How prescribed burns are planned

How do prescribed burns work?

Prescribed burns are meticulously planned, and always include a thorough assessment of the environment and associated risks such as nearby assets, wind, temperature, dryness of vegetation, and geography of a site.

Environmental assessments are worked on for 1 to 2 years in advance and leading up to the burn, while risk assessments are undertaken in the weeks leading up to and immediately prior to burning. As staff go through this assessment they might decide to go ahead with the burn, postpone it, cancel it, or build in actions to reduce any negative impacts that have been identified.

Deciding where to burn

Strategic fire management plans guide activities in high fire-risk areas of the state, to reduce bushfire risk to human life, property, infrastructure and the environment.

The plans show fire management zones that identify the objectives of an area. Understanding the zone’s objective lets us know how and when each zone should be treated, and where we should be planning prescribed burns. The activities depend on the zone type and objectives.

Annual work schedules are developed from fire management plans and list sites proposed to be burnt each year, taking into consideration the plants and animals present, past fires, cultural heritage significance and the location of neighbouring properties.

Considering the environment and cultural heritage

Before an area is considered for burning a huge amount of planning and assessment is done, including looking at the big picture and asking: what plants and animals live there? How will they respond to fire? Are there big trees that provide shelter to birds and mammals that need to be protected?

That’s why an environmental assessment is built into the planning process and an ecologist is involved in developing strategies in a fire management plan. They also review the plan and approve all burns before they can be implemented.

The potential impact on native animals and plants is assessed, especially fire-sensitive species that may need to be excluded from a prescribed burn. Threatening processes such as Phytophthora infestations are also identified, with procedures detailed in a prescribed burn operations plan to minimise the chance of this ‘root rot’ disease spreading. This includes carrying out hygiene procedures on vehicles, equipment, machinery and footwear. These hygiene procedures also reduce the spread of weeds.

The environmental assessment also ensures enough unburnt habitat is in the landscape for populations to use while burnt habitat regenerates, along with identifying cultural heritage sites.

It’s important to note that a prescribed burn is of a much lower intensity than a bushfire, is generally considerably smaller and of a shorter timeframe. This minimises the chance of wildlife being affected.

Fire crew also conduct pre burn weed control and site surveys to protect environmental assets. Follow-up assessments after the burn tell us if our objectives have been met.

Do prescribed fires get out of control?

To limit the chance of prescribed burns getting out of control, they are planned months in advance using NPWS’ skilled team of fire specialists to ensure everyone stays safe. This includes research, planning and approvals before staff ignite each burn.

Over 97% of NPWS prescribed burns are conducted as planned, and don’t escape or turn into bushfires.

A prescribed burn ‘prescription’ means a number of conditions must be met. Safe and effective prescribed burns need the right combination of fuel load; fuel moisture; temperature; relative humidity; and wind direction and speed, which along with the slope, determine the intensity and speed at which a site will burn.

This means before every prescribed burn, NPWS carefully assesses the weather, dryness of the vegetation and site geography to manage any risk factors. They help make a burn safer by creating control lines (brushcutting, verging tracks, etc.); planning the number, location, and position of trucks and firefighters; measuring the fuel load and moisture; and making sure there are adequate water supplies nearby.

This contingency planning ensures we have enough resources (people and trucks) with fallback positions identified and local CFS brigades notified.

Working with CFS, Bureau of Meteorology and letting neighbours know, all contribute to a successful burn.

Is prescribed burning effective?

Prescribed burns are planned when there is a suitable level of moisture in the landscape to make fire easier to control (usually spring or autumn), and when weather conditions are warm and dry enough for fires to start and spread but not too hot or windy that they could get out of control.

The right combination of fuel load, fuel moisture, temperature, relative humidity, and wind speed is all needed for a prescribed burn to be conducted safely and effectively.

These planned burns won’t stop bushfires in heightened fire danger conditions, but the low fuel areas they create can reduce fire behaviour, provide a safer environment for firefighters to work from, increase defendable space around assets, and provide earlier containment options once conditions subside.

Prescribed burns not completed in one season are rolled over and may be prioritised the following spring or autumn.

How are prescribed fires started?

The dryness of the vegetation is carefully assessed in the days and weeks leading up to a prescribed burn to figure out the optimal time to schedule the operation. Then once the planning and weather comes together, the burn commences with a test burn to confirm conditions are right.

The weather is used by NPWS to carry a fire and to put it out, and fire crew are in consultation with Bureau of Meteorology to know when there might be a change in wind direction or forecast rain.

Knowing how a fire behaves is important. Fire behaviour is affected by fuel type (e.g. coarse, fine), connectivity and dryness; climatic conditions (wind, temperature, humidity); and slope. This helps determine lighting methods and patterns, which are tailored to each burn to manage fire intensity and to make sure prescribed burn objectives are achieved.

A prescribed burn always plans for how a fire will spread, and sometimes what's needed is a warm and windy day to carry the fire. This is useful in regions with mallee, as the fuel of this vegetation is broken up by areas of bare soil and there is no continuous vegetation.

Throughout the day firefighters communicate with each other and then mop up and patrol the area day and night to ensure it is safe and doesn't rekindle.

New life out of the ashes

After a prescribed burn is complete, staff monitor the site to record how plants and animals respond and use this information to improve future burns.

Weeds can often come up after fire and there are staff dedicated to treating any weeds to stop them from becoming a problem.

What next?

Fire managers play the long game of continuously planning, assessing, and monitoring, to minimise risks and maximise benefits for the best results of reducing bushfire risk to communities, and preserving and enhancing biodiversity.

Through ongoing fire monitoring and research, and as we gain experience with new techniques, it’s hoped that new ways to carry out prescribed burns will emerge. This will allow us to take greater advantage of the small windows of opportunity influenced by the changing climate, which results in less frequent and favourable burning weather.