Tsunami evacuation zones and warnings
Tsunami evacuation zones show the areas that you should move out of if you feel a long (more than a minute) or strong (hard to stand up) earthquake, or if there is an official tsunami warning.
You can find out where Canterbury’s tsunami evacuation zones are on our interactive map
What do the tsunami evacuation zones mean?
The red zone includes beaches, estuaries, harbours and river mouths. You should leave this area as a precaution if you feel a long or strong earthquake, or in any official tsunami warning (a ‘Beach and Marine warning’ or a ‘Land and Marine warning’). Most tsunamis aren’t big enough to flood land, but even small tsunamis can cause strong and unpredictable currents and surges in the water that you don’t want to get caught in.
You can expect to evacuate the red zone several times in your lifetime.
The orange zone is the area that could be inundated in a tsunami big enough to flood land. You should leave this area as a precaution if you feel a long or strong earthquake, or in an official warning of a tsunami that could flood land (more than 1 metre wave height above sea level at the time - a ‘Land and Marine warning’).
You can expect to evacuate this zone a few times (maybe 2 or 3 times) in a lifetime.
If you feel a long (more than a minute) or a strong (hard to stand up) earthquake, move out of both the red and orange evacuation zones as soon as the shaking stops. Do not wait for an official warning, an emergency mobile alert, or for someone to tell you to go.
Yellow zoneChristchurch City and Banks Peninsula also have a yellow zone, which will only be evacuated in a very large tsunami (more than 5 metres wave height above sea level at the time). Our tsunami modelling to date has not shown any tsunami sources close to shore that would generate a tsunami larger than 5 metres wave height above sea level at the time in areas south of Hurunui district. You do not need to evacuate this zone if you feel a long or strong earthquake, but are free to do so if you want to, for your own comfort and wellbeing.
We only expect to evacuate this zone once every several hundred years, if there is a large tsunami coming from several hours away. While it is possible you will have to evacuate this zone sometime in your lifetime, it is unlikely.
Note that in most other parts of New Zealand you need to evacuate all zones (including yellow) if you feel a long or strong earthquake, because the risk of a large tsunami being generated close to shore is higher than in most parts of Canterbury. You should check out the local tsunami evacuation zones and what they mean if you are near the coast in other parts of New Zealand.
If you are in a red or orange tsunami evacuation zone and you feel a long (more than a minute) OR strong (can’t stand up) earthquake you should move out of the evacuation zones (or up – see below) as soon as the shaking stops and stay out until you get the all-clear from Civil Defence.
It is very unlikely that a tsunami has been created, but until you can confirm that the earthquake has not generated a tsunami, you should assume that one could arrive within five minutes to three hours. The first wave may not be the largest.
There will not be time for Civil Defence to issue an official warning, an emergency mobile alert, or to sound sirens where they are installed – do not wait for sirens, the earthquake is your warning.
However, it is your responsibility to decide if you and those with you will evacuate and where you should go, depending on your circumstances. Think about this beforehand.
Things to consider include:
- How easily you and the other people you are with can move quickly – can you get out of the evacuation zone within 5 minutes?
- If you cannot get out of the evacuation zone within 5 minutes, can you get to the second story of a two-storey building (not the roof) instead?
- Rock falls – be aware that if the ground shaking is strong, there may be unstable cliffs and rock falls.
- If you do evacuate, walk or bike if you can. You are much more likely to get out and you will leave more room on the road for those people who must use a car.
- Do not climb up onto the roof of a building – the chances of going onto the roof and falling off, especially with young children, are much higher than the chances that a damaging tsunami has been generated.
It takes a big earthquake under the sea floor (larger than about magnitude 7) to move the sea floor enough to create even a small tsunami.
A ‘long’ earthquake is an earthquake that shakes for longer than one minute. The bigger the earthquake magnitude, the longer the shaking. So if the earthquake lasts for longer than a minute, you know that it is big, somewhere (probably over magnitude 7.5 – big enough to possibly create a damaging tsunami if it was under the ocean).
A ‘strong’ earthquake is an earthquake where the shaking is so strong that it is hard to stand up – the sort of earthquake where furniture starts moving around and things fall over.
If you are near a big earthquake, the shaking will be long AND strong – like how the 14 November 2016 earthquake felt to people in northern Hurunui and Kaikoura. But a big earthquake further away from you may be felt as a long but mild or moderate, rolling earthquake – like how the 14 November 2016 earthquake felt like to people in Christchurch. A big earthquake far away may still have created a tsunami, it will just take longer to reach you than if it was just offshore. So this is why the message is long OR strong, rather than long AND strong.
Check out the Ministry of Civil Defence & Emergency Management’s long or strong video.
If you feel a long (more than a minute) or strong (hard to stand up) earthquake you only need to move out of the orange and red evacuation zones – i.e. inland far enough so that you are no longer in the red or orange zones.
If you can, it is best to walk or bike, to reduce the number of cars on the road. If you are driving, it is best to go further than the edge of the zone, to make room for those coming behind. Go to friends or family outside of the zone if you can. Civil Defence will open Civil Defence Centres for those without friends or family handy, and broadcast the location of these, but this may take some time.
If you are in a yellow zone, or not in a tsunami evacuation zone at all, you do not have to move inland or to higher ground, but are free to do so for your own comfort and wellbeing if you want to.
Note that in most other parts of New Zealand you need to evacuate all zones (including yellow) if you feel a long or strong earthquake because the risk of a large tsunami being generated close to shore is higher than in most parts of Canterbury. You should check out the local tsunami evacuation zones and what they mean if you are near the coast in other parts of New Zealand.
Tsunamis can travel a surprising way up rivers – this is called a ‘bore’. Even small tsunamis can create strong currents and surges in river mouths, and this is why we tell people to stay away from river mouths in any tsunami, even a small one that won’t flood land. In developing the tsunami evacuation zones, we have taken the way tsunamis behave in rivers into account, which is why the zones go further up rivers than along the open coast.
You will only get an official warning for a tsunami created more than an hour or two away – off the coast of the North Island or Fiordland, or in the Pacific Islands or across the Pacific Ocean. You may or may not need to evacuate, depending on how big the tsunami is likely to be.
If a tsunami is coming from close to our shore (less than an hour away) there will not be time to issue an official warning, sound sirens (where installed) or to send emergency mobile alerts. The long or strong earthquake IS your warning to evacuate the red and orange zones.
Most official tsunami warnings are Beach and Marine warnings, which means that the tsunami is not likely to flood land, but could cause unusually strong and unpredictable currents in harbours, estuaries and river mouths. In these warnings, people do not need to evacuate their homes but should stay out of the water and off beaches and coastal rocks until the all clear is given.
Occasionally, perhaps a few times in a lifetime, a tsunami will be big enough to flood land and Civil Defence will issue a Land and Marine warning. You will need to evacuate the red and orange tsunami evacuation zones (and possibly the yellow tsunami evacuation zones in Christchurch and Banks Peninsula) in a Land and Marine warning.
You can find out where the tsunami evacuation zones are on our interactive map.
Warnings will be broadcast on television, radio and social media. You can do your bit by passing these warnings on to family, friends and neighbours, to make sure they know. In a Land and Marine warning civil defence and emergency services will also go through the evacuation zones, if it is safe to do so, to get people out.
You will only hear sirens, where they are installed, for tsunamis coming from more than a few hours away.
There are no local tsunami warning systems, including sirens, in New Zealand for tsunamis created close to our shore. This is because the time between the tsunami being created and hitting the shore is too short.
It takes many minutes for GeoNet to accurately determine the location and size of an earthquake and whether or not a tsunami has been created. A tsunami may have arrived at the coast near the earthquake at that time.
Because of this, there will not be time to give an official warning or to sound any sirens for a tsunami created close to our shore. After a long (more than a minute) or strong (hard to stand up) earthquake do not wait for an official warning, or for any sirens to sound, to evacuate. In Canterbury, leave the red and orange tsunami evacuation zones as soon as the shaking stops.
Sirens installed along the Christchurch coastline, and other parts of the Canterbury coast, are not intended to warn you about a tsunami created close to our shore.
They are for tsunamis created in the Pacific Islands or across the Pacific Ocean and, if there is time, for tsunamis created off the Fiordland or North Island east coast. A long or strong earthquake will be your only warning of a tsunami created close to our shore.
Tsunami sirens are not fool-proof and can, in fact, do more harm than good. In the 2011 Japanese tsunami, many sirens were damaged by the earthquake and didn’t work. Thousands of people died because they waited for the sirens instead of heeding the natural warning – the earthquake – and moving to higher ground straight away.
If you are told to evacuate in an official warning you may have up to several hours to leave a tsunami evacuation zone.
Things you need to consider:
- Take valuables and important documents, as well as clothes, toiletries, medicines and supplies for children and pets. Know where these things are if you need to pack them up quickly. Depending on the impact of the tsunami you could be away from your home for days or weeks.
- Where will you go? If possible, stay with family or friends outside the evacuation zone. Civil Defence Centres will be opened for people who need emergency accommodation.
- Secure your home as you normally would when leaving for an extended period.
- Check on your neighbours and vulnerable people you know of to see if they need help – Police and Civil Defence resources will be stretched in an evacuation.
- What is the best route for you to take? In an official evacuation, there will likely be traffic management in place, but you need to have thought about this in advance.
- Take your pets with you if you can – they are your responsibility. Civil Defence Centres generally will not accept pets, apart from service animals, so you need to have somewhere you can take your pet. Some Civil Defence Centres will have arrangements for pets nearby, so make sure you take pet food, bowls, leash, muzzle and kennel if possible.
- Residents will be allowed into evacuation zones to pick up family and pets if there is time, provided it is safe to do so before the threat becomes imminent.
- Schools are required to have evacuation plans for a tsunami and are responsible for evacuating children to the outside of the evacuation zone.
Tsunami evacuation zones are not tsunami hazard zones, or tsunami inundation zones – they do not show areas that will be inundated by any one tsunami. The zones are areas that we recommend people evacuate from as a precaution after they feel a long or strong earthquake, or in an official tsunami warning.
The area that would be flooded in any particular tsunami depends on many factors, including the size of the earthquake, how the earthquake fault moved, the direction the tsunami is coming from and the tide level when the waves arrive. Every tsunami will be different and we can never say for sure exactly which areas within a zone will be flooded.
When drawing tsunami evacuation zones we consider many different tsunami scenarios. The inland boundary of the evacuation zones do not represent one tsunami scenario, rather they are drawn to encompass the flooding from many different tsunamis that we could expect in a 2500 year time period – this includes what we call ‘maximum credible events’. There is no one tsunami that would flood an entire zone.
The alternative to this approach is to have hundreds of different evacuation zones for hundreds of possible tsunami scenarios, which would be really confusing and hard to communicate.
The zone boundaries, particularly in urban areas, also usually follow some sort of feature that is easy to see on the ground, like roads, so that you easily know whether you are in or out of the zone. We also consider the locations of schools, rest homes, parks and golf courses. For example, if part of a park could be flooded in a tsunami, we will generally include the whole park in the evacuation zone, as it is much easier to simply close an entire park, rather than just part of it.
You can download our report Developing tsunami evacuation zones for Christchurch City and Banks Peninsula, which describes how the Christchurch City and Banks Peninsula zones were drawn and the models that they are based on.
Tsunami evacuation zones in other parts of Canterbury will be reviewed in 2019, using the results of modelling being undertaken in 2018.
Canterbury’s tsunami evacuation zones are based on the best information, including tsunami modelling, that we have at the time.
Our understanding of New Zealand’s tsunami risk is rapidly improving and we plan to continue developing the tsunami models that underpin Canterbury’s tsunami evacuation zones over the coming years.
We regularly review the evacuation zones and will change them if new modelling shows a significant change in our understanding of Canterbury’s tsunami threat, or if national guidance on the way tsunami evacuation zones are developed changes.
If you want to know more information about tsunami warning systems in your area, and where to go during a tsunami warning, contact the emergency management officer at your local city or district council.