Bay of Plenty rivers and streams running dirty after erosion from rain

Bay of Plenty waterways, including Pokopoko Stream, are discoloured due to erosion from heavy rain. Photo / Bay of Plenty Regional Council

Multiple slips and erosion in the upper reaches of catchments across the region are washing sediment into local rivers and estuaries causing them to discolour, the Bay of Plenty Regional Council says.

The council said there had been an average of 200 per cent of normal rainfall over the first three months of the year at sites it measured, meaning that catchments were receiving around twice as much rain as usual.

The council’s compliance team leader, Trudy Richards, said after rain events, the council’s Pollution Hotline often received reports of sedimentation or discolouration of streams, rivers, and estuaries.

“Our team investigates reported incidents to locate the source of the sediment, assess the environmental impact and whether there is any non-compliance,” Richards said.

“Since early January, we have been receiving reports of the Ōmanawa River running dirty.

“Our investigation shows a significant landslip that is still discharging sediment into the river. The landslip system has been eroding long-term, however previous remedial work undertaken has worked well up until this point.

“There is also a groundwater spring in the middle of the slipped face, along with surface water that flows over it during rain.”

Richards said a number of teams within the council were currently working together to quantify the effects of the sediment discharge and consider options for run-off control.

While there are construction sites further downstream in the Tauriko area, the compliance team had confirmed the river was discoloured before it reached the earthworks areas, she said.

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The earthworks sites were closely monitored with their own dedicated environmental teams on site and council compliance officers inspected regularly.

“More recently the Little Waihī Estuary has also been discoloured. Investigations throughout the catchment revealed the Pokopoko stream and the Pongakawa stream were running brown and turbid due to multiple slips and erosion in the upper reaches,” Richards said.

“We would like to thank our communities for reaching out to us to report their concerns about damage to the environment. Sediment in streams and estuaries does have a negative effect on the ecosystems so it is important that we hear about it and are able to track it back to the source.

“If the team finds non-compliant activities taking place in the catchments, this will be further investigated and enforcement action considered.”

To call the 24/7 Pollution Hotline, phone 0800 884 883.