Building today for a wildfire future

This Issue This is a part of the Fire safety feature

By and - , Build 191

The occurrence of wildfires is growing and is no longer only the concern of fire services. Designers and builders must start thinking now about the houses they construct and how resilient they will be in a world of increased fire risk.

Damage from the Port Hills fire in February 2017.
Figure 1: Extreme wildfire climate conditions by 2100 under different emissions scenarios – if carbon levels in the air are reduced (RCP2.6), stay the same (RCP 4.5) or continue to increase (RCP 6.0 and RCP 8.5) relative to today. Ranking shows the severity from 1 (a low smouldering ground fire) to 6 (an extreme wildfire beyond most firefighting).
The Lake Ohau wildfire in October 2020 burned 5,000 ha and destroyed 48 houses.

FIRE SAFETY in the Aotearoa New Zealand building sector has generally focused on addressing structure fires. In contrast, the risk to homes and businesses from wildfires has been given relatively little attention – wildfire risk is not mentioned in the Building Code or most council planning rules.

Historically, this made sense because we have not faced wildfires with either the frequency or severity seen in Australia, Canada or the US, and relatively few homes in New Zealand are lost to wildfire compared to individual structure fires.

Damage from the Port Hills fire in February 2017.

Increasing incidence of wildfires

However, the picture is changing dramatically, and extreme fire weather and fire behaviour are becoming increasingly common here.

The 2016/17 and 2020/21 wildfire seasons each saw more homes destroyed than in any of the previous 100 years, including the

devastating 2020 Lake Ōhau fire, which burned 5,000 ha and destroyed 48 houses.

Recent modelling by Scion’s Rural Fire Research Team, Victoria University of Wellington’s National Climate Change Research Institute and Climate Prescience shows that climate change will increase the frequency, severity and season length of wildfire in many areas of New Zealand.

The wildfire risk is likely to become appreciably worse through the rest of the century compared to the past two decades, regardless of climate mitigation efforts.

In the most likely climate change scenario, the average area burned by wildfire each year is expected to double by 2050.

The greatest absolute increases in risk, both in the potential for extreme wildfire behaviour and fire season length, will be in areas with already elevated risk in inland southern Canterbury, inland Otago and central Marlborough.

Weather conditions capable of creating very extreme wildfires on par with those during the Australian Black Summer fires in 2019/20 have already been seen in parts of these areas and will become more frequent, occurring every 3–20 years by the year 2100 (see Figure 1).

However, the impact is not limited to areas with existing risk. Even places where the risk is currently lower may start to see comparatively larger and more frequent wildfires.

Figure 1: Extreme wildfire climate conditions by 2100 under different emissions scenarios – if carbon levels in the air are reduced (RCP2.6), stay the same (RCP 4.5) or continue to increase (RCP 6.0 and RCP 8.5) relative to today. Ranking shows the severity from 1 (a low smouldering ground fire) to 6 (an extreme wildfire beyond most firefighting).

More housing on urban limits will raise the risk

As the likelihood of severe wildfire increases, the number of new housing developments in the rural-urban interface – the fringes of towns and cities where development and vegetation meet – is also increasing.

This means there are both more human-related possible causes of wildfire and more people and assets exposed to wildfires when they occur. Taken together, climate change and housing development are converging to radically increase the likelihood that lives, homes and livelihoods will be lost.

Fire and Emergency New Zealand and local councils have been engaging with communities in rural and rural-urban interface areas with high wildfire risk to help them reduce the risks around their homes.

However, recent social research has suggested that most engagement comes too late, long after housing developments have been designed, homes have been built and landscaping planted, when substantial changes are difficult and costly.

The problem may be even greater where wildfire risk is currently low and far from the minds of designers or home buyers. Homes built today are rarely built with the wildfire risk of tomorrow in mind.

Industry can reduce wildfire risk

There is much that the design and construction industry could do to reduce our current and future wildfire risk. We can learn from experience overseas where they have been developing wildfire smart-design principles and, in some cases, applying specific building codes for wildfire-prone areas.

 Aspects to consider include:

  • site selection – consider the effects of wind and slope on wildfire spread
  • development and infrastructure planning that incorporates fire breaks and enables rapid evacuation
  • building materials and designs that make houses less susceptible to ember ignition
  • landscaping that resists the spread of wildfire.

These can all reduce the chance that people, or homes will be harmed.

Scion has compiled a list of wildfire mitigation designs and actions recommended overseas that people can take to prepare themselves and their homes to reduce the risk from wildfire. It includes reducing fire fuels, creating a fire break, having a water source, providing access and working together with the local community.

The Lake Ohau wildfire in October 2020 burned 5,000 ha and destroyed 48 houses.

Extreme wildfire programme launched

Now Scion, its international collaborators (US Forest Service, San Jose State University, Karlsruhe Institute of Technology and RMIT) and national collaborators (GNS, and Canterbury, Lincoln and Massey Universities) are undertaking the 5-year MBIE-funded Extreme wildfire programme.

This research aims to increase the understanding of wildfire spread and extreme fire behaviour to improve fire prediction, inform risk mitigation and support firefighting.

The programme includes:

  • further testing our new theory of wildfire spread
  • modelling how wildfire behaves as it crosses from vegetation into towns and suburbs
  • gathering mātauranga Māori and technical knowledge of native forest flammability
  • developing tools to support firefighters when responding to wildfire operations.

Take leadership and incorporate into your work

Most relevant for the building sector, part of this research is investigating how decisions throughout the planning, design and construction system lead to homes being built with either higher or lower wildfire resilience.

Working top down and through time from national to household scales, we are exploring how decisions upstream create cascading contexts and constraints for decisions at each following step, ultimately shaping community wildfire risk.

This research should provide the knowledge and tools to prepare New Zealand for a future with extreme wildfire, but it will take leadership from within the building industry to put this knowledge to use.

The risk is already rising, and this is no longer an issue only for fire services and civil defence to worry about. Professionals across the planning, design and building system need to be aware of the increasing risk and incorporate wildfire into their thinking now.

Download the PDF

More articles about these topics

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

Damage from the Port Hills fire in February 2017.
Figure 1: Extreme wildfire climate conditions by 2100 under different emissions scenarios – if carbon levels in the air are reduced (RCP2.6), stay the same (RCP 4.5) or continue to increase (RCP 6.0 and RCP 8.5) relative to today. Ranking shows the severity from 1 (a low smouldering ground fire) to 6 (an extreme wildfire beyond most firefighting).
The Lake Ohau wildfire in October 2020 burned 5,000 ha and destroyed 48 houses.

Advertisement

Advertisement