Tsunami

What is a tsunami?

A tsunami is a series of waves generated when a large volume of water in the sea is rapidly displaced. A tsunami can be caused by large submarine or coastal earthquakes; underwater landslides; or volcanic eruptions beneath or near the sea. A tsunami can violently flood coastlines, causing devastating property damage, injuries and loss of life.

Where are tsunami inundation areas identified?

New Zealand's entire coast is exposed to tsunami.

The District Plan maps do not currently identify any tsunami inundation areas. Council does however hold other maps showing potential tsunami inundation areas within the District.

You can view these maps below by entering your property address.

Search your property - current natural hazard maps

To show the natural hazard map for your property please click here and enter a valid Address or Parcel ID.

Or you can browse the natural hazards by using MAPI – Public Viewer (new) and selecting the Hazards Theme from the bottom of the Layers tab.

Tsunami inundation maps

Tsunami inundation maps show where water could reach if a tsunami occurred. They help with understanding the risk to land and buildings and planning for subdivision or land use.

GNS Science (now known as Earth Science New Zealand) have prepared a report which documents the methodology, results and limitations of the modelling undertaken to produce comprehensive tsunami inundation mapping for the Bay of Plenty region. The scope of the report is the Bay of Plenty coastline and offshore islands.

The new tsunami inundation maps show the area of land that could potentially be flooded by:

A tsunami caused by a rare offshore earthquake that has a wave height ranging between 8m and 15m along the Bay of Plenty coast. The likelihood of a tsunami like this occurring in any year is calculated as 0.04% (which is a 1 in 2,500 chance).
A 5m high tsunami caused by a rare offshore earthquake. The likelihood of a tsunami like this occurring in any year is different along the Bay of Plenty shoreline. The likelihood in any year is calculated as ranging between 0.33% in the east and 0.13% in the west of the region (which is a range between a 1 in 300 chance in the east and a 1 in 750 chance in the west).

Tsunami evacuation zone maps

The tsunami evacuation zone is the coastal area that people should move away from in a tsunami threat.

The evacuation zone is based on the tsunami described above in the first bullet point under the heading “Tsunami inundation maps”.

The development of the tsunami evacuation zone also considers other factors such as how easy it would be for people to evacuate, safety aspects, the road network, how many people live in different areas, and other social factors.

These maps can be viewed on the Regional Council’s Bay eXplorer.

Information about how people can prepare for a tsunami can be found at Tsunami - Emergency Management Bay of Plenty.

Technical Reports

Here is the technical report supporting the new tsunami maps:

Regionwide study

GNS Science - Comprehensive Tsunami Inundation Modelling and Evacuation Zone Mapping: Final Report 2025 (PDF 28.5MB)

Frequently asked questions about tsunami

How long would it take a tsunami to reach us and how should we respond?

A tsunami triggered from a major Kermadec Trench earthquake would arrive in less than one hour. The first and best tsunami warning is an earthquake. Do not wait for official warnings. Natural tsunami warning signs are:

Any earthquake that lasts a long time (more than a minute)
A big earthquake that is very strong (knocks you off your feet or is very difficult to stand up)
Strange ocean behaviour. Like loud or strange noises, sudden change in sea level, or ocean drawing away from the shore.

If any of these things happen, don't wait for an official warning. Grab your emergency pack and walk as quickly as you are able to a safer location or to high ground. Remember LONG, STRONG, GONE. Refer to the Get Ready Get Thru website for more information.

What if I need assistance?

With less than an hour after a major earthquake before a tsunami arrives, emergency services will not be able to get you out in time. The reality is that you're on your own. The community's best chance to survive a tsunami is to work together as a community. Make an evacuation plan with your neighbours, especially if you know they will need help getting to a safe area. If you live in a retirement village or gated community, make sure you know what their emergency plan is.

Why do I need an emergency pack?

Tsunami can arrive in several waves over a long period of time, and the first wave is not always the biggest. That is why you need your emergency pack. Pack anything you think you will need, like medicine and a water bottle. You must be prepared to wait for many hours before the water subsides.

What are the requirements if I am wanting to subdivide or develop my property?

There are no requirements to address tsunami in the building consent process. There are also no specific tsunami rules for subdivision and development in the District Plan.

The Resource Management Act does however allow councils to address significant natural hazard risk including from tsunami through the resource consent process. This may for example require evacuation routes to be considered for larger subdivisions and developments.

Got a different question?

If you have any further questions, please contact Mark Ivamy - Senior Natural Hazards Planner at the Regional Council on 0800 884 881 ext 8372 or at mark.ivamy@boprc.govt.nz.