Appendix D - Bushfire Risk Assessment and Management Plan

                         Ecological Natural Area Management


6.3    Assessment of radiant heat shielding
The 2m fence will afford radiant heat shielding from the flame reducing the view factor that a house
has of the flame.
The method for calculating this radiant heat shielding uses Couch (2010) is as follows:
   • Determine the view factor of the unshielded flame,
   • Determine the view factor for a flame length equivalent to the effective height of the shield
        and holding flame angle constant,
   • Calculate the difference in the two view factors,
   • Set a flame length which gives a view factor equal to the difference in view factors
        calculated above; again holding the flame angle constant and
   • With this shielded view of the flame, determine the expected radiant heat load.




Figure 13: Diagram showing how a radiant heat shield such as a fence shields part of the bushfire flame
reducing the view factor of the flame



6.4    Bushfire parameters used in the bushfire behaviour modelling
These bushfire attacks use bushfire attack parameters as specified by Bushfire resilient Communities
North west bushfire attack
This modelled fire burns up-slope through Eucalyptus spp, Corymbia intermedia open forest to
attack from the north west.
    • This attack uses fuel loads specified for VHC 9.1 Moist to dry eucalypt open forests on
       coastal lowlands of 17.5 t/ha surface fuel & 24.2 t/ha total fuel ,
    • Separation of the house from the hazard as required for an appropriate Asset Protection
       Zone and to assess radiant heat loads,
    • Slope in the vegetation = 1.60
    • Site slope = 1.60
    • Fire run = 40m leading to a reduction of the bushfire rate of spread to 0.40 of the full quasi-
       steady state rate of spread
    • Radiant heat shield height of 2m and the assessment uses radiant heat loads of greater
       than 40kW/m2 as the distance for BAL FZ as allowed in NSW RFS Planning for Bushfire
       Protection to take account of the shield and
    • FFDI = 53



Bushfire Risk Assmnt & Mngt Plan for a “Community housing” development at 55 Carpenters Rd, Cooroy   February 2022

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