Bushfire risk to life and property
The figure below
shows the Port Phillip region’s risk profile for the period 1980–2019 and projected changes in bushfire risk until 2022. It shows that:
- in 2018–19, bushfire risk was 80%
- bushfire risk fell sharply after the 1983 Ash Wednesday bushfires and again after the 2009 Black Saturday bushfires, reaching less than 40% in 2010
- since 2009, bushfire risk has increased as large areas of fuel have re-accumulated in wetter, mountainous, forest areas, which are normally too damp for planned burning, and several high-risk towns in the region adjoin forest that cannot be safely fuel-reduced with planned burning: this makes other activities (such as mechanical works, improved preparedness and community education) essential
- bushfire risk was reduced as a result of bushfires in 2018–19, particularly the Gembrook-Helmet Track fire in Bunyip State Park
- fuel management activities will reduce risk to a projected 79%, but without fuel management risk will continue to rise to a projected 85% by 2022.
Bushfire risk profile, Port Phillip Region, 1980–2022
Bushfire risk to the environment
The figure below shows the tolerable fire interval (TFI) status of vegetation on public land in the Port Phillip region since 1980.
The figure shows that in 2018–19 about 64% of the vegetation was below minimum TFI; this is an increase of 2% from the previous year. This represented the largest single-year shift in the proportion below TFI in the region since 2007-2008, after a ten-year period in which the proportion had increased more gradually from 60% to 62% between 2008 and 2018. The increase is attributable to the significant bushfires that occurred in the region during 2018-19. About 3% of the vegetation in this landscape was burnt while already below TFI in 2018-19. Almost all of this impact was due to bushfire, not planned burns, showing that our fire management strategies are carefully considering and planning our burns to reduce our impacts on vegetation below minimum TFI.
TFI status of vegetation on public land, Port Phillip region, 1980–2019
The figure below shows the growth stage structure (GSS) status of vegetation on public land in the Port Phillip region since 1980.
The figure shows about 43% of the landscape was in the juvenile and adolescent growth stages in 2018–19, and about 45% was in the mature and old growth stages. This reflects a small increase in the older growth stages compared to the previous year, resulting from the vegetation succession of areas burnt in previous large bushfires. It will take many years before the proportion of older growth stages recovers to the pre-2009 Black Saturday fires distribution.
Threatened species (such as Leadbeater’s Possum and Smoky Mouse) rely on vegetation in the mature and old growth stages for habitat (including features such as hollow-bearing trees and coarse, woody debris). It will take a long time for the landscape to recover to these growth stages, as some vegetation communities can take up to 50 years or more to reach maturity.
GSS status of vegetation on public land, Port Phillip region, 1980–2019
The TFI and GSS cannot be determined on public land with no recorded fire history.
Activities to reduce bushfire risk
Port Phillip region fuel management, 2018–19
Area treated by planned burning:
Area treated by other fuel management methods
Total area treated to reduce bushfire risk
Victorian Bushfire Monitoring Program
In the Port Phillip region, we monitor fuel hazard, fire severity and fuel moisture. We also conduct fire ecology monitoring projects and research projects.
During the year, we assessed fuel hazard on sites pre- and post-burning using the 2010 Overall fuel hazard assessment guide and the Arc Collector app. We use the data to evaluate the effectiveness of planned burns against the objectives for each burn. We only assessed a small number of sites post-burning this year, due to the limited burn window and the extended bushfire season, but we completed many pre-burn assessments to prepare for burns in coming seasons. In all, we assessed over 200 sites this year.
We map fire severity using aerial imagery (for larger burn units) and on-ground assessments. We use the mapping data to update statewide fire history datasets and map layers so they record the time since the last fire and the burn severity. This information in turn informs our risk and ecological modelling at the landscape scale.
We collect fuel moisture data manually in the field using the Arc Collector app for burn units on the upcoming burn plan. We use this data as well as automatic weather station data to inform our burn scheduling.
During the year, Yarra fire district staff continued to monitor and collect data for Hairpin Banksia, a key fire response species, so local crews can identify it and mitigate the ecological risks to it of planned burning. The monitoring also improves the datasets we have about the species’ tolerable fire interval.
The Yarra district also monitored the Greater Glider using surveying techniques developed by the Arthur Rylah Institute, which will be applied across the state to improve the quality and consistency of data. The Port Phillip region is working with Hume region staff to transition to the new techniques.
We survey sites pre- and post-planned burning, and we also survey post-bushfire sites. We can then compare data from post-bushfire sites to data both from unburned sites and post-planned-burning sites. We observed Greater Gliders at post-planned-burning and at post-bushfire sites. The data improves our knowledge of the response of this species to bushfires and planned burning, and we can also use the data to plan future survey work.
During the year, we ran a Fire Ecology Forum with our Bushfire Strategy Advisory Group, showcasing our monitoring work and answering questions from landowners and stakeholders.
There is strong community interest in the Hairpin Banksia and Greater Gliders. The Hairpin Banksia species is regionally important as a source of nectar. Our work with Greater Gliders and the Hairpin Banksia has proactively responded to local interest, and it continues to improve how we understand, manage and mitigate impacts on these key species locally.
During the year, we worked with The University of Melbourne on an Australia-first research project to better understand the properties of mulched fuel and the impacts of mechanical mulching on bushfire risk on the site of a bushfire on the Mornington Peninsula two years ago. The research aimed to:
- quantify the differences in fuel properties and flora diversity between mulched and untreated fuel
- estimate how fire behaviour differs between mulched and untreated fuel
- make recommendations about integrating mechanical treatments into risk evaluation processes.
Research such as this helps us communicate with our stakeholders with confidence, knowing we have independently validated the impact of fuel treatment on risk and fire behaviour.
We also worked with the Arthur Rylah Institute to better understand the post-fire dynamics of Cool temperate rainforest in the O’Shannassy Reservoir catchment. The project, instigated by Parks Victoria and funded through Safer Together, assessed compositional and structural changes in the rainforest after the 2009 bushfire by comparing burnt and unburnt plots. The main finding was quite concerning: the 2009 fire has led to the loss of about two-thirds of the Cool temperate rainforest previously mapped in the catchment.
Page last updated: 23/12/20