Appendix B - Bushfire Management Plan

6.3       Anticipated severity of bushfire attack

For Site 1, the fuel values from Section 3 are applied along with the other inputs for calculating design fire
parameters, summarised in Table 3 below.

 Fire Scenario West, north and east        Fire Scenario SW, S, SE               Fire Scenario Site 1 West

 Method 2 AS3959-2018                      Method 2 AS3959-2018                  Method 1 AS3959-2018
 FDI 50                                    FDI 50                                FDI 40
 Forest @ 21/24.2t/ha.                     Forest @ 21/24.2t/ha.                 Forest
 Effective Slope under vegetation 0⁰       Effective Slope under vegetation 0⁰   Effective Slope under vegetation 0˚
 Fire Intensity (Byram, 1959)              Fire Intensity (Byram, 1959)
 15 754kW/m (”MEDIUM”)                     15 754kW/m (”MEDIUM”)

 Rate of Spread (Noble et al, 1980)        Rate of Spread (Noble et al, 1980)
 1.26kph                                   1.26kph
 Flame Height (modified Mc Arthur V        Flame Height (modified Mc Arthur V
 equation, NSW RFS 2001) 11.09m            equation, NSW RFS 2001) 11.09m
 Flame Width 100m                          Flame Width 20m
 Elevation of Receiver 2.4m                Elevation of Receiver 2.4m
 BAL FZ within 10m of intact               BAL FZ within 9m of intact            BAL FZ within 10m of intact
 unmanaged vegetation                      unmanaged vegetation                  unmanaged vegetation
 BAL 40 from 10 - <13m                     BAL 40 from 9 - <12m                  BAL 40 from 10 - <13m
 BAL 29 from 13 - <19m                     BAL 29 from 12 - <15m                 BAL 29 from 13 - <20m
 BAL 19 from 19 - <27m                     BAL 19 from 15 - <19m                 BAL 19 from 20 - <28m
 BAL 12.5 from 27 – 100m                   BAL 12.5 from 19 – 100m               BAL 12.5 from 28 – 100m

Table 3. Calculated values for potential bushfire characteristics for Site 1 and methods used.

Projected fireline intensity from the west is approximately 15 754 KW/m, equating to “MEDIUM” rather than
“HIGH” as indicated under latest Council and State bushfire hazard mapping. The assessment validates
classification of the area as BPA with required compliance against AS3959-2018.

Whilst Method 2 indicates lesser setybacks to be viable than Method 1, particularly to the SW, S and SE,
precaution should be taken given the nature of the vegetation and isolation of the site. In this instance it is
recommended that Method 1 be applied to building construction and associated setbacks.

Note that these minimum setbacks are less than the permitted clearing distance for essential management
purposes, of 1.5 times the tallest tree height. The clearing required to meet these minimum setbacks is
necessary for the construction of a dwelling to be considered acceptable risk.

Any Class 10a structure built within 6m of the dwelling shall be constructed in accordance with this Standard.

The significance of the radiant heat flux levels discussed is shown below in Table 4.




Report compiled by Bushfire Risk Reducers for The Planning Place, July 2021                             Page 16