Why did our phone and internet services fail so badly in Cyclone Gabrielle? The Detail asks whether there's any easy way to build more resilience in our communications networks.
The fibre-optic cables that connect us to phone and internet services are just a few centimetres in diameter.
"They're not overly robust," University of Auckland computer science senior lecturer Ulrich Speidel tells The Detail.
"When you've got a situation where the hillside comes down ... it takes those cables out with it."
And that's exactly what happened when Cyclone Gabrielle hit vast swathes of the North Island last month.
There was no power, no landlines, no cellphone coverage and no internet service.
It was, for many thousands of people, a communications blackout.
"For cell sites in particular to operate ... you actually need power," Speidel says.
"A cell site or a roadside cabinet will have an uninterruptible power supply in it. If the mains supply to the site goes down, the uninterrupted supply will keep it going for anything between a few hours to maybe a couple of days.
"But when you're having a cyclone and you have widespread power outages - because there's lots of slips and flooding that's taking bridges out - then both your power cables go and the cables which supply those cellphone sites with the phone and internet signals."
And that has huge implications: during Cyclone Gabrielle, EFTPOS machines, cash registers, ATMs all went down. Without cash, people couldn't stock up on essentials. Without power and internet, shops and supermarkets struggled to operate.
Richard Mowll, a PhD student who's researching infrastructure planning for emergencies, thinks New Zealand's infrastructure networks are well-prepared for "smaller bumps, knocks and blips".
"I think when you get to those larger events, we have a bit of a spectrum here - some people are really well prepared and knowledgeable ... but that's not the case for a large proportion of the population. I think we have more work to do at the public level. There are things that we can do in planning and resilience infrastructure."
He talks about having more "redundancy" in our networks and better back-up systems.
Solar and wind-powered networks could also work, if people can afford them.
"If you're thinking of that kind of solution, you have to think of it before the event, and those solutions can be costly."
But in a big disaster, things can get "pretty ragged pretty quickly", Mowll says.
And in those situations, he says you might be left with just a couple of basic options, to try and get connected again: "Going to a friend's or neighbour's house that has power or going to the community emergency hub at a Civil Defence centre where there might be power."
Hear more about the fragility of our communication networks in the full podcast episode.
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