Understanding and Mitigating Hazards

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Tasmania bushfires, February 2016. Photo by Mick Reynolds, NSW Rural Fire Service
Tasmania bushfires, February 2016. Photo by Mick Reynolds, NSW Rural Fire Service

Project Status:

Fire behaviour in dry eucalypt forests in Australia (and in many other vegetation types to a lesser extent) is characterised by the occurrence of spotfires—new fires ignited by the transport of burning debris such as bark ahead of an existing fire. Under most burning conditions, spotfires play little role in the overall propagation of a fire, except where spread is impeded by breaks in fuel or topography and spotfires allow these impediments to be overcome. However, under conditions of severe bushfire behaviour spotfire occurrence can be so prevalent that spotting becomes the dominant propagation mechanism and the fire spreads as a cascade of spotfires forming a ‘pseudo’ front. It has long been recognised that the presence of multiple individual fires affects the behaviour and spread of all fires present. The converging of separate individual fires into larger fires is called coalescence and can lead to rapid increases in fire intensity and spread rate, leading to the phenomenon of a ‘fire storm’. This coalescence effect is frequently used in prescribed burning, with multiple point ignitions used to rapidly burn out large areas.

The team has demonstrated the performance advantages of fire propagation models incorporating curvature dependence when applied to simple wind-driven fires at both laboratory and field scales. The research has also produced fundamental insights into how the shape of the fire line affects the dynamic behaviour of the fire as a whole. Coupled fire-atmosphere modelling was used to investigate how fire-induced air movements (pyroconvection) can produce significantly enhanced rates of spread for certain fire shapes.

Fire coalescence and mass spotfire dynamics - project overview

Fire behaviour in dry eucalypt forests in Australia is characterised by the occurrence of spotfires—new fires ignited by the transport of embers ahead of an existing fire. Under most burning conditions, spotfires play little role in the overall propagation of a fire, except where spread is impeded by breaks in fuel or topography. Spotfires allow these impediments to be overcome.

However, under conditions of severe bushfire behaviour, spotfire occurrence can be so prevalent that spotting becomes the dominant propagation mechanism and the fire spreads as a cascade of spotfires forming a ‘pseudo’ front.

It has long been recognised that the presence of multiple individual fires affects the behaviour and spread of all fires present. The converging of separate individual fires into larger fires is called coalescence and can lead to rapid increases in fire intensity and spread rate, leading to the phenomenon of a ‘fire storm’. This coalescence effect is frequently used in prescribed burning, with multiple point ignitions used to rapidly burn out large areas.

This project is focusing on:

  • Fire coalescence to provide better predictions of fire propagation
  • The intrinsic dynamics of flame front propagation as a contributor to fire spread across different spatial and temporal scales
  • Within a simulation framework an end-to-end model of the behaviour of mass spotfires, from firebrand/ember launch to fire coalescence.

The modelling and simulation aspects of the project have contributed to understanding the processes that drive fire coalescence and dynamic fire spread. In particular, the research has addressed the role that fire-line geometry (especially curvature) plays in the dynamic propagation of bushfires.

The team has demonstrated the performance advantages of fire propagation models incorporating curvature dependence when applied to simple wind-driven fires at both laboratory and field scales. The research has also produced fundamental insights into how the shape of the fire line affects the dynamic behaviour of the fire as a whole. Coupled fire-atmosphere modelling was used to investigate how fire-induced air movements (pyroconvection) can produce significantly enhanced rates of spread for certain fire shapes.

Utilising the research outcomes will include development of education and training materials relating to dynamic fire behaviour and extreme fire development, which will incorporate the research findings on fire coalescence and mass spotfires.

Research findings will also be used to develop metrics of relevance to the National Fire Danger Rating Project. In particular, existing measures of ‘convective fire power’ based solely on information relating to the fire perimeter will be extended to include contributions from within flaming zones where spot fire coalescence can contribute significantly to pyroconvective release.

Post fire field work
17 November, 2017
New journal articles and reports on CRC research are available online.
Fire Australia cover
27 February, 2017
Firestorms, disaster resilience and fire preparation in Bangladesh are featured in the latest edition of Fire Australia magazine, with Issue One for 2017 out now.
Post fire field work
19 December, 2016
New journal articles and reports on CRC research are available online.
CRC sign
17 November, 2016
New journal articles and reports on CRC research are available online.
A large smoke plume from the 2014 Grampians bushfire. Photo: Wayne Rigg, CFA
11 November, 2016

Project leader A/Prof Jason Sharples article on firestorms has been featured in The Conversation special series on natural hazards.

A cool change approaches the 2015 Hastings fire in Victoria. Photo: Glenn Thompson
11 November, 2016
A special edition of the journal Climatic Change, featuring CRC researchers, documents the historical record and projected change of seven natural hazards in Australia: flood; storms (including wind and hail); coastal extremes; drought; heatwave; bushfire; and frost.
14 September, 2016
New journal articles and reports on CRC research are available online.
Wind accounts for much variability in fires. Photo: New Zealand Fire Service
8 April, 2016
Why is it that when it comes to the “wicked problem” of bushfire, we have put uncertainty to one side for so long?
Caroline Wenger giving her three minute thesis presentation in September. Photo by ANU.
14 October, 2015
Three CRC PhD students have shown off their communications skills by making it to their three minute thesis university finals.
Year Type Citation
2017 Conference Paper Rumsewicz, M. Research proceedings from the 2017 Bushfire and Natural Hazards CRC and AFAC Conference. Bushfire and Natural Hazards CRC & AFAC annual conference 2017 (Bushfire and Natural Hazards CRC, 2017).
2017 Conference Paper Sharples, J. J. A unified approach to fire spread modelling. AFAC17 (Bushfire and Natural Hazards CRC, 2017).
2017 Report Sharples, J. J., Hilton, J. & Sullivan, A. Fire coalescence and mass spotfire dynamics - experimentation, modelling and simulation: annual project report 2016-17. (Bushfire and Natural Hazards CRC, 2017).
2016 Journal Article Sharples, J. J. et al. Natural hazards in Australia: extreme bushfire. Climatic Change 139, 85-99 (2016).
2016 Journal Article Hilton, J., Sharples, J. J. & Sullivan, A. Curvature effects in the dynamic propagation of wildfires. International Journal of Wildland Fire 25, (2016).
2016 Report Sharples, J. J., Hilton, J. & Sullivan, A. Fire coalescence and mass spot fire dynamics: experimentation, modelling and simulation: Annual project report 2015-2016. (Bushfire and Natural Hazards CRC, 2016).
2015 Presentation Sharples, J. J., Hilton, J. & Sullivan, A. Dynamic modelling of fire coalescence. (2015).
2015 Report Sharples, J. J. Fire coalescence and mass spotfire dynamics: Experimentation, modelling and simulation - Annual project report 2014-2015. (Bushfire and Natural Hazards CRC, 2015).
Nature Abhors Curvature - Fires Included! Modelling Spot Fire Coalescence
18 Aug 2015

Spotting can be the dominant fire propagation mechanism during times of extreme fire weather. Spot fires can merge and collapse on one another creating regions of deep flaming, which produce violent pyroconvection. Understanding and modelling the intrinsic dynamics of spot fire coalescence is an important step in providing ways of mitigating the effects of extreme fires.

James Hilton Conference Poster 2016
14 Aug 2016

Predictive models of natural hazards have become a necessity for emergency management, mitigation and adaptation planning.

Experimental investigation of junction fire dynamics, with and without wind
29 Jun 2017

Junction fires occur when two oblique fire lines intersect with one another. The interaction of the two fire lines means that junction fires can exhibit unexpected fire behaviour, with enhanced rates of spread in the vicinity of the junction point. Quantifying these interactions is essential for the development of next generation fire spread models, which will allow prediction of dynamic fire propagation.

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