Insurance cost explosions are going to be the new normal - we just had a 30% increase in the Home and Contents and never make claims......for decades. We are not built in any risky zone/geology either.
See the new, latest flooding issues on the North Is East Coast.......another few hundred millions/Billion of damages ??? that We will need to pay for - (via increased taxes and insurances)
NZ will become and increasingly expensive place to live......or something has to give in a big way!
Brace: NEW taxes and much higher insurances are required.
So the entirety of NZ is stuffed perhaps??
- Maybe it is nationally, for the global reinsurers.......we just need to suck up the comming years of 10 to 40% increases and be happy about it.
I can afford to pay these increases, but I know some who just cannot and may drop the insurances altogether.
What will the banks do when the heavily mortgaged house, no longer has cover/or has inadequate cover?
Yes NZ is the next Greece in making and that too much worse. Greece had big European population around it to soften the blow.
What has NZ got? Pacific islands to come to our saviour?
The greed of previous generation had killed any hope for the next. Any intelligent who is under 35 and reading this post, make plans to leave this country as soon as possible. This place will be the playground of the rich and if don't want to be cleaning thier houses and washing their laundry, then leave now.
Hi Nguturoa, Sounds like Hawaiiki all over again. Last time your ancestors emigrated it worked quite well. Just exterminate the existing occupants and take over. But where will you go this time? Better off making the best of what we are all extremely lucky to have here in NZ.
Pa1nter. Only the ill-informed. Respected Geotech engineer Ian McCahon completed a study long before the ChCh EQ sequence, which predicted with uncanny accuracy the liquefaction effects following a decent shake. In the late 1800's ChCh's cathedral spire was toppled in a large quake. An early Early ChCh settler family, the Deans, chronicled large earthquakes that went on for multi year periods. The projected effects of the Alpine fault movement had been also well studied before then. AMI insurance drastically under allowed for the known effects of EQs in the city (for reasons that have never been fully explored).
You may be right about the floods but you may not be. Prior to this year for example it appears Auckland has had less extreme weather than we used to get in the 80’s. One year doesn’t make a trend.
I’m not a global warming denier, but we don’t actually know what global warming will do to our weather.
But that's the problem, they do come crying when it goes tits up. Look at all the cases all over the country where people are taking councils to court saying you must let us build this ugly as wall on the beach. Yes it will cause all the sand to the wash away, and ruin the amenity of the area for the public, but I need it to protect my coastal property.
Cities don't exist where they are because it was the geologically ideal place for people to live, they exist where they are because these where areas that had access to natural amenities like harbors, ports, fresh water, trading routes, fortifications etc.
Quiet aside from that I doubt government, having found even KiwiBuild far too difficult to manage, will ever propose a new city. In fact they won't even move the central government out of Wellington.
Yep, there are houses in my city that are built where engineers in the past said they shouldn’t be built (I was chatting to an old engineer about it), sure enough a couple of them are now uninhabitable and I believe others can’t get slip insurance. From my understanding it was local council who rubber stamped it all so what do you do….
Right now, large subdivisions are being planned very close to, or even within, areas around Napier flooded by Cyclone Gabrielle. I mean, sure there's been multiple major floods in the area recorded as far back as the 1860s, but it'll never happen again.
And let's not worry about the liquefaction risks in the areas south of Napier where fencers have great issues finding solid ground to support posts. Since the only large earthquake that will ever hit the area has already happened, this is no longer something to be considered.
We welcome your comments below. If you are not already registered, please register to comment.
Remember we welcome robust, respectful and insightful debate. We don't welcome abusive or defamatory comments and will de-register those repeatedly making such comments. Our current comment policy is here.