A nature-based approach to river management could bring greater protection against flooding than building bigger stop-banks, new research suggests.

Giving rivers space to roam rather than increasing conventional flood infrastructure to control them would help keep human settlements safer in a changing climate while also supporting freshwater ecosystems, says University of Canterbury | Te Whare Wānanga o Waitaha (UC) School of Biological Sciences Associate Professor Jonathan Tonkin.

“Dynamic rivers can restore critical habitats for rare species, improving biodiversity. It’s time to embrace a new paradigm for river management - one that sees rivers not as threats to be controlled, but as lifelines to be protected and restored.”

Associate Professor Tonkin and lead author, UC PhD student Christina McCabe, have published new UC and University of Otago research in Nature Water highlighting the extensive ecological flow-on effects of giving floodplain rivers more room.

Associate Professor Tonkin says the impact of flooding is getting worse, and there’s a need to reassess current approaches to river management.

“Large floods are expected to increase in frequency with climate change, and the effects of such floods are exacerbated by the artificial confinement of floodplain river systems.

“Giving rivers room to move is being considered as an alternative to increasing fortification of existing flood infrastructure. Our research also shows that there are key co-benefits to ecosystems that have previously been overlooked.”

He says sustainable river management should consider a broader range of values, beyond flood mitigation alone. “Healthy, free-flowing rivers provide significant contributions to people, from flood resilience to freshwater provision and recreation.”

Associate Professor Tonkin says Aotearoa New Zealand is at a crossroads with flood management. “Do we continue to build bigger stop-banks to protect our towns and cities, or do we begin to give rivers back the space they need to roam on the landscape?”

McCabe says variability is a defining characteristic of floodplain rivers and it’s important to understand their dynamic ecology. “Maintaining this natural variability across landscapes and through time must be a primary focus of ongoing management.”

She says rivers that are left free to roam provide a diverse range of habitats, which supports unique combinations of plants and animals. “Even exposed gravel, which is made possible in rivers that have the space to move, can be critical nesting sites for endangered birds. For instance, the banded dotterel travels long distances to nest on exposed braided-river gravels each spring.

“The ‘command and control’ approach to flooding risk should make way for a more sustainable adaptation to living rivers,” McCabe says.

The new research is highly relevant to policymakers and river managers who make decisions about freshwater management, she says.

Traditionally, flood management has prioritised infrastructure and human safety, often at the expense of river ecosystems.

“By considering the ecological benefits of dynamic rivers, decision-makers can implement solutions that enhance biodiversity, improve water quality, and build resilience to climate change.”

McCabe’s work was funded by a University of Otago Master's Research Scholarship and Postgraduate Writing Bursary and supervised by Associate Professor Tonkin and University of Otago Professor Christoph Matthaei at the time the research was undertaken.

Associate Professor Tonkin’s research is supported by a Rutherford Discovery Fellowship administered by the Royal Society Te Apārangi, Te Pūnaha Matatini, a Centre of Research Excellence funded by the Tertiary Education Commission.

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