Lessons for Aotearoa on avoiding the worst of future floods

Communities devastated by severe weather at the start of 2023 are facing buyout logistics and hard decisions this Christmas. After stopbanks failed and neighbourhoods flooded, there were calls for a change in the way we manage our rivers and build flood protection, and whispers of managed retreat. Could inspiration be drawn from a massive, transformative river project in The Netherlands? Or from a small town west of Brisbane which moved to higher ground? Kate Green reports.

The Dutch project 'Room for the River' seems, on paper, almost too ambitious to be true. One hundred and fifty homes were bought out and relocated - many in areas not at risk of flooding - to be replaced by river bypasses and floodplains and ensure the safety of 4 million people.

The catalysts were two big storms - the first in 1993, then in 1995, heavy rain and snow melt caused water levels in the Rhine, Meuse and Waal rivers to rise dangerously, weakening flood defences and forcing 250,000 people to evacuate.

Dr Frans Klijn, a specialist in integrated river management at Deltares, a Dutch research institute, and professor at Delft University of Technology, said in the aftermath it was clear something had to change.

"We said, 'This is not going well. Are we going to continue raising our embankments over and over again, or should we do something else?'"

The danger of building ever-higher embankments was the feeling of security it provided, which led to more development in those areas, which in turn led to calls for increasing protection when the water levels caught up and threatened their safety once again.

What was needed was a change of paradigm, Klijn said.

"Let's give the river a bit more room, because it appears that climate is changing, and that the river needs more room for discharge."

Klijn had been involved in the programme for the past 15 years - first in the research team, and then in the quality team, assessing whether each of the approximately 36 projects delivered on 'spatial quality'.

This, he explained, was the key to its success. The solution had to provide more benefits than just flood protection to win the support of the people, particularly those who were being forced to move, albeit with compensation.

In Nijmegen, 50 houses had to be demolished to make an additional channel for the river, lessening the flow in the main channel.

"Those 50 people were, of course, not so happy."

The status-quo solution - bigger and better embankments - tended to be ugly, and there year-round, despite only fulfilling its function on rare occasions when the river was in flood.

The answer, Klijn said, was to make the solution beautiful.

Changes were made at 30 locations, making flood plains broader, moving dikes inland, repurposing land into conservation or recreation areas rather than suburbs to minimise potential flood damage, as well as deepening the river bed and creating additional channels alongside the main river to send more water out to sea as fast as possible.

"The many years of uncertainties, that was of course not nice for the people," Klijn said. "'Are the plans going on? How are we going to be compensated?' Years of trouble. But afterward they all say, 'Well, it has become very beautiful and nice to live here.'"

It took two decades, with research beginning in 1996, the green light given in 2005 and the whole thing finished by 2016.

The final price tag was €2.4 billion (NZ$4.3b). Klijn said it was the only mega project in the world he was aware of that had stayed within budget.

So did it work? Put simply, Klijn said, its limits were yet to be tested. Designed for a flow rate of 16,000 cubic metres of water per second, so far, it had not experienced more than 9000.

"We have built it for a flood that should happen about every thousand years or so, so that you'll get it in the next 10 years is a small chance."

But around the world, countries were beginning to look to the Netherlands and wonder if the same could not be done at home.

Klijn said he and his institute had advised on a number of projects internationally, where Room for the River appeared to be a transferrable solution - Bangladesh, Vietnam, Indonesia, the United States and Canada.

But every river was different.

"Don't copy our solutions, copy the way we approach it."

That was, with good problem analysis, solid investigation of possible solutions and discussion with the people. If possible, aim for dual-purpose design.

"Don't build something which works but is terrible to look at."

And the bottom line: "There's only one solution to flood risk management, and that's stay out of harm's way. Don't build where the flood hits."

An Aotearoa approach

So is it possible in New Zealand? National conservation group Forest & Bird's freshwater advocate Tom Kay says yes.

"Historically our rivers had space to move across their floodplains," he said, speaking to a room full of expectant Napier locals in October. "They built the plains - the Heretaunga Plains, the Canterbury Plains, they are built by rivers moving around, depositing sediment."

But the modern method of managing rivers was very different.

"The Western approach to river management was the rivers should stay in one place, we can use the land around it, we'll get the water out to sea as fast as possible when it floods, and we'll turn the river into a big straight drain, basically."

We built stopbanks, removed willows, ruined river habitats by concreting riverbeds, and built neighbourhoods right up to the banks. And that worked well enough, most of the time.

Kay pointed out there had been major flooding events in Auckland, Nelson, Tai Rāwhiti repeatedly, Westport, Canterbury at the Ashburton and Rangitata rivers, Edgecomb and Manawatu in only the past 20 years.

Climate science tells us severe weather events are going to get worse and more frequent.

As one-in-100 year storms began happening every 50, even every 20 years, the chance of stopbanks being overtopped increased, too.

Like in the Netherlands, stop banks also meant a greater false sense of security, causing development to creep closer and closer to riverbanks.

"You tend to start chasing your tail when you start managing rivers like this," Kay said.

Getting out of the way

A very different solution was to retreat out of harm's way entirely.

The Australian town of Grantham, west of Brisbane, was heavily affected by flooding in 2011.

"It put more or less the entire state of Queensland underwater over the course of a few months."

Grantham was - unfortunately - in the way of the water, and it left extensive property damage and some loss of life.

Urban and environmental planner at Griffith University, Tony Matthews, said it became a landmark case. Traditionally, the response would have been to rebuild - often in the path of the previous disaster, and therefore, at risk in the future.

"In breaking with any tradition that had ever existed before, the planners that were responsible for Grantham took a spontaneous decision to relocate 100 houses to higher ground."

Planners designated a new patch of land on higher ground, and then built a road pointing in its direction - and the people moved. Rebuilding homes took years, but the redesignation of the town's borders took only a few months.

"Under normal circumstances, such a bold move would probably have never been tolerated," Matthews said. "But given what had happened to that particular community in Grantham, so much loss, so much grief, such an urgent need to respond, given the circumstances the planners got away, in a sense, with this very bold move, and created a very famous… example of a community relocation."

Integral to its success was buy-in from the community. There were up to 100 people attending meetings every morning, for at least a week - Matthews was fairly sure they took place in a very large tent.

"You couldn't possibly hope to successfully relocate a community without the community wishing to relocate," he said.

It might have been a landmark case, but it had not sparked a surge in moving communities - relocation was and should be the final option, Matthews said.

And the stars needed to align. Was there suitable, available land? Was it safe? Did it meet the community's needs? Could it be bought?

Having policy and planning frameworks in place for carrying out a relocation before a disaster occurred would help, Matthews said. It could happen without, but "you'll get a better result if you have proper policy frameworks".

Another key factor was, of course, money. Queensland was not short of cash, Matthews said, its mining wealth providing a comfortable purse with which to fund disaster recovery - not something New Zealand had to draw on.

Our country was not all that similar to either the Netherlands or Grantham. Scale, wealth, geography and population vary greatly. But when future storms threaten the safety and sanctuary of homes in places like Eskdale, Te Karaka, Tolaga Bay and Wairoa, something will need to change.