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Council weighs up gravel removal

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Nelson City Council has removed nearly 14,000m³ of gravel from 22 sites across the city’s rivers following the weather events across June and July 2025.

Council operates under a global resource consent, that sets strict rules on when and how gravel can be removed. This avoids repeated applications for each job, while ensuring safeguards are in place to prevent over-extraction.

The importance of this balance was highlighted during the severe weather events that hit Nelson Tasman in June and July 2025.

“Flood events can shift large amounts of gravel within a river and most Nelson rivers are susceptible to large gravel movement during events,” says Group Manager Infrastructure Alec Louverdis.

“When this material is displaced and carried downstream, it can build up in new areas, reducing the river’s capacity, redirecting flows, and creating erosion or flooding risks where they didn’t exist before. In these situations, we need to remove the gravel.”

But while removal is sometimes the right solution, it isn’t always the best option.

“Gravel naturally shifts in riverbeds,” says Alec.

“Taking it out can destabilise the channel and upset the river’s natural balance. In erosion-prone areas, extraction can make the problem worse, leading to collapsing riverbanks and damage to nearby land. Gravel removal can also destroy habitats used by native fish for breeding and feeding.”

He says the issue has to be carefully planned for ahead of new river projects.

“The upcoming Maitai Flood Mitigation project is a good example,” he says.

“To noticeably reduce the kind of flooding seen in August 2022, we would need to extract an enormous amount of gravel from the Maitai. Doing so would leave deep channels with constantly eroding banks, which would threaten nearby properties, roads and infrastructure.”

Rather than remove gravel for this project, Council will improve flood management through a combination of raising stopbanks, installing flood walls and expanding the floodway.

Outside of flood events, Council regularly monitors gravel traps and riverbeds to manage risks before they become problems. If a build-up is found to be reducing stream capacity, Council considers the best way to address it, whether through removal or other river management measures.

Council has several permanent, purpose-built gravel traps in Saxton Creek, Poorman Valley Stream, Brook Stream, Jenkins Creek, and the Maitai.

“It’s like a holding zone for gravel,” says Alec.
“These are specially designed areas where gravel and coarse sediment can settle, allowing us to collect and remove it efficiently before it causes problems downstream. They’re located in predictable, accessible spots, which makes extraction straightforward and safe for workers. That means lower maintenance costs and less environmental and ecological disturbance.”

Gravel build-up can also put Council assets at risk. Around bridges and fords, excess gravel can raise water levels, leading to flooding and potential damage.

“It’s always about striking the right balance, protecting our community from flood risks while respecting the natural rhythms of our rivers,” says Alec.

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