Scientists have created a model to see how many people might be at immediate risk during a volcanic eruption in Auckland and how long it would take to evacuate.
The model came about after looking at demographic information, like population distribution and vehicle ownership, as well as geospatial tools.
The findings were recently published in the Journal of Geothermal and Volcanology Research.
With advance warning of where a volcanic eruption could occur in Auckland, the scientists found it could take up to about 49 hours to evacuate affected residents, which were estimated at 320,000.
If the location of the affected area is less certain, the scientists said both those numbers increase.
They also found the region's residential suburban areas would require the largest and longest evacuations.
Their findings come after they looked at the time it takes to complete different stages of the evacuation process, from when decision-makers were advised of a hazard to when the last people were clear of the evacuation zone.
Although an eruption is unlikely in our lifetime, experts know one will occur in the future.
Previous work, led by Marco Brenna of the University of Otago, suggested Auckland may have five to 15 days warning of an impending volcanic eruption.
However, lead researcher Alec Wild said not knowing where the next eruption in the Auckland Volcanic Field would be made things difficult.
He hopes the model will help address such unpredictability.
Wild said the next step in their research is to develop maps and tools to support decision-making during volcanic crises.
This research will also help refine regional emergency management and evacuation planning for volcanic eruptions.
"An eruption in the Auckland Volcanic Field is one of the region’s most impactful hazards and comes with a lot of different risks,” Kate Crawford, general manager of Auckland Emergency Management (AEM), said.
"Evacuations themselves can be dangerous and asking people to leave their homes during an emergency, possibly for an extended period of time, is one of the hardest calls any emergency decision-maker will have to make," she said.
"That is why research to help us understand how much time we might have, and how long it will take to get people to safety is so valuable to us."
Dr Adrian Pittari, a senior lecturer in volcanology from the University of Waikato, said the study offered a good plan for authorities to work with to organise an evacuation.
Ben Kennedy, a professor in physical volcanology at the University of Canterbury, said the study was a key contribution to better preparing Auckland for a volcanic event.
"The paper does well to explain that this will be less if 1) the population is prepared, 2) the eruption occurs in less populated areas, 3) roads are less congested, and 4) we know exactly where the eruption will be ahead of time."
Unlike the big volcanoes in the central North Island, eruptions in the Auckland Volcanic Field are usually smaller, and are in a new location each time. There are currently 53 identified volcanic centres, which have created the cones and some lakes we see around the
city.
In the event of a volcanic threat in Auckland, AEM will work with police - who lead the evacuation control team - and welfare and support agencies, to help those impacted.
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