Sea level may rise by over 1 metre in Hawke’s Bay by 2120, increasing the impact of erosion and inundation.
In response to these challenges, the strategy is looking at two main hazards along the coast: coastal erosion and coastal inundation.
Coastal erosion is when waves and storms wear down or carry away sand, gravel and rock along the coast, eroding the beach and foreshore areas.
Coastal inundation is when low-lying land near the coast is flooded from the sea during high tides or storms that over-tops the beach.
Sea level rise and vertical land movement
The impacts from coastal erosion and coastal inundation will increase as we experience changes in sea level.
Global sea levels have changed significantly over Earth’s history – it has been much higher than it is now, and it has been much lower.
The key drivers of sea level rise are:
- Ocean temperature (thermal expansion)
- Adding water to the ocean from melting glaciers, ice sheets etc
- Changes in winds and ocean currents
- Land subsiding (vertical land movement)
In New Zealand, tide records show that we have already experienced a rise in mean sea level of around 0.2 m since 1900, with the rate of rise increasing over time.
We can’t predict what future sea levels will be, but we can make projections using different inputs and assumptions.
One of the most important assumptions is trajectories of global emissions – will we do a good job of reducing emissions, carry on as we have been, or somewhere in the middle?
Other hazards
Other hazards will be incorporated into the Strategy in future reviews, as new science and information becomes available, such as the risks associated with increasing groundwater levels that may be caused as sea levels increase.
We are basing our strategy on the most recent research, and are planning for sea level rise based on a variety of future possible scenarios based on current knowledge. Risk estimates for hazards along the coast will need to be reassessed as time goes on, our knowledge increases, and future impacts become clearer.
Alongside technical reports prepared by experts for our coastline, we get our latest research from a range of sources including:
