Record rain across the rohe causing erosion and river discolouration

Slips and erosion are washing sediment into local rivers and estuaries and causing them to discolour.

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

At sites measured by the Bay of Plenty Regional Council, there has been an average of 200 per cent of normal rainfall over the past three months (January, February, March 2023) – this means that catchments are receiving around twice as much rain as usual.

Regional Council compliance team leader Trudy Richards says after rain events, the council’s pollution hotline often receives 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 says.

“Since early January, we have been receiving reports of the Omanawa 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. A number of teams within the council are currently working together to quantify the effects of the sediment discharge and consider options for run-off control”, she says.

Richards says while there are construction sites further downstream in the Tauriko area, the compliance team has confirmed the river is discoloured before it reaches the earthworks areas. The earthworks sites are closely monitored, with their own dedicated environmental teams on-site and council compliance officers inspecting regularly.

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

“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.