The evacuation maps are based on a maximum credible tsunami wave that rises to 14m above sea level when it reaches the coastline. To provide an extra buffer, the tsunami evacuation areas on the maps extend beyond the area of land that is predicted to be flooded by a maximum credible tsunami.
Why are the maps now blue and not yellow, orange and red?
Our Emergency Management team works closely with our local community to incorporate feedback into our planning. The community have told us three evacuation zones is confusing, which is why we now only have one evacuation zone and colour. This makes our maps simpler and easy to read.
Where would a maximum credible tsunami come from?
The maximum credible tsunami could be generated by an earthquake along the Kermadec Trench, north-east of New Zealand. To produce a tsunami of this height, the earthquake would need to be greater than magnitude 9.
What about tsunami from other areas?
Most other tsunami scenarios modelled are not as damaging as the Kermadec scenario. While most tsunami have potential to affect our marine and beach areas, only a rare tsunami could potentially overtop some of the dunes along our coastline. A tsunami from White Island is unlikely to overtop the dunes.
Could a tsunami exceed the maximum credible event?
The evacuation maps are based on our current best knowledge. The knowledge includes in-depth studies undertaken in 2012, 2013, 2014, 2015 and 2020 by GNS Science and Tonkin and Taylor. These studies are peer reviewed by technical experts to ensure they are accurate and utilise the most up to date information and methods of research available. They have also included learnings from international tsunami examples to ensure we are working to the best information possible.
How can Blake Park be safe?
Our dune system is an excellent first line of defence against all tsunami. The tsunami water will lose a lot of power as it encounters the dunes, even as it overtops them or travels around them. There is also a secondary dune system at Mount Maunganui. Some of the roads sit quite a bit higher than the streets either side. The tsunami water will lose a lot of power as it encounters the dunes, overtops them or travels around them. Meanwhile, the tsunami entering from the harbour side will be significantly lower than the ocean side because much of its energy and power is lost as it squeezes through the harbour entrance.
How can the high ground at Gordon Spratt Reserve be safe?
The dune system along Papamoa has an average height above mean sea level of about 8m, so when a 14m wave hits the dunes, only the top 6m of the wave flows onto the land. Once a tsunami hits land it loses about 1m of height for every 300m it travels inland. Tsunami water will also lose a lot of energy when it crosses the Wairakei Stream. The top of the high ground sits at least 3m above the highest predicted water level. It is designed to survive an earthquake, liquefaction, and scouring from tsunami water.
Why have the evacuation zone boundaries in Pāpāmoa East changed?
As extensive development has occurred in Pāpāmoa East more recent modelling was done to capture the new landform.
Some areas have now reduced in boundaries, with far Pāpāmoa East no longer within an evacuation zone boundary. Previous models forecasted what the developed landform would look like, reducing ground elevation to account for predicted developments across Pāpāmoa. As the land has now been earth-worked, and most developments completed, we have greater confidence in final elevations and can now identify these as not being flooded.
Will there be future changes to evacuation zones?
Science is always improving with new modelling techniques and more accurate analysis. Currently a Level 4 tsunami model is being commissioned for the entire Bay of Plenty coastline. This is will enable us to further review our evacuation zones. This may result in future changes to your evacuation zones and safe locations.
We encourage community to regularly review their evacuation zones to incorporate any changes and replan their evacuation route if needed.
How will I know if a tsunami is coming?
A long or strong earthquake is the natural warning for a tsunami. If you feel an earthquake that is longer than a minute or strong enough that it’s hard to stand up, evacuate as soon as the shaking stops. Do not wait for an official warning as a tsunami wave could reach our coastline within 40 minutes.
If an earthquake occurs further away we may not feel it. If there is a tsunami threat to New Zealand, the national warning will be issued and Emergency Management Bay of Plenty can provide alerts and information on areas, if any, that need to be evacuated. This can be done through Emergency Mobile Alerts, radio, TV broadcasts, social media, and local council websites.
How should I evacuate?
Walk, run, or cycle if you can.
The time it takes to reach a tsunami safe location is modelled on a very conservative walking pace, and the evacuation maps we have provided show safe locations and zones that can be reached by foot from most parts of the coast within 50 minutes. Trying to reach a tsunami safe location by car can quickly result in traffic gridlock.
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. Make sure you and your family know the evacuation route to your nearest safe location. Discuss evacuation with your neighbours, especially if you know they will need help getting to a safe location. If you live in a retirement village or gated community, make sure you know what the emergency plan is.
Why do I need an emergency pack?
Tsunami can arrive in several waves over a long period of time, and this is why you need an emergency pack or grab bag. Include anything you think you will need, like medicine, food and a water bottle. You should be prepared to wait for several hours before the water subsides.
Where can I view tsunami inundation maps?
Inundation maps are different to the evacuation maps. Inundation maps show with more precision areas where tsunami water is predicted to flood. If you are interested in viewing these you can view them on our mapping system, called Mapi in the Natural Hazard section. You will need to select the Natural Hazards layer, then select either Max Tsunami Flood Depth at 14m or Tsunami Evacuation Zone.