Information about the tsunami risk in Selwyn

Selwyn Tsunami Evacuation Zone

The Blue Zone - If you feel a LONG (more than a minute) or STRONG (it's hard to stand up) earthquake, move inland as soon as the shaking stops so that you are out of the blue tsunami evacuation zone.

DO NOT wait for an official warning, an emergency mobile alert, or text message. A tsunami could arrive within minutes or within a couple of hours depending on how far away the earthquake was. Stay out of the zone until you are told it is safe to return.

If you are outside the blue tsunami evacuation zone, you do not need to evacuate. Areas outside the evacuation zone are not expected to be flooded, even in the 'worst case' tsunami.

If a tsunami is coming from the Pacific Islands or across the Pacific Ocean you will not feel the earthquake but there will be time for an official warning.

The Blue zone covers the coastal area of Selwyn and around the edge of Te Waihora Lake Ellesmere. The boundaries for this zone are based on scientific advice of the maximum credible event that could impact Selwyn. They are regularly reviewed to take into account the latest research. Find Canterbury tsunami hazard reports here.

If Civil Defence issues a warning to evacuate the Blue Zone, all people in this zone should immediately implement their emergency plan and evacuate – preferably to a relative or friend’s address outside the Blue Zone, or otherwise to one of the two Emergency Centres listed below.

Evacuation Centres
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Southbridge Hall – this centre will be staffed by volunteers from Southbridge. It will provide information and basic refreshments to evacuees.

Lincoln Event Centre - this centre will be staffed by volunteers from Lincoln and Selwyn District Council staff. LEC is a designated welfare centre for Selwyn District and has emergency power and the capacity to provide emergency shelter to evacuees for a period of days if necessary. If evacuees are required to stay overnight they will be transported from Southbridge to LEC.

How Official Warnings Are Communicated

In Selwyn district we make use of the Selwyn Gets Ready system. The systems allows Civil Defence personnel to send emergency and evacuation warnings via text message and email. You can sign up for your home.

Warnings will also be sent via the Emergency Mobile Alert (EMA) system that is managed by Canterbury CDEM Group.

Volunteer Community Response teams will also door-knock in affected areas if there is time.

In a Blue Zone evacuation council and emergency service personnel will also attempt to warn residents using emergency vehicle sirens in affected communities.

However, if a tsunami is created close to our shores there may not be time to issue an official warning. You need to act on the natural warning.

  • If you feel a long (more than a minute) OR
  • Strong (hard to stand up) earthquake OR 
  • See the sea behaving strangely, move inland so that you are out of the Blue tsunami evacuation zone.

General Tsunami Advice

A tsunami is a series of powerful, long waves that move through the ocean or a lake.  They are caused by a sudden disturbance to the water like an earthquake, volcanic eruption, or a landslide into or under the water.

A tsunami can cause strong and dangerous currents and surges in harbours, estuaries, river mouths and on beaches.  Occasionally, a tsunami is big enough to rapidly flood land with debris-laden water, causing damage and injuries.  A tsunami has caused damage, deaths and injuries in New Zealand in the past.

The first tsunami wave or surge may not be the biggest.  The largest wave can arrive hours after the first wave and waves can continue for many hours or days.

Types of Tsunami:

Distant-source tsunami are generated from a long way away, such as off the South American coast.  In this case, we will have at least three hours and in some cases up to 14 hours or more warning time for New Zealand.

Regional-source tsunami are generated between one and three hours travel time away from their destination. A large earthquake in the Kermadec Trench to the north of New Zealand, or a Puysegur Trench to the south, could generate a regional tsunami.

Local-source tsunami are generated very close to New Zealand. This type of tsunami is very dangerous because we may only have a few minutes warning.

Have a look at this video from Taranaki Civil Defence and GNS Science which shows the difference between normal wave action and a tsunami:


Surviving a Tsunami

Before a Tsunami

Getting ready before a Tsunami strikes:

  • If you have a disability or special requirements, arrange with your support network to alert you of any warnings and emergency broadcasts. You will need to have your own evacuation plan in place as emergency services will be stretched.
  • Develop a Household Emergency Plan
  • Have a Getaway Kit ready
  • Know where you will evacuate to (this could be a relative or friends house outside the Blue Zone or an Emergency Centre at Lincoln or Southbridge). Plan your escape route for when you are at home, as well as for when you may be working or holidaying near the coast.

During a Tsunami

  • Take your Getaway Kit with you if possible. Do not travel into the areas at risk to get your kit or belongings
  • Take your pets with you if you can do so safely
  • Move immediately to your safe area (this could be a relative or friends house outside the Blue Zone or an Emergency Centre at Lincoln or Southbridge)
  • If you are on the water and can beach or dock your boat and evauate outside of the Blue tsunami evacuation zone within half an hour then this is your best option. If you cannot do this then head for deeper water, preferably outside of the harbours and bays of Banks Peninsula.
  • Never go to the shore to watch for a tsunami. Stay away from at-risk areas until the official all-clear is given. This message will be sent by text and email on Selwyn Gets Ready. Make sure you are signed up so you receive these messages
  • Listen to the radio or television for Civil Defence advice.

After a Tsunami

  • Continue to listen to the radio or television for Civil Defence advice and do not return to the evacuation zone until authorities have given the all-clear
  • Be aware that there will likely be more than one wave and it may not be safe for up to 24 hours, or longer. The first wave is not necessarily the biggest
  • Check yourself for injuries and get first aid if needed. Help others if you can
  • Do not go sightseeing
  • When re-entering homes or buildings, use extreme caution as floodwaters may have damaged buildings. Look for and report broken utility lines to appropriate authorities
  • If your property is damaged, take notes and photographs for insurance purposes. If you rent your property, contact your landlord

If you would like further information, please contact the council’s Emergency Management team on 03 347 2800.