Abstract
One approach to increase community resilience to wildfire impacts is the enhancement of residential construction standards in an effort to provide protective shelters for families within their own homes. Current wildfire models reviewed in this study assume fire growth is unrestricted by vegetation fuel bed geometry; the head fire has attained a quasi-steady rate of spread; and the shielding effects of urban development are ignored. As a result, radiant heat flux may be significantly overestimated for small vegetation fires in road reserves, urban parklands, and similar scenarios. This paper proposes two new models to address this issue, and utilises two case studies for comparison against existing approaches. The findings are significant as this is the first study to analyse these factors from a fire engineering perspective, and to demonstrate that the use of landscape scale or siege wildfire models may not be appropriate within the urban context. The development of enhanced wildfire models will have a significant impact on town planning and construction practices in areas prone to wildfires, as well as firefighting suppression efforts when these events occur.
Highlights
Wildfires continue to impact communities across the globe, requiring vast resources and extended suppression efforts
The level of radiant heat flux corresponds to various “Bushfire Attack Levels”, which subsequently prescribe the enhancements required to the normal construction standard [1]
The models such as those described in [2,3] assume fire growth is unrestricted by vegetation fuel bed geometry; the head fire has attained a quasi-steady rate of spread; and the shielding effects of urban development are ignored
Summary
Wildfires continue to impact communities across the globe, requiring vast resources and extended suppression efforts. As opposed to relying on fire engineers to determine various design wildfires for analysis, [2,3] both require the assumption of the absolute worst case scenario, regardless of how realistic it may be The models such as those described in [2,3] assume fire growth is unrestricted by vegetation fuel bed geometry; the head fire has attained a quasi-steady rate of spread; and the shielding effects of urban development are ignored. This suggestion is supported by fire services incident reporting data, which identified that in Western Australia between 1998–2008, there were 24,784 vegetation fires within metropolitan urban and peri-urban areas, a total area of less than one hectare [6], whereby multiple factors (not fire suppression alone) prevented unrestricted wildfire growth In these scenarios, and without modification as reported in this paper, the models of [2,3] will be likely to significantly over-estimate radiant heat flux on receiving bodies [4]. The models detailed in this paper are extended from the work of [4,5] and are intended for integration with existing wildfire models [2,3], they may be suitable for application to similar models reliant on fuel load densities [7,8,9] and which represent an approaching wildfire head fire as a geometrically defined radiant heat panel, such as those described in [2,3,10,11,12]
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