Tsunamis - vertical evacuation advice
We get a lot of queries about vertical evacuations during tsunamis. ‘Vertical evacuation’ in this case means evacuating to a high floor of a building, instead of leaving the tsunami evacuation zone.
Japan has structures specifically designed for vertical evacuations, and the US has building standards for it, including foundations that are very deep, and reinforced to a higher standard than most buildings and a ground floor level that is open to allow water to flow through.
Unfortunately, New Zealand doesn’t yet have its own building standards for vertical evacuation structures, so we haven’t assessed or constructed buildings to that standard, and can’t currently say that any building in an evacuation zone is suitable as being a safe place in a tsunami. The Ministry of Civil Defence & Emergency Management (MCDEM) and the Ministry of Business, Innovation and Employment (MBIE) have established a project to develop guidance for tsunami vertical evacuation structures (purpose built and retrofitted), appropriate to New Zealand’s requirements.
Our primary advice is to not remain in the evacuation zones, so if you evacuate, make sure you exit the building carefully, being aware of the possibility of falling debris. But we do understand that people who are in a high rise building may decide to stay there. They may feel uncomfortable leaving their building and making their way through streets – possibly in the dark, and with damage from the earthquake. This is something you and your household or workplace will need to discuss and decide.
Vertical evacuation could be a better option in some circumstances, but you need to be aware that the building might not be built to withstand the impact of a tsunami. There is also the chance you could be isolated in the building for days before help can get to you, and there is the risk of fire. If you choose to evacuate vertically, you should go above the 4th floor, so if your building doesn’t have a 5th floor, staying there is not a good option!
Each option has significant levels of risk such that we cannot advise one over the other. You need to take ownership over whichever choice you make.
Whatever you decide works for you, we strongly recommend you spend some time putting together a grab bag, and practicing the route you would take if you do leave the building. Knowledge is power, the more you can prepare for this now, the better.
Our general message for tsunamis remains – If you feel an earthquake that is either longer than a minute OR strong enough that it’s hard to stand up, then get to high ground, out of all zones (past the blue line, if present), as soon as the shaking stops. If it’s long or strong, get gone.