‘Significant’ amount of forestry debris sitting in wait on Gisborne’s hillsides

Sunday, 28 December 2025

Footage of the Mangatokerau Bridge near Tolaga Bay shows damage and a river choked by forestry slash.

A large amount of potentially destructive forestry debris is sitting, legally, on steep hillsides across the Tairāwhiti/Gisborne region and, with a risk of intense storms this summer, poses a major threat, says a senior lecturer in environmental management.

The east coast region has in recent years become accustomed to the damage and cost of forestry debris washing out of forestry blocks, wreaking havoc and costing ratepayers and taxpayers tens of millions of dollars in clean-up costs.

National forestry regulations (National Environmental Standards for Commercial Forestry) require slash to be removed from slopes unless it is unsafe or impracticable to do so.

Senior lecturer in environmental management at Lincoln University, Steve Urlich, has long held concerns about this issue and says “vast amounts of slash are still being created across the Tairāwhiti region on very steep landforms, and being left in headwater basins, deep gullies, and rivers”.

This image uses AI data to show the concentration of large woody debris in Tairāwhiti/Gisborne. Very high concentrations are shown in red.

Urlich acknowledges the work Gisborne District Council has carried out through aerial imagery and AI analysis recently, but says this has highlighted areas that require assessment of volumes and risks of mobilisation.

“Depending on where the material lies, it may be mobilised in floods or as debris flows under intense rainfall, posing risks to infrastructure, livelihoods, lives, and aquatic ecosystems,” Urlich said.

For some time he has been calling for urgent amendments to national forestry standards and the council’s rules to prevent harvesting and/or replanting of steep gullies and headwater basins.

Forestry slash knocked out Hikuwai Bridge, north of Tolaga Bay, after Cyclone Gabrielle.

“The [resource] consents need to take a preventative rather than risk assessment approach. Compliance monitoring and enforcement orders are essentially mitigation, whereas avoidance of slash creation in high-risk areas is needed,” he said.

“There is a significant risk of intense storms this summer according to NIWA, with potentially catastrophic effects. Should this occur, it may not only be a regional emergency, but also have significant implications for the national economy, given the Treasury estimates of $9-14 billion from Cyclone Gabrielle.”

In a response to an OIA request from Stuff, the council said it had recently obtained access to AI data and heat map aerial imagery showing woody debris across the region and it was using this information to assess risks in river catchments.

Forestry slash covering Tolaga Bay beach in 2019.

The data showed that “major concentrations of woody debris occur in the Waiapu catchment particularly the upper Mata River and Ihungia River” with further concentrations near Tokomaru Bay and Tolaga Bay.

The council said it had removed significant amounts of debris from the Waimata catchment, meaning the debris landing on Gisborne city beaches should lessen, unless there was a significant storm.

The council said situations where slash could not be safely removed resource conditions could require the consent holder to take a number of steps, including the installation of slash catchers.

There were also still significant debris in the Waipaoa catchment, the Nuhaka catchment, the Wharerata forest and the upper Te Arai River.

“Overall, the data shows that the efforts to clean up the beaches and lower catchments since Cyclone Gabrielle have been successful but also shows that there is a volume of large woody debris remaining within the Tairāwhiti pine forests,” the council said.

It said in situations where slash could not be safely removed, resource conditions could require the consent holder to take a number of steps, including providing assessments for management of slash, providing photographic evidence, making post-rainfall inspections, and possibly the installation of slash catchers.

Dr Steve Urlich is a senior lecturer in Environmental Management at Lincoln University.

The council said compliance was assessed through site visits, especially in higher-risk catchments, and aerial assessments by helicopter or drone.

Since the start of 2024 staff had undertaken 630 inspection visits of high-risk catchments.

They had found 59 instances of significant non-compliance, 48 instances of moderate non-compliance and 103 instances of minor non-compliance.

The council has issued 41 abatement notices over that time and had been granted three enforcement orders, against Aratu Forests Ltd. and Samnic Forest Management Ltd. and Woodlett Investments Ltd. There were three further enforcement orders made in 2023.

“Woody debris and slash on steep, erosion-prone hill country in Tairāwhiti continues to pose risks during severe weather events. Gisborne District Council remains focused on reducing risk, improving land resilience and supporting responsible land management across the region,” the council said in its response.

It noted that a review of the Tairāwhiti Resource Management Plan was underway and said the council was planning to seek an exemption from the current plan-stop legislation to progress a change that would improve how highly eroding and erosion-prone land was managed in order to reduce sediment and woody debris entering waterways.

The council had also completed a transition business case that was a transformational plan that would see the region’s most erosion-prone land put into permanent vegetation cover.