Combating the growing fire risk

This Issue This is a part of the Climate change feature

By - , Build 174

Wildfires can threaten homes on the urban-rural fringe, and the risk is growing. Scion is developing research tools to help communities and firefighters, but there are also simple home design considerations that can help protect people and homes.

THE PORT HILLS fire of February 2017 was New Zealand’s most devastating wildfire of recent times. Occurring on the outskirts of Christchurch city, it burned 1,660 hectares, destroyed nine homes and damaged five others and resulted in the evacuation of more than 1,400 residents.

In February this year, extreme fire threatened homes again. The Tasman fire in Pigeon Valley near Nelson was New Zealand’s largest forest fire in more than 60 years, burning 2,300 ha and causing the evacuation of more than 3,000 people and 700 livestock.

Wildfire risk is rising

The risk of extreme fire events will increase with climate change. In 2011, Scion looked at 21 weather stations across the country to assess what the projected changes in temperature, humidity, wind speed and rainfall would mean for fire danger.

What was quite surprising is that some of the areas that wouldn’t currently be perceived as having high fire risk will see quite dramatic increases in the future. That’s areas like coastal Otago, the Manawatū and around Wellington.

Whanganui is also expected to see a dramatic increase. Areas that already had severe fire risk – Marlborough, Canterbury and the North Island’s East Coast – were only expected to increase slightly over current levels.

As well as more severe fire weather days with climate change, fire seasons are also expected to get longer. They are likely to start earlier and extend longer in many areas.

What many people also don’t realise is that warm wet winters add to the fire risk. The rain and warmer conditions increase vegetation growth, which then dries out causing higher fuel loading. More dry fuel means greater risk of fires, higher fire intensity and more difficulty in controlling fires when they do break out.

Scion developing prediction tools

The Scion Rural Fire Research Group has been developing tools to predict smoke and fire behaviour as part of a 5-year MBIE-funded research programme to help fire fighters better manage incidents.

These tools range from simple paper-based field manuals and fire behaviour calculation software to sophisticated fire simulation models.

The tools look at the fire weather conditions, the terrain and the types of vegetation that are likely to burn to estimate how fast a fire will spread, how intensely it will burn and where the smoke will go.

During the Tasman fire, these tools were put to work on site to support the operations. The real-time fire behaviour information helped determine the number of resources required, the likelihood of fire escaping based on smouldering hot-spots that were detected, and where these outbreaks might impact further properties or forests.

Fire behaviour information also helped inform the need for evacuations and define the triggers for when residents could safely be allowed back in.

New system, better information by 2020

The idea is that fires will be detected with satellite-based thermal sensors. This will link into the latest weather forecast and run the fire behaviour prediction model in real time. From that, Fire and Emergency New Zealand (FENZ) will be able to determine where the smoke is likely to go, how the fire is likely to spread, and what communities and other values are at risk.

By 2020, Scion hopes to have a prototype of the complete system to trial with FENZ who would run it as part of their day-to-day operations. It would give them better and faster information on fire occurrence, spread and potential impacts.

More accurate predictions of fire behaviour and the likely impacts allow emergency services to make much more informed decisions. In incidents like the Port Hills and Tasman fires, knowing that the fire was likely to get so big so fast allows FENZ to scale up resources and bring them in from other areas more quickly.

Building industry can reduce fire risk

The building industry can also contribute to the safety of New Zealand homes, as can homeowners. Home designers can take fire risk into account when selecting a site and choosing materials and with specific design features.

Consider fire risk when selecting site

When selecting a site in a rural area or on the rural-urban fringe, it’s important to be aware of the surrounding vegetation. Home sites are often selected for the views, so it’s important to think about what kind of vegetation is below and to understand that fire will be likely to spread uphill to the house.

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Materials for high-risk areas

Building from materials and systems that have a low flammability performance should be considered in particularly high-risk areas. This includes, but is not limited to, materials like brick or concrete or using a fibre-cement siding.

Open eaves or vents where embers can get caught and continue to burn should be avoided in the design. Open wooden decks are another risk where fire can spread underneath and ignite the house.

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Defensible space around house

Around the house, create a defensible space – a zone where there are sparse plantings or a mix of lawns, well maintained gardens, paths, driveways and patios.

It doesn’t have to be clear and sterile and can comprise a mix of open areas and well maintained plantings. Also think about planting low-flammability species like broadleaf New Zealand natives and avoid species with resins and oils that will ignite more easily like pine and eucalypt.

A defensible space of about 10 m should be as clear as possible, with well maintained gardens extending further out to about 30 m around the house, especially on the downslope side of the property.

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Fire sprinkler systems

In some cases, fire sprinkler systems can be attached to eaves, but even a standard garden sprinkler system can be a good defence. Scion is currently developing sensors that would automatically detect fire and set off home sprinkler systems.

Take steps to reduce risks

As climate change threatens to increase the frequency and severity of wildfires, every possible measure needs to be employed to reduce the risk to homes and lives.

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For more

For further information, visit www.ruralfireresearch.co.nz or follow their blog, ruralfireresearch.wordpress.com. Also see fireandemergency.nz.

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Articles are correct at the time of publication but may have since become outdated.

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