Raphaele Blanchi

Meteorological conditions and wildfire-related houseloss in Australia

Wildland fires or bushfires occurring under very severe weather conditions are likely to be destructive to infrastructure. This paper reports an analysis of the statistical relationship between house loss and the fire weather under which it occurred. A dataset was derived from 54 bushfires that occurred in Australia between 1957 and 2009, which resulted in the destruction of 8256 houses. The dataset was statistically compared with relevant local meteorological conditions, and a standardised calculation of the McArthur Forest Fire Danger Index (FFDI) applied. The analysis highlights how house loss statistics in Australia are dominated by a few iconic events that have occurred during very intense fire weather with the majority of losses occurring on days when the FFDI exceeds 100. Virtually all of the house loss has occurred above the 99.5th percentile level in the distribution of daily FFDI for each of the regions considered. Regulatory tools will need to focus on the most appropriate fire weather potential of a local area in order to ensure that infrastructure is adequately designed. In Australia, little house loss has occurred on days where the FFDI did not exceed 50, suggesting that historic building practices may be maintained in regions where this level is not likely to be exceeded.

Incorporating vegetation attenuation in radiant heat flux modelling

Models of radiant heat flux (RHF) are critical for understanding wildfire behaviour and the effect a fire may have on homes and people. Various models have been presented in the literature for wildfire RHF, many being based on the Stephan–Boltzmann equation for radiative heat transfer. Most models simplify the fire and receiver interaction by considering a single fuel type at a given separation distance from a receiving point (e.g. on a building requiring protection). However, wildfire is an inherently spatial phenomenon, in that a fire may progress across the landscape towards a building across complex terrain and through spatially varying fuel types. This spatial variation influences the fire behaviour as well as the level of RHF incident on the building. In this study, we present methods for incorporating spatially varying topography and fuels into existing RHF modelling equations. In this way, we achieve a time-dependent profile of the RHF incident on homes, while accounting for attenuation due to fuels and topography that lie between the building and the fire front. The model is applied to the prediction of damage in a fire that occurred in South Australia in 2005. Although only coarse spatial information was available for determining the spatial distribution of fuels, modelled RHF was a significant indicator of house damage. Attenuation due to vegetation between homes and the fire was shown to reduce the modelled RHF exposure of homes. However, this was not shown to increase the significance of predicted house damage in the case of this fire event.

Summary of workshop large outdoor fires and the built environment

Large outdoor fires present a risk to the built environment. Wildfires that spread into communities, referred to as Wildland-Urban Interface (WUI) fires, have destroyed communities throughout the world, and are an emerging problem in fire safety science. Other examples are large urban fires including those that have occurred after earthquakes. Research into large outdoor fires, and how to potentially mitigate the loss of structures in such fires, lags other areas of fire safety science research. At the same time, common characteristics between fire spread in WUI fires and urban fires have not been fully exploited. In this paper, an overview of the large outdoor fire risk to the built environment from each region is presented. Critical research needs for this problem in the context offire safety science are provided. The present paper seeks to develop the foundation for an international research needs roadmap to reduce the risk of large outdoor fires to the built environment.