Information response MCU13/0030

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         Step 2: Assessment of slope

A3.15   Studies have shown that :fires bwn more quickly and with greater intensity up slopes,
        generally doubling every 10 degrees of slope. Also, the steeper the slope the more
        difficult it is to construct ring roads, firebreaks and provide access for emergency crews.
         Trees situated downhill from structures will have their crowns close to the structures. This
        presents busbfire hazards particularly for exposed structures such as timber decks. Table
        A3.2 presents the hazard scores for different categories of slope.


         Table A3.2: Hazard scores for stope




         [Note:For site-specific assessmentofbushfire hazard, ifthe site is downhi/lfrom the hazard. the slope         II
                                                                                                                       "

         effect may be taln as zero as thefire intensity will be less. However. burning heavyfuels may roll downhill
         and trees mayfall down, so recommended setbacksfrom the hazard still need to be observed.]




         Step 3:Assessment of aspect

A3.,,6 Aspect affects busbfire hazard due to the effects that exposure to direct sunlighthas on
         different vegetation communities, including the drying rates of fuels. Aspect also
         correlates closely with exposure to low humidity winds that increase bushfire intensity. In
                                                                                                                       fl
          extremely broken country where there is a variety of aspects, the predominant aspect                             I



          should be used.
                                                                                                                       ’I


A3.17 As aspect has only a minor influence on flatter land, aspect is not considered to be
          significant on land with a slope less than 5%. Table A3.2lists the hazard score for
          different aspects and Figure A3.1 illustrates the compass degree ranges for each R$pect
          category.

          Table A3.2: Hazard score for aspect


                                Aspel’t                                            H zard scon’
                                             ~.;.~.., ._,,,~""’L.,..,-~._""
           North to North-West                                                         3.5
            North-West to West                                                          3

            West to South                                                               2

            North to East                                                               1

            East to South and all land under 5% slope                                   0




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        See Appendix 10 for the methodology for calculating slope.




  spp Guideline 1/03                                                                                     June 2003
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