Resilience of networks tested by extreme weather events

Months of extreme weather has put much of New Zealand's infrastructure under strain, as well as those called on to repair services in emergencies.

Matthew Stewart is Downer's South Island regional manager for Telco, where they've responded to a 1000 more faults than usual last month.

"Last month we did 6000 faults around the place. It's just been hectic," he said.

"Trying to work in those conditions, work safely, under the pressure of getting customers back up again. It's been relentless."

He says they'd usually get a chance to recharge in between weather fronts, but a short window between numerous systems has made life even tougher for those out on the front line.

"This time of year is always hard, working in cold wet conditions as it is... Generally when we can get through one storm event, we can recover and get ready for the next one, but this year with them being pretty close together we're still trying to fix the last one when the current next one hit."

READ MORE: Heavy rain lashes parts of North Island, snow for upper South

It's been a similar picture in the Manawatū and Tararua region, where Downer's Nigel Timms says the wettest July on record has forced them to reprioritise jobs, leaving them with a bigger backlog.

"We often use June/July as a construction period because the ground is still fairly firm, and we can get into paddocks. But that's not been the case this year that's for sure."

Most of the region has faced some level of issue with water levels in the ground is increasing the risk of trees being blown onto power lines.

"We're only in August, typically our windy period is September, October," Timms said.

"I've been around a wee while and I've seen some years worse than others. It is changeable, I haven't got a pattern, this one is just wetter and started a lot earlier."

He says property owners can help alleviate some of the pressure by felling 'at risk' trees.

Both Timms and Stewart say generally the resilience of their networks, Telco and power, is pretty robust.

Stewart admitted: "Mother nature's forces does what it wants to do and we just have to clean up afterwards."

Civil engineer Roger Fairclough, who has decades of experience advising infrastructure projects on resilience, admits making a network 100% resilient in New Zealand is all but impossible.

"We (NZ) are hazardous. We're exposed to pretty much all natural hazards that come around and meet people around the world."

"What we've been encouraging for a number of years is that as part of any consideration of how you maintain assets or infrastructure, or how you invest in new infrastructure, you do so actively consider the topic of resilience."

He says there are some network 'hotspots' more vulnerable than others.

"This is where you get intersections geo-spacially, where there's a lot of infrastructure in one common area. One of the classics is here in Wellington, which is around Kaiwharawhara (and the) Interisland ferry terminal.

"I'll pretty much say we've got every bit of infrastructure except an airport. We have gas, we have electricity, we have water, and we have road and we have rail. So all of those in that one same area."

That could make the whole network more vulnerable to a major-level event, be it extreme weather or earthquake.

"There are opportunities to reduce the relative risk in that Kaiwharara area. For example we could shift some of our networks, and give some geographic diversity to where things are. That has been considered as part of the Wellington Resiliency Project."