Distances of between 30m and 100m are usually sufficient to mitigate the

Distances of between 30m and 100m are usually

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level. Distances of between 30m and 100m are usually sufficient to mitigate the effects of direct flame contact and radiant heat, depending on the circumstances. 18 This was the established consensus before the February 2009 Victorian bushfires. Given the unknown behaviours (both physical and social) that led to the unprecedented loss of life in the recent 2009 Victorian bushfires, the recommended cleared distance between vegetation and buildings may change. Findings from these recent Victorian fires will be used to further inform the recommendations for setback and fuel reduced zones. 5. Managed vegetation, ground cover, and construction elements including other houses are all potential sources of embers, which is why losses were experienced 700m into the Canberra urban boundary during the 2003 Canberra fires. However, there are ways to decrease a building’s flammability. Ember resistant building design and thoughtful urban design are necessary to limit the effect of fire and ember attack for many hundreds of metres into an urban interface. 6. In the past, it was assumed that when bushfires entered residential areas, they moved so fast that buildings in the path ignited explosively and burned rapidly. However, studies show that after a bushfire, there are often houses that have escaped damage while neighbouring houses are destroyed. The reason, as research has shown, is that 90 per cent of buildings survive the fire front passing, but are then ignited by embers catching on combustible components such as wooden window frames, curtains, furniture and floorboards, and burn over a few hours. 19 Burning debris can enter the roof and under floor spaces, not only through window frames. Also, radiant heat from nearby burning fuel can lead to broken windows. 7. The first comprehensive study in Australia to show how buildings are affected in bushfires was by the scientist George Barrow 20 following the 1944 bushfire at Beaumaris on the outskirts of Melbourne. The bushfire burnt 280 hectares of land containing 118 houses. Fifty-eight houses were destroyed and eight were damaged. Barrow, performed a study of the affected houses to determine the extent to which their construction influenced, either positively or negatively, their resistance to external fire hazards. Barrow found that, ‘ in a fire of the type that swept Beaumaris, the chances of a house surviving are determined more by the nature of the surroundings and the details of construction than by the materials used in the walls. With two exceptions, all the really destructive fires started inside the houses, i.e., in the roof space, in rooms, or under the floors, the immediate cause of ignition in such cases being the entrance of flame, sparks and burning debris through openings such as ventilators, eaves and windows .’ 21 17 Chen K. & J. McAneney (2004) Quantifying bushfire penetration into urban areas in Australia , Geophysical Research Letters , Vol. 31, L12212, doi:10.1029/2004GL020244, 2004 18 Ellis, P. (2000) Review of Current Methodology of Assessment of Bushfire Hazard and the Proscription of Appropriate Separation Distances and Building Standards. The Development of a Robust Model to Achieve this for Different Vegetation Types
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