Reference Document - Bushfire Risk Assessment & Bushfire Risk Management Plan

                         Ecological Natural Area Management

North west bushfire attack
This modelled fire burns up-slope through Eucalyptus spp open forest to attack from the west.
   • Fuel loads used are the “woodland” fuel loads of Australian Standard AS3959 of 15t/ha
      surface fuel & 25t/ha total fuel.
   • Separation of the house from the hazard: 12m
   • Slope in the vegetation = 0.40.
   • Site slope = 0.40
   • Fire run = 280m reducing the rate of spread to 0.69 of the quasi-steady state ROS
   • Flame width = 30m

7.6       Results of bushfire attack modelling
Table 9: Assessed Bushfire Attack Levels (BAL) for the modelled bushfire attacks
                                                                 Modelled bushfire attack
Modelled bushfire parameter          North bushfire attack         East bushfire attack     North west bushfire attack
Separation from the hazard                   16 m                          14 m                       12 m
Vegetation                           Woodland                      Woodland                   Woodland
Modelled surface fuel load                   15 t/ha                       15 t/ha                    15 t/ha
Modelled total fuel load                     25 t/ha                       25 t/ha                    25 t/ha
Vegetation slope (degrees)                  5.3 0                         0.4 0                      0.4 0
Site slope (degrees)                        5.3 0                         0.4 0                      0.4 0
Fire run                                    350 m run                     500 m run                  280 m run
Proportion of QSS ROS                      0.73                          0.78                       0.69
QSS ROS                                    1.30 km/h                     0.93 km/h                  0.93 km/h
Modelled rate of spread                    0.95 km/h                     0.73 km/h                  0.64 km/h
Flame width                                 100 m                         100 m                       30 m
Radiant heat                              17.86 kW/m2                   17.79 kW/m2                17.56 kW/m2
Modelled fire line intensity             12271 kW/m                      9429 kW/m                  8267 kW/m
Modelled flame length                      9.18 m                        7.74 m                     7.16 m
Level of construction (BAL)             BAL 19                        BAL 19                      BAL 19

The worst case scenario from Table 9 above is BAL 19
See Appendix 2 for a detailed software reports from which the above table was generated.

7.7       Bushfire Attack Levels for each building elevation
Australian Standard AS3959 specifies that the Bushfire Attack Level for the building elevation
opposite the bushfire attack direction can be reduced one level due to radiant heat shielding by the
house but as more than one bushfire attack id assessed as BAL 19, no shielding is available so the
Bushfire Attack Levels for each of the building elevations is:
      •    BAL 19 for all building elevations

7.8       Assessment of vegetation clearing
      •    The only clearing of vegetation is within the approved building envelope which achieves the
           bushfire risk mitigation recommendations in this bushfire management plan.




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

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