Reference Document - Bushfire Risk Assessment & Bushfire Risk Management Plan

                         Ecological Natural Area Management


7 Assessment of the Bushfire Attack Level
7.1       Assessment of the Bushfire Attack Level: Methodology
The National Construction Code of Australia references Australian Standard AS3959 Construction
of buildings in bushfire-prone areas for Deemed to Satisfy building requirements for bushfire risk
management construction of buildings. This section assesses the construction Bushfire Attack
Level (BAL) for the house using Method 2 of Australian Standard AS3959 to determine a level of
construction required to achieve the objective of the Standard which is to “prescribe particular
construction details for buildings to reduce the risk of ignition from a bushfire while the fire front
passes”. (Standards Australia, 2018). This report uses software developed by Newcastle Bushfire
Consulting which models the Bushfire Attack Level using Method 2 of Australian Standard AS3959.

7.2       Modelled bushfire attacks
Three bushfire attacks were modelled based on the proximity of the hazardous vegetation.
Bushfire attack attenuation was included in the bushfire behaviour modelling due to:
      •    Constrained fire runs of bushfires due to a short fire run from residential areas leading to a
           reduced bushfire rate of spread.
           (A reduced bushfire rate of spread attenuates bushfire attack parameters such as bushfire
           intensity, flame length and radiant heat. The assessment of reduction of the rate of spread
           from the quasi-steady state rate of spread used the method of Cheney & Gould (1997). The
           effect of a reduced bushfire forward rate of spread on the reduction of assessed bushfire
           attack parameters was modelled using the method of Tan (2006)
      •    The flame width for the north west bushfire attack constrained to 30m due to cleared rural
           residential lots and the sheds and tanks on the subject lot




           Figure 10: Map showing the modelled bushfire attacks




Bushfire Risk Assessment and Management Plan for a house at 64 Pheasant Lane, Doonan         September 2020

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