An aerial photo of Anzac Pde on June 21, 2015. Photo /NZME
It has been 10 years since Whanganui was hit with its worst flooding on record, and experts are leaving nothing to chance as they prepare for the next major event.
From June 19, 2020, Whanganui and its surrounding districts experienced 131mm of rain in 48 hours, with the Whanganui River breaching its banks just before midnight on June 20.
Hundreds of people were forced to evacuate, and there was widespread damage to homes, farms, businesses and infrastructure.
Whanganui Civil Defence emergency manager Tim Crowe said a lot of current flood planning was based on his team’s experiences in 2015.
“If you go back to then, we didn’t even have a weather warning,” he said.
“Now, we use a lot more resources to monitor.
“We go early and we go to the best benefit of people.”
Leading up to the 2015 event, MetService did not issue a severe weather warning because there had been no indication the rain would be so heavy.
Crowe said team member Anthony Edwards was part of Civil Defence’s emergency management assistance team (EMAT), and he provided observations and information about other weather events he attended.
“We can look at whether that will improve our own systems and incorporate it into what we do locally,” Crowe said.
“A lot of it is around organising our teams and how we evacuate, to make it as quick and efficient as we can and to give people time.”
Edwards was named as part of EMAT in 2019.
Nga Tangata Tiaki o Whanganui chief executive Nancy Tuaine said the 2015 flooding was a major factor in the organisation partnering with Australia’s Griffith University to build catchment resilience.
Part of that work included 3D mapping of the district’s surface using Lidar (light detection and ranging) technology.
Tuaine said wetland restoration, rehabitation and land retirement all helped to mitigate flooding, but it was important they were in the right place.
“When you’ve got bare land, which we do in the upper [Whanganui River] catchment particularly, water is going to rush off really fast,” she said.
“We are at the receiving end down here in the city.
“From our perspective, we are focussed on data-informed decisions about what we need to do, where we need to do it and how much it will cost.”
Horizons Regional Council group manager for catchment operations Dr Jon Roygard said during the 2015 event, flows in the river were among the highest ever recorded.
In the decade since, the council had completed a suite of work to make the area more resilient, from river management asset improvements to studies into flood risk, he said.
Sites along the Whanganui River stopbank near Kowhai Park were strengthened in 2022.
“Previously, there were three areas where roads passed through the stopbank,” Roygard said.
“This required staff to install flood barriers during rain events to fill the gaps created by the roads.
“These gaps were infilled and compacted to be the same height as the rest of the stopbank.”
Crowe said shortly after the 2015 floods, a weather-monitoring system was installed on the Whanganui River at Ranana, which allowed rainfall in the middle reaches of the river to be monitored “with up-to-date accuracy”.
That data, and a lot of other weather monitoring information, was easily accessible to the public, he said.
Dealing with major weather events and building resilience was “a team game”, and communities across the district were more connected than ever.
“That could be police, Red Cross, Fire and Emergency, ambulance or local groups like The Community Led Team (TCLT) up the river,” Crowe said.
“We have really good links with them, and they’ve only improved with time.”
TCLT community connector Ramari Te Uamairangi said emergency management plans were now in place for all the villages along the Whanganui River Rd.
“Our villages up the river are quite resilient because our people have been living that way for a long time,” she said.
“We just needed to put a bit of a frame around it and get things down on paper.
“It was a slow process, with a lot of engagement.”
Te Uamairangi said the 2015 event reminded people that there was “one road in and one road out”.
Straight away, marae were identified as emergency shelters, she said.
“It goes without saying, you want to have an emergency power source at the marae.
“That’s where we installed diesel-powered generators because diesel is easily flown in and out.”
Defibrillators had also been installed in each community, she said.
Roygard said Horizons’ environmental data equipment and software had been upgraded in recent years, and monitoring sites had more methods of data transfer, faster transfer times, and backup power generation.
Horizons senior emergency management advisor Matt Putt said the council had also invested significantly in flood modelling.
“We rely quite heavily on our environmental modelling team – hydrologists, river engineers, flood experts,” he said.
“There is no crystal ball, but it can give us an understanding of who might be impacted, and a general sense of when, so we can start informing communities of the potential risk.”
Horizons’ emergency management officer Chay Hook said the public could sign up to the council’s river alert system, which automatically called people if rivers and streams reached a certain height.
“They can make decisions themselves about self-evacuation and that type of thing,” Hook said.
“For us, it’s about preparing for the next event. We take the lessons learned and lessons identified previously, and put it into practice with the resources we’ve got.”
Putt said local knowledge also had to be tapped into.
“When it starts raining, people know what will happen to the stream behind their house,” he said.
“Tim has done a great job of engaging with iwi around Whanganui, who have a long history of lived experience.”
Roygard said Horizons, Whanganui District Council and NZ Transport Agency Waka Kotahi were working with the Pūtiki community emergency response group to update flood modelling for the area and identify potential mitigation options.
Residents in Pūtiki, a low-lying area next to the Whanganui River, were evacuated due to flooding in 2015, 2017 and 2021.
Houses along Anzac Pde were also badly affected in 2015.
Roygard said after that flooding, Horizons appointed Massey University to facilitate community engagement, which led to the Anzac Parade Flood Resilience Strategy, launched in 2022.
He said flood mapping work was ongoing, and would eventually include a flood risk assessment for the approximately 50 towns and settlements in the Horizon region.
Te Uamairangi said if there was heavy rain up the river, Crowe and Edwards would send a warning email, with TCLT contacting community leaders straight away.
“We can quickly ascertain who needs help, and who we need to keep an eye on.
“It’s about connectivity – going out to the network and getting a situational update.”
She said her house on Anzac Pde was flooded in 2015.
“We’ve had a first-hand experience of water coming through your home and have to be evacuated.
“People have said we are crazy to stay there, but we are very aware of what could happen, and what will happen.
“We’ve put things in place, here and up the river, to have a much better situation when the time comes to act.”
Crowe said emergency response teams ran exercises four times a year, up from two or three pre-2015, that covered a range of scenarios.
“There will be a main river flood threat [exercise] once a year, with things like localised flooding, closed roads and landslides built in to complicate things a bit more,” he said.
“We need to make sure we don’t overlook issues, so people can practice making calls and use information tools.
“It builds your team’s experience and confidence.”
Despite technology advancements, teams still practised with “old fashioned paper back-ups” in case power and internet was lost, Crowe said.
“We are always looking at ways to improve, and planning makes it easier to do stuff when you need to do it in a hurry.
“There can’t be a single point of failure when it comes to dealing with people’s lives, pets and possessions.”
Tuaine said there was still a lot of work to do, but groups were “coming together better than ever before”.
“There is a whole wealth of knowledge to draw on,” she said.
“Essentially, that’s what the Te Awa Tupua [2017 Whanganui River Claims Settlement] legislation is about – coming together as people of the river.
“It’s not just iwi, it’s communities finding solutions at place – where they live. They are part of those decisions.”
Mike Tweed is a multimedia journalist at the Whanganui Chronicle. Since starting in March 2020, he has dabbled in everything from sport to music. At present his focus is local government, primarily the Whanganui District Council.
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