Flood experts are bracing for a “new norm” after extreme weather saw the Bay of Plenty Regional Council issue 54 flood warnings in five months.
That was 10 more than it issued for the entire year to June 2022.
Now, a new “global boiling” era has arrived as scientists calculate that this month has been the hottest on record and probably the warmest since human civilisation began.
According to MetService, Tauranga recorded 1411mm of rainfall since January, nearly double the average amount of 806mm. Rotorua recorded 1478mm compared to the average of 867mm.
NZME reported last month that May was the wettest month Rotorua had experienced since official records began in 1963. In March, Tauranga had its wettest summer since 1984, according to the National Institute of Water and Atmospheric Research (Niwa).
Bay of Plenty Regional Council presented a report to its Monitoring and Operations Committee in June, which showed the region had consistently experienced “above average” rainfall in the past 12 months due to cyclones Hale, Gabrielle, the Auckland Anniversary Day storm and other significant weather events.
The council’s environmental monitoring system collects data on heavy weather events, including rainfall and river levels, to help the public and agencies such as Civil Defence make informed choices when it comes to helping the community in crisis.
To date, the council’s monitoring stations have captured a total rainfall across the region of 273 per cent of the normal amounts recorded behind Te Puke and 130 per cent at the Tarawera River.
The extra rainfall has seen the regional council issue 54 flood warnings from January to May this year, compared with 44 between July 2021 and June 2022. Two flood warnings were issued last month.
The council also took 317 phone calls from the public about flooding in the same timeframe, compared with 68 between July 2021 and June 2022.
Bay of Plenty Regional Council engineering manager Mark Townsend said climate change was making weather patterns “increasingly unpredictable”.
“What we anticipate and are planning for is the new norm of more intense, inconsistent weather patterns that would see more extremes hitting our region (such as) extreme dry or extreme wet.”
Townsend said flooding was the most common natural hazard in Aotearoa, with a major flood event occurring on average every eight months.
“As the climate changes, communities across New Zealand are adapting to meet the challenges of a rising sea level and more frequent, more significant rain events that may cause flooding.”
Townsend said the warning system applied to the seven major rivers: Kaituna, Whakatāne, Tauranga, Rangitāiki, Tarawera, Waioeka and Ōtara.
A first warning was issued when a river rose to the top of its normal channel capacity and a second was issued when it rose above the river channel and flooded the area directly next to the river but well within the “flood defences”, he said.
Understanding what was happening in our backyard was critical in helping communities to become resilient in the face of climate change.
“One of the ways we do this is through our flood forecasting models, which we have developed for six of our major rivers.”
The models supplement weather forecasts from MetService with rain radar and other environmental information from its network of monitoring sites to produce the impact of the rainfall on rivers and floodplains. The flood forecasts help the council during and after an event.
The extra rainfall was putting pressure on the regional council’s rivers and drainage operation team, which has been working to set up temporary mobile pumps to pump floodwaters off rural properties, remove debris from rivers, erosion repair and monitor stopbank seepage.
Bay of Plenty Regional Council data services manager Glenn Ellery said the council had been investing in the region’s monitoring sites since the April 2017 floods and there were now 204 monitoring sites installed.
Overall, it added 13 rain and river level gauges to key areas including the upper Rangitāiki, lower Whakatāne, Te Kaha, around the Kaituna, Ngongotahā and Waiotahi, which cost about $300,000.
MetService meteorologist Andrew James said Tauranga recorded 1411mm of rainfall since January and Rotorua recorded 1478mm.
The average rainfall for Tauranga was 806mm and 867mm for Rotorua.
James said 2023 and 2022 had both been significantly wetter than normal due to more systems coming out of the northeast under La Niña, an oceanic and atmospheric phenomenon that is the colder counterpart of El Niño.
He said weather events had been “on the extreme end of the spectrum” and there were “big jumps” in February when Cyclone Gabrielle hit, and May and June due to low-pressure systems of tropical origin – a hallmark of La Niña.
“The climate is warming and warmer air can hold more moisture than cooler air.
“We are seeing these events bringing more rain.”
The World Meteorological Organisation and the European Union’s Copernicus Climate Change Service proclaimed on Thursday that July’s heat was beyond record-breaking, with the Earth’s temperature temporarily passing over the internationally accepted goal of limiting global warming to 1.5C above pre-industrial levels.
United Nations Secretary-General Antonio Guterres told reporters in a New York briefing that climate change was here and “it is terrifying”.
“The era of global warming has ended; the era of global boiling has arrived.”
Emergency Management Bay of Plenty (EMBOP) manager of planning Stace Tahere said there had “definitely” been more extreme weather.
“Climate change is not as straightforward as just warmer temperatures and it does mean we need to be prepared for damaging weather events.
“We know that once people have experienced a flood (or other severe weather events like landslips), heavy rain and wind can be really anxiety-provoking, so we try to get useful information out to people as fast as we can.”
In the last national test of the Emergency Mobile Alert system, it reached more than 90 per cent of people (more than 5 million phones), Tahere said.
Phones ringing, the tip-tapping of computer keyboards, a constant hum of conversation and the binging of alerts as rolling weather updates arrive.
Those are the sounds of the Bay of Plenty Regional Council’s Flood Room in full response mode.
The Flood Room was established to provide a dedicated space to support the regional council’s flood response.
“We regularly train on specific aspects of the flood team’s roles and hold exercises to prepare our team members for small- and large-scale events,” engineering manager Townsend said.
“There are frequent field trips across the region to ensure everyone has a good understanding of how and where the community could be impacted.”
Flood management at the regional council operated in two modes, he said: monitoring and activated.
In the monitoring mode, a regional council duty flood manager is on call 24 hours a day to closely monitor the weather, flood forecasts and environmental data and provide real-time information to supporting agencies (such as local councils and Waka Kotahi).
“The duty flood manager will receive assistance from the wider flood team as necessary depending on the severity of the flood event.”
Activated mode means the weather event was so severe it needed the flood team’s “undivided attention”.
“The flood team is then set up in the Flood Room and operations team are helping in the field.”
To prepare:
If you need to leave your home:
If you need to stay home:
Source: Emergency Management Bay of Plenty
Zoe Hunter is an assistant news director for the Bay of Plenty Times and Rotorua Daily Post. She has worked for NZME since 2017.