When British settlers founded Christchurch 170 years ago, they took one look at the nearby Waimakariri River - a globally rare braided river twisting from the South Island's alps - and decided the best approach was to largely ignore it. The river, however, had other plans, periodically flooding and dumping tonnes of shingle wherever it pleased.
By the 1920s, authorities declared the Waimakariri a "flood menace" suffering from a "deficiency of nature, which must be made good by the art of man." And so began a century-long campaign of stopbanks, exotic tree planting, and gravel extraction to force the river into submission. Now, as river engineer Fred Brooks of Environment Canterbury puts it, "It has been intervened in so much at this point, you have to keep intervening." Diggers and trucks now extract gravel most days just to prevent the river from flooding tens of thousands of homes.
New Zealand hosts about 150 braided rivers - 60% concentrated in Canterbury - with similar systems found only in Alaska, Canada, and the Himalayas. Unlike single-channel rivers, these dynamic waterways split, weave, and fan out across wide areas, often carving new channels after heavy rain. But decades of farming, development, and flood control have narrowed them dramatically: a study of nine Canterbury rivers found they had shrunk by 50% on average, and over 90% in some segments.
The consequences are piling up. Salmon populations in the Rakaia River have crashed from over 20,000 in 1996 to just 608 in the 2024-25 season - so dire that this year's annual salmon fishing competition went ahead with a surprising caveat: no fishing allowed. "Maybe it will become a monument to the past," worries competition president Chris Agnew of the town's 11-metre-high salmon statue. Bird species are declining too, thanks to introduced weeds and exotic willow trees that were meant to prevent erosion but now create predator cover and disrupt natural flow. Stokell's smelt, a once-abundant native fish, is now nationally critical.
Water quality hasn't fared better. Environment Canterbury found nearly a third of Canterbury's lakes and rivers - especially near urban and agricultural areas - were unsafe to swim in due to E. coli and pathogens in 2025. The South Island iwi Ngāi Tahu took a landmark case against the Crown in 2017 seeking recognition of their governing authority over waterways; a High Court decision is imminent. "Braided rivers are fundamental to how we exist as a tribe," says Gabrielle Huria, the tribe's freshwater strategy chief, who stopped traditional food gathering after finding cow faeces in her fishing nets.
The core question, according to river geomorphologist Jo Hoyle, is: "How much room do these rivers actually need to be a river, to support ecological life and have enough room to flood without causing too much damage?" Landowners legally move onto riverbeds when water retreats - a process called agricultural encroachment - and then resist when the river tries to return, ratcheting the channels ever narrower. Scientists and advocates want that law changed, and managed retreat explored. "The land on either side is really valuable day-to-day, but it is really vulnerable to big floods," Hoyle says.
Resource management minister Chris Bishop says he's looking forward to select committee recommendations on the encroachment law, while conservation minister Tama Potaka insists the government is "committed to protecting and restoring" braided rivers. But Hoyle fears the community has grown detached from the rivers' plight. "Having those discussions … around how we want to live alongside our rivers needs to happen," she says, turning a river stone over in her hand. "The only way we will get change is making the community more aware of what the risks are and what we stand to lose."