SUPERSEDED Compiled Approved Plans for OPW20-0145 05

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                     4.2. Vegetation Communities
                             The Australian bush varies greatly around the country. There are regions of open woodlands,
                             grassland savannas, dense rainforest. Different types of vegetation burn differently. Generally, fuel
                             is classified as being fine (grasses and twigs that are less than 6 millimetres in diameter) or heavy
                             (branches, logs or stumps). Finer fuels burn more easily, increasing the spread of the fire. Another
                             key factor is fuel moisture content, or how dry the fuel is. The drier the fuel, the more easily it will
                             burn. The dryness of the fuel depends on seasonal rainfall and temperatures.

                     4.3. Topography
                             Fires burn faster uphill. This is due to the radiation and convection a fire creates preheating the fuel.
                             A 10-degree increase in slope results in a doubling of the speed of the fire. Fire will spread up a 10-
                             degree slope two times as fast as it will along flat ground (Figure 7).

                               The aspect of a slope (direction that a sloping piece of land is facing) influences a fire's
                               behaviour. Northern and western aspects receive more direct heat from the sun, drying both the soil
                               and the vegetation more than on southern or eastern slopes. The fuels on northern and western
                               aspects are often drier and less dense than fuels on slopes with a different aspect.




                                                                           Figure 7


                     4.4. Fire Weather
                              Fire weather affects bushfire risk levels on a daily, weekly or seasonal basis. The South-east
                              Queensland weather pattern is dominated by a maritime effect. The most common winds are
                              southeast and northeast, the latter being very common during the summer months as an afternoon sea
                              breeze. The most severe fire weather in the area is associated with a northwest wind generated on
                              the back of a high pressure system moving slowly from west to east or from a situation where there
                              is intense low pressure activity in the southeast of Australia extending a trough into southern
                              Queensland (Just, 1978). However, the frequency of these situations in the region is low, being
                              generally of the order of one to two days or fewer per year. The exception can occur in bad fire
                              seasons when fuel conditions are very dry as a result of prolonged dry periods. In Queensland, these
                              bad fire seasons occur about once a decade and are infrequent when compared with the fire situation
                              that prevails frequently in southern Australia.




                                                                                        Bushfire Planning Specialists | qldbushfireplanning.com.au
Document Set ID: 21753628
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Version: 1, Version Date: 12/01/2022
                          24/03/2021