Auckland Eruption! What To Expect From An Evacuation

What would you do if there were signs of an impending eruption in Auckland? Jump in your car with loved ones and a few chosen items and flee from the city?

Well, that might be a mistake. Some fellow DEVORA researchers have a new paper out describing the results from transport modeling during an Auckland evacuation. The lead author, Erik Tomsen, was an MSc student in DEVORA at Auckland Uni in 2009-10.  His article is open-access, meaning anyone–you!–can take a read at the link below:

Evacuation planning in the Auckland Volcanic Field, New Zealand: a spatio-temporal approach for emergency management and transportation network decisions

What did he find?

Stuff has a great article with quotes from our researchers and funders about the findings.

But since news articles can’t cover everything, and because journal articles are often written just for other scientists, I’ve summarized some of the findings here:

  1. A 5 km ‘exclusion zone’ around the vent would need to be evacuated. Worst case scenario, up to 500,000 people would need to evacuate their homes very quickly (with 48 hours’ warning or less). Using the current 5 km evacuation radius, the chance that an eruption would take place in an area that would NOT cause an evacuation demand (read: TRAFFIC JAM!) within Auckland is unlikely (4%). No surprise there–as anyone who has driven through Auckland between the hours of 7 am and 7 pm can attest. 
    evac traffic jam

    What Auckland may look like during an evacuation. This shows an evacuation from Hurricane Rita in Texas in 2005. By Ashish from Houston, TX (I-45 & louetta… Rita Evacuation) [CC-BY-2.0 (, via Wikimedia Commons

  2. Don’t leave Auckland. I know, sounds weird, right? But the goal is to stay safe from the eruption. If all the evacuees try to leave the city by car at once, using the very few roads that lead off of our isthmus, this will result in DAYS of massive congestion, as modelled. Living in a car on the SH1 for that long is not my idea of a good time! It is therefore highly recommended that evacuees move to a safe place within Auckland rather than outside of it if possible—this reduces the time to clear roads to 1 to 9 hours. I suggest making some good friends in all corners of the city…
  3. Maybe evacuate at night. Daytime evacuations would cause higher demand than night time evacuations due to the large number of people in the Central Business District and other populated areas, therefore it may be easier to move around at night. This is also perhaps more dangerous due to limited visibility, however. 
    evac by boat 1991 pinatubo

    People evacuated by boat during the 1991 Pinatubo eruption. By PH2 Patrick Muscott, USN.Fastbean at en.wikipedia [Public domain], from Wikimedia Commons

  4. Evacuate by boat or rail. It is also highly recommended that neighborhoods with water access but few exits are evacuated via the harbour to reduce demand on roadways. It is somewhat likely (13-39%) that one or more of the four motorway bridges leading out of Auckland will be within the 5 km evacuation zone, making this option even more attractive. Rail could also be an effective mode of evacuation. I also suggest making friends with someone with a boat!
  5. Certain neighborhoods are more difficult to evacuate. Specific neighbourhoods were identified as having the most difficulty evacuating based on the number of cars, households, and available road exits: Mt Mangere, E Howick Beaches, Gulf Harbour, Sunnynook, West Tamaki, and Hingaia. Luckily these are all near water.
  6. Do not evacuate if you don’t have to. When people flee an area on their own without a Civil Defence recommendation, it is called a ‘shadow evacuation.’ This study was based on the assumption that no one did this. The traffic jams will be even worse if you leave without being told to, and folks who are actually in the danger zone will have more difficulty leaving. So protect your fellow Aucklanders and stay put unless you have to leave.

Erik gave a great talk summarizing his findings to the Auckland Council before he graduated. The .pdf of the talk slides can be found here.

How did he make his model? (For the curious)

Erik used ArcGIS (Graphic Information Systems) and TransCAD (a specialized GIS for transport) to model evacuation demand in Auckland. A ton of information went into running his macrosimulations and producing his model, including but not limited to:

  • 2009 census data (to obtain night time population whereabouts, ages along with Ministry of Education data to figure out where kids were attending school during the day, number of cars per household),
  • infrastructure files (road data such as maps, flow directions, speed limits, number of cars that can be traveling on it at any one time),
  • business demographics statistics to figure out where people were working during the day,
  • estimated boundaries of the Auckland Volcanic Field, and
  • scientific and civil defence planning data, such as the estimated 5 km exclusion zone around the expected vent (this can be found in the Auckland Volcanic Field Contingency Plan).

He set two destinations for evacuees: south to Hamilton, and north to Whangerei. He compared demand at night vs day, considered how people without cars may evacuate, and accounted for the fact that one or more of the major motorway bridges, which funnel all traffic in/out of the Auckland isthmus, could be rendered useless by the eruption.

Because we don’t know where the next eruption will take place, all points within the field were considered equally likely as a vent location.

What is being done now?

The findings of this research could be concerning, but the good news is that only a small area would need to be evacuated, and eruptions in Auckland are quite small compared to most eruptions.

The findings are also great jumping off points for further studies on how to improve Auckland’s road network so that evacuations run more smoothly. Rest assured, we are not throwing up our hands and giving up. Follow up research is underway as we speak, with one PhD project within DEVORA looking at how ash will affect roads in Auckland, and another project planned by the University of Auckland’s Transportation Engineering research group. They’ll be running microsimulations of scenarios, which introduce real-life hiccups such as car breakdowns, traffic light malfunctions, and individual driver error during an evacuation (this was out of the scope of Erik’s MSc study). As with anything, the more we know…the more we can do.

What can you do?

Our job is to figure out what might happen so that Civil Defence can plan and prepare for the worst as much as reasonably possible; your job is to make sure you can take care of yourself for at least 3 days during an emergency. We don’t know what will happen to some of the lifelines during an eruption: power and water supplies, etc. could be affected.

Before and during an emergency, Civil Defence will tell you everything you need to know, including how to take care of yourself. You might not even be in the exclusion zone for the eruption, and could stay at home and not have to deal with the evacuation at all! In fact, your place might be a safe haven for someone else at risk. As always, prepare with emergency kits and plans and you’ll be set for any disaster.

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