The rapid acceleration of climate change has prompted an urgent warning from scientists that our rivers need more room to flood.
As the frequency of extreme weather events increases, experts are calling for a national 'Room for Rivers Plan' to help councils with managed retreat and flood mitigation funding.
It was a terrifying sight last February. Rivers in Te Matau a Māui/Hawke's Bay burst their banks during Cyclone Gabrielle, flooding homes and resulting in hundreds of rooftop rescues.
It's something Tom Kay said could have been avoided.
"Historically we've straightened our rivers, we've channelised them and tried to get water out to sea as fast as possible but basically, that means water builds up behind stop banks and when it overtops it's catastrophic," said Kay, a freshwater advocate from Forest & Bird.
Like in Pākōwhai, near Heretaunga/Hastings. The Tūtaekuri and Ngaruroro Rivers used to run separately out to the ocean, but humans engineered the rivers away from their natural path to join them together.
That created a bathtub effect where the two rivers meet in Pākōwhai.
"When those rivers overtopped those stop banks they filled up that area and people were then rescued from rooftops with helicopters and boats," Kay told Newshub.
He said the area has since been red-zoned.
"We need to make space for rivers. That energy needs space to dissipate its energy. There's a whole bunch of benefits to that too, and it means we have safer communities."
But making space is hard, as rivers nationwide have been constrained by stop banks and willow trees.
"The problem is the river will keep trying to break out beyond that," said river geomorphologist Jo Hoyle from NIWA.
"And with a changing climate that's more and more likely to happen."
Which is what happened when the Ashburton River flooded in 2021.
In 1959, it was a windy, braided riverbed, but today it's much narrower and straighter.
And further south, the Rangitata River has also been forced in but during floods, the old river channels fill back up with water.
"You can see how the river has reoccupied flow paths that it used to be able to take," Hoyle told Newshub.
Hoyle is a braided river expert.
"You can see the multiple river channels. That's what makes this river a braided river - it has multiple 'braids'."
And she's warning that the devastation we saw in Cyclone Gabrielle will happen again.
"A changing climate means we're going to have more frequent and more extreme floods, and so the rivers will keep breaking out," said Hoyle.
"We need some new direction that accounts for climate change and the importance of rivers in our landscapes," Kay said.
Now, it's a direction some councils are taking.
The Hutt River is prone to flooding, so the local council is widening it by raising its stop banks, and demolishing homes and buildings to make more room for the river.
But there are also calls for better legislation to give councils more power.
"They need stronger tools to give them the ability to stop development in problematic areas and to actually start to move people out of these problematic areas," Kay told Newshub.
"Ultimately our rivers need space - and if we're not going to give it to them, they are going to take it."
