Vertical evacuation: Napier will actively pursue idea of building tsunami towers

Napier City Council says it will actively pursue the idea of building tower-like structures for people to climb to avoid an incoming tsunami, once guidelines are released by the Government.

Napier, a coastal city near to NZ's most dangerous offshore fault, the Hikurangi, has several communities that would struggle to reach high ground in a worst-case scenario earthquake.

The majority of the city is in a tsunami evacuation zone.

East Coast LAB's latest modelling has sparked a conversation about how low-lying communities in Napier would be affected by a tsunami from a Hikurangi subduction zone earthquake.

In one recently publicised scenario, a tsunami could hit Napier within 20 minutes of initial shaking.

One option being mooted to give those in communities like Te Awa or Westshore options to flee is vertical evacuation buildings, which saved lives in Japan when a devastating earthquake and tsunami struck in 2011.

These structures are currently being considered by the Ministry of Business, Innovation and Employment, and the Ministry of Civil Defence and Emergency Management.

MBIE Team leader of Engineer, Engineering, Design and Science, Jenni Tipler said vertical evacuation buildings are designed to withstand the pressure of a tsunami, giving people an option to go upwards rather than inland.

"They are a last resort, risk mitigation, in areas where you might expect to only have a short warning time between an earthquake and a tsunami arriving.

"In that case, it's possible to seek refuge in upper stories of building structures."

The guidelines will ensure buildings can withstand the pressure of a tsunami, and could either be multi-purpose, for example a carparking building, or used only for evacuation purposes.

A spokesperson for Napier City Council said it is waiting for the guidelines from MBIE.

"It is our hope that this guidance will be available soon so that we can start to actively work with our community to identify where structures are required and how they should be built."

Group manager of Hawke's Bay Civil Defence Ian Macdonald said people should wait for MBIE guidance before designing any vertical evacuation buildings.

After a long or strong earthquake, the best response is to get gone, he said.

"New Zealand doesn't have building standards for tsunami vertical evacuation structures, so we can't say that any building in an evacuation zone is a suitable safe place in a tsunami."

He understood there were people who were worried about their ability to get out of an evacuation zone in time.

He said if people planned to evacuate upwards, look for reinforced concrete or structural steel buildings, and go to at least the third floor.

Hikurangi response plan lead at East Coast LAB Natasha Goldring said subduction zones like Hikurangi, are known to produce the largest tsunami and earthquakes.

"It is important that everyone makes a plan and works out what they will do by thinking about the things they need every day and work out what to do if they didn't have them."

She said practicing to "drop, cover and hold" and tsunami hikoi, making a household plan, and checking whether the places you live work or visit are in tsunami evacuation zones, are all practical ways to prepare for an emergency.