Volcanic eruption could cripple Auckland's transport network: scientists

Tuesday, 11 April 2017

Scientists have modeled the effects of an eruption on Auckland's roads; red is 'no service' and orange is 'limited service.'

A volcanic eruption could bring Auckland to its knees, crippling transport networks and displacing almost one-third of its population.

Scientists from the University of Canterbury have modelled what would happen to the city's transport networks if there was an eruption - hardly a doomsday scenario, given the Super City is situated on an active volcanic field.

Auckland is built on one of the densest volcanic fields in the world, with more than 50 vents dotted around the city.

The study looked at a hypothetical two-month-long disaster centred near Mangere Bridge, south of the CBD. It is one of a series of studies using this scenario to model the impact of an eruption on Auckland.

The study, released on Tuesday, found Auckland's difficult geography would limit transport and evacuation routes.

Rangitoto Island was the scene of Auckland's most recent volcanic eruption.

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The most significant disruption across all transport networks would happen around six days before the eruption, because of the establishment of evacuation zones.

These would block crucial north-south links across Auckland, and at times cause up to 435,000 residents to be displaced.

Researcher Thomas Wilson said any eruption could have 'potentially big consequences' for the city's urban area.

'Auckland is on an isthmus, so there's quite a small land area where a number of different infrastructure networks run through. A mass evacuation puts a lot of pressure on Auckland's transport.'

The team found that most physical damage to road and rail would happen from the volcanic eruption itself, destroying anything within a 0.5 to 2.5km radius, but with little impact from earthquakes leading up to the eruption.

Auckland Airport would not be directly affected by physical damage, but would have restricted access due to evacuation zoning and airspace restrictions, forcing limited domestic and cargo flights to redirect to Whenuapai and Ardmore Aerodrome.

Volcanic ash deposits on roads and rail lines would cause disruption for more than a month after the eruption, until clean-up and re-entry to most evacuation zones was completed.

The study said the most important factors for keeping the transportation network open would be removing volcanic ash from bottleneck areas such as bridges.

The city would also need to ensure electricity supply for trains, airport and traffic signals, as well as ensuring continued fuel supply.

Wilson said it was important for Auckland residents to be prepared in the event of a disaster.

'Looking at similar volcanic fields overseas, there's every expectation there will be a future volcanic eruption. The challenge is that we're not really sure where the next eruption will come up.'

The last eruption within the Auckland volcanic field happened at Rangitoto Island around 500 years ago.

Auckland has a seismic monitoring network that will pick up the small tremors likely to precede any volcanic activity.