Coastal Change

2478 Lloyd Homer GNS Science

Coastal change research at GNS Science is working to help Aotearoa New Zealand’s communities adapt effectively to the physical, social and economic impacts of climate and environmental change in coastal and near-coastal settings.

Where our land meets the sea, it also meets the changes we’ve made, from housing to land use. Our coasts are home to much of our significant infrastructure, like roads, telecommunications, housing and fuel supply lines.

Our landscape is considered “active" – thanks to our position on the edge of two tectonic plates. We  need to understand more about how this affects our coastline.

sea level thumb
Why do small amounts of sea-level rise matter? | NZ SeaRise: Te Tai Pari O Aotearoa transcript

We're sitting here on the south coast of Wellington on a on a pretty nice day. It's very little wind, weather's fine. There's a little bit of a swell and we can sort of see the level of the ocean and you sort of might wonder why do we really need to worry about a slight change in that level of the ocean. 10 centimeters, 20 centimeters in the coming years.

I can see here that with 10 to 20 centimeters of sea level rise, the seagulls sitting on the beach might have to migrate up the beach a little bit to, to sit where they are. Who cares, right?

But you imagine this place on a, on a day with a swell as large is a big storm coming in, and we already know that when that happens, the road behind us is inundated by waves, waves crash across the road.

Now, you add 20 centimeters to the average sea level and put that same storm on top of it, and those waves are going to inundate even further up the coast. So that's the big problem, is that change in mean sea level, and you put a storm on top of it, and it has a big impact on the coast.

Our coasts are changing dramatically. There are more frequent and severe flooding events, storms and storm surges. Our groundwater aquifers may also be affected by these changes. As our coasts take a literal climatic pounding, we will need to contemplate a retreat further inland. 

How do we respond?

How will changing climate and rising sea level impact our natural, economic and built coastal environments, and how can we adapt to these changes?

Our researchers and technical staff combine their diverse skillsets to help understand these processes and the impacts they have on our communities. This puts them in front of some of biggest climate questions we’ve ever faced related to the following topics:

  • Biodiversity, long-term records of environmental change to help inform the future; Ka mua, ka muri – “walking backwards into the future”
  • Sea-level rise predictions
  • Impacts upon coastal aquifers
  • Education
  • Integration of social science and Mātauranga Māori as key components of research programmes
  • Numerical modelling to explore the impacts of changing coastal environments on people, society, and infrastructure
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Subsidence can effectively double expected sea-level rise | | NZ SeaRise: Te Tai Pari O Aotearoa transcript

Generally New Zealand is going up because of that convergence across the plate boundary. Something interesting is happening off the eastern margin of the North Island of New Zealand, and that is where the Pacific plate is going down, being pushed down under the Australian plate. And it locks, it grips and it pulls the land down.

So in the Lower North Island and on the eastern side of the Lower North Island, the land is actually subsiding, going down at quite high rates of up to eight millimeters per year. Right here, the subsidence is three to four millimeters per year, which is effectively doubling the amount of sea level rise we can expect right now and in the coming decades and centuries.

So this part of New Zealand is exposed to some fairly big swell waves that get generated down around Antarctica. So this part of New Zealand already gets big storm events that at a high tide causes coastal flooding. And these buildings around us are often in the news and getting damaged by those storm events.

Now, the problem with the subsidence is that it's really amplifying the amount of sea level rise we will get over the coming decades. So by 2050 globally we would expect an average sea level rise of about 30 centimeters.

You can double that for this spot. So that'll be 50 to 60 centimeters in the coming decades and that cannot be avoided. That is already baked in from the global warming so far.

So what that means is that the hundred year coastal flooding event we currently get now, that does a lot of damage to the roads and the houses around this part of Wellington will become an annual event with just 30 centimeters of global sea level rise but 60 centimeters right here because of the land going down.

Our expertise

We deliver consistently high-quality research projects and subsequent data, tools and resources by using our expertise in:

  • Sedimentology
  • Paleontology
  • Geomorphology
  • Coastal erosion and slope stability
  • Numerical modelling of coastal and landscape evolution, sea-level changes, sediment pathways and societal impacts
  • Organic and inorganic geochemistry
  • Microbiology
  • Sediment-core laboratory processing services
  • Radiocarbon dating

Want to know more?

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