Bushfire risk

Forest Fire Management Victoria’s fuel management program – and all activities it undertakes to reduce bushfire risk – are designed to meet the bushfire management objectives outlined in the  Code of Practice for Bushfire Management on Public Land 2012:

1. To minimise the impact of major bushfires on human life, communities, essential and community infrastructure, industries, the economy and the environment. Human life will be afforded priority over all other considerations.

2. To maintain or improve the resilience of natural ecosystems and their ability to deliver services such as biodiversity, water, carbon storage and forest products.

Bushfire risk to life and property

No single strategy or action alone can manage bushfire risk. Currently Forest Fire Management Victoria (FFMVic) employs a range of activities including management, prevention of ignition and first attack suppression. Fuel management is just one strategy for reducing bushfire risk.

Bushfire risk to life and property is measured as the likelihood of a fire starting, spreading and impacting the places where people live. This analysis considers multiple factors including topography, fuel type and an extreme bushfire weather scenario. Managing fuel in the landscape is one key way to reduce bushfire risk, and we manage fuel mainly by planned burning and by mechanical treatments (such as slashing and mowing). Bushfires in the landscape also reduce fuel loads and therefore risk.

Fire Management Zoning guides the application of planned burning and mechanical fuel treatments in our forests and parks. In the Asset Protection Zone – close communities, assets, critical infrastructure and industries – planned burning is applied to reduce radiant heat and ember attack from bushfires. In Bushfire Moderation Zones, fuel management is used to break up the landscape, slowing the spread of bushfires, and providing opportunities for our firefighters to undertake successful back burning operations during bushfire response. This means we can reduce the chance of major bushfires developing, spreading uncontrolled, and impacting on the things we value the first place.

Planned burning is also used in Landscape Management Zones, where it is applied for both ecological and bushfire risk reduction purposes. Backcountry or landscape mosaic burning involves application of cool and patchy planned burns over large areas to reduce the spread and intensity of bushfires – making it easier for forest firefighters to bring bushfires under control reducing impacts on people, property and the environment.

FFMVic also works closely with communities, fire services and other land managers to align the management of bushfire risk across public and private lands. By safely and effectively reducing fuel loads in the landscape, we decrease the chance of major bushfires starting, spreading out of control and impacting on people, property and the environment.

In Victoria, there will always be some bushfire risk. FFMVic assesses current bushfire risk as the percentage of risk ‘left over’ after fuel in forests has been reduced, either through fuel management or bushfire. In that sense, bushfire risk is sometimes referred to as residual risk: risk left over after fuel has been reduced.

The fuel management program aims to reduce bushfire risk to below 70% of Victoria’s potential maximum bushfire risk. Regional bushfire risk targets vary from the statewide 70% due to the relative proportion of the statewide risk that the regional landscape holds and the capacity to minimise the impact of bushfires on life and property in that landscape.

Victoria’s bushfire risk in 2018–19 has been modelled to be 69%. Here, FFMVic use the best data available and sophisticated software to model the fuel load and account for other factors such as fuel type, topography and weather.

FFMVic strives to map and account for areas treated by planned burning as accurately as possible. As our technology improves and better data becomes available, past mapping of treated areas can improve and modelled bushfire risk can change; for more information on these changes please see Data and model output improvements. Enhancements to our fire history data have improved the accuracy of our maps of treated areas, so we have updated our modelling and revised the modelled bushfire risk for 2017–18, which is now modelled as 68%.

The 1% increase in bushfire risk from 2017–18 to 2018–19 has occurred due to:

• ongoing re-accumulation of fuel across Victoria after significant landscape fires through the 2000s
• bushfires last summer, although extensive, mostly occurring in remote mountain areas where the risk to property is relatively small, although the Bunyip fire likely led to some reduction of risk in the Port Phillip region
• limited planned burning opportunities, particularly due to drier-than-average forest fuel
• an extended fire season that started early and finished late, meaning personnel were tied up in firefighting duties during what is normally the planned burning season.

The figure below shows Victoria's bushfire risk profile from 1980 to 2019 and its forecast risk through to 2022. It tells a story of how bushfire risk changes over time, based on bushfire history and our fuel management activities. We use this information to predict how risk will change because of our future planned burning and to compare the effectiveness of different bushfire management strategies. Victoria’s fuel management program on public land aims to achieve a statewide target to maintain bushfire risk at or below 70% of Victoria’s maximum bushfire risk.

Victoria’s bushfire risk increased slightly from last year. Despite limited opportunities to do planned burning due to the poor weather conditions, our risk modelling technology helped us determine places where planned burning would most effectively reduce risk while paying regard to ecological health and resilience.

The figure above shows that bushfire risk:

• rose steadily after the devastating 1983 Ash Wednesday bushfires as fuel re-accumulated across the state, reaching a peak of 81% in 2002
• fell significantly as major bushfires in the 2000s, particularly the 2009 Black Saturday bushfires, reduced fuel hazards (although at the price of catastrophic losses of life and property)
• has increased in recent years as fuel has re-accumulated in areas where significant bushfires occurred in the 2000s.

Re-accumulating fuel in Victoria’s forests can quickly increase bushfire risk if the fuel is not properly managed through regular fuel management activities. As the figure above shows, if we implement our Joint Fuel Management Program (JFMP) and there is little bushfire activity, modelling indicates bushfire risk will be 62% by 2022. If we cannot implement the program and there is little bushfire activity, modelling indicates that bushfire risk is likely to rise steeply to 80% over the next three years.

At this scale the fuel hazard maps don’t provide the whole picture of risk to communities. The bushfire risk measure is more appropriate as it considers a larger number of factors across the whole landscape.

The modelled fuel hazard data for Victoria is derived from analytical models which consider estimated fuel loads across the state. The fuel load dataset is derived from the state-wide fuel dataset, fire history dataset and fuel accumulation equations based on vegetation types (fuel types). This modelling estimates fuel accumulation (ton/ha) by fuel types which can be broadly categorized into an overall fuel hazard category (low, moderate, high, very high and extreme). 

This dataset provides a visual illustration of the model-estimated average fuel-hazard across the landscape. It does not account for localised variability. As such, fuels hazard in any specific location may be higher or lower than are estimated here. Experts opinion and local knowledge should be sought when applying this data to finer scale decision-making processes.

Bushfire risk to the environment

We manage fuel and conduct ecological burns to maintain or improve ecosystem resilience. Ecosystem resilience is the environment’s ability to bounce back after a fire.

To understand the effects of fuel management on the environment, we measure and monitor the timing and number of fires in different vegetation types using tolerable fire interval (TFI) and the ages of different vegetation types using growth stage structure (GSS). We also partner with universities and institutes to undertake research to improve how we measure and represent ecosystem resilience.

The figure below shows the area of public land in Victoria burnt by bushfires and planned burning while below minimum TFI since 1980. We try to minimise the amount of area that is burnt while below minimum TFI because it can be detrimental to ecosystem resilience. However, planned burning may be needed in some areas already below minimum TFI to reduce bushfire risk to life, property or priority ecosystems. In 2018-19, there was an increase in the amount of vegetation burnt below TFI across the state, with approximately 2% of the vegetation in Victoria being burnt while below TFI, compared to <1% during the previous year. This increase was largely due to recent bushfires that occurred in eastern Victoria, with Gippsland and Port Phillip Regions having a 5% and 3% increase, respectively, in the area burnt below TFI from bushfires. The area of vegetation burnt whilst below TFI from planned burning continued to remain at <1%.

The figure below shows the area of each fire management zone treated by planned burning while below minimum TFI since 1980. The figure below that shows the proportion of each zone treated by planned burning while below minimum TFI over the same period.

The figure below shows that in 2018–19 the greatest areas treated while below minimum TFI were in Landscape Management Zones (LMZ) and Bushfire Management Zones (BMZ), with smaller areas treated in Asset Protection Zones (APZs) and none treated in Planned Burn Exclusion Zones (PBEZ). However, the following figure, highlights that the highest proportion of planned burning, relative to a zone’s area, is within APZ. This is because APZ is relatively small in area and because we burn more frequently in APZ to protect life and property. The proportion of landscape burnt while below minimum TFI in LMZ and BMZ is low compared with APZ. Overall, the proportion of fire management zones treated by planned burning while below minimum TFI was very low in 2018-19 (<1%). This shows our strategic bushfire management planning is resulting in carefully considered planned burning to reduce the potential impacts of burning vegetation below minimum TFI.

The Code of Practice requires us to manage bushfire risk to protect people and property as well as to maintain or improve environmental values. It is important that we find the right balance between reducing fuel in the various fire management zones and minimising planned burning impacts on environmental values: doing so is part of the strategic planning process.

We will continue to improve our understanding of TFI by monitoring the responses of different species of vegetation to fire and by investing in research that improves our ability to predict these responses. We are currently testing minimum TFI thresholds by collecting data about species that are sensitive to short inter-fire intervals (such as Banksia spinulosa var. cunninghamii).

We are also improving the mapping of TFI through the use of species distribution models for key flora species that define minimum TFI. This enables TFI to be mapped more accurately.

The TFI and GSS cannot be determined on public land with no recorded fire history.

Page last updated: 23/12/20