Why NZ Homeowners Are at Risk (and How InSAR Helps)
- Avant
- Aug 21
- 4 min read
Updated: 6 days ago
Owning a home in Aotearoa comes with a bit more than just a mortgage and a lawn to mow. Our country’s wild landscapes are the result of some serious underground forces, and they haven’t stopped moving. With active faults, creeping hillsides, coastal erosion, and volcanic zones across both islands – many homeowners are sitting on land that’s subtly shifting beneath them.
Especially for Kiwis, a lot of this movement happens too slowly to notice… until it doesn’t.
What makes New Zealand homes vulnerable?
New Zealand’s property risk profile is unique. Our homes are built on land that’s being stretched, squeezed, lifted and dropped as two tectonic plates grind past each other. Some of the risks to homeowners include:
Landslides: Heavy rain or saturated slopes can cause gradual hillside creep – or sudden, catastrophic collapse.
Subsidence: The ground slowly sinks over time, damaging foundations, driveways, and underground services.
Fault movement: In places like Wellington, Kaikōura, and Napier, active faults can shift suddenly, tearing up streets and cracking homes.
Coastal erosion: Homes close to the shoreline are losing metres of land each decade – and the process is accelerating with sea-level rise.
Volcanic deformation: Areas in the central North Island can subtly bulge or sink due to changes underground, long before an eruption is even on the radar.
The challenge for homeowners is that traditional property inspections don’t pick up on these long-term, underlying issues. Builders check the house. LIM reports check the council file. But who’s checking the land itself?
That’s where satellite monitoring – and InSAR satellite data comes in.
How InSAR watches the land move
InSAR (Interferometric Synthetic Aperture Radar) is a satellite-based system that tracks tiny ground movements with millimetre precision. It works by comparing radar scans of the same place taken days, months or years apart.
Think of it like a time-lapse… but instead of seeing visual changes, InSAR sees distance changes. Even a 3mm drop in the ground surface can be detected by comparing how long the radar signal took to bounce back.
This isn’t just theory. It’s already being used worldwide to monitor:
Earthquake zones
Landslide-prone hills
Cities with sinking infrastructure
Volcanic activity before eruption
Coastal areas losing elevation over time
And now, it’s being used in New Zealand, for the exact purpose of assessing residential land stability.
Real risk, real examples
Let’s look at a few local cases:
Matatā, Bay of Plenty: After years of concern, parts of the town were declared too unstable to live in due to risk of debris flow. Movement in the terrain was happening gradually over time, invisible to the eye but not to InSAR.
Wellington hillside suburbs: Suburbs like Karori and Ngaio are built on unstable slopes that have shown consistent ground movement. These areas are considered high risk for future land failure, especially after major rain events.
Kaikōura earthquake (2016): This 7.8 magnitude event caused more than 10 metres of surface rupture across multiple fault lines. Sentinel-1 satellite data produced striking interferograms that mapped the deformation across the region, validating the power of InSAR for post-event analysis.
Why this matters for property owners
Ground movement doesn’t always show up on the surface until it’s too late. Cracks in your walls, uneven flooring, or jammed windows could be signs of deeper problems.
What InSAR offers is a way to identify trends early – before they cause serious damage or insurance headaches. It gives property owners insight into what their land has been doing for the past 10 years.
This is especially useful when:
Buying or selling property in a risk zone
Building on new or subdivided land
Living near hills, faults, or reclaimed areas
Dealing with insurance claims for subsidence or slip
Planning long-term developments or infrastructure upgrades
It’s about shifting from reactive to proactive. Not waiting for the cracks to show before asking questions.
LandSure: Bringing InSAR to the homeowner
Until recently, this type of technology was only used by large infrastructure projects, energy companies, mine sites or universities. But that’s changing.
Avant, in partnership with UK-based InSAR specialists SatSense, has developed LandSure. It's a digital reporting tool that turns raw satellite data into a readable land movement report for any property in New Zealand.
What you get:
A 10-year historical analysis of vertical ground movement
A clear “traffic light” risk indicator (green, amber, red)
Easy-to-read maps showing the stability of the land
A summary for engineers, insurers, or planners to reference
You simply enter an address, and the report is generated. No site visit. No wait time.
LandSure is leading the way in making this high-end geotechnical monitoring available for everyday Kiwis – giving buyers, sellers, and property owners confidence in the land beneath their feet.
A tool every Kiwi homeowner should know about
In a country as dynamic as ours, the stability of the land is just as important as the structure on top of it.
InSAR gives us the ability to see risk forming before it becomes a crisis. It turns guesswork into data. And with services like LandSure now available, that data is finally in the hands of the people who need it most: you.
Comments