Preparing New Zealand for extreme fire

Five years of Scion extreme fire research came to an end in December 2021, changing the way knowledge is shared to stop fires starting, predicting extreme fire spread paths and developing tools for firefighters. It built on Scion’s 25-year fire research programme and deep knowledge of forest ecology and forest management.

In 2016, Scion warned about the risk of extreme wildfires in New Zealand. Since then, we have witnessed large tracts of land blackened and homes destroyed in the Christchurch Port Hills (2017), Pigeon Valley (2019), Deep Stream (2019), Pukaki Downs (2019), Lake Ohau (2020) and in the Far North (February 2022), as well as the cataclysmic fires in Australia and North America.

It was not hard to predict the higher incidence of wildfires after so many years of record global temperatures. Five out of the last six years have beaten all previous records. Higher air temperatures and more droughts naturally result in more and bigger blazes. Firefighters are struggling to manage them using conventional strategies.

Scion’s general manager for Forests and Landscapes, Dr Tara Strand, says New Zealand urgently needed new methods and tools for managing extreme fire and this is what sparked the research.

“The annual average direct impact of rural fire on New Zealand’s economy is over $67 million, with indirect costs estimated to be at least two to three times this, plus intangible indirect impacts as much as 30-60 times direct costs.”

An article in the UK Guardian newspaper (23 February 2022) on increasing wildfires due to climate change, claimed that in relative terms, governments spend a good deal on emergency services and a tiny amount on prevention. However, in 2016, Scion received over $10 million from the Ministry of Business, Innovation and Employment’s (MBIE’s) Contestable Research Fund for a five-year research programme to ‘identify, mitigate and adapt to’ the growing threat of extreme fires.

Scion’s Preparing New Zealand for Extreme Fire programme investigated four main areas: a new fire spread theory crucial to predicting and reducing the extreme fire risk, innovative decision support tools for providing real-time information, creating new tools for preventing extreme fire, and developing targeted protection plans for communities and taonga species.

It has delivered on its promises, as outlined in a very practical and detailed final report, released in August 2021 and available on the Scion website [link to this report will be available here soon].

A rural fire scientist monitors a large-scale experimental burn of gorse at Rakaia Gorge in March 2020.

A new understanding about spread

First and foremost, experiments tested the emerging ‘convective fire spread hypothesis’ and development of models and data analysis that followed.

The world-class international team working on the project included scientists from Scion, US Forest Service Missoula Fire Sciences Laboratory, University of New South Wales, San José State University, US Forest Service Pacific Northwest Laboratory, Te Tira Whakamataki (TTW), and University of Canterbury. Together they challenged the existing understanding of fire behaviour and formulated the ‘convective fire spread hypothesis’.

Burn experiments in cereal crop stubble and gorse scrub fuels further validated findings by the Missoula Fire Science Laboratory that convection plays a large role in wildfire spread, compared to previous theory where ignition through radiation dominates fire spread. Fire spread by convection is when colder air sweeps in to replace the warm air rising at the fire front, pushing the flames forward to ignite the fuels and gases through direct flame contact.

Analyses of the data collected during the experimental burns started to explain the role of atmospheric turbulence in the transition to extreme fire behaviour.

This new knowledge has already been included in New Zealand’s fire behaviour training, supported by videos showing real flame-front dynamics. It is hoped that in the near future it will lead to greater safety for firefighters and communities, and improved decision-making strategies and tactics around where and how to safely and effectively suppress extreme fires.

Safer burns by farmers and landowners

Over the years, a number of farmers and firefighters have been killed or injured by planned burns getting out of control or suddenly moving in unexpected directions and trapping them.

Unfortunately, COVID-19 prevented live-burn training sessions. But with input from international experts from The Nature Conservancy, based in Virginia, USA, who have significant experience in burning on private lands, Scion produced online ‘best practice’ training materials for farmers and land managers, which Fire and Emergency NZ (FENZ) and Federated Farmers have been promoting since August 2021.

Swapping knowledge with the firefighting community, Māori, the forestry industry, Department of Conservation and other kaitiaki

A very rewarding part of the programme, led by TTW, was bringing together the scientists, FENZ, Māori, and other interested parties to learn from one another at several hui, and a Fire Fair in Northland. The group discussed values and potential risks around fire, protection priorities, mitigation strategies and developed targeted fire protection plans. These are now templates that can be used by other communities and iwi.

Meetings and interviews with communities were cut short by COVID-19, but enough progress was made to draw some useful conclusions and mutual understandings.

Two preventive strategies were of particular interest: the newly developed heat sensors/automatic sprinkler systems and creating low flammability buffer zones using native plant species – the ones with big shiny leaves such as coprosmas, broadleaf and karaka.

Other new firefighting tools

Using existing technologies, the research team developed and tested fire alert heat sensors. This technology can warn forest managers and landowners of imminent danger from burn escapes and re-ignitions, and could automatically switch on sprinklers. The sensors can also be used to monitor heat build-up and possible spontaneous combustion in forestry slash piles and will be explored further in the next research programme.

Prototypes for several new firefighting tools were developed, including a smouldering hotspot temperature probe and a battery-powered backpack spray unit for preventing fire re-ignition and burn escapes.

Predicting fire and smoke behaviour

Fire and smoke behaviour prediction tools have been integrated into a new NZ Fire Registry – an online public information and planning resource that supports operational decision-making for wildfires and prescribed burning. For example, the Fire Registry tool was used to predict fire spread during the 2020 Pukaki and Lake Ōhau wildfires, and to predict smoke movement and health risk from the recent large wildfires and the February 2021 Amberley tyre storage facility fire. The prototype wildfire smoke prediction tool can be used to assess potential smoke impacts from wildfires. Find the tool at www.ruralfireresearch.co.nz/tools

Using the opportunity to learn from the Lake Ōhau fire, where 48 homes were destroyed at frightening speed, Scion reconstructed fire spread pathways and mechanisms of fire-attack to fire damaged properties. Scion surveyed over 60 homes for contributing factors such as nearby vegetation, lack of defensible space, construction materials, glazing, and presence of exposed wooden decks, outdoor furniture, firewood or other flammable materials. Visits were conducted to the affected sites within a week of the fire and analysis was conducted over the following six months.

FENZ is using the results of this work to develop improved guidance information on how homeowners can reduce wildfire risk. FENZ and MBIE are also using the results around building design and construction materials to produce guidelines for building in these fire-prone areas.

What next?

FENZ wildfire scientist Grant Pearce says there were many great achievements right across the research programme, and these were a major factor in the successful 2021 funding of the follow-on ‘Extreme Wildfire: Our new reality’ bid by Scion.

“This now means the convective theory can be fully validated through the planned crown fire experiments, and findings and tools adopted by FENZ and other end-users can really make a difference in protecting communities and the environment,” he says.

For further information contact

Tara Strand or visit
www.ruralfireresearch.co.nz


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