Reference Document - Bushfire Risk Assessment & Bushfire Risk Management Plan

                                      Ecological Natural Area Management


7.3                 Assessment of fuel loads
Australian Standard AS3959 allows for the use of two fuel loads for assessing Bushfire Attack
Levels for bushfire attacks from open forest and woodland vegetation communities. The two fuel
loads allow for worst-case scenarios for woodland and open forest vegetation associations.
Table 7: Surface and total fuel loads for use in AS3959 Method 2 assessments of BALs
AS3959 vegetation descriptor                                  Surface fuel load                 Total fuel load
                             Forest                                25 t/ha                           35 t/ha
                            Woodland                               15 t/ha                           25 t/ha

Notwithstanding the names of the two fuel loads are “woodland” and “forest”, the names are
AS3959 descriptors for fuel loads and do not relate to the Specht vegetation formation names of
open forest and woodland.
The reasons that the two fuel loads are specified instead of allowing the consultant to input any fuel
loads based on an assessment of the extent vegetation is to ensure that the fuel loads used reflect
the maximum potential fuel accumulation and to allow for a worst case scenario. An assessment of
the fuel loads in the extant vegetation could potentially be less than the maximum fuel accumulation
if the assessment is conducted after vegetation management works such as prescribed burning.
Figure 15 below shows fuel accumulation curves for open forests in eastern Australia which indicate
that none exceeds 20 t/ha maximum fuel accumulation.
                   30
Fuel load (t/ha)




                   20


                   10


                   0
                   30
Fuel load (t/ha)




                   20


                   10


                   0
                        0     5         10          15        20     30      0    5     10         15         20       30
                                      Time since fire (years)                         Time since fire (years)

Figure 11: Fuel accumulation curves for open forests in eastern Australia
It is to be noted that, Gilroy & Tran (2006) showed that open forest and woodland ecosystems in
coastal south-east Queensland do not achieve the high fuel loads for equivalent hinterland
vegetation communities in New South Wales and Victoria due to higher humidity leading to a
higher rate of breakdown of leaf litter and so reducing the potential maximum fuel accumulation in
these ecosystems.



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

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