080623 BlueCare Bushfire Assessment Report_Iss B_screen version.pdf [As Published] · 132008.1128

                                                                                        Bushfire Protection Assessment
                                                                                                              BlueCare
                                                                                       Grass Tree Court, Sunrise Beach

community and or are modified by site conditions. Important variables for the design fires include the wind
speed, flame temperature and fuel load.

Wind Speed has been used at 45km/h in accordance with accepted practice, however the heathland is
surrounded by taller forest vegetation which would have a reducing effect on wind speed. The actual affect
on a given day is almost impossible to define. However the presence of these trees would tend to have a
calming effect on fire behaviour in the heathland.

Flame temperature is the single most important factor in determining bushfire setbacks and is being debated
among the Australian Standards Committee for the forthcoming redraft of AS3959: Construction of Buildings
in Bushfire Prone Areas. Flame temperatures of 1090K (816 deg C), 1000K (726.85 deg C) and 910K
(636.85 deg C) are being considered by the committee. There is also recent research including Project Vesta
conducted by the CSIRO that flame temperature varies within the column of the flame itself, with the top of
the flame being the coolest. The change in flame temperature has large implications for the ability of a
building to withstand the incident predicted radiant heat flux. It is the authors opinion that for very intense
fires a higher flame temperature is likely to result. The selection of an appropriate flame temperature for
legislative requirements is under keen debate among the bushfire community.

No detailed fuel accumulation studies have been undertaken for heathland vegetation in Queensland to the
authors knowledge. In this regard fuel loads of 15t/ha (short heath) and 25t/ha (tall heath) have been
selected as used in NSW and accepted by the Australian Standards Review Committee for all of Australia.
On-site visual inspection confirmed that these fuel loads are appropriate. Burning of the vegetation would
have the effect of temporarily reducing the fuel load.




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                                                © 23 June 2008
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