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

                                                                                              Bushfire Protection Assessment
                                                                                                                    BlueCare
                                                                                             Grass Tree Court, Sunrise Beach

The following graph indicates the radiant heat flux profile of the modelled fire under the 45km/h wind
scenario for the Liecester Model for the low heath which is the predominant vegetation of the National Park.


                                    Radiant Heat Flux Profile (Heathland) using Leceister Model



                               70


                               60
   Radiant Heat Flux (kW/m2)




                               50


                               40


                               30


                               20


                               10


                               0



                                                   Distance from Un-managed Vegetation (m)




                                                                                                                      2
The resultant radiant heat flux using the Leicester Model at 15m setback (building facade) is 24.64kW/m in
                                                                    -1
the low heath. The fire line intensity is 23794kW/m which is a very intense fire. Direct suppression with
water is not possible with this intensity of fire.

The radiant heat flux at the building facade would require the provision of a level 2 standard of construction
under AS3959 using the Leicester model for the low heath and level 3 std for the tall heath.

The flame length of the design fire for the low heath is predicted to be 7.99m and 12m for the tall heath. The
proposed setback of approximately 15m is of sufficient distance to not allow flames to directly touch the
proposed buildings.

Use of the View Factor Model for the calculation of radiant heat flux indicates a lower level of incident radiant
heat flux than the Leicester Model. The View Factor Model is the more recent and preferred model among
bushfire practitioners. The incident radiant heat is still such that a level 3 std of construction is warranted
where buildings adjoin the tall heath and a level 2 std of construction where buildings adjoin the low heath.

The modelling results need to be tempered and in reality may be over conservative. The models rely on
determining a number of mathematical variables which are open to conjecture among the bushfire



                                                                                                                          15
                                                               © 23 June 2008
                                                               Reference: 1285