Tsunami Maps Q&As
Q&As on the new tsunami inundation assessment report and maps showing inundation zones for the Gisborne / Tairawhiti region. The report and maps are based on new research into modelling of local tsunami generated from a magnitude 8.9 earthquake centred in the Hikurangi Subduction Zone off the East Coast.
Here's the maps and reports
- Why are we releasing the maps now?
The Tsunami Inundation Assessment Report final peer review by GNS Science was completed this week (17 Dec). Initially it not due until February 2020.
On 18 December, Council as the Civil Defence Emergency Management Group approved publishing the report following confirmation that the information met the required national standard for tsunami modelling.
- What do the red, orange and yellow zones mean?
Red zone is the highest risk zone, it's the first place people should evacuate from in all types of tsunami warnings (natural or official) generated near and far.
Orange zone indicates the area that should be evacuated in most, if not all distant and regional tsunami threats.
Yellow zone indicates inundation generated from an 8.9 earthquake in the local Hikurangi subduction zone off the East Coast.
- Why have the maps and zones changed so much?
After the 2011 Japan tsunami, new technology and research has allowed for more accurate reporting on the impact of a locally generated tsunami based on a plausible 8.9 magnitude earthquake in the Hikurangi Subduction Zone off the East Coast.
- Is this a likely scenario?
The new modelling provides inundation information for a 15 metre wave that's equal to a one-in-2500-year event, similar to the 2011 Japan tsunami.
Experts agree an event of this size will happen but there's no way to predict when it would happen.
It's a worst case scenario that we will use as the planning tool for this type of disaster.
- Any chance a tsunami could go further than the yellow zone?
Yes, there's always a chance the earthquake will be more significant and generate a larger tsunami.
- What size earthquake means I have to evacuate from the yellow zone?
Everyone in an inundation zone who feels a long (1 minute or more) or strong (difficult to stand up) earthquake should evacuate to higher ground as fast as possible.
The magnitude of an earthquake is not the only indication of its strength, depth and length are also key indicators. If it feels big to you, trust your instincts and self-evacuate immediately.
- How were the zones developed?
Computer modelling generates an inundation which is independent of property boundaries.
The tsunami zones were developed by NIWA and eCoast Limited, who have experience with tsunami events in Palu Sulawesi Indonesia, Anak Krakatoa, Japan and Sumatra.
GNS Science also reviewed the report to confirm the zones identified are acceptable.
- How long will it take for water in the yellow zone to subside?
It could take several hours to drain away on land that's normally well drained, ie connected to culverts etc. Water may pond for several days or weeks in poorly drained areas, leaving silt, rubbish and debris, Appropriate hygiene precautions should be taken including gloves and face mask for cleaning up.
- What about communities on the East Coast?
The maps show inundation zones for the entire East Coast. We're working through evacuation plans for each community starting with the city, where the potential for the greatest loss of life is present. Evacuation routes will be added to the maps as they're completed.
- How long do I need an emergency kit to last?
Be prepared for 3 days. Here's information on www.getready.govt.nz
- Should I stash my emergency kit on a hill somewhere?
Your emergency kit should be easily accessible - hanging in a closet, in the car boot or under your desk. You need it as close to you as possible, not in a different location.
- How do I know how far above sea-level my house is?
A number of websites can help you determine this - Google, find my altitude
- Will our bridges withstand a large earthquake?
All city bridges are at code now which means they're earthquake strengthened.
In an emergency event it will depend on the extent of the earthquake damage.
- What warning will we get?
The earthquake is the only tsunami warning you may get, trust your instincts and evacuate to higher ground as fast as possible.
If you feel and earthquake that's long (1 minute or more) or strong, get gone.
Tsunami generated by a localised earthquake may arrive within 15 minutes. Do not wait for official warnings.
Recognise the natural warnings signs - if it feels like a big one or a long rolling one - move as quick as you can after the shaking has stopped.
- How long is LONG?
One minute or longer.
- What is STRONG?
A strong earthquake that makes it hard to stand up and causes damage to structures and buildings.
- What are other signs a tsunami may hit?
A sudden rise or fall in sea level. Or a loud or unusual noise from the sea.
- Why don’t we have an evacuation siren?
The earthquake that generated the tsunami in Japan caused damage to many of the tsunami sirens which resulted in zero warning.
Do not wait for an official warning, if it’s long (1 minute or more) or strong earthquake evacuate to higher ground as fast as possible.
You may or may not receive an Emergency Mobile Alert (EMA), don’t wait – heed the warning and self-evacuate.
- What magnitude quake would generate a tsunami?
If the earthquake throws you to the ground or makes it hard to stand up, self-evacuate.
Magnitude is only one indication of earthquake strength, depth and length are also key factors.
- What’s likely to cause more damage, the earthquake or the tsunami?
The earthquake will have a wider impact across the region. But the tsunami will cause more damage in the inundation zones.
- How many waves are there likely to be?
There's no exact number.
A tsunami is a series of ocean waves with very long wavelengths, typically hundreds of kilometres, caused by large-scale disturbances of the ocean. The deeper the water, the greater the speed of tsunami waves will be.
- Are these maps for local or distant tsunami?
The red and orange zones indicate how far a tsunami could come inland as a result of a distant tsunami.
The yellow zone is based on a magnitude 8.9 earthquake centred in the local Hikurangi Subduction Zone.
- How many people live in the yellow zone? How many fatalities could there be?
With this report, we're gathering information about who will be affected.
Approximately 900 people will become casualties from an earthquake of 8.9 magnitude. Casualties caused by tsunami are unknown.
- How much time would we have to get out?
You should plan to evacuate the inundation zone within 15 minutes, walking quickly.
Avoid driving as the roads may not be safe.
- Where is it safe to evacuate to?
As soon as the shaking stops, move immediately to the nearest high ground - up a hill - or go inland, keep moving as far as you can walking or biking. Avoid driving as roads and bridges may not be safe.
- What happens with unsecured objects like logs in the port?
A tsunami surge will contain a potentially lethal mix of large and dense objects like debris, toxic substances and electricity.
- Is it safe to drive through shallow water, about a metre, in a big truck?
No. Do not drive through water.
- Should we head to townships like Patutahi, Te Karaka etc?
No. Evacuate to the nearest high ground quickly, that's walking not driving. Do not travel any further than necessary.
- Where are the welfare centres outside of the zones?
We're currently reviewing the welfare centres based on the revised inundation zones and will update our communities as soon as possible.
- Are there recommended roads we should follow to get out of the city?
We'll have recommended evacuation routes on our website very soon.
- What happens if supermarkets and shops are closed, what do we do?
Your emergency kit should include everything you need to survive for 3 days. In an emergency event, once response efforts are complete the next focus is recovery, including services.
- What happens if the airport is affected?
There's a number of air landing options outside the inundation zone.
- What happens if cell towers are out? How will we know what to do or where to get help?
Your emergency kit should include a battery operated radio with extra batteries. In an emergency event, many of the local radio stations will broadcast information about how to access help. Tune in and stay informed.
- Will we have emergency services, given that many of them are in those zones?
Yes. Emergency services will relocate to and operate out of Gisborne Hospital.
- What does it mean for house insurance?
Check with your insurance provider.
- What should I do if my neighbour has a disability and is not able to evacuate quickly?
Discuss evacuation plans with your neighbours and neighbourhood network.
- Is there a buddy system, active neighbourhood watch?
Find out now if you have neighbourhood watch or a network set up.
Council can provide advice and support the development of a neighbourhood group. Contact us to discuss email firstname.lastname@example.org
- Is it safe to be outside when aftershocks are happening?
Stay clear of unstable paths, roads and tall structures.
- Will any tsunami towers be built?
We're looking into many evacuation options, including tall buildings and structures in the yellow zone that may be able to withstand the earthquake and a tsunami.
- If I can get on a roof, should I?
We’ll assess buildings in the yellow zone to determine if there's options for vertical evacuation. Getting to higher ground like a hill or inland, for example in the city towards Whataupoko, Mangapapa and Kaiti is the safest option.
- How will I know if my business is safe?
The first priority is survival. Your business will be assessed in the recovery phase.
- What should I do if my health depends on electricity?
Evacuate if you're in the yellow zone. Find the nearest welfare centre or head to Gisborne Hospital.
- If this happened during a school day, how will I know where my children are?
You need to discuss evacuation plans with your children's schools.
- Is the hospital able to deal with large numbers needing medical assistance?
Gisborne Hospital is equipped for first response, additional medical assistance from other regions will be requested as needed in an emergency event.
- Will you communicate evacuation routes?
On-foot evacuation routes will be added to the maps online as soon they're completed.
- Can we take pets to the welfare centres?
The first priority is your survival. Include your pets in your evacuation plan and emergency kits.
Pets can accompany you to a welfare centre but resources are prioritised for human survival first.
- Where is the Emergency Coordination Centre?
Council is currently investigating a permanent ECC with revised tsunami inundation zones in mind.
- Will I be safe going out in my boat?
Our advice is to move inland or get to higher ground before the inundation surge arrives. Tsunami waves are volatile and your boat may not be equipped to withstand this.
- What are the top priorities?
The first priority is survival.
Our sole focus would be to 'get through' a magnitude 8.9 earthquake and tsunami in the best condition possible, with limited casualties and limited damage.
The second priority is restoring normality, this is often referred to as the ‘new normal’ to reflect the re-establishment of routine post-disaster.
- How do we make decisions during an event?
Plan and practice your evacuation both day and at night, at home, work, school, sports or from any of your regular activities you do. This will ensure that in an earthquake you will be familiar with what decisions to make.
- What if I lose my medication?
Your emergency kit should include your medication for at least 3 days. Talk to your doctor. In an emergency, if you rely on life preserving medication and you don't have it, your evacuation plan needs to be to Gisborne Hospital.
- Is there an emergency response plan?
This response plan is currently being developed with our local emergency agencies.
It may take hours to days for Civil Defence and local agencies to coordinate an emergency response to our communities.
An event like this could impact regions along the coast of the North Island.
The Hikurangi Response Plan (HRP) is based on a similar scenario but its aim is to develop a nationwide coordinated Civil Defence Emergency Management response to a subduction zone earthquake and subsequent tsunami.
- Do I need to have cash in my emergency kit?
You should include some cash in your emergency kit as bank facilities could be unavailable.
- How will we buy groceries if the bridges are out?
The first priority is survival. Establishing routine activity such as buying groceries will be addressed in the recovery phase.
- Will the army come in to help?
In an emergency, Civil Defence will assess and request support where and when it's needed.
- Can we store life preserving supplies outside inundation zones in a weather-proof container like an ark?
You should plan for yourself and your loved ones and have your emergency kits nearby – car boot, closet, under your desk etc
- Should people who aren't affected by the disaster volunteer is assist?
In an emergency, Civil Defence will coordinate the response including volunteers.
For more information about becoming a Community Link, email email@example.com
- What information do people in the safe zone need to know?
Plan and practice your evacuation just in case and always have an emergency kit.
Utilities may not be available for some time. Stay alert and informed by radio.
Civil Defence is the controlling authority, they appoint a Controller who oversees the Emergency Coordination Centre response.
- Can we defend our property?
Anyone in an inundation zone who feels a long (a minute or more) or strong (difficult to stand up) earthquake should evacuate to higher ground as fast as possible.
- Am I covered by EQC for tsunami?
Contact your insurance provider.
- How long do we have to wait before we can return home?
You'll receive this information after the initial response to the emergency event. Please wait for the all-clear before returning.
- Is there something we can do now to help in case of an emergency?
Familiarise yourself with the information on getready.org.nz
Also the new tsunami inundation maps for our region.
For more information about becoming a Community Link, email us at firstname.lastname@example.org
- What would the repair process look like?
This can only be determined following a post-disaster assessment. As an example, repair and recovery efforts are still in progress in Christchurch.
- What if my business relies on deliveries from outside the region?
Establishing routine activity such delivering goods will be addressed in the recovery phase.
- How will potential infectious diseases be managed?
Any disease threat will be assessed and managed as and if they arise.
- How long would it take to get government help to respond and recover?
The reality is, Tairawhiti will be cut off like an island for many days or weeks in such an event.
National assistance will be deployed through a priority system. Tairawhiti is unlikely to be a priority. The disaster would impact on our region’s roads heavily and aid into the region would become a major challenge.
Law and order will be compromised and social breakdown is highly likely. We would need to be self-reliant for a couple of weeks.