Bushfire Hazard Assessment and Management Plan

Parameter                                     Results                                     Reference
Fire Intensity                                25,184 kW/m                                 (Byram 1959)
Rate of Spread                                1.72 km/h                                   (Macarthur 1973; Noble et al. 1980)
Flame Length                                  14.56 m                                     (Noble et al. 1980)
Flame Width                                   100 m                                       (AS3959:2018)



6.8       Radiant Heat Exposure
Radiant heat flux measures the heat energy emitted from a firefront. It influences the potential for structures to ignite and
determines appropriate setbacks from hazardous vegetation. Site-specific fire modelling, undertaken following Method 2 of
AS3959:2018 and the Bushfire Resilient Communities Technical Reference Guide (QFD 2019), has been conducted to predict the
radiant heat flux from identified hazardous vegetation areas.
The results of this modelling inform the required separation distances between the development and the bushfire hazard to
mitigate exposure to radiant heat. Radiant heat flux is also used to determine Bushfire Attack Levels (BAL), which specify
construction requirements under AS3959:2018.
The following table (refer to Table J below) provides the results of radiant heat flux modelling and associated minimum setback
distances from HA1, HA2 and HA3. These results are represented spatially in Figure 10. It is noted that a Flame Temperature of
1200oK has been adopted in the analysis to reflect the recommendations provided by QFD in the Bushfire Resilient Communities
Guidance Material (QFD 2019).

Table J - Radiant Heat Flux Modelling (Method 2 - AS3959:2018)
                               Distance from Hazardous Vegetation
 Radiant Heat
                               HA1                                  HA2                              HA3
 Flame Zone                    0 m - < 14.9m                        0 m - < 14.7 m                   0 m - < 17.1 m
 40 kW/m2                      14.9 m - < 20 m                      14.7 m - < 19.8 m                17.1 m - < 22.8 m
 29 kW/m2                      20 m - < 28.7 m                      19.8 m - < 28.4 m                22.8 m - < 32.4 m
 19 kW/m2                      28.7 m - <39.7 m                     28.4 m - < 39.3 m                32.4 m - < 44.2 m
 12.5 kW/m2                    39.7 m - < 46.5 m                    39.3 m - < 46.1 m                44.2 m - < 51.5 m
 10 kW/m2                      46.5 m – 100 m                       46.1 m – 100 m                   51.5 m – 100 m


Based on the above radiant heat estimates, a greater risk profile can be interpolated for the new lots proposed to hold
residential dwellings. It can been seen in Figure 12, the northern boundary of the subject site is exposed to heat greater than
40kW/m2. The northern extent of the proposed southern lot is exposed to radiant heat no greater than 10kW/m2, with the
balance being located outside of bushfire prone area.
Given the estimated heat exposure, the potential risk to life and property can be managed through appropriate mitigation
strategies to achieve a tolerable risk outcome. The proposal demonstrates that bushfire hazards can be mitigated to acceptable
levels. Therefore, the site is considered suitable for development. Appropriate treatments to further reduce the risk associated
with the hazard are discussed in Section 7 below.




www.thereforgroup.com.au    24-0565E/BF | Sunshine Butterflies | Bushfire Management Plan | 12.03.2026 | Version 1.0            26