Science fights bushfires on a multitude of fronts
Science fights bushfires on a multitude of fronts
08 December 2014
published by www.theage.com
Australia — Summer is upon us and along with the lazy hazy days spent relaxing on the beach come a potentially higher risk of bushfire.
In the southern and eastern states, spring has been unseasonably dry, with temperatures during October and November much higher than usual. All of this has helped dry out the vegetation.
With near-El Nino conditions, the forecast is for a hotter and drier summer than normal, says Dave Griggs, the director of the Monash Sustainability Institute. “As a result, the forecast is for above-normal fire conditions this summer across many parts of south-eastern Australia.”
Meteorologically, of course, there is not much that can be done to keep bushfires at bay other than by minimising the risks with a longer-term strategy of cutting fossil fuel emissions to reduce the greater extremes of climate change.
“The risk of bushfires, both in terms of their frequency and intensity, will increase as a result of climate change,” Professor Griggs explains. “So, by mitigating climate change, you also mitigate the increase in future extreme bushfire conditions.”
Monash climate scientist Nigel Tapper agrees.
“The state with the biggest problems is Victoria at least in terms of greatest-magnitude fires and largest loss of life nationally,” Professor Tapper says.
“To reduce the risks, we must simultaneously reduce our reliance on fossil fuels and learn to adapt to the effects climate change. And, in the shorter term, we must reduce fuel loadings in fire-prone areas as much as possible.”
As a society, we are still not taking bushfires very seriously, says Janet Stanley, chief research officer at the Monash Sustainability Institute. “In Victoria, only about 1 per cent of arsonists are convicted of the offence and many of those convicted don’t receive a custodial sentence.”
“Relatively few resources are directed to assist children and youths, with a propensity to light fires, to change their behaviour,” Dr Stanley says.
“Schools can usually identify children who need help in this regard but there are not the resources to assist teachers with these children. The federal government is moving to require pastoral student welfare, in place of trained counsellors, a move which is less likely to offer the necessary treatment for troubled children and youths who light fires.”
Plan of action
Scientists agree that there is much to be done to stop bushfires starting and spreading even when conditions are conducive to fire.
“We should engage in prescribed burning to reduce fuel loads, clearing around properties and making sure power-lines are in good condition,” says Professor Griggs.
“Planning laws need to be enacted to prevent houses being built in fire-prone areas,” adds Dr Stanley. “And we need to control urban sprawl into forested areas on the edge of large urban centres.”
Science, she points out, has much to offer. “Housing design that reduces the risk of ignition is not commonly enforced in high fire-risk areas,” she says. “More research is also needed into the best ways to prevent bushfires.”
Preparation
Scientists mostly use computer models to try and predict likely paths of bushfires from their source of ignition.
Victoria uses specialist software and technology to provide advice during fires and flooding. The software models the likely extent of a bushfire, as well as the intensity and time it might take to impact on communities.
Phoenix Rapid Fire, as the software is called, can also predict flame height and how far embers will travel and the variety and density of vegetation involved.
Drones
The CSIRO’s division of Land & Water is experimenting with the use of multi-rotor unmanned aerial vehicles, better known as drones, to monitor and, in the future perhaps, to fight fire.
To this end, the Swedish telecommunications company Ericsson donated four Draganfly X-8 drones, built by a Canadian company, to support the CSIRO research.
“One of the main objectives of our fire studies is to understand the spread of fires in natural vegetation and where wild land interfaces with the urban environment,” says CSIRO Bushfire Dynamics and Applications scientist Miguel Cruz.
Working in conjunction with local fire authorities, researchers are using the drones to track the progress of experimental and controlled burns. Time-lapse images or high-resolution video with thermal cameras can be used to measure changes in fire intensity as a fire-front spreads across an area.
“We use drones to measure the rate of spread, flame height and so on,” says Dr Cruz. “In this way, we can better capture the data we need to conduct research into modelling the behaviour of bushfires. The data gained from drone images are valuable to our research and the findings we share with fire authorities will result in more accurate predictions of fire propagation.”
The drones provide researchers with a birds-eye view of three-dimensional phenomena that are not easily observed from the ground. “For our researchers, the drones have large advantages over the use of piloted aircraft, such as helicopters,” Dr Cruz says.
Advantages include
* Low cost: a commercially available drone for research cost 5 to 10 per cent of the weekly rental charges for a helicopter.
* Flexibility: a relatively small drone can be hover in one place above a fire at no risk to operators. “Manoeuvring and having a helicopter stationary over a fire can become a hazardous proposition,” Dr Cruz explains.
* Availability: bushfire behaviour research often needs to be scheduled at very short notice. “Having a helicopter available to support research would require advanced notice,” Dr Cruz says.
* Non-intrusiveness: A research drone has no effect on a burning fire, whereas a helicopter flying low over an experimental fire can cause downdrafts that fan the flames and artificially change fire behaviour.
The CSIRO researchers are now planning to fit the drones with other sensors, such as infra-red cameras, to enable them to monitor fire propagation through dense smoke and at night.
Meanwhile, laser-scanning devices will provide highly detailed pictures of features, such as vegetation type, that affect the progress and intensity of fires.
Planning ahead
Bushfire-resistant homes are gaining in popularity as the ravages of climate change and progressively drier conditions raise the risk of fire nationwide.
Buildings come under attack in three ways: through flying embers, radiant heat and/or flame contact. Embers and windborne burning debris enter houses by nipping underneath them, into roof cavities or through windows that break.
Research has shown that most houses destroyed in bushfires survive the passage of the fire front, only to burn down thereafter as fire spreads from ignitions caused by windborne burning debris.
A key factor seems to be maintaining the integrity of a building envelope to resist ignition by embers or radiant heat and penetration of embers into the interior.
Researchers are familiar with the mechanisms, with some adopted in the Building Code of Australia, which refers to Standards Australia’s construction of buildings in bushfire-prone areas.
Crossover
Many recommended materials also promote energy efficiency and health. In this sense, there is something of a crossover between bushfire-resistant houses and houses that incorporate environmentally sustainable design.
In addition to mud-brick and straw bale, environmentally sustainable materials that are bushfire-resistant and non-toxic include rammed earth, stone, recycled heavy timber and steel. Each material has an associated energy cost, including whether it is locally produced.
Landscape controls
Before building, researchers advocate planning the landscape. Dwellings can be protected from wind-driven embers using natural or artificial land forms and shelter belts.
* Use low-flammability plants that drop little litter.
* Clear fuel from under trees and shrubs and remove lower branches, loose bark, twigs and leaves.
* Surround buildings with open spaces mown lawns, grazed paddocks and driveways or paths.
* Use hills or gullies, or construct earth mounds and cut-and-fill terraces or retaining walls to block heat radiation and deflect embers and wind-driven debris.
* Plant hedges and windbreaks using largish trees and shrubs of low flammability and with dense foliage to catch embers and debris and reduce wind.
* Keep trees at least 20 metres from dwellings.
Building design strategies
Scientists know which building designs and construction materials are safest. From plan shapes to roofs, and walls to windows, the wealth of advice includes such tips as:
* Avoid building on hilltops as fires travel faster uphill.
* Minimise corners and vulnerable junctions such as verandas or pergolas where embers might lodge. Separate pergolas from dwellings.
* Simplify roof profiles, but keep them relatively steep to help shed leaf litter or burning debris. Clad them in metal or fibre-cement and ensure they have no crevices or valleys; seal roof spaces and cavities.
* Use sarking waterproof sheets to cover gaps in roof coverings. Roof cladding and supporting structures should withstand gale-force winds.
* Eliminate roof gutters, if possible, and instead collect rainwater in trenches. Or make gutters wide to facilitate cleaning and fit leaf guards.
* Provide fire plugs for filling downpipes and roof gutters with water.
* Use concrete slab constructions to eliminate underfloor spaces but if this is impossible, enclose spaces beneath timber floors, or line undersides with fire-resistant materials.
* Use non-combustible materials for walls, columns and posts supporting floors. If columns and posts are combustible, use metal sheaths.
* Use concrete or steel grates for decks and steps.
* Make external doors and windows flush with the external edges to stop litter gathering. Cover screen door thresholds and window sills with metal mesh.
* Use double glazing and toughened glass in windows or wired glass or glass bricks.
* Use non-combustible shutters for outside glass doors and windows and to cover leadlight windows. Treat timber window frames and other exposed timbers with weather-resistant fire retardant.
* Beware of flammable outbuildings and storage facilities that are too close to the house.
* Provide adequate, reliable and independent supplies of water and power including a diesel generator.
* External sprinkler systems should have metal not soft-soldered pipes and be capable of saturation.
* Store gas tanks out of harm’s way and point vents away from walls.
* Use non-combustible fences.
(Sources: Landscape and Building Design for Bushfire Areas, Fire Protection Association Australia)
Timber tips
Some high-density timbers that need no fire retardant include blackbutt, kwila (merbau), red ironbark, river red gum, silvertop ash, spotted gum and turpentine. Some varieties of acacia are relatively fire-resistant and thus suited for use as firebreaks.
Analysis
Back in 2007, the Intergovernmental Panel on Climate Change had this to say: “An increase in fire danger is likely to be associated with a reduced interval between fires, increased fire intensity, a decrease in fire extinguishments and faster fire spread. In south-east Australia, the frequency of very high and extreme fire danger days is likely to rise by 4 to 25 per cent by 2020 and by 15 to 70 per cent by 2050.”
The growth in greenhouse gases has been tracking at the worst case-scenario, Dr Stanley says: “So the IPCC’s estimate is conservative.”
This is borne out by a report, published jointly by Australia’s Bushfire Co-operative Research Centre, the CSIRO and the Bureau of Meteorology, warning that days of extreme fire danger each year could soar by 65 per cent by 2020 and by up to 300 per cent by 2050.
