New Zealand Officials Defend Braided River Interventions as Necessary for Flood Protection and Farming

British settlers established Christchurch near the Waimakariri River more than 170 years ago. By the 1920s an official report had described the braided river as a “flood menace,” according to Environment Canterbury river engineer Fred Brooks. Authorities responded with stopbanks, exotic tree planting and gravel extraction.

Brooks said intervention is unavoidable. “People say you shouldn’t be interfering with the river; the outcome if we don’t is worse. It has been intervened in so much at this point, you have to keep intervening,” he stated.

The Waimakariri requires ongoing maintenance, including regular gravel extraction by diggers and trucks, to prevent breaches of stopbanks that could flood tens of thousands of homes and affect nearby infrastructure and the airport. There are about 150 braided rivers in New Zealand, 60 percent of them in Canterbury. Similar systems exist in Alaska, Canada and the Himalayas.

A study of nine Canterbury rivers found they had narrowed by 50 percent on average, with some segments narrowed by more than 90 percent. Landowners are legally allowed to move onto braided riverbeds when water levels retreat. Environment Canterbury biodiversity manager Frances Schmechel linked changes in the rivers to sediment buildup, pollution and altered flows.

Nearly a third of Canterbury’s lakes and rivers were deemed unsafe to swim in due to E coli and pathogens in 2025, according to Environment Canterbury data.

On the Rakaia River an 11-metre-high salmon statue remains a local landmark. The annual salmon fishing competition proceeded this year with no fishing permitted. Fish & Game counted 608 salmon in the Rakaia during the 2024-25 season, down from more than 20,000 in 1996.