Computer modelling has identified potential evacuation "choke points" in Napier after an earthquake.

A two-year, multi-agency study has looked at how long it may take to get to safe locations in Westshore, Ahuriri, Pandora, Napier South, Maraenui, Te Awa and Marewa to avoid a tsunami.

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Areas of congestion are now being compiled into a report for councils and other agencies to be used to plan quicker and safer evacuations.

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Early indications show pressure points in Napier CBD and outlying areas, from people leaving on foot. Obvious areas such as Marine Parade are highlighted but an indicative map also shows congestion caused by earthquake damage.

The city, along with Christchurch and Lower Hutt is involved in the pilot programme, 'Quicker Safer Tsunami Evacuations' conducted by researchers from GNS Science, Massey University, East Coast LAB (Life at the Boundary) and the University of Canterbury.


Dr William Power, a tsunami modeller at GNS Science, says the models simulate the movement of people on foot, after a long or strong earthquake that could cause a large tsunami.

"They show likely congestion areas during daytime and night-time scenarios and look at options such as vertical evacuation."

In the animation for Napier, red dots swarm the streets, each representing a person moving on foot to the evacuation-zone boundary, which is shown as a blue line.

When the simulated person slows because of overcrowding, their colour changes to purple. One person in 100 is marked in white to make it easier to follow their path.

Ian Macdonald, Group manager at the Hawke's Bay Civil Defence Emergency Management group, said the models highlight the importance of knowing how to evacuate quickly and safely, by foot or bicycle.

"It is also important that people walk their evacuation route and consider any hazards that may appear after an earthquake such as fallen power lines or damaged bridges."

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Project Leader of East Coast LAB (Life at the Boundary) ​Kate Boersen said the issues that arise following a long or strong earthquake including congestion, road damage, liquefaction and fallen power lines would mean evacuating might not be as easy as some may have first thought.

She said it was a "different" way of looking at what issues we might have in the future if there was to be an evacuation after a long or strong earthquake.

She said the "local knowledge and information" gained, and subsequently put into the models had been invaluable. In some cases, they had mapped routes that weren't possible in real life, and other routes that were possible were then added.

The interest from the community has been "far more" than they anticipated, with more than 120 people attending a workshop earlier in the year.

"This is a real issue for most Napier residents so they're definitely interested in learning how they can make their evacuations quicker and safer."

The project, which is now drawing to a close, had been a series of steps, Boersen said, with each model refined.

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Areas of congestion identified in the modelling recommendations are currently being compiled into a report and will be made available to council and other agencies as to how routes might be improved.

"Most people's immediate thinking is to evacuate by car but we know that there's going to be other hazards after the earthquake that will make it really difficult for people to evacuate by car, Boersen said.