Brett Hood, a director at Northland-based planning and surveying firm Reyburn and Bryant, said a lot of Northland’s infrastructure is not designed to cope with severe weather events. Photo / Michael Cunningham
Being smarter about where homes are built, and making Northland’s failing infrastructure more resilient are key to curbing the impact of future severe weather events, experts say.
Te Tai Tokerau will be mopping up
the impact of Cyclone Gabrielle for many months, with widespread road closures and power lines to remedy, along with flooding damage to homes, buildings, and marae.
It’s safe to say this summer has been the ultimate washout.
And it’s not just this summer.
In February 2022, severe winds from tropical Cyclone Dovi battered the region as well, causing power outages for 23,000 Northlanders.
Brett Hood, a director at Northland-based planning and surveying firm Reyburn and Bryant, said improving the region’s infrastructure – particularly roading, power and telecommunications – is key to getting through future natural disasters unscathed.
The Northland Regional Council has “done some great work” mitigating flood hazards in the Whangārei CBD (Kotuku Dam), Kāeo and Kaitāia, he said.
“But a lot of infrastructure is not designed to cope with those events, storm water networks are overwhelmed and turn into overland flow paths and run down a road.
“I don’t think it is feasible to avoid the impacts of all hazard events, especially when they exceed the 100-year event, but we should focus on infrastructure resilience, especially in our most vulnerable areas.
“In the last three weeks the whole region has been cut off two or three times, because we don’t have an overly resilient road network.
“Some rural townships have one power line and when it gets knocked over the power goes out.”
Hood said avoiding building in “hazard areas”, is also a factor.
“The problem we have all round the country is that we haven’t always located our towns and infrastructure in areas that are hazard free.
“Modern development and extensions of townships are cognisant of coastal hazards, and flood areas.
“They either avoid known hazard areas, or engineering solutions are employed to avoid the hazard.
“It’s the existing areas that tend to get hit much harder.
“It’s about getting it right going forward and I think planning is doing that generally.”
Northland architect Grant Harris said he’d never build on a clifftop, along a coastline or by a river.
“There’s a certain amount of risk in everything we do, but in so many instances we’re building in the wrong places.
“The biggest problem, ever since we started building in this country, we built by the rivers and by the coast because they’re fantastic locations.
“We build by the water because we have a connection with that.
“The hard part is when things go wrong, they go very wrong and that’s the tragedy of it.”
Harris, the principal architect at HB Architecture in Whangārei, said historically, homes in New Zealand have been made with building frames that are too light.
Since the Canterbury earthquakes they have become more robust, he said, but that’s still no match for the forces of nature.
“Since then the building codes have tightened up, and there’s more engineering involved; frames have got stronger, window frames are better.
“But they’re still not going to withstand 100-mile-an-hour winds or tonnes of water pressure.
“We might care about nature, but nature doesn’t care about us, and nature will do what it wants.
“We seriously have to consider the geographic location of where we build.”
So far this year Whangārei has copped 832.9mm of rain, when the average is about 150mm. That’s more than five times the normal amount.
Kaikohe has had 755mm of rainfall in the year to date, compared to the average of 174mm, while Kerikeri had 631mm while the average is 196mm.
MetService meteorologist Lewis Ferris said this summer “has not been normal”.
“It’s been very unusual in terms of rainfall especially for Whangārei.
“It’s been an incredibly wet summer, and there’s a pretty good chance Whangārei will have the wettest summer on record.”
Ferris said there is always a chance that a tropical cyclone will form north of New Zealand during the cyclone season of November to March.
The last three summers have seen an increased risk of tropical cyclones due to La Niña, he said.
“Any year there’s a risk some of those will wind their way down… and Northland is the first port of call.
“The last three summers we’ve been under La Niña, which increases the risk of tropical cyclones forming up in the tropics, and they’re more likely to be in a position to affect Northland.”
The good news, Ferris said, is this stint of bad weather is not something we have to get used to.
“It’s unlikely we’ll see another long run of summers like this,” Ferris said.
Niwa urban aquatic scientist Annette Semadeni-Davies said more protection and better systems are needed.
Semadeni-Davies, whose background is in stormwater engineering, recommends building storage tanks underground, and diverting water, so “instead of flooding houses it will flood the local football field”.
“Some parks or playing fields with streams can be designed as flood basins. They are large areas which are meant to flood, the water is diverted and held there.”
For smaller cities like Whangārei, investing in “real-time control” is feasible, Semadeni-Davies said.
This is where sewer pipes with sensors in them can tell when there’s too much water, close off valves or gates, and divert water from critical infrastructure.
For rising rivers that break their banks and spread onto flood plains, more stop banks are needed, she said.
About 70 Northland towns and localities are projected to be significantly affected by coastal flooding, erosion and permanent inundation through sea level rise over the next 100 years and beyond.
The Tai Tokerau Climate Adaptation strategy, adopted by Northland’s four councils and tangata whenua representatives in April 2022, aims to tackle the pressing problem.
Ferris said climate change would have played a part in the latest weather events.
A warming planet and warmer sea surface temperatures means more evaporation and more fuel for rain, he said.
“In decades to come it’s unlikely there will be more tropical cyclones but likely that they’ll be more intense because of that warmer air and evaporation.
“Northland could have extremes of both, you could get wetter summers, or droughts could be more intense.”