Compiled Plans & Documents OPW18-0342 02

                                                                       Bushfire Emergency Provisions
                                   Residential Aged Care Facility – 6 Grasstree Court, Sunrise Beach

dead plant material less than 6mm thick, and live plant material thinner than 3mm. On this basis, it
stands to reason that different vegetation groups yield very different fire behaviour and intensity by
virtue of their characteristics and fuel load output. The characteristics are not necessarily related to
ecological values but remain a function of the propensity for certain groups of vegetation to ignite
and sustain fire due to fuel load and arrangement, it can guide estimates on how quickly fire might
spread and the likely fire behaviour and intensity which may occur.

Vegetation type, density and arrangement can further influence fire behaviour and intensity.
Vertical and horizontal continuity is also a significant element. Thus, vegetation forms a critical
element of analysis throughout this report.

Topography
Topography (effective slope) and to a lesser degree, aspect, are also factors which influence fire
behaviour and intensity. Topography can have a drastic affect, with the rate of speed doubling for
every 10 degrees of upslope and slowing by half for every 10 degrees of downslope, as a general
rule. Aspect can also affect bushfire behaviour where areas with northerly and / or westerly aspects
experience a higher level of solar access than those areas with a southern or eastern aspect.
Notwithstanding, in times of drought and below average rainfall moisture levels in soil and
vegetation in more sheltered areas with southerly and easterly aspects can also decrease
substantially giving rise to significantly higher fuel abundance where the preceding fire regime has
been less frequent or intense. Thus, aspect can be of less consequence.

Fire Weather
It remains important to understand the influence of fire weather with regard to how it can affect
bushfire risk levels on a daily, weekly or seasonal basis.

In South East Queensland, hot-air fire wind is typically generated by west, north-west and south-
westerlies and cool-air fire wind is generated by south-westerlies which are prevalent during
Southern Queensland’s fire season which extends from August to March, annually. In some situations
however, south-easterlies can also drive bushfire behaviour on occasion.

Notwithstanding the above, it is noted bushfires do not always conform to widely-accepted
characteristics. Other fire weather conditions must also be contemplated such as preceding
weather conditions (such as low rainfall or drought), air temperature and relative humidity. If the
area has been subject to drought or low rainfall for a period of time, vegetation health tends to
deteriorate with increased leaf drop, curing and drying. This contributes to increased ground fuel
loads and general ignition susceptibility. Prolonged dry periods also reduce soil moisture content.

Air temperatures of above 30 degrees Celsius are typically conducive to increased fire weather, as
are extended periods of higher than average air temperatures. In conjunction, low relative humidity
(i.e. low air moisture content) is also a contributing factor to increased fire weather.

In concert, all of the above factors can impact on the ability for fire to propagate, and alter
behaviour and intensity characteristics and as such, fire weather is a significant component of
bushfire hazard. Whilst an assessment of vegetation types, fuel loads, effective slope and other
factors can be readily undertaken, fire weather can fluctuate across days, weeks and seasons and
can have a significant impact on the potential for bushfire threat as well as influence bushfire
behaviour and intensity.

The Forest Fire Danger Index (FFDI) is a commonly used method to readily advise the community of
the likely ability of fire suppression based on fire weather, which is used to inform the Fire Danger
Rating (FDR) System at Figure 4. It is important to maintain awareness as to the level of local fire
danger during the fire season.




Status: Provisions                                                                          December 2018
Project No.: 18-030                                                                              Page 10