The Sea Level Rise Gap in Auckland's Unitary Plan: What Coastal Buyers Need to Know

If you're buying near the coast in Auckland, there is a gap between what the planning rules say and what the science says about sea level rise. Whether that gap closes or not, it is something coastal property buyers should understand before signing.

§ 1.0The short version

Three numbers you need to understand before buying coastal Auckland property.

§ 2.0What the current rules actually say

Auckland's Unitary Plan defines three coastal hazard areas: the coastal erosion hazard area, the coastal storm inundation 1% AEP area (present-day risk), and the coastal storm inundation 1% AEP plus 1 m sea level rise area. It is this last one — known as CSI1 — that matters most for property buyers.

Under Chapter E36 of the Unitary Plan, if you want to build or extend a home in the CSI1 area, the finished floor level of any habitable room must be above the 1% AEP coastal storm inundation level plus 1 metre of sea level rise. This is a legal rule with real consequences: it determines your consent requirements, your minimum floor level, and whether certain types of development are even possible on your site.

The CSI1 overlay is what appears on your LIM report. If your property boundary intersects this layer, you will see a coastal inundation notation on your LIM, and any development will need to address the coastal flood risk.

§ 3.0What you can actually see on council's maps

Auckland Council's GeoMaps viewer actually shows five different coastal inundation scenarios under the 1% AEP event, not just the 1.0 m one. The available layers range from present-day risk (no sea level rise) through 0.5 m, 1.0 m, 1.5 m, and up to 2.0 metres of sea level rise.

This means you can already see, for free, what the coastal flood zone looks like under the MfE-recommended range. The 1.5 m layer roughly aligns with what the science recommends for most of Auckland's coast. If you are buying near the coast, toggle between the 1.0 m layer (the current AUP control) and the 1.5 m layer, and check whether your property falls inside the larger zone.

These additional layers do not trigger any legal requirements today. But they give you a picture of what could happen under different futures — and that is useful information when you are making a decision about where to put your money.

§ 4.0What the scientists recommend

In 2024, the Ministry for the Environment updated its national guidance on coastal hazards and climate change. This guidance draws on the latest international climate science and on a New Zealand research programme called NZ SeaRise, run by NIWA.

The key finding: for most of Auckland's coastline, the sea is expected to rise by more than 1.0 m by 2130. The actual number depends on your exact location, because of something most people do not think about — the land itself is moving. In most parts of Auckland, the ground is very slowly sinking. A tiny amount each year, but over a century it adds up. When the sea is rising and the ground is sinking at the same time, the water ends up higher relative to your property than the global average would suggest.

NZ SeaRise has calculated location-specific projections for every 2 kilometres of New Zealand's coast. For most Auckland coastal areas, the projected sea level rise by 2130 under a medium-high emissions scenario is roughly 1.2 to 1.6 m — not 1.0 m. You can check the projection for your stretch of coast yourself at searise.nz.

§ 5.0How much difference does it actually make?

More than you might think. The difference between 1.0 m and 1.5 m of sea level rise does not just raise the water line by 50 cm. Because many coastal Auckland properties sit on flat or gently sloping land, even a small increase in sea level rise projections can push the inundation boundary a significant distance further inland.

It also affects the minimum floor level for new buildings. Auckland's Stormwater Code of Practice requires new habitable floors to be set at least 500 mm above the peak flood level. If the peak flood level is calculated using a higher sea level rise figure, the required floor level goes up — affecting building design, foundation costs, and potentially whether a site is economically viable to develop at all.

§ 6.0What you can do right now

If you are buying or already own a coastal Auckland property, here is what to check.

§ 7.0The bottom line

There is a gap between the sea level rise figure in Auckland's planning rules and the figure the government's scientists recommend. Whether that gap closes through rule changes, stays as it is, or lands somewhere in between is something nobody can predict with certainty. What you can do is look at both numbers, understand what each means for the property you are considering, and make your decision with the full picture in front of you. The tools to do that are free and publicly available — the question is whether you use them before or after you have signed.