Bushfire Hazard Assessment

Bushfire Hazard Assessment
14 Serenity Close, Noosa Heads




6.2 MODEL


6.2.1        PATCH AND CORRIDOR FILTERING


Hazardous vegetation within rural and urban landscapes is frequently fragmented, giving
rise to smaller patches and narrow corridors of vegetation that are likely to have lower
fireline intensities than larger expanses of continuous vegetation.

The spatial context of these patches and corridors of vegetation has a major influence on
the likelihood of fire arrival, the severity of a fire at the boundary of the patch, and the
behaviour of a fire within the patch.

Because of the potential contribution of grass fires to the intensity of fire in tree or shrub
dominated hazardous vegetation, bushfire hazard assessment of patches and corridors
needs to take account of the fuel properties of adjacent vegetation or other land uses.

Continuous vegetation, such as forest, shrubland or grass, has a generally uniform
distribution of fuel that supports a continuous flame front under a range of weather
conditions. In contrast, non-continuous vegetation or land uses, such as built-up areas or
water bodies, are not expected to support a continuous flame front because they do not
contain sufficient fuel load to carry a fire.

Patch and corridor filtering rules are therefore required to identify and amend the
estimated hazard potential of narrow or small patches of vegetation likely to prevent a
running fire front from reaching the potential fireline intensity levels estimated by
Equation 1 (Refer to Section 4.2.2).

Patch and corridor filtering rules were applied to the locally refined vegetation hazard
class map in accordance with Leonard and Opie (2017) and Bushfire Resilient
Communities (Queensland Fire and Emergency Services 2019) to reflect the likelihood of
lower fireline intensities in smaller vegetation patches and narrow vegetation corridors,
particularly where those patches are otherwise surrounded by fragmented and
discontinuous fuel sources, such as small patches and narrow corridors of vegetation
within established urban areas.


6.2.2        POTENTIAL FIRELINE INTENSITY


The modelling included the following measures of fire behaviour:

        i.    Potential bushfire fireline intensity (PFI, kW/m);
     ii.      Potential rate of fire spread (metres/second);
    iii.      Potential flame lengths (m).

Fuel load, VHC, landscape slope and FFDI were represented spatially in 10m resolution
input rasters. The input rasters were modelled using GIS software to generate a model of
potential fire behaviour for the 5% AEP event. Maps 7 to 9 indicate the site-specific




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