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Research explores impacts of hypothetical volcanic eruption in Auckland - 03/03/2017

Understanding the possible impacts of a volcanic eruption in Auckland is one of the first steps in preparing the city to survive and even thrive after such an event, scientists said today.

Browns Island and Rangitoto in Auckland’s Hauraki Gulf are two of the 50-plus volcanoes in the Auckland Volcanic Field which have erupted in the recent geological past. Photo – Lloyd Homer, GNS Science

Browns Island and Rangitoto in Auckland’s Hauraki Gulf are two of the 50-plus volcanoes in the Auckland Volcanic Field which have erupted in the recent geological past. Photo – Lloyd Homer, GNS Science

In a research paper released this week, scientists have looked extensively at what could happen during an eruption in Auckland, and revealed that critical infrastructure can still provide some services in the face of extreme conditions.

The study is based on a hypothetical two-month-long unrest and eruption sequence near Mangere Bridge and explores the implications for evacuation and the impact on critical infrastructure such as water, electricity, and transport.

As well as looking at how evacuations might be managed, there is a focus on how electricity networks would cope with an eruption.

The paper is the first complete eruption scenario developed for Auckland since the 1990s and it updates and expands earlier work by scientists in this area. It also represents a new approach of looking beyond direct physical damage to assessing a range of consequences.

The eruption scenario includes the emergence of a new volcano, several pyroclastic surges, a series of small volcanic earthquakes, ash fall, lava flows, and some ballistic blocks hurled into the air. The researchers say all are considered realistic possibilities, though it is unlikely they would all be happening at once.

It is the first of three multi-institution research papers examining the impacts of a hypothetical eruption in Auckland. Subsequent studies, also based on a Mangere Bridge eruption scenario, will look at other ramifications.

The paper, published this week in the Journal of Volcanology and Geothermal Research, was written by researchers from GNS Science, the University of Canterbury, and Massey University.

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If we can understand what is possible and credible, we can better plan for it. It was very rewarding to see the level of collaboration we had with all the parties involved; infrastructure providers, universities, and GNS Science all worked together to develop this study 

Dr Natalia Deligne

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The scientists worked closely with utility company Vector Ltd, as well as a number of other agencies.

Lead author Natalia Deligne, a Volcanic Hazard and Risk Modeller at GNS Science, said a key lesson from the study was the value of working with infrastructure providers to help determine realistic impacts and also consider evacuation zones and staff health and safety when examining what might happen during an eruption in Auckland and the subsequent recovery.

“We found this produced a more credible scenario and also had other benefits for all those involved including shared learnings, stronger networks, and greater mutual understanding of volcanic risk for infrastructure networks,” Dr Deligne said.

She emphasised that the study was not a ‘how to guide’ for managing a drawn-out eruption, but it laid a comprehensive framework for further work in this area.

The evacuation areas used in the study are based on current civil defence plans. Using the plans as a basis, the researchers developed a series of maps for pre-eruption evacuations, as well as evacuations during and after the event.
 
It was hard to overstate the importance of the interplay between evacuated areas and restoring critical services such as electricity, gas, water, and transport networks, Dr Deligne said.

“Access to raw materials and trained staff who are available to work are other critical concerns.

“By looking at the infrastructure network and the impact of a volcanic eruption, we can better understand how we can live with this kind of risk in our backyard.

“If we can understand what is possible and credible, we can better plan for it. It was very rewarding to see the level of collaboration we had with all the parties involved; infrastructure providers, universities, and GNS Science all worked together to develop this study, “ Dr Deligne said.
 
The work received support from two multi-institutional research projects - Economics of Resilient Infrastructure (ERI), and Determining Volcanic Risk in Auckland (DEVORA). ERI is funded by the Ministry of Business, Innovation, and Employment and DEVORA is funded by the Earthquake Commission and Auckland Council. The research was also supported by GNS Science and the Natural Hazards Research Platform.

A selection of media coverage of this story:

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Contact:
Dr Natalia Deligne, Volcanic Hazard Modeller, GNS Science, M: 021-047-9025 (Lead author)
Dr Tom Wilson, Assoc Prof in Disaster Risk and Resilience, University of Canterbury, M: 021-434-596

Note:
Auckland city is built on the Auckland Volcanic Field which covers 360sqkm, has more than 50 eruption centres (vents), and has erupted more than 55 times in the past 190,000 years. The field will almost certainly erupt again and it is very likely the next vent will be in a new location within the field. In spite of considerable efforts by scientists, they have been unable to identify any patterns in the eruptions. In fact the oldest vent (Pupuke) and the youngest (Rangitoto) are located next to each other.

The size of the next eruption is also hard to forecast. The most recent eruption, Rangitoto, accounts for nearly half of the erupted volume of the field, and it is unclear if this eruption was an anomaly or if it signals a change in the eruptive behaviour of the field.