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Bushfire Resilient Communities Technical Reference Guide for the
State Planning Policy State Interest ‘Natural Hazards, Risk and
Resilience - Bushfire’
October 2019
2
Bushfire Resilient Communities – October 2019
2
© State of Queensland, October 2019. Published by Queensland Fire and Emergency Services.
Licence: This work is licensed under the Creative Commons CC BY 4.0 Australia Licence. In essence, you are free to copy and distribute this material in any format, as long as you attribute the work to the State of Queensland (Queensland Fire and Emergency Services) and indicate if any changes have been made. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.
Attribution: The State of Queensland, Queensland Fire and Emergency Services.
The Queensland Government supports and encourages the dissemination and exchange of information. However, copyright protects this publication. The State of Queensland has no objection to this material being reproduced, made available online or electronically but only if it is recognised as the owner of the copyright and this material remains unaltered.
Disclaimer: While every care has been taken in preparing this publication, the State of Queensland accepts no responsibility for decisions or actions taken as a result of any data, information, statement or advice, expressed or implied, contained within. To the best of our knowledge, the content was correct at the time of publishing.
Any references to legislation are not an interpretation of the law. They are to be used as a guide only. The information in this publication is general and does not take into account individual circumstances or situations. Where appropriate, independent legal advice should be sought.
An electronic copy of this report is available on the Queensland Fire and Emergency Services website at www.qfes.qld.gov.au
© The State of Queensland (Queensland Fire and Emergency Services) 2nd October 2019.
The Queensland Government, acting through Queensland Fire and Emergency Services, supports and encourages the dissemination and exchange of publicly funded information and endorses the use of the Australian Governments Open Access and Licensing Framework http://www.ausgoal.gov.au/
All Queensland Fire and Emergency Services’ material in this document – except Queensland Fire and Emergency Services’ logos, any material protected by a trademark, and unless otherwise noted – is licensed under a https://creativecommons.org/licenses/by/4.0/legalcode
Queensland Fire and Emergency Services has undertaken reasonable enquiries to identify material owned by third parties and secure permission for its reproduction. Permission may need to be obtained from third parties to re-use their material.
Sources for the images used in this document: Front and back covers – Source: QFES
Authors: For further information on this publication, please contact: The Sustainable Development Unit, Queensland Fire and Emergency Services Email: sdu@qfes.qld.gov.au Telephone: (07) 3635 2540.
Disclaimer: To the extent possible under applicable law, the material in this document is supplied as-is and as-available, and makes no representations or warranties of any kind whether express, implied, statutory, or otherwise. This includes, without limitation, warranties of title, merchantability, fitness for a particular purpose, non-infringement, absence of latent or other defects, accuracy, or the presence or absence of errors, whether or not known or discoverable. Where disclaimers of warranties are not allowed in full or in part, this disclaimer may not apply. To the extent possible under applicable law, neither the Queensland Government or Queensland Fire and Emergency Services will be liable to you on any legal ground (including, without limitation, negligence) or otherwise for any direct, special, indirect, incidental, consequential, punitive, exemplary, or other losses, costs, expenses, or damages arising out of the use of the material in this document. Where a limitation of liability is not allowed in full or in part, this limitation may not apply.
Acknowledgement: QFES would like to extend its appreciation to the Department of State Development, Manufacturing, Infrastructure and Planning (DSDMIP), other State Government Departments, Local Governments, Industry Associations and individuals who contributed to the review process of these guidelines.
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Table of Contents
1. Purpose 5
2. Policy approaches 9
2.1 Context 9
2.2 Policy approaches 9
3. Background 11
3.1 State Planning Policy Interactive Mapping System approach 12
3.2 Factorsaffectingbushfirehazardandrisk 13
3.2.1 Potentialfirelineintensity 13
3.2.2 Fireweatherseverity 13
3.2.3 Slope 14
3.2.4 Fuelloadandvegetation 15
3.3 Potentialbushfireimpactsandattackmechanisms 15
3.3.1 Directflameattack 15
3.3.2 Heat exposure 16
3.3.3 Emberattack 17
4. Process for preparation and review of statewide SPP IMS bushfire prone area mapping 18
4.1 Introduction 19
4.2 MethodologyusedforpreparingtheSPPIMSbushfireproneareamapping 19
4.2.1 Creationofvegetationhazardclassandpotentialfuelloadmaps 19
4.2.2 Creationofslopemaps 19
4.2.3 Creationofpotentialfireweathermaps 19
4.2.4 Creationofpotentialfirelineintensitymaps 19
4.2.5 Creationofpotentialbushfireintensityandpotentialimpactbuffermaps 19
4.2.6 Modifypotentialintensityofsmallpatchesandcorridors 20
4.3 MethodologyforlocalgovernmentreviewofSPPIMSbushfireproneareamapping 23
4.3.1 Undertakereliabilityassessment 23
4.3.2 Locallyrefinemapping 23
5. Process for undertaking a Bushfire Hazard Assessment 25
5.1 Introduction 25
5.2 Overview:thethreestagesofaBHA 25
5.3 Stage1–Reliabilityassessment 25
5.3.1 Approach 25
5.3.2 Datasources 26
5.3.3 Procedure 26
5.4 Stage2–Hazardassessment 26
5.4.1 Approach 26
5.4.2 Procedure 27
5.5 Stage3–Separationandradiantheatexposure 28
5.5.1 Approach 28
5.5.2 Procedureforcalculating 28
6. Process for undertaking a Vegetation Hazard Class Assessment 29
6.1 Introduction 30
6.2 Process 30
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Bushfire Resilient Communities – October 2019
7. Process for calculating asset protection zones 39
7.1 Introduction 39
7.2 PurposeoftheBushfireassetprotectionzonewidthcalculator 39
7.3 Optionsforcalculatingtheradiantheatexposure 39
7.4 Bushfireassetprotectionzonewidthcalculatorcomponents 39
7.5 Bushfireassetprotectionzonewidthcalculatorinputparameters 40
7.5.1 Fireweatherseverity 40
7.5.2 Vegetationhazardclass(VHC) 41
7.5.3 Remnantstatus 41
7.5.4 Slopetype 41
7.5.5 Effectivefireslope 41
7.5.6 Siteslope 41
7.5.7 Distancefromhazardousvegetation 41
7.6 Parametricconstraintsandvariations 42
7.7 Bushfireassetprotectionzonewidthcalculatorsoftwareandhardwarerequirements 42
7.8 UsingtheBushfireassetprotectionzonewidthcalculator 43
7.9 Bushfireassetprotectionzonewidthcalculatorresults 43
7.10 Defaultassetprotectionzonewidthformula 44
8. Process for preparing a Bushfire Management, Vegetation Management or Landscape Maintenance Plans 45
8.1 Introduction 46
8.2 Managementplanreporting 46
8.3 BushfirehazardreportsandBushfireManagementPlans 46
8.4 VegetationManagementPlans 46
8.5 LandscapeManagementPlans 46
8.5.1 Landscapedesign 46
8.5.2 Plantselection 47
8.5.3 Landscapemanagement 48
8.5.4 Barriers 48
9. Information that may inform development conditions 49
9.1 Staticwatersupply 50
9.2 Assemblyandevacuationareas 50
9.3 Protectivelandscapetreatments 50
9.4 Assetprotectionzonesforvulnerableuses,storageormanufactureofmaterialsthatare 50 hazardousandcommunityinfrastructureforessentialservices
10. Expertise 51
10.1 Introduction 52
10.2 Suitablyqualifiedandexperienced 52
11. Acronyms and abbreviations 53
12. Glossary 54
13. Figures 56
14. References 57
51. PURPOSE
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Bushfire Resilient Communities – October 2019
1. Purpose
Thetechnicalguidanceinthisdocument,Bushfireresilientcommunities(BRC),supportstheStatePlanningPolicyJuly2017(SPP)andassociatedStatePlanningPolicystateinterestguidancematerial–Naturalhazards,riskandresilience–Bushfire(SPPguidance).
TheSPPoutlinesthestateinterestsinlanduseplanninganddevelopmentthatunderpinthedeliveryoflocalandregionalplansanddevelopment.Thesestateinterestsincludenaturalhazards,includingbushfire,andriskandresiliencemeasures.
TheSPPguidanceassists:
• localgovernmentstomakeoramendlocalplanninginstruments
• assessmentmanagersandpractitionerswhenapplyingtheSPPassessmentbenchmarkstodevelopmentapplications(onlywherethestateinterestshavenotbeenintegratedinlocalplanninginstruments).
TheBRCprovidestechnicalguidanceandthepolicypositionsofQueenslandFireandEmergencyServices(QFES)tostateagencies,localgovernments,andpractitionersengagedinlanduseplanningforbushfirehazardanddevelopmentactivitiesthatmaybeaffectedbybushfirehazard.Thisincludes:
• makingoramendingstateandlocalplanninginstrumentssuchasplanningschemesorregionalplans
• designatinglandforcommunityinfrastructure
• makingorassessingdevelopmentapplications.
Figure1,illustratestherelationshipbetweentheSPPandsupportingguidancematerial.
TheBRC:
• outlinesfactorsaffectingbushfirehazardandpotentialbushfirerisksandimpacts
• outlinesthemethodologyusedtopreparethestatewidemappingofbushfireproneareasincludedintheStatePlanningPolicyInteractiveMappingSystem(SPPIMS)
• providestechnicalguidanceonproceduresfor:
– reviewingSPPIMSbushfireproneareamapping
– undertakingaBushfireHazardAssessment(BHA)and VegetationHazardClassAssessment
– calculatingassetprotectionzoneprovisions
– preparingaBushfireManagementPlanandLandscape Maintenance Plan
• providesadditionalinformationtoinformdevelopmentconditions
• guidestheidentificationofsuitablyqualifiedpeopleforassessmentsidentifiedintheBRC.
ThisscopeissummarisedinFigure2.
Figure1:TherelationshipbetweentheStatePlanningPolicy(SPP)andtheSPPnaturalhazardsguidancematerial.
State Planning PolicyPart E state interest statement,
state interest policies & assessment benchamarks
Supporting Material
State interest: natural hazards, risk and resilience
SPP - guidance material - Natural hazards risk and resilience - bushfire
Bushfire resilient communities
7
Figure2:Overviewofbushfireplanningandassessmentprocesses.
STATE SPP-IMS MAPPING METHODOLOGY:
LOCAL GOVERNMENT MAPPING REVIEW PROCESS:
DEVELOPMENT ASSESSMENT PROCESSES:
State Government initiated mapping
Local Government initiated review of state-wide SPP-IMS mapping
Applicant initiated site level verification by undertaking a Bushfire Hazard Assessment (BHA)
A new methodology for Statewide mapping of bushfire prone areas in Queensland (CSIRO, 2014) process
HazardassessmentSection 5 – 5.4
X X =
Fireweatherseverity–Section 3 – 3.2.2
Weather variables
Mapping tasks:
Forestfiredanger index
Climate change
Slope– Section
3 – 3.2.3
Create vegetation hazardclassandfuel loadmaps
Section 4 – 4.2.1
Create slope maps
Section 4 – 4.2.2
Create potential fireweather
maps Section
4 – 4.2.3
Create potential fireline
intensity maps
Section 4 – 4.2.4
Create potential firelineintensityandpotentialimpact buffer
maps Section
4 – 4.2.5
Modify potential
intensity of small patches andcorridor
Section 4 – 4.2.6
SPP-IMPmapping:
–Veryhighpotential bushfireintensity
–Highpotential bushfireintensity
–Mediumpotentialbushfireintensity
–Potentialimpactbuffer
Fuelload and
vegetation– Section
3 – 3.2.4
Potential firelineintensity–
Section 3 – 3.2.1
UndertakereliabilityassessmentSection 4 – 4.3.1 LocallyrefinemappingSection 4 – 4.3.2
Select representative
‘cells of interest’
Tally reliability
results
FollowtheprocessusedtocreateSPP-IMSmapping,usingimprovedlocalvegetationand/orslopemapping
consider suitability
of mapping
Assess reliability of BPAandVHC
mapping
Reliabilityassessment
Section 5 – 5.3
Vegetationhazardclass(VHC) assessment
Section 5 – 5.4 and Section 6
Prepare updated mapping–
Section 5 – 5.4.2
Re-calculate radiantheatflux levels–Section
5 – 5.5 and Section 7
Identify fire
weather severity
Identifysite slopeand effective
slope
DEVELOPMENT ASSESSMENT PROCESSES:
Reports documenting outcomes of Bushfire hazard assessment, and to demonstrate achievement of code assessment benchmarks
BushfireManagementPlan*(BMP)– Section 8 – 8.3
VegetationManagementPlan(VMP)– Section 8 – 8.4
LandscapeManagementPlan(BMP)– Section 8 – 8.5
Bushfirehazardreportdocumenting outcomesofBHA
2. POLICY APPROACHES8
Bushfire Resilient Communities – October 2019
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2.1 Context
Bushfirescancauseextensivesocial,economicandenvironmentaldamage.Withtheincreasingoccurrenceofdaysofextremeheatandfrequencyofseverefireweather,thepotentialimpactofbushfiresisofincreasingconcerninQueensland.Theimpactofbushfireswillvaryacrossthestate,dependingontheseverityofthebushfire,theproximityandexposureofpeopleandpropertytohazardousvegetation,andthevulnerabilityofdifferentlandusestobushfirehazard.Bushfireimpactscanaffectpeopleandpropertythroughflameattack,emberattack,radiantheatexposure,windandsmokeattack,andconvectiveandconductiveheatexposure.
Landuseplanningforbushfirehazardisonepartofanintegrateddisastermanagementstrategyinmitigatingtherisksassociatedwithbushfireeventstoanacceptableortolerablelevel.
2.2 Policy approaches
TheQFESpolicyapproachestolanduseplanningforbushfirehazardincludethefollowingtenpositions.
Policy 1 – Mapping is robust and locally relevant.
Asaminimum,theStatePlanningPolicyInteractiveMappingSystem(SPPIMS)bushfireproneareamappingmustbeidentifiedandappliedtolocalgovernmentplanningschemes.
LocalgovernmentsshouldrefinetheSPPIMSbushfireproneareamapping,usingtherefinementprocessoutlinedinthisdocument,andthenadopttherefinedmappingintheirspecificplanningscheme.QFESmaybeabletoassistlocalgovernmentswithlimitedresources,inthisprocess.
Policy 2 – A fit-for-purpose risk assessment informs plan-making or amendments to achieve an acceptable or tolerable level of risk to people and property in bushfire prone areas.
Localgovernmentsshouldundertakeariskassessmentwhenmakingoramendingaplanningscheme.
Tounderstandtheconsequencesofapotentialbushfireevent,theriskassessmentshouldconsidertheexposure,vulnerabilityandresilienceofcommunitiesandtheirassetstoabushfireasafirststepinproposingaplanningresponse.Ariskassessmentisamethodicalassessment,consideringthespecificcircumstancesofthelocalgovernmentarea.Preferably,theriskassessment:
• willbeconsistentwithAS/NZSISO31000:2018RiskManagement–PrinciplesandGuidelines1
• isundertakenbyasuitablyqualifiedperson(furtherdetailedinSection10).
Acomprehensiveriskassessmentmaynotberequiredforeveryplanningschemeamendment,dependingonthescopeoftheproposedinstrumentandwhetheranassessmenthasbeenpreviouslyundertaken.
QFEScanprovideadvicetolocalgovernmentsearlyintheplanningprocesstoscopeariskassessmentthatissuitedtothenatureoftheproposedschemeamendments(i.e.ariskassessmentthatisfit-for-purpose).Note–TheQueenslandGovernmenthasendorsedtheQueenslandEmergencyRiskManagementFramework(QERMF)asthestate’sapproachtoemergencyanddisasterriskmanagement.State–wideassessmentsconductedunderthisframeworkprovidekeyinformationrelevanttolocalassessments,andareheldbyLocalorDistrictDisasterManagementGroups.
Policy 3 – The planning scheme or amendments following a risk assessment are based on the principle of avoidance as the first priority, and then mitigation of the risk to an acceptable or tolerable level.
Theoutcomesoftheriskassessmentshouldinformthedraftingofthelocalplanningstrategicframeworkandassessmentbenchmarkstoensureaclearapproachtomanagingbushfirerisk.
Avoidanceoftheriskwouldincludealocalgovernmentminimisingtheexpansionorincreaseddensityofexistingdevelopmentinmappedbushfireproneareas,particularly:
• vulnerableuses
• communityinfrastructureforessentialservices
• materialsthatarehazardousinthecontextofbushfirehazard.
Afterthis,managingbushfireriskshouldbebasedonachievinganacceptableortolerablelevelofriskforbothexistingandnewdevelopmentinbushfireproneareas.
Anacceptable riskisalevelthatissufficientlylowtorequirenonewtreatmentsoractionstoallowcommunitiestolivewiththeriskwithoutfurtheraction.
Atolerable riskislowenoughtoallowtheexposuretoanaturalhazardtocontinuebuthighenoughtorequirenewtreatmentsoractionstoreducethatrisk.Communitiescanlivewiththislevelofrisk,butasmuchasisreasonablypracticalshouldbedonetoreducetherisk.Thismayincludeplanningresponsesfor:
• reducingthelikelihoodoftherisk(avoidance)
• reducingtheconsequencesoftherisk(mitigationandhazardmanagementovertime).
Whatconstitutesanacceptableortolerablelevelofriskwillvaryamonglocalgovernmentareasandcommunitycontext.Ifappropriate,communityconsultationcouldbeundertakentounderstandtolerancelevelstobushfireriskandidentifypossibletreatmentoptions.Note–Otherresponsesmayalsobesuitableforimplementationviaspecificlocalgovernmentinstrumentssuchaslocallawsorassetmanagementplans.
Policy 4 – Disaster management capacity and capabilities are maintained to mitigate the risks to people and property to an acceptable and tolerable level.
Mitigationinvolvesalocalgovernmentincludingprovisionsinitsplanningschemetoensuresubdivisionlayout:
• locateslowfuelseparationareas,suchasroads,managedopenspacesandlargelots,toseparatepeoplefromhazard
• doesnothinderemergencyserviceaccessandfunctionsthroughactivemeasuresincluding:
– ensuringsufficientaccessareas(e.g.viaperimeterroads orfiretrailandworkingareas)forfirefightersand vehiclesbetweenassetsandvegetation
– allowingforvegetationmanagementandwildfire responsetoprovideopportunitiestoestablish controllinesfromwhichhazardreductionorback- burningoperationscanoccur
2. Policy approaches
1 It is acknowledged that ISO 31000–2018 is a generic standard for a broad range of risk assessments.
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Bushfire Resilient Communities – October 2019
• allowssafeaccessandegressroutes
• ensureswatersupplyinbothreticulatedandnon-reticulatedareas.
MitigationalsoinvolveslocalgovernmentsincludingprovisionsintheirplanningschemeforBushfireManagementPlans(BMPs)forongoingvegetationmanagementthatmaintainsidentifiedlowfuelseparationareas.
Policy 5 – Lot and neighborhood layout and design mitigates the risks to people and property to an acceptable and tolerable level.
Mitigationinvolveslocalgovernmentsincludingprovisionsintheirplanningschemefor:
• newsubdivisiondesigntominimisetheinterfacewithbushfireproneareasandfacilitateconnectionstosafeevacuationroutes
• landscapedesignandmanagementthatdoesnotincreasethelevelofbushfireriskormechanismsofbushfireattack.
Thekeymitigationapproachforhousesinvolvealocalgovernmentdefiningallorpartofitsareaasadesignatedbushfireproneareainaccordancewithsection12oftheBuildingRegulation2006.ThisinturntriggerstherequirementforadherencetoAustralianStandard3959–2018Constructionofbuildingsinbushfire-proneareasatthebuildingdevelopmentapplicationstage.
Policy 6 – Vulnerable uses are not located in bushfire prone areas unless there is an overwhelming community need for the development of a new or expanded service, there is no suitable alternative location and site planning can appropriately mitigate the risk.
Thelocalgovernmentshouldincludeprovisionsinitsplanningschemewhicharticulatethispolicyposition.
Iflocatedinabushfirepronearea,vulnerableusesmaintaindisastermanagementcapacityandcapabilities,andmitigatetheriskstopeopleandpropertytoanacceptableandtolerablelevel(seePolicy4).
Policy 7 – Revegetation and rehabilitation avoids an increase in the exposure or severity of bushfire hazard.
Localgovernmentsshouldincludeprovisionsintheirplanningschemeswhicharticulatethispolicypositionanddonotresultinanunacceptablelevelofriskoranincreaseinthepotentialbushfireintensitylevel.
Policy 8 – Development does not locate buildings or structures used for the storage or manufacture of materials that are hazardous in the context of a bushfire within a bushfire prone area unless there is no suitable alternative location.
Thelocalgovernmentshouldincludeprovisionsinitsplanningschemewhicharticulatethispolicyposition.
Iflocatedinabushfirepronearea,theriskstopublicsafetyandtheenvironmentfromthereleaseofthesematerialsduringandafterabushfireeventmustbemitigatedbypositioningit:
• outsideanyassetprotectionzoneapplyingtootherbuildingsorstructuresonthesite
• asclosetotheedgeofthebushfireproneareaaspossible.
Iflocatedinabushfirepronearea,thestorageormanufactureofmaterialsthatarehazardousinthecontextofabushfiremustbemanagedthrough:
• maintenanceofappropriatedisastermanagementcapacityandcapabilities
• mitigationoftheriskstopeopleandpropertytoanacceptableandtolerablelevel(seePolicy4).
Policy 9 – The protective function of vegetation arrangements that can mitigate bushfire risk are maintained.
LocalgovernmentsshouldincludeprovisionsintheirplanningschemestomandateBMPsthatupholdtheprotectivefunctionofvegetationarrangements,suchasspeciesselection,landscapedesignandongoingvegetationmanagement.
Policy 10 – Community infrastructure for essential services are not located in bushfire prone areas unless there is an overwhelming community need for the development of a new or expanded service and there is no suitable alternative location, and further, the infrastructure can be demonstrated to function effectively during and immediately after a bushfire event.
Localgovernmentsshouldincludeprovisionsintheirplanningschemeswhicharticulatethispolicyposition.
Iflocatedinabushfirepronearea,communityinfrastructureforessentialservicesmustbesecuredby:
• maintenanceofappropriatedisastermanagementcapacityandcapabilities
• mitigationoftheriskstopeopleandpropertytoanacceptableandtolerablelevel(seePolicy4).
113. BACKGROUND
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Bushfire Resilient Communities – October 2019
3. Background
3.1 State Planning Policy Interactive Mapping System approach
TheStatePlanningPolicyJuly2017(SPP)identifiesbushfireproneareasasthosewithamediumpotentialbushfireintensity,highpotentialbushfireintensityorveryhighpotentialbushfireintensitywithanadditional100metrepotentialimpactbuffer,representingthatpartofthelandscapethatcouldsupportasignificantbushfireorbesubjecttosignificantbushfireattack.
Bushfireimpactsinabushfireproneareaarepotentiallyharmfultopeopleandproperty.
Theareasmappedasmedium,highorveryhighpotentialbushfireintensityintheStatePlanningPolicyInteractiveMappingSystem(SPPIMS)bushfireproneareamappingincludepotentiallyhazardousvegetationthatcouldsupportasignificantbushfire.Theseareashavea4,000–20,000,20,000–40,000or40,000+kW/mpotentialfirelineintensityrespectively(furtherdescribedinSection3.2.1).
Bushfiresintheseareashavethepotentialforhightoextremelevelsofflameattack,radiantheatandemberattackasaresultofhighpotentialfuellevels,slopeandfireweatherseverity.
PotentialimpactbufferareasintheSPPIMSbushfireproneareamappingcompriselandadjacenttopotentiallyhazardousvegetationthatisalsoatriskofsignificantbushfireattackfromembers,flamesorradiantheat.Potentialimpactbufferareasincludealllandwithin100metresofareasmappedasmedium,highorveryhighpotentialbushfireintensity.This100metrewidthwasinformedbyfindingsindicating78percentoffatalitiesoccurwithin30metresand85percentoffatalitiesoccurwithin100metresofhazardousvegetation(theforestedge)inAustralia.2
Themappingofthesetwodifferentlayers–potentialintensityandimpactbufferareas–identifiesthepotentialseverityofbushfiresandtheirpotentialexposureasseenbelowinFigure3.
Potential Impact Buffer
High Potential Bushfire Intensity
Figure3:Exampleofamappedbushfirepronearea,includingthepotentialimpactbuffer (landwithin100linearmetresofmappedvegetationofgreaterthan4,000k/Wmfirelineintensity).Source:SPPIMS
2 Life and house loss database description and analysis - https://publications.csiro.au/rpr/download?pid=csiro:EP129645&dsid=DS2
13
3.2 Factors affecting bushfire hazard and risk
3.2.1 Potential fireline intensity
AnewmethodologyforstatewidemappingofbushfireproneareasinQueensland(CSIRO,2014)3,4,5,usedtoproducethecurrentstatewideBushfireProneAreamapimproveduponthepreviousSPP1/03bushfirehazardmappingmethodologyapproachbyprovidingmorein-depthconsiderationofregionaldifferencesinfireweatherseverityanddiversityofvegetationtypes.Accordingly,bushfireproneareaswereidentified,mappedandcategorisedasafunctionofpotentialfirelineintensity(kW/m).
Potentialfirelineintensityisafunctionoffireweatherseverity(measuredbytheForestFireDensityIndexorFFDI),landscapeslopeandfuelload(referFigure4)basedonclassifiedvegetationcommunitiesaccordingtothemethoddescribedbytheCSIROmethodologycitedabove.
Firelineintensityisameasureofenergyreleasedfromtheflameorcombustionzone,oneofwhosesidesisaunitlengthoffirefront(measuredinkilowattspermetreofflamingfront).7 The intensitydependsontheheatofcombustionofthefuel,theforwardrateofspreadandtheamountoffinefuelconsumedintheflamingfront.Thisisagoodpredictoroftheavailableenergythatcanbereleasedfromafirebasedoncertainweather,fuelandtopographicalinformation.Theimpactofthisreleasedenergyaffectsthesuccessofsuppressioneffortsandscaleofdamage.
Potentialfirelineintensityisastandardisedmeasureoftheratethatanadvancingheadfirewouldconsumefuelenergypersecond,permetreofthefirefront.8
Areasidentifiedasamedium,highorveryhighpotentialbushfireintensityintheSPPbushfireproneareamappinghavea4,000k/Wm+firelineintensity.
Afirelineintensityof4,000 kW/misestimatedtobetheapproximatethresholdfortheeffectiveandsafedirectattackonaheadfirewithaircraftandmachineryasveryvigorousorextremelyintensesurfacefirecontroleffortsonheadmayfailandbedangerous.9
Thethresholdforcontinuouscrownfireis10,000 kW/m. Controlinthisscenarioisextremelydifficultandalleffortsatdirectcontrolarelikelytofail.Directattackisrarelypossible.Suppressionactionmustberestrictedtotheflanksandbackofthefire.10
Crownfireshavethepotentialtodramaticallyincreasefireintensitywiththeadditionofthecrownfuelandchangestothewindfield.Thiswillproducearelatedincreaseinemberproductionandspotting.
Firelineintensitygreaterthan30,000 kW/miscommonlyunderstoodasblow-upconditions.Intensitiesexceeding30,000kW/mwereadefiningfeatureofthe2009BlackSaturdayFires.11
Vegetatedpartsofthelandscapethatwouldcarryavegetationfireataintensitylowerthan4,000kW/marecategorisedasgrassfirepronelandorlowhazardareas(e.g.rainforestorwateror
non-vegetatedurbanareas).Intheeventofafire,directmanualattackatfire’sheadorflanksbyfirefighterswithhandtoolsandwaterispossible.Thisistheleveloffirelineintensitywheremostplannedburningtakesplace.
Verylittlespotfireactivityoccursatlessthan1,000kW/m.12 Constructedbreaksshouldholdfiresattheupperendofthescale,however,willstillbechallengingifthefuelsarepronetoemberproductionandspotting.13
3.2.2 Fire weather severity
Fireweatherseverity(FWS)forlanduseplanninginQueenslandisdeterminedusingthreeinputsunderthemethodology.Theseareweathervariables,FFDIandclimatechange.
Weather variables
FWSisinfluencedbyarangeofweathervariablesincludingwindspeed,relativehumidity,temperatureandatmosphericstability,aswellprecedingdroughtconditions.
Windsincreasetherateoffirespreadby‘driving’ortiltingflamesforward,increasingtherateatwhichtheunburntfuelsaheadofthefirearepreheated,thusincreasingtherateofspreadandtheintensityofbushfires.14
Windandconvectiveupdraughtscarryburningembersaheadofthefirefront.Embersaremainlyburningfragmentsofbark,leavesandtwigs,whichhavethepotentialtoignitenewfiresinsuitablyrecipientfuelsand/orinfrastructure.Strongwindscanalsocauseburningtreesorbranchestostrikebuildingsorfencesandblockaccessandevacuationroutes.
3 Leonard, J., Newnham, G, et al. (2014), A new methodology for State-wide mapping of bushfire prone areas in Queensland.4 The method for determining potential fireline intensity for small patches and corridors of vegetation has been refined as
described in Leonard, J. and Opie, K (2017), Estimating the potential bushfire hazard of vegetation patches and corridors.5 Potential fuel loads and vegetation hazard classes were updated for SEQ in 2017, information available from QFES. 6 Leonard, J., Newnham, G, et al. (2014), A new methodology for State-wide mapping of bushfire prone areas in Queensland.7 Byram, GM (1959), Combustion of forest fuels and Tangren CD (1976), The trouble with fire intensity.8 Leonard, J. and Blanchi, R (2012), Queensland bushfire risk planning project.9 Alexander and DeGroote (1989) https://fireandemergency.nz/assets/Documents/Research-and-reports/Report-21-Fire-
Behaviour-as-a-factor-in-Forest-and-Rural-Fire-Supression.PDF10 Ibid.
11 Cruz et al. (2015), Empirical based models for predicting head fire rate of spread in Australian fuel types.12 Gould et al. (2008), Project Vesta: Fire in Dry Eucalypt Forest: Fuel structure, Fuel Dynamics and Fire Behaviour.13 Alexander and DeGroote (1989) https://fireandemergency.nz/assets/Documents/Research-and-reports/Report-21-Fire-
Behaviour-as-a-factor-in-Forest-and-Rural-Fire-Supression.PDF14 Byram, GM (1959), Combustion of forest fuels.
Figure4:Methodforcalculationofpotentialfirelineintensity.6
FUEL LOAD
FIRE WEATHER SEVERITY
POTENTIAL FIRELINE
INTENSITYSLOPE
14
Bushfire Resilient Communities – October 2019
Relativehumidity(RH)istheratioofmoistureactuallyintheairversusthemaximumamountofmoisturewhichtheaircouldholdatthesametemperature.RHisameasureofthedryingpoweroftheairandthisaffectsthefinefuelmoisturecontent.RHisexpressedasapercentagewithmoisturesaturation(fog)being100percent.Asaircanholdmoremoistureathighertemperatures,theRHalonedoesnotgiveanabsolutemeasureofmoisturecontent.
WhentheRHishigh,thefinefuelsabsorbmoisturefromtheatmosphere.Underdryingconditions(decreasingRH),themoistureofthefinefuelsisdesorbedtotheatmosphere,loweringthefinefuelmoisturecontentandincreasingthelikelihoodoffireignition.Verylowlevelsofhumiditysupportextremebushfirebehaviour.
Airtemperaturealsoplaysasignificantroleinaffectingatmosphericconditions,windsandfuelmoisturecontent.
Weathervariablesdonotoperateinisolationfromeachother(orotherfactorsthatinfluencefirebehaviour).Forexample,lowhumiditycoupledwithhightemperaturesandhotwindsdryoutvegetation,increasingbushfirepotential.
Forest Fire Danger Index
TheMcArthurForestFireDangerIndex15(orFFDI)isthemostcommonproxyoffireweatherseverityinAustraliaandisusedforbushfirehazardassessments,emergencymanagementandinregulationssuchastheAustralianStandard3959–2018Constructionofbuildingsinbushfire-proneareas.
UnlikeQueensland’sadoptionofAS3959–2018thatusesasingleFFDIvalueforallofQueensland(40),theestimateoffireweatherseverityusedasaninputtoidentifyingtheSPPbushfireproneareasinQueenslandrecognisesthatweatherconditionsvaryacrossthestate.
Spatiallyexplicit5%annualexceedanceprobability(AEP)fireweathereventFFDIvaluesforQueenslandhavebeenestimatedfromagridded(83kilometre,three-hourlyresolution)predictionofFFDIfromlong-termspatialweatherproductsproducedbytheAustralianBureauofMeteorology(BoM).16 TheadoptedFFDIvaluesreflecta5%AEPweatherevent.AdoptedFWS(i.e.5%AEPfireweathereventFFDI)valuesforQueenslandvaryfrom50inSoutheastQueenslandandCapeYorkbioregionsto130inthesouth-westernpartsofthestate.17
Theidentificationoflocation-specificFWSforthepurposesofdeterminingbushfirehazardisdescribedinsection5.4.2ofthisdocument.SPPmappingdataofFWScanbeobtainedinrasterformatfromtheQueenslandGovernmentdata portal underthetitle‘Bushfirehazardarea–Bushfire-pronearea–inputs–Queensland’.
Climate change
Climatechangeprojectionsindicateanincreaseinthelikelihood,intensityandextentofareasaffectedbybushfiresandextendedfireseasons.ClimatechangeprojectionswereincorporatedintotheSPPmappingofbushfireproneareas.
Thiswasachievedbyincorporatinganadjustmenttothegriddedweathertemperatureandrelativehumiditydatausedtocalculate5%AEPfireweathereventFFDItoreflecttheexpectedclimatein2050usinganIntergovernmentalPanelonClimateChangeA1FIclimatescenario.18
3.2.3 Slope
Theslopeofthelandisamajordeterminantoffirebehaviour,particularlytheslopeofthelandundervegetationthatcontributestobushfirehazard.
Fireburnsfasterasittravelsupaslope,viapreheatingofunburntfuelsaheadofthefire,increasingtherateofspreadandfirelineintensity.Conversely,firesmovemoreslowlyastheytraveldownslope.Firelineintensity(kW/m)isafunctionoftherateofspread.19
Asageneralrule,therateoffirespread(andfirelineintensity)doublesupa10-degreeslopeandquadruplesupa20-degreeslopeoftheland.20,21
Whereslopeunderhazardousvegetationislocateddownhillfromtheedgeofthehazardousvegetationnearesttotheassetlocation,itisconsidered‘downslope’irrespectiveoftheslopeoflandbetweentheassetandtheedgeofthehazardousvegetation.
Wheretheslopeunderhazardousvegetationislocateduphillfromtheedgeofthehazardousvegetationnearesttothesite,itisconsidered‘upslope’irrespectiveoftheslopeoflandbetweenthesiteandtheedgeofthehazardousvegetation.
Accordingly,developmentlocatedabovehazardousvegetation(thevegetationis‘downslope’)istypicallysubjecttohigherlevelsofpotentialemberattack,radiantheat,convectiveheatingandlongerflamelengthsthandevelopmentwhichislocatedbelowhazardousvegetation(thevegetationis‘upslope’).
Astatewide25metreresolutiondigitalterrainmodel(DTM)wasusedtoproduceastatewidemapofmaximumlandscapeslope,representingthemaximumpotentialslopeofthelandscapewhichcouldinfluencetherateofbushfirespreadandfirelineintensity.22TheSPPmapofmaximumlandscapeslopecanbeobtainedinrasterformatfromtheQueenslandGovernmentdataportalunderthetitle‘Bushfirehazardarea–Bushfire-pronearea–inputs–Queensland’.
Themethodologyusedinsection5describesproceduresformeasuringlocalisedslopewhendeterminingsuitableassetprotectionzonewidthsfromhazardousvegetation.
15 McArthur, AG (1967), Fire behaviour in eucalyptus forests.16 Leonard, J., Newnham, G, et al. (2014), A new methodology for State-wide
mapping of bushfire-prone areas in Queensland.17 Ibid.18 Ibid.
19 Byram, GM (1959), Combustion of forest fuels.20 Assumes that slope and wind direction are aligned.21 Leonard, J. and Blanchi, R (2012), Queensland bushfire risk planning project. 22 Byram, GM (1959), Combustion of forest fuels.
15
3.2.4 Fuel load and vegetation
Vegetationistheprimarysourceoffuelandcombustionoffuelpowersabushfire.
Ingeneral,vegetationcommunitieswithahigherquantityoffuelavailabletoburn(i.e.fuelload)willtendtogiverisetohigherintensityfiresandpresentahigherrisktopeopleandproperty.However,thefuelarrangementandcomposition,notjustthequantity(load)alsocontributestotherateoffirespreadandfirelineintensity.Onlytotalfuelloadisusedinthisplanningprocess.
UndertheSPP’splanningparameters,thepotentialfuelloadthatavegetationcommunitywouldnormallyaccumulate10yearsafterafireisusedtoestimatethefirelineintensityandbushfirehazard,nottheactualfuelloadonanyparticulardayoryear.Thisapproachensuresconsistencyinplanninganddesign.
Thepotentialfuelloadrepresentstheambientfuelloadthatiscombustibleundersevereweatherconditions.Itiscalculatedasthesumofsurfacefuelload,near-surfacefuelload,elevatedfuelloadandstandingbarkfuel.Thepotentialfuelloadrepresentsthe80thpercentilefuelloadforeachfuelcategorybasedonthelong-termunburntcondition.23
Long-termandsustainedreductionoffuelloadbyclearing,cultivationormanagementofvegetationreducesthepotentialfirelineintensityandhazardlevel.
Theavailabilityoffuelisafunctionofitsmoisturecontent,type,structure,arrangementandthesizeandseverityofthefire.
Finefuelload,structureandcomposition,isdescribedusingaseriesofvegetationhazardclasses(VHCs).VHCsarebasedontheQueenslandHerbarium’sstatewideregionalecosystemmappingatthebroadvegetationgroup24level,andseveralothermappingdatasetssuchasfoliageprojectivecovermapping.
Hazardousvegetationwithinruralandurbanlandscapesisfrequentlyfragmented,givingrisetosmallerpatchesandnarrowcorridorsofvegetationthatareverylikelytohavelowerfirelineintensitiesthanlargerexpansesofcontinuousvegetation.
Thespatialcontextofthesepatchesandcorridorsofvegetationhasamajorinfluenceonthelikelihoodoffirearrival,theseverityofafireattheboundaryofthepatch,andthebehaviourofafirewithinthepatch.
Becauseofthepotentialcontributionofgrassfirestotheintensityoffireintree-orshrub-dominatedhazardousvegetation,bushfirehazardassessmentofpatchesandcorridorsneedstotakeaccountofthefuelpropertiesofadjacentvegetationorotherlanduses.
Continuousvegetation,suchasforest,shrublandorgrass,hasagenerallyuniformdistributionoffuelthatsupportsacontinuousflamefrontunderarangeofweatherconditions.Incontrast,non-continuousvegetationorlanduses,suchasbuilt-upareasorwaterbodies,arenotexpectedtosupportacontinuousflamefrontbecausetheydonotcontainsufficientfuelloadtocarryafire.
TheSPPVHCandassociatedpotentialfuelloadinputdatacanbeobtainedinshapefileformatfromtheQueenslandGovernmentdataportalunderthetitle‘Bushfirehazardarea–Bushfire-pronearea–inputs–Queensland’.TheformatforVHCcategorizationinQueenslandisdescribedinFigure6.
3.3 Potential bushfire impacts and attack mechanisms
Themainsourcesofdirectbushfireattackthatgiverisetolossoflife,anddamagetopropertyandinfrastructureare25:
• directflamecontact
• radiantheatexposure
• convectionandconduction
• emberattack
• windandsmokeattack.26
Theseattackmechanismsarenotmutuallyexclusiveandrarelyoperateinisolation.Peopleandpropertyareoftensubjecttoacombinationofbushfireattackvectors.
Althoughbushfireattackvectorsoperateatarangeofspatialscales,measurestoreduceormitigatetheeffectsofdirectflamecontact,radiantheatexposureandemberattackoccuratscalesthatcanbeaddressedvialanduseplanninganddevelopmentassessmentframeworks.Thefollowingsectionsdescribethesethreebushfireattackmechanismsandtheirpotentialimpacts.
3.3.1 Direct flame attack
Directflamecontactoccurswhenflamesfromabushfireareindirectcontactwithabuilding,structureorpeopleresultinginignition,burnsandradiantheatexposureeffects(‘flamezone’).Directflamecontactisonlyanissuefordevelopmentthatisdirectlyadjacenttobushfireproneareas.Directflamecontactcancause:
• rapid,pilotignitionoffuelandstructuresconsistingofflammablematerialssuchastimberfences,powerlinepolesandtimberhomes
• burnstoexposedskin.
Flamecontacthasobviousandsignificantimpactsonpeople,propertyandemergencyservices.
23 The long-term unburnt condition represents greater than 10 years without burning. For further information see Leonard, J., Newnham, G, et al. (2014), A new methodology for State-wide mapping of bushfire-prone areas in Queensland.
24 Neldner, VJ, and Niehus et al. (2015), The vegetation of Queensland: Descriptions of broad vegetation groups.25 Leonard, J. and Blanchi, R (2012), Queensland bushfire risk planning project. 26 Wind attack is an indirect or secondary source of bushfire attack. Wind-driven attack may extend flame lengths and height, increasing ignition likelihood and radiant
heat exposure. Wind is also responsible for promulgating burning embers and smoke. Although smoke has a negligible impact on buildings and structures, direct impacts on civilians and emergency services can be significant in terms of health and visibility.
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Bushfire Resilient Communities – October 2019
3.3.2 Heat exposure
Heattransferoccursviathreeprocesses:
1. Convection:thetransferofheatviathemovementofhotair.Undercertaincircumstances,bushfirescangeneratesufficientheattomodifytheatmosphericconditionsaroundthefire,creatingaconvectioncolumnthatcantransportembersandburningdebris.Thisrepresents60percentto80percentofthetotalheatgeneratedbyabushfire.
2. Conduction:thetransferofheatwithinthefuelitself.Thisissignificantduringtheinitiationofabushfirebutinsignificantintermsofradiantheatexposure.Thisrepresentsabouttwopercentofthetotalheatgeneratedbyabushfire.
3. Thermalradiationorradiantheat:thetransferofheatbymeansofelectromagneticwaves.Thetransferofheatbyradiationinvolvesthecarryingofenergyfromanorigintothespacesurroundingitinstraightlinesinalldirections.Theenergyiscarriedbyelectromagneticwavesanddoesnotinvolvethemovementortheinteractionofmatter.Thisrepresents20percentto40percentofthetotalheatgeneratedbyabushfire.
Exposuretoradiantheatcan:
• distort,crackandwarpmaterials(e.g.glasswindowsandplastictanks)leadingtostructuralfailureandprovideopportunitiesforemberattack
• causeignitionofexposedmaterialssuchaswalls,fencesandpowerlinepoles
• limittheabilityofemergencyservicestosafelyoperate(refertoFigure5)
• causedeathorinjurytopeople,evenatlowlevelsofradiationexposure(refertoFigure5).
Thepotentialimpactsofradiantheatexposureonpeople,propertyandemergencyservices(expressedasradiantheatflux,kW/m2)areindicatedinFigure5.
Evidencesuggeststhatfatalitiesinsidestructuresarestronglyassociatedwithhighlevelsofradiantheatexposureandpossibleflamecontact.27,28
27 Blanchi, R, Leonard, J, et al. (2012), Life and house loss database description and analysis: Final report. 28 Blanchi, R, Leonard J, et al. (2014), Environmental circumstances surrounding bushfire fatalities in Australia 1901-2011.29 Subject to exposure time, timber species and dryness of timber.30 Blanchi, R, Leonard, J, et al. (2012), Life and house loss database description and analysis: Final report. 31 NSW Rural Fire Service (2010), Planning for bush fire protection.
Radiant heat flux (kW/m2) Potential effects
Greater than 40
• unpilotedignitionoftimberwallsandfences
• directflamecontactlikely
• extremelevelsofradiantheat
29–40
• failureoftoughenedglass
• directflamecontactpossible,extremelevelsofradiantheat
• unpilotedignitionofsometimberspeciesafterprolongedexposure(e.g.severalminutes)29
19 • failureofscreenedfloatglass
16 • blisteringofskinwith>5secondsexposure
12.5• failureofplainglass
• pilotedignitionofdrytimberelementsafterprolongedexposure(e.g.severalminutes)30
10
• fabricsinsideabuildingcouldignitespontaneouslywithlongexposure
• criticallimitforemergencyservices–firefighterscannotoperate
• lifethreateningwith<1minuteexposureinprotectiveclothing.
7 • fataltoanunprotectedpersonafterexposureforseveralminutes
4.7 • firefighterinprotectiveclothingwillfeelpain(60secondsexposure)
3 • firefighterscanoperateforashortperiod(10minutes)
2
• painisfeltonbareskinafter1minuteexposure(non-fatal)
• firefighterswithprotectiveclothingcanwithstandthisexposurelevelforafewminuteshowever, theyarelikelytoexperienceriseincorebodytemperature
1 • maximumforindefiniteskinexposure
0.5 • directsunlightatnoononabrightsunnyday
Figure5:Potentialeffectsofradiantheat.31
3.3.3 Ember attack
Embersaresmallpiecesofburningfoliage,twigsandbarkwhicharetransportedbywind,oftenaheadofthefirefront.Themainsourcesofembersaretreebark,finelitterandotherfinefuels.
EmberattackisthemaincauseofdamagetoandlossofhousesinAustraliaduetobushfire.Burningor‘live’embersareproblematicbecausetheycan:
• Travellongdistancesandleadto‘spotting’bystartingnewfiresaheadofthefirefront(includingfuelsourcesaroundhomessuchasfences,outdoorfurnitureandsurfaceandnear-surfacefuelsingardens)upto40kilometresundersevereconditions;however,80percentof‘spotting’occurswithin100metresofhazardousvegetation.
• Penetratesmallgapsandholes,infiltratingbuildingsandstructures,resultinginsingleormultiplesourcesofignition.
• Accumulatearoundvegetation,buildingsorotherstructures(e.g.roofgutters,decksandpatios),resultinginslowonsetignitionwhichcanthenengulfbuildingsandstructuresduringorafterafirefrontpasses.Theaccumulationofembersandemberdensityareestimatedtoberesponsibleforupto90percentofignitionsleadingtobuildinglossinanurbanenvironment.32
Throughspotting,embersareamajorcontributortothefailureoffirecontainmentmethodsandsuppression.Thiscanhavedirectimpactsonpeopleandpropertyduringabushfire.
1732 Blanchi, R, Leonard, J, et al. (2012), Life and house loss database description and analysis: Final report.
4. PROCESS FOR PREPARATION AND REVIEW OF STATEWIDE SPP IMS BUSHFIRE PRONE AREA MAPPING
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Bushfire Resilient Communities – October 2019
19
4.1 Introduction
TheStatePlanningPolicyJuly2017(SPP)identifiestheStatePlanningPolicyInteractiveMappingSystem(SPPIMS)bushfireproneareamappinglayerasatooltobelocalisedfor,andappropriatelyintegratedinto,localgovernments’planninginstrumentsinawaythatachievesthestate’sinterest.
Insomecircumstances,thebushfireproneareafootprintmaychangeafterlocalverification,moreaccuratelydepictingpotentialbushfirehazard.Thisprovidesahigheraccuracyproducttoinformhazardandriskassessmentprocessesfordecisionmakers.
4.2 Methodology used for preparing the SPP IMS bushfire prone area mapping
ThecreationoftheSPPIMSbushfireproneareamappinginvolvedthefollowingstepsandprocesses.
4.2.1 Creation of vegetation hazard class and potential fuel load maps
Vegetationhazardclasses(VHCs)andassociatedpotentialfuelloadmapsarepreparedfromacombinationofregionalecosystemmaps,foliageprojectcovermaps,landusemaps,waterbodymapsandtreeplantationmaps(foradditionalinformation,refertosection6).
VHCsaredescribedaccordingtoabinomialcodingsystem,acombinationofthevegetationcommunity’sbroadvegetationgroup(BVG)classification(1:2million)andthestructuralcharacteristicsofthevegetation(Figure6).
ThefirstpartoftheVHCcodereferstothe35broadvegetationgroups(1:2million)inQueensland,accordingtoNeldneretal.(2015)33,withanadditionaleightcategoriesrepresentingbuilt-upareassuchasurbancentresandtowns,developedruralareas,cultivatedareas(intensiveandbroadacreagricultureandplantations)andwaterbodies.Thesecondpartofthecodedescribessixvegetationstructureclasses(referFigure16)rangingfrommid-densetreestoshrubstonilvegetation.
Whereapatchorcorridorofcontinuoustree-orshrub-dominatedvegetationissurroundedbyacontinuousfueltype(suchasunmanagedgrassland,horticultureorcroppingareas),firesthatenterthatpatchoftreesorshrubsfromtheadjacentgrasslandcanquicklyachieveafirelineintensitycomparabletolargerpatchesofcontinuoustreeorshrubvegetation.
Ontheotherhand,whereapatchorcorridorofhazardoustree-orshrub-dominatedvegetationissurroundedbydiscontinuousfuel(suchasgrasslandunder10centimetersorlow-hazardareassuchasdenselybuilt-upareasorwater),alargerpatchsizeandwidthofvegetationisrequiredbeforeafirewouldreachsufficientintensitytoposeasignificantthreattolifeorproperty(i.e.firelineintensitygreaterthan4,000kW/m).
Detailsoffuelcontinuityofvegetationhazardclasses,lifeform,height,andrelativedensityofvegetationstructuralclassesareprovidedinFigures12to16insection6.
4.2.2 Creation of slope maps
Landscapescaleslopemapsarecreatedfroma25metreresolutiondigitalterrainmodelbycalculatingthemaximumslope(indegrees)fromthecentralpixelinagroupof9x9cellstotheeightadjoiningcellsinthatgroup.
4.2.3 Creation of potential fire weather maps
Apotentialseverefireweathermapiscreatedbyafour-stageprocess:
1. DevelopagriddedpredictionofFFDIforQueensland,onan83kilometregridandatthree-hourlyintervals,overtheperiodfrom1979to201134fromtemperature,wind,relativehumidityandprecipitationweatherproductsproducedbyBoM.
2. Incorporatefutureclimatetrendsto2050byadjustingtemperatureandrelativehumidityusingtheIntergovernmentalPanelonClimateChangeA1FIclimatescenario.35
3. Calculatethe5%AEP(i.e.5%chanceofoccurringinanygivenyear)FFDIbasedonastatisticaldistributionofFFDIforeachcelloftheadjustedBoMweathergrid.
4. Resamplethe83kilometreBoMgridto25metreandtomodifynear-coastalFFDIestimatestoaccountforanunderestimationofFFDIinBoMgridcellsthatspanbothland and ocean.
4.2.4 Creation of potential fireline intensity maps
Thethreeinputs–potentialfuelload,potentialseverefireweatherandmaximumslope–arecombinedusingequation1belowtocalculatepotentialfirelineintensity(PFI).
Equation1.Calculationofpotentialfirelineintensity:
PFI = 0.62 PFL2FFDIexp(0.069Slope)
Where:
PFI=potentialfirelineintensity(kW/m)
PFL=potentialfuelload(tonnes/ha)
FFDI=potentialseverefireweather(FFDI)
Slope=maxslope(+20<slope<-15,degrees)
4.2.5 Creation of potential bushfire intensity and potential impact buffer maps
Potentialbushfireintensitymapsaregeneratedbyclassifyingthepotentialfirelineintensityforinclusioninthebushfireproneareaas4,000+kW/m,withanadditionalpotentialimpactbufferof100linearmetreswidthdelineatedaroundtheextentofhazardousvegetationidentifiedasbushfireprone.Thepotentialimpactbufferformspartofthebushfirepronearea.
4. Process for preparation and review of statewide SPP IMS bushfire prone area mapping
22. 1•Broadvegetationgroup(1:2m)
•VegetationStructureClass
33 Neldner, VJ, and Niehus et al. (2015), The vegetation of Queensland: Descriptions of broad vegetation groups. 34 This year range maybe extended to the present year depending on available datasets from the BoM.35 This report and additional information regarding more recent climate scenarios can be found at https://www.ipcc.ch/report/emissions-scenarios/ accessed August 2019.
Figure6
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Bushfire Resilient Communities – October 2019
4.2.6 Modify potential intensity of small patches and corridors
TheSPPIMSbushfireproneareamappinglayerhasbeenfurtherrefinedinsomeregionsofQueensland.Thisprocessinvolvesapplyingthefollowingpatchandcorridormappingrulestoreflectthelikelihoodoflowerfirelineintensitiesinsmallervegetationpatchesandvegetationcorridors.
Step 1
Removesub-hectareareasofcontinuousfuel(i.e.surroundedbyeithernofuelornon-continuousfuel)thatarefurtherthan100metresfromanyothercontinuousfuelgreaterthan
twohectares.Theseareasarenotlikelytoigniteduetotheirdisconnectionwithfuelsthatcancarryrunningfirefronts.Ifignitedtheyaremostlikelytobecausedbypointignitionsthatrequirebothdistanceandareatodevelopintoafirefrontofconsiderablehazard.
Ifafirefrontemergesfromaonehectarepatch,itislikelytobenarrowandsignificantlylessintensethanafirefrontthathashadsufficienttimeandareatodevelop.Thecombinationoftheselikelihoodandintensityestimatesdeemittobeequivalenttoalessthan4,000kW/mfirelineintensityand,accordingly,areconsideredaslowhazardforthepurposeoflanduseplanninganddevelopmentassessment.
Step 2
Downgradetheeffectivefuelloadofcontinuousvegetationpatchesmeasuring(a)1to2hectares(by66percent),and(b)2-3hectarepatches(by50percent)ifthepatchissurroundedbyeithernon-continuousfueloralow-hazardvegetationorlandusetype,andifthepatchisfurtherthan100metresfromanyothercontinuous-fuelvegetationpatchgreaterthantwohectares.
Patchesofthissize(<3hectares)andproximitytolargerpatchesofcontinuousvegetationarelesslikelytoigniteduetotheirdisconnectionwithvegetationthatcancarryrunningfire
fronts.Ifignited,thesepatchesaremostlikelytobeignitedbypointignitionsthatrequirebothdistanceandsizetodevelopintoasignificantfirefrontofhighintensity.
Ifafirefrontemergesfromthesepatches,itislikelytobenarrowandofsignificantlylowerintensitythanafirefrontthathashadsufficienttimeandsizetodevelop.Thecombinedeffectofbothlowerignitionlikelihoodandlowerfirelineintensityislikelytoresultinafirelineintensitythatissignificantlylessthanlargerareasofcontinuousvegetation.
(a)Exampleofvegetationpatchesof<1hasurroundedby discontinuous-fuellandcoverandvegetationpatch>1ha
(b)ResultingBushfireProneAreamappingittustratingremoval ofsmallisolatedvegetationpatches<1ha
Figure7:Characteristicsofappropriatesub-hectarearearemoval.Source:Leonardetal2017.
PATCH SIZE APPROX. PATCH DIMENSIONS ASSUMED DECREASE OF FIRE-LINE INTENSITY
(a)0.5–2hectares 100mx100m–100mx200m 66%
(b)2–3hectares 100mx200m–150mx200m 50%
21
(a)Greaterthan2hectarespatchpriortofuelloaddowngrade (b)Lessthan2hectarespatchafterfuelloaddowngrade
Figure8:Characteristicsofeffectivefuelloaddowngradesforsmallpatches.Source:Leonardetal2017.
(a)Patchbetween2to3hapriortofuelloaddowngrade (b)Patchbetween2to3haafterfuelloaddowngrade
22
Bushfire Resilient Communities – October 2019
Step 3
Removenarrowcorridorsandareasofcontinuousfuel<50metresinwidththatarenotsufficientlywidetosupportafullydevelopedflamefront.Theseareasarelesslikelytoigniteduetotheirdisconnectionwithfuelsthatcancarryrunningfirefronts.Ifignitedbyapointorlineignition,theseareaswill
limitthefireheadwidthand,asaresult,thefirelineintensity.Thecombinedeffectoflowerignitionlikelihoodandlowerintensityislikelytoresultinfirelineintensityoflessthan4,000kW/m,andthispresentsalowhazardtolanduseplanninganddevelopmentassessment.
Step 4
Smallfragmentsareremovedbecauseofthevariedqualityofthevegetationmappinginputs.Onlypatchesoftreeorshrubdominatedvegetationgreaterthan0.5hectaresareconsistentlyobservedwithhighconfidence.Smallerpatchesareoftenobservedtocontainmixturesofdifferentlandusesorcontinuousanddiscontinuousvegetation.Asaconsequence,isolatedpatchesofhazardousvegetationlessthan0.5hectares
insizearenotlikelytogenerateafirelineintensityof4,000kW/morprovidehighexposuretobuiltassets.
Therefore,isolatedpatchesoflessthan0.5hectares,ofveryhigh,highormediumpotentialbushfirehazardaredowngradedtolowhazard.Anypatchlessthan0.5hectaresofthesameclassisdowngradedtolowhazard(nolongerbushfirepronearea).
(a)Continuousfuel50matnarrowestpartofcorridor (b)Narrowcorridor<75mhasbeenremoved
Figure9:Characteristicsoftheeffectiveremovalofnarrowcorridorslessthan50m.Source:Leonardetal2017.
(a)Hazardousvegetationpatches<0.5ha (b)Patchesofhazardousvegetation<0.5haremoved
Figure10:Characteristicsofeffectiveremovalofsmallfragments<0.5ha.Source:Leonardetal2017.
23
4.3 Methodology for local government review of SPP IMS bushfire prone area mapping
AlocalgovernmentmayseektolocallyrefinetheSPPIMSbushfireproneareamappingbyfollowingthesestepsandprocesses.
4.3.1 Undertake reliability assessment
Estimatethereliabilityofmapsproducedusingthismethodology.Thestepsare:
Step 1 – Select representative ‘cells of interest’
Decideonanadequatenumberofrepresentative1kilometrex1kilometre‘cellsofinterest’tocovertherangeoflandscapesandlandusesinthelocalgovernmentarea,whileconsideringfuturedevelopmentpriorities,thediversityoflandforms,vegetationtypesandotherfactorsaffectingtheriskofbushfirestopeopleandproperty.Theminimumnumberof‘cellsofinterest’is45,butcanbeincreasedto120fordiverselocalgovernmentareas.Theserepresentative‘cellsofinterest’shouldincludeoneorbothofthesetwosamplesets:
• sampleset(a):randomlyselectedcellstoconfirmthereliabilityofmappingacrossthelocalgovernmentarea
• sampleset(b):subjectivelyselected(non-random)cellsinknownareasofpoorreliabilityforinitialoriterativerefinementofthemapping.
Alllocalgovernmentswillneedtocompletesampleset(a)toconfirmthereliabilityofbushfireproneareamapping,whereasset(b)isonlyrequiredwherethelocalgovernmentisseekingtoimprovemappinginconjunctionwithQueenslandFireandEmergencyServices(QFES).
The‘cellsofinterest’shouldspanallbushfireproneareacategories–veryhighpotentialbushfireintensity,highpotentialbushfireintensity,mediumpotentialbushfireintensityandpotentialimpactbuffer.
Step 2 – Assess and record the reliability of the bushfire prone area and VHC mapping
Withineach1kilometrex1kilometre‘cellofinterest’,undertakeadesktopassessmentofthereliabilityofbushfireproneareaandVHCmappingforeachofthefour200metrediametercircularassessmentareas.Anexpertwithexperienceinbushfiremanagementandvegetationmanagementshouldestimatethereliabilityofthemappingbyreferringtorecentaerialphotography,othermappingsourcesandlocalknowledge.
ReferencetotherelevantversionoftheQueenslandHerbarium’sregionalecosystemmappingisparticularlyuseful.Theassessmentshouldalsoaddressthebushfireproneareamappingmethodology,relevantinputdatasets(e.g.potentialfireweatherseverity,maximumlandscapeslope)andtheapplicationofthisinformationforlanduseplanning,bushfiremitigationplanningorriskassessment.
Thereliabilityofeachcircularassessmentareashouldberecordedaseither:
• Satisfactory(S):
> mappedboundariescoincidewiththeextent ofvegetationorlanduseboundariesevidentonaerial photography;differencesareusuallywithin25metres andoccasionallywithin50metres,and
> mappedhazardclassesprovideacloseapproximation ofthepotentialbushfireintensityclasses.
or
• Notsatisfactory(N)
> mappedboundariesarequitedifferentfromcurrent vegetationandlanduseboundaries;differencesare often50metresormore,and
> mappedclassesprovideapoorapproximationof potentialbushfireintensityclasses,or
> mappingfailstoadequatelyidentifysignificant areasofhazardousvegetation,whereeitherpotentially hazardousvegetation(potentialbushfireintensity classes)isnotmapped(omission)ormappingindicates thepresenceofpotentiallyhazardousvegetationthatis absent(commission).
Step 3 – Tally reliability results
Resultsofthereliabilityassessmentshouldbesummarisedforallareasofinterestbycalculatingthenumberandpercentageofcircularassessmentareasestimatedassatisfactory(S)ornotsatisfactory(N)fortherandomlyselectedcells.
Step 4 – Consider suitability of mapping
Areportofbushfireproneareamappingshouldbepreparedtosummariseresultsofthereliabilityassessmentandthesuitabilityofmapsforplanningpurposes.Ingeneral,areliabilityof90percentorgreaterforbushfireproneareamapsisconsideredsuitableforthepreparationoflocalgovernmentplanningschemesandotherstrategicplanningdecisions.
4.3.2 Locally refine mapping
Wheremappingisnotofsufficientreliability,localgovernmentsmayseektoeither:
• liaisewithQFEStoconfirmandresolveidentifiedmappingissuesinstatewidebushfirehazardareamaps,or
• preparelocalscalebushfirehazardareamapsusingimprovedlocalvegetationorslopemappingapplyingthesamemethodologyasthestateusedinpreparingthe SPPIMSbushfireproneareamapping,asdescribedinsection4.2.
5. PROCESS FOR UNDERTAKING A BUSHFIRE HAZARD ASSESSMENT
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Bushfire Resilient Communities – October 2019
25
5. Process for undertaking a Bushfire Hazard Assessment
5.1 Introduction
Thissectionisapplicablewherealocalgovernment’splanningschemecontainsprovisionsthatenableorrequireanapplicanttoundertakeaBushfireHazardAssessment(BHA)toreviewtheapplicablebushfireproneareamappingforanindividualassessmentarea.
Theapplicantisthenabletodeterminetheextentofbushfireproneareasandlevelofrisktowhichasiteisexposed,includingassessmentofspatialfactorsthatcontributetobushfirehazard.Inturn,thisenablesanapplicanttoproposealternativeassetprotectionzonewidthstotheacceptablelevelscontainedintheplanningscheme.
Localgovernmentsmayprovidethisoptiontoapplicantswhentheybelievesthereismeritinallowinganapplicantto:
• verifytheprecision,accuracyorcurrencyofthemapofbushfireproneareasormapinputdatasets(refertosection2forfurtherexplanationofwhythisisoftenjustifiable),or
• modifyanyoftheinputvariablesappliedincreatingtheplanningschememappingtoreflectchangesthatmayhaveoccurredovertime,suchasvegetationhazardclass.
Inaddition,aBHAmayberequiredbyalocalgovernmentaspartofadevelopmentproposalthatinvolvesareasdesignatedforrevegetationandrehabilitation,toensurethiswillnotcreateanew/expandedareathatwouldmeetthecriteriaofbecomingabushfireproneareaifassessedinaccordancewiththemethodologyusedtogeneratetheStatePlanningPolicyInteractiveMappingSystem(SPPIMS)mapping.
ConclusionsofadetailedBHAaretypicallypresentedasabushfirehazardreportoraspartofaBushfireManagementPlan(BMP).Refertosection8.3fordetailstobeincludedinabushfirehazardreportorBMP.
AlocalgovernmentmaywishtoeitherreferapplicantstothistechnicalguidancedocumentorprovideinformationaboutundertakingaBHAandpreparingabushfirehazardreportorBMPinitsplanningscheme(forexampleasaplanningschemepolicy).
5.2 Overview: the three stages of a BHA
TheBHAprocessconsistsofthreestages:
1. Reliabilityassessment:ThepurposeofthereliabilityassessmentstageistoverifythereliabilityofexistingbushfireproneareamappingandstreamlinethedetailedBHAprocess.
2. Hazardassessment:Thereliabilityassessmentstagedeterminestheextentofbushfireproneareasandlevelofrisktowhichasiteisexposed,includinganassessmentofspatialfactorsthatcontributetobushfirehazard.Wheretheoutcomesofthereliabilityassessmentsuggestthattheprecisionand/oraccuracyofthebushfireproneareamapormapinputdatasetsareinsufficientoranapplicantseekstomodifyinputdata,ahazardassessmentinvolvingfieldinvestigationsorgroundtruthingmayberequired.Thiswouldincludetheprovisionofsufficientevidencetosupportachangetobushfireproneareainputdataandremapping,orclassificationoftheextentofbushfireproneareasandpotentialimpactbufferforthepurposesofthedevelopmentapplication.
3. Separationandradiantheatexposure:Usingthesitespecificassessmentoffactors,thisstagecomprisescalculatingtheassetprotectionzonewidthneededtoachievetheradiantheatfluxlimitsidentifiedintheplanningscheme,usingtheBushfireassetprotectionzonewidthcalculatoroutlinedinsection7.
Figure11belowprovidesanoverviewoftheBHAprocess.
Figure11:AnoverviewoftheBushfireHazardAssessment(BHA)process.
1. Reliability assessment
2. Hazard assessment
3. Separation and radiant Heat
Verifythe reliabilityof:
• Map of bushfire-proneareas
• Mappinginputs.
Calculation of separation distanceand radiantheatflux.
Assessmentofspatialfactors:• fireweather severity/FFDI(5%AEPfireweatherevent)
• VegetationHazardClass(VHC)
• slopeincludingeffectivefireslopeandsiteslope.
Model potential firelineintensity:• site-specificmapof bushfire-proneareas.
TheBHAprocessadaptsthemethodusedtogeneratetheSPPIMSbushfireproneareamappingdescribedin‘AnewmethodologyforState-widemappingofbushfireproneareasinQueensland’.
Theprocessenablesapplicantstoeither:
• adopttheinputvaluesforFFDI(5%AEPfireweatherevent),vegetationhazardclasses(VHCs)andmaximumlandscapeslopefromtheSPPbushfireproneareamappingandproceedtocalculatefirelineintensityandradiantheatfluxlevels,or
• createalocalscalebushfireproneareamapbasedonfieldsurveys,mappingandmodellingofspatialfactorsthatcontributetopotentialfirelineintensity.
5.3 Stage 1 – Reliability assessment
5.3.1 Approach
Althoughstatewidebushfireproneareamappingisregularlyupdated,landuseandvegetationcover,keycontributorstobushfirehazard,aresubjecttochange,particularlyregardingtheextentofhazardousvegetation.
Accordingly,firststepoftheBHAistoundertakeareliabilityassessmenttodeterminewhetherthesite’sobservedcharacteristicsareconsistentwiththeinputsusedtocreatethemappingandthemappingoutputs.
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Bushfire Resilient Communities – October 2019
Areliabilityassessmentisundertakenforthesiteandalllandwithin150metresoftheproposeddevelopment.
Whereexistingmappingofbushfireproneareainputdataisassessedassatisfactory,themapinputdatacansimplybeappliedtodetermineradiantheatfluxandassetprotectionzonewidthandthenusersproceeddirectlytoStage3-calculationofseparationandradiantheatexposure.
Wheretheprecisionand/oraccuracyofthebushfireproneareamapormapinputdatasetsareinsufficient,thereliabilityassessmentprovidesamechanismtoundertakeamoredetailedassessmenttoconfirmtheextentofbushfireproneareas.
5.3.2 Data sources
Whenundertakingareliabilityassessment,relevantdatasourcestobeconsultedinclude:
• bushfireproneareamappinginputs:
> inlocalgovernmentplanningschememapping,or
> iflocalgovernmentplanningschemesreferenceout totheSPPIMS,dataisavailableinrasterformat fromtheQueenslandGovernmentdataportalas ‘bushfirehazardarea–bushfire-pronearea–inputs– Queensland’
• recentaerialphotography
• localknowledge
• fieldobservations.
5.3.3 Procedure
Theprocedureforundertakingasitereliabilityassessmentinvolvesthreesteps:
1. Confirmtheextentofmappedbushfireproneareascorrelateswiththeextentofhazardousvegetation. Thisensurestheareasmappedasbushfireproneactuallycontainhazardousvegetation.Thisstepcanbeundertakenusingacombinationofrecentaerialphotography,otheravailablemappingandsiteobservations.
2. ConfirmtheclassificationofhazardousvegetationisconsistentwiththemappedVHC.Thisensurestheunderlyingvegetationhazardclassisconsistentwiththemappedhazardclass(e.g.areasmappedasVHC9actuallycontain‘moisttodryeucalyptclosedtoopenforestsusuallyoncoastallowlandsandranges’.
3. Confirmsiteandeffectiveslopesaregenerallyconsistentwiththemappedmaximumlandscapeslope.36Thisensurestheunderlyingslopesareconsistentwiththemappedmaximumlandscapeslope.Althoughslopeisunlikelytochangesubstantially,landscapeslopemaybeaffectedbydevelopmentandearthworksonadjoiningsites.Observedslopesthatarewithintwodegreesofthemappedmaximumlandscapeslopeareconsideredreliable(i.e.themaximumlandscapeslopecanbeusedasaninputtotheStatePlanningPolicyJuly2017(SPP)Bushfireassetprotectionzonewidthcalculator).
Assessorsshouldproceedtothehazardassessmentstagewheretheresultsofanystepindicatethaterrorsoromissionsinthemappingexist.
Wheretheresultsofthisprocedureindicatetheinputmappingisreliable,assessorscanusethemapinputdataandproceedtostage3tocalculateseparationandradiantheatexposureusingtheBushfireassetprotectionzonewidthcalculatoroutlinedinsection7.
5.4 Stage 2 – Hazard assessment
5.4.1 Approach
ThesecondstepoftheBHAinvolvestheidentification,groundtruthingandmappingofspatialfactorsthatcontributetopotentialfirelineintensityandproductionofasitespecificmapofbushfireproneareas.
Thehazardassessmentmustincludethedevelopmentfootprintandalllandwithin150metresofthedevelopmentfootprint.
Thehazardassessmentmayrequirethere-modellingofbushfirebehaviourandallowforpotentialre-mappingoftheextentofbushfireproneareas.Re-modellingwouldrequireaccesstoskillsinspatialanalysisandmodelling,includingtheuseofspecialistgeographicinformationsystem(GIS)software.
Example:
Thebushfireproneareamapindicatesthatpartofthesiteislocatedwithinthepotentialimpactbufferandwithin100metresofmappedareaswith a medium, high or very high potentialbushfireintensity.
Site inspection and comparison of aerialphotography taken over a period indicatesthat some of the nearby vegetation on landmapped with a medium, high or very highpotential bushfire intensity has been clearedand replaced with sparsely vegetated areasandbuilt-upareas.
A detailed assessment may be necessary todemonstrate changes in the level of hazardand/or the location of the potential impactbuffer.
The development area may require re-mapping of vegetation hazard classes andspatial modelling of bushfire prone areas,together with sufficient supporting evidence(e.g.timeseriesaerialphotography).
36 Available in raster format, from the Queensland Government data portal if mapping is referenced out to the statewide interactive mapping system.
27
5.4.2 Procedure
Theprocedureforundertakingahazardassessmentinvolvesfoursteps:
1. Identify fire weather severity
IdentifyallFFDI(5%AEPfireweatherevent)valueswithintheassessmentarea.Datacanbeobtainedfromthebushfirehazardarea–bushfire-pronearea–inputs–Queensland,whichisavailableinrasterformatfromtheQueenslandGovernmentdata portal.
Note–Thesite-specificFFDI(5%AEPfireweatherevent)indexvalueistobeadoptedforhazardassessmentandmodellingpurposes.TheFFDIvalueof40,adoptedinmethod1ofAS3959–2009,shouldnotbeusedasitfailstoconsiderregionaldifferencesinweatherseveritythatmightbeexpectedforthe5%AEPfireweatherevent.TheadoptionoflocallyapplicableFFDI(5%AEPfireweatherevent)valuesdoesnotconflictwithAS3959–2018,whichexplicitlyallowsforrefinementofFFDIvalueswheresufficientclimatedataandmodellingisavailable(refertonotes,Table2.1,AS3959–2018).
2. Identify vegetation hazard class within the site assessment area from map of VHC
AlthoughthepotentialfuelloadsforaVHCcannotbemodified,analternativeVHCmaybeproposedwheretheresultsofareliabilityassessmentorsitespecificbotanicalsurveydemonstratedifferencesbetweentheobservedclassificationorextentofVHCsandthoseindicatedbythemappinginputsforvegetationhazardclasswhichisavailableinEsri®shapefile(.shp)format,fromtheQueenslandGovernmentdataportal(iflocalgovernmentplanningschememappingrefersouttothestatewideinteractivemappingsystem).
WherealternativeVHCsareproposed,fieldassessmentofvegetationcommunitiesmustbeundertakenaccordingtotheVHCassessmentmethodology.Fine-scaleassessmentofVHCsshouldbecarriedoutbyasuitablyqualifiedpersonwithexperienceinbotanicalsurveymethods.Fieldassessmentsmaybesupportedbyotherformsofevidenceincluding:
• airphotointerpretationusingcurrent,highresolutionaerialphotography
• QueenslandHerbariummappingofbroadvegetationgroups(BVGs)andregionalecosystems.
VHCsarethenidentifiedandmappedaccordingtotheproceduredescribedinsection6.TheoutputsoftheVHCassessmentaretoincludethefollowingmapsasspatialdata:
• Observedvegetationhazardclasses.
• Apostdevelopmentvegetationhazardclassmap,asaminimum,whichincorporatestheeffectsoftheproposeddevelopmentontheconfigurationofvegetationwithintheassessmentareaincludingallnecessaryclearingtosupportthedevelopmentandinfrastructureortomeetrequirementsforrevegetation,landscapingorenvironmentaloffsets.
Note–Developmentapprovalsonlandwithintheassessmentareacanmodifytheextentofhazardousvegetationwithinthelandscapeinwaysthatincreaseordecreasepotentialfuelloads:
> Intheshortterm,currentdevelopmentapprovalsthatpermitclearingbutarenotactedupon(inwholeorinpart)tendtomaintainorincreaselevelsofhazardwithinthelandscape.Assuch,wherethereislandwithinthesiteassessmentareainthiscircumstance,thevegetationistobemappedandclassifiedaccordingtoitscurrentextent.
> Conversely,whereareasofrevegetationareproposed,orcurrentdevelopmentapprovalsrequirerevegetationofclearedareastoachieveenvironmentaloutcomes,anincreasedhazardwithinthelandscape,notapparentduringtheinitialstagesofdevelopmentcanoccur.Wherethereislandwithinthesiteassessmentareainthiscircumstance,thevegetationistobemappedaccordingtotheapprovedrevegetationextentandthenclassifiedasthoughthevegetationhadreachedits‘remnantstate’,includingrulesforpatches
andcorridorsofvegetation.
• Potentialfuelloadsbasedonthepostdevelopmentdistributionofvegetationhazardclasseswithintheassessmentarea.
3. Identify site slope and effective slope from the mapping inputs for maximum landscape slope and determine whether the proposed lots or buildings are upslope or downslope of hazardous vegetation
Twoslopeinputparametersarerequiredfortheestimationoffirebehaviourandseparation:
1. Effectiveslope–themoreimportantofthetwo,referstotheslopeofthelandunderhazardousvegetationmeasuredindegrees.Effectiveslopehasadirectinfluenceonthepotentialrateoffirespreadandrateoffuelconsumption.
2. Siteslope–istheslopeofthegroundbetweentheedgeoftheproposeddevelopmentorsiteboundaryandtheedgeofhazardousvegetation.
Forsimpleassessmentstheeffectiveslopeisidentifiedaccordingtothefollowingprocedure:
• Determinetheslope(indegrees)ofalllandwithintheassessmentarea,includingtheslopeundereachVHC.WheremultiplecombinationsofslopesandVHCsexist,aconservativeapproachshouldbeadoptedtoensuretheriskofbushfireattack,particularlyflameattack,isadequatelyassessed.
• DeterminewhethertheVHCswithintheassessmentareawhichcontributetobushfirehazard(‘hazardousvegetation’)arelocatedupslopeordownslopeoftheproposeddevelopmentorlotboundaryinaccordancewithAS3959–2018:
> wheretheslopeofthelandcontaininghazardousvegetationisdownhillfromtheproposeddevelopmentorlotboundary,itisconsidered‘downslope’irrespectiveofthesiteslope
> wheretheslopeofthelandcontaininghazardousvegetationisuphillorisflat(i.e.0degrees)fromtheproposeddevelopmentorlotboundary,itisconsidered‘upslope’irrespectiveofthesiteslope.
Siteslopecanbedeterminedusingeitherthestatewidemapofmaximumlandscapeslope,localgovernmentdataorbasedonpostdevelopmentsiteslope,forexample,afterearthworksarecompleted.
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Bushfire Resilient Communities – October 2019
Note–Topographicdatamaybeusedtocreateanalternativemapoflandscapeslopewithintheassessmentareasfrom:
> acontourmapavailablefromtheQueenslandSpatialCatalogue(or Qspatial)
> viasurveypreparedbyaSurveyorsBoardQueenslandregistered surveyor
> digitalterrainmodelorLiDARdataavailablefromtheQueensland SpatialCatalogue.
4. Prepare detailed mapping updates of potential bushfire intensity and potential impact buffer locations and intensity levels
WhereachangetothedistributionorclassificationofVHCswithintheassessmentareaisproposed,re-modellingofbushfirehazardmaybeundertakentodeterminehowthechangestoVHCs(andfuelloads)affectpotentialfirelineintensity.
Potentialfirelineintensityfortheassessmentareashouldbecalculatedinaccordancewiththemethoddescribedin‘AnewmethodologyforState-widemappingofbushfireproneareasinQueensland’.37
Thisupdatedsitespecificmapofbushfireproneareasandanyinputmapsproducedviathehazardassessmentmaythen‘replace’theSPPmaporplanningschememapforthepurposesofassessingtheapplication.
5.5 Stage 3 – Separation and radiant heat exposure
5.5.1 Approach
Radiantheatexposuremaybecalculatedusingeither:
1. TheBushfireassetprotectionzonewidthcalculator(preferred),or
2. Method2ofMethod2ofAS3959–2018,subjecttoadoptionof:
> SitespecificvaluesofFFDI(5%AEPfireweatherevent)determinedinaccordancewithprocedure5.4.2,Step1.
> Sitespecificvegetationhazardclassesandtheirassociatedpotentialfuelloadsdeterminedinaccordancewithprocedure5.4.2Step2,togetherwithmodifiedsurfacefuelloads(w)forcertainvegetationhazardclasses.
Forallforestandwoodlandvegetationhazardclasseswherefueliscontinuous,surfacefuelload(w)isthesumofsurfaceandnearsurfacefuelloadforthepurposesofcalculatingtherateofspreadinStep6ofMethod2inAS3959–2018.Figures13,14and16indicatefuelloadandstructuralclassesforforestandwoodlandVHCs.
> Effectivesiteslopesdeterminedinaccordancewiththeprocedurein5.4.2Step3.
Whereareliabilityassessmentwasundertakenandtheresultsofallstepsindicatetheinputmappingisreliable,assessorsshouldusethemappinginputdata(bydefault)asinputdataforthecalculationofradiantheatflux.WhereasitespecificBHAhasbeenundertaken,thedatafromsteps1to3insection5.4.2shouldbeusedforthecalculationofradiantheatflux.
5.5.2 Procedure for calculating
Theprocedureforcalculatingseparationandradiantheatexposureinvolvestwosteps:
1. Measure asset protection zone width between the development and hazardous vegetation
Theassetprotectionzoneshouldbemeasuredinaccordancewithclause2.2.4ofAS3959–2018foreachVHCandslopecombinationtowhichadevelopmentisexposed.
Theassetprotectionzoneisthehorizontaldistance(i.e.measuredinplan)betweentheedgeofhazardousvegetation(edgeofcanopyforforest,woodlandandheathtypeVHCs)andfor:
• subdivisions(reconfigurationofalotorRAL:theclosestpointonalotboundaryorabuildingenvelope(whereapplicable)
• materialchangeofuse:
> theclosestpointofabuildingenvelope,or
> theexternalwallofabuilding,or
> forpartsofthebuildingthatdonothaveexternalwalls(e.g.carports,decks,landingsetc.),thesupportingpostsorcolumns.38
Theedgeofhazardousvegetationshouldbedeterminedbyasitesurveyoftheedgeofthevegetationcanopy.Alternatively,aplanshowingtheedgeofthedevelopmentfootprintinrelationtohazardousvegetationmaybeused.
2. Calculate radiant heat exposure
TheBushfireassetprotectionzonewidthcalculatorenablesapplicantstodetermineradiantheatexposureorradiantheatflux(RHF,kW/m2)usingeithermappinginputdata(FFDI[5%AEPfireweatherevent],VHCandmaximumlandscapeslope)ortheinputdataobtainedviasteps1to3ofthehazardassessmentprocess:
• FFDI(5%AEPfireweatherevent)
• vegetationhazardclass
• siteslope(degrees),effectiveslope(degrees)andwhethertheeffectiveslopeisupslopeordownslopeofthedevelopment.39
Land,wheretheeffectiveorsiteslopeis‘flat’,shallhaveaminimumslopeof1degree.Usingavalueof1degreeisrequiredtosatisfythemathematicalformula,howeverithasnegligibleimpactonthecalculations.
Userscanadjusttheassetprotectionzonewidthtodeterminethedistancenecessarytoachievetheidentifiedacceptablelevelsofradiantheatflux.
FurtherinformationontheuseoftheBushfireassetprotectionzonewidthcalculatorisinsection7.
37 Leonard, J, Opie, K, et al. (2014), A new methodology for State-wide mapping of bushfire-prone areas in Queensland.
38 Drysdale, D (2011), An introduction to fire dynamics.39 Where adopting the SPP IMS mapping input data, refer to hazard assessment
step 3 in section 5.4.2 for determination of whether the effective slope is upslope or downslope of the development.
296. PROCESS FOR UNDERTAKING A VEGETATION
HAZARD CLASS ASSESSMENT
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Bushfire Resilient Communities – October 2019
6. Process for undertaking a Vegetation Hazard Class Assessment
6.1 Introduction
Thissectionisapplicablewherealocalgovernment’splanningschemecontainsprovisionsthatenableorrequireanapplicanttoundertakeaBushfireHazardAssessment(BHA)toreviewtheapplicablebushfireproneareamappingforanindividualassessmentarea.
FuelloadsneedtobedeterminedwhenpreparingaBHA.AVegetationHazardClassAssessment–theprocessforidentifying,classifyingandmappingvegetationhazardclasses(VHCs)basedonbotanicalsurveyofvegetationcommunitieswithinanassessmentarea–canidentifythesepotentialfuelloads.
AlocalgovernmentmaywishtoreferapplicantstothistechnicalguidancedocumentorprovideinformationaboutundertakingaVHCassessmentinitsplanningscheme(forexampleasaplanningschemepolicy).
6.2 Process
TheprocessforidentifyingandclassifyingVHCsinvolvesabotanicalsurveyofthesiteandalllandwithinthesiteassessmentarea(150metresaroundthesite)accordingtothefollowingprocedure:
1. DeterminethelifeformoftheecologicallydominantlayeraccordingtolifeformcategoriesinFigure15.
Theecologicallydominantlayeristhestructurallayerwhichcontainsthegreatestamountofabovegroundbiomassand,becauseofitsphysiognomyandrelativecontinuity,dominatestherestofthecommunityinthesensethatitconditionsthehabitatsofotherstrata.40,41
Althoughavisualestimationisgenerallysufficienttoidentifytheecologicallydominantlayer,itmaybenecessarytomeasuretheheight,densityandcoverofeachlayerandtocalculatethelayer’sapproximatebiomassvolume.42Asanexample,treesarelikelytobetheecologicallydominantlayerwithinopenforestandwoodlandecosystems.
2. DetermineanddocumenttheaverageheightoftheecologicallydominantlayeraccordingtoheightclassesinFigure15(e.g.trees10-30metres).
3. EstimateanddocumenttherelativedensityoftheecologicallydominantlayeraccordingtoFigure15(e.g.closed-mid-dense).
4. Determinevegetationstructuralclassviathecombinationoflifeform,heightandrelativedensityaccordingtoFigure15(e.g.treesclosed–mid-dense=vegetationstructuralclass1).
5. DeterminethedominantplantspeciesintheecologicallydominantlayeranddeterminetheBroadVegetationGroups(BVGs)43fromVegetationofQueensland:DescriptionsofBroadVegetationGroups.44
TheidentificationofBVGsforremnantvegetationcanalsobedeterminedviagroundtruthingofcurrentregionalecosystemsonasiteaccordingtoMethodology for Survey and Mapping of Regional Ecosystems and Vegetation Communities in Queensland.45
Note–Vegetationcommunitiesarerarelyhomogeneous.Insomecases,itmaynotbepossible,norusefulfromamodellingperspective,tomapeachindividualvegetationcommunityseparatelywithintheassessmentarea,particularlyatscaleslessthan1:10,000.TheminimumpatchsizefordiscreteVHCsis1hectare.Incircumstanceswherethevegetationhazardclassisfoundtobeheterogeneous,thepotentialfuelloadisthesumoftheproportionsofthepotentialfuelloadforeachobservedVHC.TherelativeproportionofeachVHCwillneedtobedeterminedandthetotalpotential
fuelloadcalculatedaccordingtothesumoftheproportions:
Where:
=thesumofproportionsofpotentialfuelloadofnVHCs
pi=thepercentageoftheVHCcomprisedofthei thvegetationcommunity(VHC)
wi = the potential fuel load of the i thvegetationcommunity(VHC)intonnes
per hectare.
Thesameformulashouldbeusedwhethercalculatingtotalorsurfacefuelcomponents.Inthiscase,w
iisthepotentialsurfacefuelloadofthe
i thvegetationcommunity(VHC)intonnesperhectareandisthesumofsurfacefuelandnearsurfacefuelcomponentsfortheVHC.
6. DeterminetheVHCviathecombinationofBVG(1:2million)andvegetationstructuralclassaccordingtoFigure6onpagex.Figure6providesanexampleofthecombinationofBVGandvegetationstructuralclasstocreatethevegetationhazardclasscode.
7. CreateamapofobservedVHCs.
8. Developapost-developmentVHCmap.
Thisshouldincorporatetheeffectsoftheproposeddevelopmentontheconfigurationofvegetationwithintheassessmentareaincludingnecessaryclearingtosupportthedevelopmentortomeetrequirementsforrevegetation,landscapingorenvironmentaloffsets.Patchorcorridorfilteringrulesdescribedinsection4.2.6shouldbeappliedtothefinaldetailedmapofvegetationhazardclassestoproduceafinalmapofpostdevelopmentVHCs.
9. Derivepotentialfuelloadsbasedonthepostdevelopmentdistributionofvegetationhazardclasses,andcorrespondingfuelloadsfromFigure14.
WhereradiantheatexposureisproposedtobeassessedaccordingtoMethod2ofAS3959-2018,modifiedsurfacefuelloads(w)applyforcertainVHCs.Forallforestandwoodlandvegetationhazardclasses,calculatethesurfacefuelload(w)asthesumofsurfaceandnear-surfacefuelloadinFigure14.
10. AssignaVHCtobuilt-upareassuchasurbancentresandtowns,developedruralareasandcultivatedareas(intensiveandbroadacreagricultureandplantations).VHCsforbuilt-upareas,ruralareas,plantations,croppingandhorticultureandwaterbodies,aredeterminedviathecombinationofVHCfrom36–43listedinthe‘Vegetationhazardclass’columninFigure14andthecorrespondingvegetationstructureclassbyfollowingsteps1to4above.
40 Beadle, NCW and Costin, AB (1952), Ecological classification and nomenclature.41 Neldner, VJ (1984), South Central Queensland – Vegetation Survey of Queensland.42 Neldner, VJ, Wilson, BA, et al. (2012), Methodology for survey and mapping of
regional ecosystems and vegetation communities in Queensland Version 3.2. 43 Broad vegetation groups are a high-level grouping of vegetation communities
and are based on floristics, structural, functional, biogeographical and landscape attributes.
44 Neldner, VJ, Niehus, RE, et al. (2015), The vegetation of Queensland: Descriptions of broad vegetation groups. Version 2.0.
45 Neldner, VJ, Wilson, BA, et al. (2012), Methodology for survey and mapping of regional ecosystems and vegetation communities in Queensland Version 3.2.
31
Figure12belowshowsanexampleofthedifferencebetweenthepublishedmapofVHCandaverifiedmapofobservedVHCspreparedaccordingtotheVHCAssessmentprocedure.
Figure13indicatesthedifferencesinfuelloadsforthesameassessmentareabasedonthechangestotheVHCs.
Figure12:Statewidemapofvegetationhazardclass(VHC)(left)andexampleofagroundtruthedmapofobservedVHCs(right).87Source:Leonardetal2017.
Figure13:Fuelloadbasedonpublishedmapofvegetationhazardclass(VHC)(left)andexampleofafuelloadrasterbasedonobservedVHCs(right).Source:Leonardetal2017.
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Bushfire Resilient Communities – October 2019
Vegetation hazard class descriptions and 80th percentile potential fuel load
Vegetation hazard class
Potentialfuelload(t/ha) Prone type46
Fuel continuity47
Surf
ace
Near-surface
Elevated
Bark
Total(Remnant)
Total(Non-remnant)
Remnant
Non-remnant
Remnant
Non-remnant
1.1 Complexmesophylltonotophyllvineforests 2.6 0.0 0.0 0.0 2.6 12.0 3 1 2 1
2.1 Complextosimple,semi-deciduousmesophylltonotophyllvineforest 3.5 0.0 0.0 0.0 3.5 12.0 3 1 2 1
3.1 Notophyllvineforest 4.5 0.0 0.0 0.0 4.5 12.0 3 1 2 1
3.3 Notophyllvinethicket 4.4 0.0 0.0 0.0 4.4 12.0 3 1 2 1
4.1 Notophyllandnotophyllpalmorvineforest 4.5 0.0 0.0 0.0 4.5 12.0 3 1 2 1
5.1 Notophylltomicrophyllvineforests 3.9 0.0 0.0 0.0 3.9 12.0 3 1 2 1
5.2 Notophylltomicrophyllvineforestwithsparseoverstorey 3.9 0.0 0.0 0.0 3.9 12.0 3 1 2 1
5.5 Sedgelandwithinnotophylltomicrophyllvineforests 3.9 0.0 0.0 0.0 3.9 12.0 3 1 2 1
6.1 MontaneNotophyllvineforestandmicrophyllfernforest 3.9 0.0 0.0 0.0 3.9 12.0 3 1 2 1
6.3 MontaneNotophyllvinethicketandmicrophyllfernthicket 3.9 0.0 0.0 0.0 3.9 12.0 3 1 2 1
7.1 Semi-evergreentodeciduousmicrophyllvineforest 6.0 0.0 0.0 0.0 6.0 12.0 3 1 2 1
7.2 Sparsesemi-evergreentodeciduousmicrophyllvineforest 6.0 0.0 0.0 0.0 6.0 12.0 3 1 2 1
8.1 Weteucalypttallopenforest 28.0 3.0 2.0 2.0 35.0 35.0 1 1 1 1
8.2 Weteucalypttallwoodland 18.0 3.1 1.7 1.0 23.8 23.8 1 1 1 1
9.1 Moisttodryeucalyptopenforestsoncoastallowlandsandranges 17.5 3.5 2.2 1.0 24.2 24.2 1 1 1 1
9.2 Moisttodryeucalyptwoodlandoncoastallowlandsandranges 11.4 3.5 1.3 1.0 17.2 17.2 1 1 1 1
9.3 Shrublandwithinmoisttodryeucalyptoncoastallowlandsandranges 7.8 3.0 1.9 0.0 12.7 12.7 1 1 1 1
10.1 Spottedgumdominatedopenforests 16.3 3.0 1.5 0.0 20.8 20.8 1 1 1 1
10.2 Spottedgumdominatedwoodlands 14.0 3.0 1.0 0.0 18.0 18.0 1 1 1 1
11.2 Moisttodryeucalyptwoodlandsonbasaltareas 7.5 4.0 0.5 1.0 13.0 13.0 1 1 1 1
12.1 Dryeucalyptopenforestonsandstoneandshallowsoils 15.0 3.5 1.5 1.0 21.0 21.0 1 1 1 1
12.2 Dryeucalyptwoodlandsonsandstoneandshallowsoils 12.0 2.6 1.8 1.0 17.4 17.4 1 1 1 1
13.1 Drytomoisteucalyptopenforestsonundulatingmetamorphicsandgranite 15.9 3.5 1.4 1.0 21.8 21.8 1 1 1 1
13.2 Drytomoisteucalyptwoodlandsonundulatingmetamorphicsandgranite 9.4 3.4 0.6 1.0 14.4 14.4 1 1 1 1
46 Prone type: 1 = Bushfire prone, 2 = Grass fire prone, 3 = Low hazard 47 Fuel continuity: 1 = Continuous, 2 = Discontinuous
33
Vegetation hazard class descriptions and 80th percentile potential fuel load
Vegetation hazard class
Potentialfuelload(t/ha) Prone type46
Fuel continuity47
Surf
ace
Near-surface
Elevated
Bark
Total(Remnant)
Total(Non-remnant)
Remnant
Non-remnant
Remnant
Non-remnant
13.3 Shrublandassociatedwithdrytomoisteucalyptwoodlandsonundulatingterrain
4.3 2.3 0.9 0.0 7.5 7.5 1 1 1 1
14.1 OpenforestdominatedbyDarwinstringybark,MelvilleIslandbloodwoodorscarletgum
22.3 1.4 2.1 2.0 27.8 27.8 1 1 1 1
14.2 WoodlandsdominatedbyDarwinstringybark,MelvilleIslandbloodwoodorscarletgum
8.4 2.4 0.8 1.0 12.6 12.6 1 1 1 1
14.3 ShrublandassociatedwithwoodlandsdominatedbyDarwinstringybark,MelvilleIslandbloodwoodorscarletgum
1.1 3.4 3.3 1.0 8.8 8.8 1 1 1 1
14.6 SparselyvegetatedareasassociatedwithDarwinstringybark,MelvilleIslandbloodwoodorscarletgum
0.0 0.3 1.3 0.0 1.6 1.6 3 3 2 2
15.1 Temperateopeneucalyptforests 23.7 0.3 1.8 1.0 26.8 26.8 1 1 1 1
15.2 Temperateeucalyptwoodlands 10.2 1.8 1.8 0.0 13.8 13.8 1 1 1 1
16.1 Eucalyptusdominatedforestondrainagelinesandalluvialplains 10.0 3.8 1.2 1.0 16.0 16.0 1 1 1 1
16.2 Eucalyptusdominatedwoodlandondrainagelinesandalluvialplains 7.5 3.6 0.5 0.0 11.6 11.6 1 1 1 1
16.3 Shrublandassociatedwitheucalyptuswoodlandsondrainagelines 5.8 2.7 0.1 0.0 8.6 8.6 1 1 1 1
16.4 Grasslandassociatedwitheucalyptusdominatedwoodlandsondrainagelines
0.3 2.1 0.1 0.0 2.5 2.5 2 2 1 1
16.5 Sedgelandassociatedwitheucalyptuswoodlandsondrainagelines* 3.9 5.0 3.5 0.0 12.4 12.4 1 1 1 1
16.6 Sparselyvegetatedareasassociatedwitheucalyptuswoodlandsondrainagelines
1.2 2.0 0.0 0.0 3.2 3.2 3 3 2 2
17.1 Dryopenforestsdominatedbypoplarbox,silver-leavedironbarkorWhite'sironbarkonsandordepositionalplains
10.6 4.1 0.3 0.0 15.0 15.0 1 1 1 1
17.2 Drywoodlandsdominatedbypoplarbox,silver-leavedironbarkorWhite'sironbarkonsandordepositionalplains
6.0 3.0 0.6 0.0 9.6 9.6 1 1 1 1
18.1 Dryeucalyptusopenforestsonsandordepositionalplains 10.8 3.4 0.6 0.0 14.8 14.8 1 1 1 1
18.2 Dryeucalyptuswoodlandsonsandordepositionalplains 7.1 3.3 0.6 0.0 11.0 11.0 1 1 1 1
18.5 Sedgelandassociatedwithdryeucalyptwoodlandsonsandordepositionalplains
3.9 3.4 3.5 0.0 10.8 10.8 1 1 1 1
19.2 Lowopeneucalyptuswoodlandsdominatedbysnappygum,CloncurryBoxorNormantonbox
4.3 3.0 0.8 1.0 9.1 9.1 1 1 1 1
19.3 Shrublandassociatedwithlowopeneucalyptwoodlandsdominatedby snappygum,CloncurryBoxorNormantonbox
1.7 1.5 1.3 0.0 4.5 4.5 1 1 1 1
19.4 Grasslandassociatedwithlowopeneucalyptwoodlandsdominatedby snappygum,CloncurryBoxorNormantonbox
1.6 3.3 0.3 0.0 5.2 5.2 2 2 1 1
20.1 Openforestsdominatedbywhitecypresspineorcoastcypresspine 12.5 2.4 0.6 1.0 16.4 16.5 1 1 1 1
34
Bushfire Resilient Communities – October 2019
Vegetation hazard class descriptions and 80th percentile potential fuel load
Vegetation hazard class
Potentialfuelload(t/ha) Prone type46
Fuel continuity47
Surf
ace
Near-surface
Elevated
Bark
Total(Remnant)
Total(Non-remnant)
Remnant
Non-remnant
Remnant
Non-remnant
20.2 Woodlandsdominatedbywhitecypresspineorcoastcypresspine 5.4 3.1 0.8 0.0 9.3 9.3 1 1 1 1
21.1 Melaleucadryopenforestonsandplainsordepositionalplains 7.8 3.7 1.4 2.0 14.9 14.9 1 1 1 1
21.2 Melaleucadrywoodlandsonsandplainsordepositionalplains 3.7 3.4 0.6 1.0 8.7 8.7 1 1 1 1
21.3 Shrublandassociatedwithmelaleucadrywoodlandsonsandplainsor depositionalplains
4.3 2.3 0.9 0.0 7.5 7.5 1 1 1 1
21.6 Sparselyvegetatedareasassociatedwithmelaleucadrywoodlandson sandplainsordepositionalplains
2.5 0.2 1.8 0.0 4.5 4.5 3 3 2 2
22.1 Melaleucaopenforestsonseasonallyinundatedlowlandcoastalswamps 15.4 8.0 3.0 2.0 28.4 28.4 1 1 1 1
22.2 Melaleucawoodlandsonseasonallyinundatedlowlandcoastalswamps 10.6 7.1 1.0 1.0 19.7 19.7 1 1 1 1
22.3 Shrublandassociatedwithmelaleucawoodlandsonseasonallyinundatedlowlandcoastalswamps
4.3 2.3 0.9 0.0 7.5 7.5 1 1 1 1
22.5 Sedgelandassociatedwithmelaleucawoodlandsonseasonallyinundatedlowlandcoastalswamps
6.0 5.0 1.8 1.0 13.8 13.8 3 1 2 1
23.2 Mulgadominatedwoodlandsonredearthplains,sandplainsorresiduals 1.2 3.6 0.2 0.0 5.0 5.0 1 1 1 1
23.3 Shrublandassociatedwithmulgaonredearthplains,sandplainsorresiduals. 1.4 3.2 0.1 0.0 4.7 4.7 1 1 1 1
23.4 Grasslandassociatedwithmulgaonredearthplains,sandplainsorresiduals 1.6 3.3 0.3 0.0 5.2 5.2 2 2 1 1
24.1 Acaciaopenforestonresiduals 6.9 2.6 0.6 0.0 10.1 10.1 1 1 1 1
24.2 Acaciawoodlandsonresiduals 4.5 2.8 0.9 0.0 8.2 8.2 1 1 1 1
24.3 Acaciashrublandsonresiduals 2.6 2.1 2.1 0.0 6.8 6.8 1 1 1 1
24.4 Grasslandcommunitiesassociatedwithacaciaonresiduals 1.6 3.3 0.3 0.0 5.2 5.2 2 2 1 1
24.6 Sparselyvegetatedareasassociatedwithacaciaonresiduals 0.3 3.6 0.0 0.0 3.9 3.9 3 3 2 2
25.1 Brigalowbelahopenforestsonheavyclaysoils 10.5 2.6 1.9 0.0 15.0 15.0 1 1 1 1
25.2 Brigalowbelahwoodlandsonheavyclaysoils 3.4 2.1 0.7 0.0 6.2 6.2 1 1 1 1
25.3 Shrublandcommunitiesassociatedwithbrigalowbelahonheavyclaysoils 2.0 1.4 0.4 0.0 3.8 3.8 1 1 1 1
26.1 Gidgeeblackwooddominatedopenforest 6.0 1.0 1.4 0.0 8.4 8.4 1 1 1 1
26.2 Gidgeeblackwoodwoodland 2.0 1.6 0.2 0.0 3.8 3.8 1 1 1 1
26.3 Shrublandcommunitiesassociatedwithgidgeeblackwoodwoodland 1.4 1.9 1.5 0.0 4.8 4.8 1 1 1 1
35
Vegetation hazard class descriptions and 80th percentile potential fuel load
Vegetation hazard class
Potentialfuelload(t/ha) Prone type46
Fuel continuity47
Surf
ace
Near-surface
Elevated
Bark
Total(Remnant)
Total(Non-remnant)
Remnant
Non-remnant
Remnant
Non-remnant
27.1 Mixedspeciesopenforestsdominatedbywesternwhitewood,boreeorwoodeddowns
2.1 0.7 0.1 0.0 2.9 2.9 1 1 1 1
27.2 Mixedspecieswoodlandsdominatedbywesternwhitewood,boreeor woodeddowns
2.0 2.5 0.3 0.0 4.8 4.8 1 1 1 1
27.3 Shrublandcommunitiesassociatedwithmixedspecieswoodlands 1.0 0.9 0.1 0.0 2.0 2.0 1 1 1 1
27.4 Grasslandcommunitiesassociatedwithmixedspecieswoodlands 0.1 4.0 0.0 0.0 4.1 4.1 2 2 1 1
27.5 Sedgelandcommunitiesassociatedwithmixedspecieswoodlands 1.6 4.3 0.1 0.0 6.0 6.0 1 1 1 1
28.1 Openforestsincoastallocationswithspeciessuchasshe-oakorswampbox 22.2 2.7 2.0 0.0 26.9 26.9 1 1 1 1
28.2 Woodlandsincoastallocationswithspeciessuchasshe-oakorswampbox 13.8 3.2 1.3 0.0 18.3 18.3 1 1 1 1
28.3 Shrublandassociatedwithwoodlandsincoastallocation 12.2 2.2 2.5 0.0 16.9 16.9 1 1 1 1
28.4 Grasslandassociatedwithwoodlandsincoastallocations 8.0 2.4 2.0 0.0 12.4 12.4 1 1 1 1
28.5 Sedgelandassociatedwithwoodlandsincoastallocations 6.0 5.0 3.5 1.0 15.5 15.5 1 1 1 1
28.6 Sparselyvegetatedareasassociatedwithwoodlandsincoastallocations 1.0 1.0 1.3 0.0 3.6 3.6 3 3 2 2
29.1 Forestsassociatedwithheathlandsandscrubs 18.1 2.6 3.2 1.0 24.9 24.9 1 1 1 1
29.2 Woodlandsassociatedwithheathlands,scrubsandshrublands 12.0 4.8 7.5 0.0 24.3 24.3 1 1 1 1
29.3 Heathlandsandassociatedscrubsandshrublands 11.6 2.9 5.6 0.0 20.1 20.1 1 1 1 1
29.4 Grasslandcommunitiesassociatedwithheathlands,scrubsandshrublands 4.8 4.4 2.0 0.0 11.2 11.2 1 1 1 1
29.5 Sedgelandcommunitiesassociatedwithheathlands,scrubsandshrublands 3.0 5.0 3.5 0.0 11.5 11.5 1 1 1 1
29.6 Sparselyvegetatedareasassociatedwithheathlands,scrubsandshrublands 0.0 2.1 0.5 0.0 2.6 2.6 3 3 2 2
30.2 WoodlandsassociatedwithMitchellgrassorbluegrass 1.0 2.9 0.1 0.0 4.0 4.0 1 1 1 1
30.3 ShrublandsassociatedwithMitchellgrassorbluegrass 0.8 2.0 1.4 0.0 4.2 4.2 1 1 1 1
30.4 Mitchellgrassorbluegrasstussockgrasslands 0.8 4.0 0.0 0.0 4.8 4.8 2 2 1 1
30.5 SedgelandsassociatedwithMitchellgrassorbluegrass 1.6 4.3 0.1 0.0 6.0 6.0 1 1 1 1
31.2 Woodlandsassociatedwithinlandforblandstotussockgrasslands 1.0 3.0 0.7 0.0 4.7 4.7 1 1 1 1
31.3 Shrublandsassociatedwithinlandforblandstotussockgrasslands 0.8 2.0 1.4 0.0 4.2 4.2 1 1 1 1
31.4 Mixedopenforblandstotussockgrasslandsininlandlocations 0.6 2.1 0.1 0.0 2.8 2.8 2 2 1 1
31.5 Mixedopensedgelandsassociatedwithinlandtussockgrasslands 0.6 0.2 0.1 0.0 0.9 0.9 3 3 2 2
36
Bushfire Resilient Communities – October 2019
Vegetation hazard class descriptions and 80th percentile potential fuel load
Vegetation hazard class
Potentialfuelload(t/ha) Prone type46
Fuel continuity47
Surf
ace
Near-surface
Elevated
Bark
Total(Remnant)
Total(Non-remnant)
Remnant
Non-remnant
Remnant
Non-remnant
32.2 Woodlandsassociatedwithcoastalclosedtussockgrasslands 2.4 4.4 0.0 0.0 6.8 6.8 1 1 1 1
32.3 Shrublandassociatedwithcoastalclosedtussockgrasslands 0.8 2.0 1.4 0.0 4.2 4.2 1 1 1 1
32.4 Closedtussockcoastalgrasslands 2.1 3.6 0.3 0.0 6.0 6.0 2 2 1 1
33.3 ShrublandsassociatedwithHummockgrasslands 0.8 2.0 1.4 0.0 4.2 4.2 1 1 1 1
33.4 Hummockgrasslandsdominatedbyspinifexorsandhillcanegrass 0.6 1.2 0.2 0.0 2.0 2.0 2 2 1 1
33.5 SedgelandassociatedwithHummockgrasslands 0.4 1.1 1.2 0.0 2.7 2.7 3 3 2 2
34.1 Openforestdominatedwetlands 6.0 3.4 5.3 1.7 16.4 16.4 1 1 1 1
34.2 Woodlanddominatedwetlands 2.5 4.0 0.2 1.3 8.0 8.0 1 1 1 1
34.3 Shrublanddominatedwetlands 1.3 3.3 2.3 0.0 6.9 6.9 1 1 1 1
34.4 Grassdominatedwetlands 1.0 4.0 0.0 0.0 5.0 5.0 2 2 1 1
34.5 Sedgelanddominatedwetlands 3.0 5.0 5.0 0.0 13.0 13.0 1 1 1 1
34.6 Sparselyvegetatedwetlands 1.1 3.1 0.0 0.0 4.2 4.2 3 3 2 2
35.1 Closedtoopenforestmangroves 0.0 0.0 0.0 0.0 0.0 0.0 3 3 2 2
35.3 Shrublandassociatedwithmangrovesandtidalsaltmarshes 0.0 0.0 0.0 0.0 0.0 0.0 3 3 2 2
35.4 Tidalsaltmarshes 1.0 2.9 0.2 0.0 4.1 4.1 2 2 1 1
35.5 Sedgelandassociatedwithmangrovesandtidalsaltmarshes 0.4 1.3 0.0 0.0 1.7 1.7 3 3 2 2
35.6 Sparselyvegetatedareasassociatedwithmangrovesandtidalsaltmarshes 0.9 1.9 0.2 0.0 3.0 3.0 3 3 2 2
36.1 Exotic&hardwoodplantation 22.3 1.5 1.2 1.0 26.0 26.0 1 1 1 1
37.1 Hoopplantations 3.0 2.0 0.0 0.0 5.0 5.0 3 3 2 2
38.4 Continuousdrylandcroppingandhorticulture 0.8 3.0 0.0 0.0 3.8 3.8 2 2 1 1
38.5 Discontinuousirrigatedcroppingandhorticulture 0.5 1.0 0.5 0.0 2.0 2.0 3 3 2 2
39.2 Lowtomoderatetreecoverinbuilt-upareas 2.0 3.0 2.0 1.0 8.0 8.0 3 3 2 2
40.4 Continuouslowgrassortreecover 0.5 4.0 0.5 0.0 5.0 5.0 2 2 1 1
41.4 Discontinuouslowgrassortreecover 0.5 2.0 0.5 0.0 3.0 3.0 3 3 2 2
42.6 Niltoverylowvegetationcover 1.0 1.0 0.0 0.0 2.0 2.0 3 3 2 2
43.6 Waterbodiesorverylowvegetationcover 0.0 0.0 0.0 0.0 0.0 0.0 3 3 2 2
Figure14:Vegetationhazardclassdescriptionsand80thpercentilepotentialfuelload.Source:QFES,2017.
37
Figure15:Lifeform,heightandrelativedensityofvegetationstructuralclasses.Source:QFES,2017.
Figure16:Vegetationstructuralclasses.Source:QFES,2017.
Density
Life form | Height 1. Closed 2. Mid-dense 3. Sparse 4. Very sparse
Trees
Tall 30 m+ 1.Treesclosed–middense
1.Treesclosed–mid-dense
2.Treessparse–verysparse
2.Treessparse–verysparse
Medium 10–30m 1.Treesclosed–middense
1.Treesclosed–middense
2.Treessparse–verysparse
2.Treessparse–verysparse
Low 2–10m 1.Treesclosed–middense
1.Treesclosed–mid-dense
2.Treessparse–verysparse
2.Treessparse–verysparse
Sclerophyllous shrubs
Tall 2–8m 3. Shrubland 3. Shrubland 3. Shrubland 3. Shrubland
Medium 1–2m 3. Shrubland 3. Shrubland 3. Shrubland 3. Shrubland
Low <1m 3. Shrubland 3. Shrubland 3. Shrubland 3. Shrubland
Succulent shrub land
Low <2m 3. Shrubland 3. Shrubland 3. Shrubland 3. Shrubland
Low vegetation
Tussock grassland Low <2m
4.Grassland 4.Grassland 4.Grassland 4.Grassland
Hummock grassland Low <2m
4.Grassland 4.Grassland 4.Grassland 4.Grassland
Herbland Low <2m
5.Sedgeland 5.Sedgeland 5.Sedgeland 5.Sedgeland
Forbland Low <2m
5.Sedgeland 5.Sedgeland 5.Sedgeland 5.Sedgeland
Fernland Low <2m
5.Sedgeland 5.Sedgeland 5.Sedgeland 5.Sedgeland
Vineland Low <2m
5.Sedgeland 5.Sedgeland 5.Sedgeland 5.Sedgeland
Sedgeland Low <2m
5.Sedgeland 5.Sedgeland 5.Sedgeland 5.Sedgeland
Nil veg 6.Nilveg 6.Nilveg 6.Nilveg 6.Nilveg
Vegetation structure class Dominant life form Density
1.Treesclosed–mid-dense Trees Closedtomid-dense
2.Treessparse–verysparse Trees Sparsetoverysparse
3. Shrubland Shrubland Closedtoverysparse
4.Grassland TussockorHummockgrassland Closedtoverysparse
5.Sedgeland Herbland,forbland,fernland, vinelandorsedgeland
Closedtoverysparse
6.Nilveg Nilvegetation Nilvegetation
7. PROCESS FOR CALCULATING ASSET PROTECTION ZONES
38
Bushfire Resilient Communities – October 2019
39
7. Process for calculating asset protection zones
7.1 Introduction
Thissectionisapplicablewherealocalgovernment’splanningschemecontainsprovisionsthatidentifyacceptableradiantheatfluxlevelstoinformassetprotectionzones(APZs).Theradiantheatflux(kW/m2)outputisgeneratedbytheBushfireassetprotectionzonewidthcalculator(thecalculator).
Thecalculatorcanbeusedtodetermineradiantheatexposure,whichthenenablesanapplicanttoidentifythenecessarylotboundarylocationorbuildinglocationplansitingforexample,toachievetheradiantheatfluxoutcomessoughtbytheplanningscheme.
Alocalgovernmentmaywishtoreferapplicantstothistechnicalguidancedocumentorprovideinformationaboutthecalculatorinitsplanningscheme(e.g.asaplanningschemepolicy).ThecalculatoriscontainedinaMicrosoftExcelspreadsheet(.xls)andcanbedownloadedfromQueenslandGovernmentdataathttps://data.qld.gov.aubysearching‘bushfiredefendablespacewidthcalculator’.
Thecalculatorisalsoapplicabletootherassessmentsand,assuch,thissectionincludescontentonthoseadditionaluses.
7.2 Purpose of the Bushfire asset protection zone width calculator
Thecalculatorcalculatesfirelineintensity,radiantheatfluxandassetprotectionzonewidthusingeitherthebushfireproneareamappinginputdataorthesitespecificinputdata.
ThecalculatorisbasedontheviewfactormethodequationsdescribedinMethod2(Appendix2)ofAS3959–2018.ThecalculatoradaptsthismethodQueensland-specificparameterstoreflecttheinputparametersadoptedbytheStatePlanningPolicyJuly2017(SPP)mappingofbushfireproneareas(Leonardetal.,201448),includingFFDI(5%AEPfireweatherevent)andvegetationhazardclasses(VHCs).
Thecalculatorenablesrapidcalculationof:
1. Potential fireline intensity (kW/m)–therateofenergyreleaseperunitlengthoffirefront,regardlessofitsdepth
2. Bushfire prone area intensity classes–theclassapplicabletolandinaccordancewiththemedium,highandveryhighpotentialbushfireintensityclassesusedintheStatePlanningPolicyInteractiveMappingSystem(SPPIMS)bushfireproneareamapping
3. Radiant heat flux (kW/m2)–accordingtoseparationbetweendevelopmentandhazardousvegetation.
Note–Radiantheatexposure,togetherwithflamecontactandemberattack,arethemainmechanismsofbushfireattackandareimplicatedinlossoflifeandhousesanddamagetoinfrastructure49,50.Atcertainlevelsofradiantheatexposure(timedependent),pilotedignitionoftimberoccurs.51Housesexposedtolevelsofradiantheatwhichexceed40kW/m2arealsoexposedtoacombinationofbushfireattackmechanismsincludingdirectflamecontactandemberattack.
Adistanceneededtoachieve29kW/m2also:
• reducespotentialexposuretobushfireattack,particularlydirectflamecontact
• reducesthelikelihoodofpilotedignitionduetoradiantheatexposure
• improvesconsistencybetweenplanningandbuildingoutcomes
• reducespotentialforconflictsbetweenplanningandbuildingapprovals
• avoidsduplicationandregulatoryburdenonhomeowners.
Adistanceneededtoachieve10kW/m2alsofallsbelowthethresholdforpilotedignitionofdrytimberandfailureofplainglass.
7.3 Options for calculating the radiant heat exposure
Radiantheatexposuremaybecalculatedusingeither:
1. TheBushfireassetprotectionzonewidthcalculator(preferred),or
2. Method2ofAS3959¬–2018¬,subjecttotheadoptionofsite-specificvaluesofFFDI(5%AEPfireweatherevent),site-specificvegetationhazardclasses,modifiedmodellingofsurfacefuelloads52andeffectiveandsiteslopesdeterminedinaccordancewiththehazardassessmentprocessinsection5.4.
Theprocedureinvolvesthreesteps:
1. Identificationormeasurementofsitespecificbushfirehazardfactorsviathehazardassessmentprocessinsection5.4.
2. Measurementofthedistancebetweenthedevelopmentandhazardousvegetationviafieldmeasurementsorscaledplans.
3. CalculationofradiantheatexposureusingtheBushfireassetprotectionzonewidthcalculator(orMethod2ofAS3959¬–2018subjecttotheadoptionofthesitespecificvaluesandparametersdescribedabove).
7.4 Bushfire asset protection zone width calculator components
TheBushfireassetprotectionzonewidthcalculatorhasthreecomponents:
1. Inputvalues–userinputsnecessarytooperatethecalculatorcorrectly.
2. Outputvalues–fuelloadsforselectedinputvaluesand,whereapplicable,thecalculatorestimatesofradiantheatflux,firelineintensityand/orbushfireattacklevel.
3. VHCdata–vegetationhazardclasscharacteristicsincludingfuelloads,fuelcontinuityandpronetypeaccordingtoremnantstatus.
Figure17showsascreenshotofthecalculatorstartscreendisplayingtheinputandoutputvaluesfields.
48 Leonard, J, Opie, K et al. (2014), A new methodology for State-wide mapping of bushfire-prone areas in Queensland.49 Blanchi, R, Leonard J, et al. (2014), Environmental circumstances surrounding bushfire fatalities in Australia 1901–2011.50 Crompton, R et al. (2010), Influence of location, population, and climate on building damage and fatalities due to
Australian bushfire: 1925–2009.51 The long term unburnt condition represents greater than 10 years without burning. For further information see Leonard,
J, Opie, et al. (2014), A new methodology for State-wide mapping of bushfire-prone areas in Queensland.52 Total potential fuel loads (non-remnant) do not include surface, near-surface, elevated and bark fuel loads.
40
Bushfire Resilient Communities – October 2019
Parameter Process to identify calculator value
Fireweatherseverity(FWS) Determinedinaccordancewiththehazardassessmentstageinsection5.4.2(1)
Vegetationhazardclass(VHC)IdentifyVHCwithintheassessmentareafromthemappinginputsforVHCs(asdescribedinsection6)orviabotanicalsurveyinaccordancewiththehazard
assessmentstageinsection5.4.2(2)andsection6
RemnantstatusIdentifywhethertheVHCisremnantvegetationasdefinedinthe VegetationManagementAct1999(Qld)ornon-remnantvegetation.
SlopetypeIdentifywhethertheproposeddevelopmentisupslope ordownslopeofhazardousvegetationinaccordancewith section5.4.2(3)orclause2.2.5ofAS3959–2018)
Effectivefireslope Identifytheslope(degrees)ofthelandunderhazardousvegetationfor eachVHCinaccordancewithsection5.4.2(3)
SiteslopeIdentifytheslope(degrees)ofthelandbetweenthesiteandhazardous
vegetationforeachVHCinaccordancewithsection5.4.2(3)
Distancefromhazardous vegetation
Measuretheassetprotectionzonewidthbetweenthedevelopmentand adjacenthazardousvegetationinaccordancewithsection5.5.2(1)
7.5 Bushfire asset protection zone width calculator input parameters
Thecalculatorrequiresseveninputparameters.Valuesforeachoftheseparametersshouldbedeterminedbeforeusingthecalculator,asoutlinedbelow:
Whereareliabilityassessmenthasbeenundertakenandtheresultsofallstepsindicatetheinputmappingisreliable,themappinginputdatashouldbeusedforthecalculationofradiantheatflux.
Whereasitespecificassessmentofinputfactorshasbeenundertaken,thedatafromsteps1to3insection5.4.2shouldbeusedforthecalculationofradiantheatflux.
Furtherinformationinrelationtoeachparameteranditsroleinthecalculationofradiantheatfluxisoutlinebelow.
7.5.1 Fire weather severity
EquivalenttotheMcArthurForestFireDangerIndex(FFDI)535%AEPfireweatherevent.54
53 Total potential fuel loads (non-remnant) do not include surface, near-surface, elevated and bark fuel loads.
54 McArthur, AG (1967), Fire behaviour in eucalyptus forests.55 Noble, IR et al. (1980), McArthur’s fire-danger meters expressed as equations. 56 Cheney, NP et al. (2012), Predicting fire behaviour in dry eucalypt forest in
southern Australia. 57 McCaw, WL, et al. (2008), Existing fire behaviour models under-predict the rate
of spread of summer fires in open jarrah (Eucalyptus marginata) forest. 58 Cruz, MG et al. (2015) Empirical-based models for predicting head-fire rate of
spread in Australian fuel types.
59 McCaw, LW et al. (2012), Changes in behaviour of fire in dry eucalypt forest as fuel increases with age. 60 Noble, IR et al. (1980), McArthur’s fire-danger meters expressed as equations. 61 Cheney, NP et al. (2012), Predicting fire behaviour in dry eucalypt forest in southern Australia. McCaw, WL, et al. (2008), Existing fire behaviour models under-predict the rate of spread of summer fires in open
jarrah (Eucalyptus marginata) forest. Cruz, MG et al. (2015) Empirical-based models for predicting head-fire rate of spread in Australian fuel types. McCaw, LW et al. (2012), Changes in behaviour of fire in dry eucalypt forest as fuel increases with age. 62 Cruz, MG et al. (2015) Empirical-based models for predicting head-fire rate of spread in Australian fuel types.
Figure17:SPPBushfireassetprotectionzonewidthcalculatorstartscreen. Source:QFES,2019.
41
7.5.2 Vegetation hazard class (VHC)
ThevegetationwhichcontributestobushfirehazardandisclassifiedaccordingtoamodifiedversionofQueensland’sbroadvegetationgroups.55TheidentificationofVHCdetermineswhetherthevegetationcontributestobushfirehazard(pronetype).
ThepronetypeisacategoricalindicatorofthestatusofVHCwithrespecttoitscapacitytosupportasignificantbushfire.Thepronetypecategoriesare:
• ForestorShrubfires(1)
• Grasslandfires(2)
• Lowhazard(3).
AllQueenslandVHCsandtheirassociatedremnantandnon-remnantpronetypearelistedintheVHC_Datasheetofthecalculatorspreadsheet.
7.5.3 Remnant status
RemnantstatusisabinaryindicatorofwhethertheVHCisremnantvegetation,asdefinedintheVegetation Management Act 1999(Qld),orotherhazardous,non-remnantvegetation.Thedeterminationofremnantstatusestablishes:
• thetotalpotentialfuelloadvalueusedbythecalculator(‘Total(remnant)’or‘Total(Non-remnant)’)
• fuelcontinuity
• rateofspreadcalculationmethod.
ForcertainVHCs,thepronetypemayvaryaccordingtotheremnantstatusoftheVHC.Forexample,certainnon-remnantrainforestVHCsfrequentlyincludesignificantavailablefuelfromwoodyorweedspeciesandmayhaveapronetypeof1,whereasthesameremnantrainforestVHCmaybeconsidered‘lowhazard’.
Remnant vegetation,asdefinedintheVegetation Management Act 1999(Qld),includesrelativelyundisturbedwoodyornon-woodyvegetation.Woodyremnantvegetation–dominatedbytreesorshrubs–hasapredominantvegetationcanopy:
• coveringmorethan50percentoftheundisturbedpredominantcanopy
• averagingmorethan70percentofthevegetation’sundisturbedheight
• composedofspeciescharacteristicofthevegetation’sundisturbedpredominantcanopy.
Non-woody remnant vegetationhasnotbeencultivatedfor15years,containsnativespeciesnormallyfoundintheregionalecosystem,andisnotdominatedbynon-nativeperennialspecies.
ForremnantVHCs,thetotalpotentialfuelloadrepresentsthe80thpercentilefuelloadforeachfuelcategorybasedonthelongtermunburnt condition56(surfacefuel,near-surfacefuel,elevatedfuelandbarkfuelload).Totalpotentialfuelloads,includingsurface,near-surface,elevatedandbarkfuelloadsforeachVHCareindicatedintheVHC_Datasheetofthecalculatorspreadsheet.
Non-remnant vegetationincludeshazardouswoodyornon-woodyvegetationthathasthepotentialtosupportasignificant
bushfirewithinthedesignlifeofanewsettlementthatdoesnotmeetthestructuraland/orfloristiccharacteristicsforremnantvegetation.Thiscanincludenon-remnantrainforest,treeplantations,othernon-nativevegetation,regrowthvegetation,heavilythinned,loggedorsignificantlydisturbedvegetation,orvegetationwithinurbanorcroppingland.Totalnon-remnant,potentialfuelloadsforeachVHCareindicatedintheVHC_Datasheetofthecalculatorspreadsheet.57
Fuel continuityisabinaryindicatorofthecapacityofremnantornon-remnantvegetationtosupportacontinuousflamefrontunderarangeofweatherconditions.Continuousfuelvegetation(‘1’)generallyhasaconsistentdistributionoffuel.Discontinuousfueltypes(‘2’)includenon-hazardousvegetationorlanduses,suchasmangroves,built-upareasorwaterbodies.
Fuelcontinuityvariesaccordingtotheremnantornon-remnantstatusoftheVHC.Fuelcontinuityvaluesforbothremnantandnon-remnantcategoriesofeachVHCareindicatedintheVHC_Datasheetofthecalculatorspreadsheet.58
Fuelcontinuityalsovariesthecalculationoftheforwardrateofspread.RecentempiricalevidenceindicatesthattherateofspreadequationsusedinMethod2ofAS3959–2018underpredictrateofspread(andhencefirelineintensity)inopenforestandwoodlandswhenonlysurfacefinefuelsareusedinthecalculations.59,60,61Thereisstrongempiricalevidencewhichsuggeststhatnear-surfacefuelcharacteristics,togetherwithsurfacefuel,isabetterpredictorofrateofspreadformoderateandhighintensityfiresthansurfacefuelalone.62 To better reflectthecontributionofnear-surfacefueltorateofspread,surfacefuelload(w)iscalculatedasthesumofsurfaceandnear-surfacefuelsforopenforestandwoodlandVHCswherefueliscontinuous.Theresultisindicatedas‘TotalSurfaceFuelLoad’inthecalculator’soutputvaluestable.
7.5.4 Slope type
Slopetypereferstowhethertheeffectiveslopeisupslopeordownslope,inaccordancewithClause2.2.5ofAS3959–2018.Wheretheslopeofthelandcontaininghazardousvegetationisdownhillfromtheproposeddevelopmentorlotboundary,itisconsidered‘downslope’irrespectiveofthesiteslope.Wheretheslopeofthelandcontaininghazardousvegetationisuphill(orisflat)fromtheproposeddevelopmentorlotboundary,itisconsidered‘upslope’irrespectiveofthesiteslope.
7.5.5 Effective fire slope
Theeffectivefireslopeistheslopeunderhazardousvegetationindegrees(referalsotoAS3959-2018).Thisisavaluebetween1and20degreesdownslopeand1and15degreesupslope.
7.5.6 Site slope
Referstotheslopebetweenthesiteandhazardousvegetationindegrees(referalsotoAS3959–2018).Thisisavaluebetween1and20degreesdownslopeand1and15degreesupslope.
7.5.7 Distance from hazardous vegetation
Referstothehorizontaldistance(i.e.measuredinplan)ofthemanagedseparationarea(oftenreferredtoasassetprotection
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Bushfire Resilient Communities – October 2019
zonewidth)betweentheedgeofhazardousvegetation(edgeofcanopyforforest,woodlandandheathtypeVHCs)andthepointidentifiedinaplanningschemeofbuildingprovisions.Thisislikelytobe:
• theclosestpointonalotboundaryorabuildingenvelope
• externalwallofabuilding
• supportingpostsorcolumnsforpartsofthebuildingthatdonothaveexternalwalls(e.g.carports,decks,landingsetc.),asperAS3959–2018.
ThisdistanceisinformedbytheVHCandslopecombinationbetweenthedevelopmentandthehazardousvegetation.
Increasingseparationreducestheintensityofbushfireattack(expressedasradiantheatflux)towhichadevelopmentisexposed.
7.6 Parametric constraints and variations
ThecalculatorincorporatesanumberofparametricconstraintswhichapplyinQueensland.Thisinclude:
1. Thecalculatordoesnotpermitmanipulationofunderlyingdata.Forexample,inaccordancewithaBushfireHazardAssessment(BHA),thecalculatordeliberatelyprohibitsthecreationofuser-definedfuelloads.Consequently,ausermustnominateaVHCaccordingtotheproceduredescribedinsection5.4.2todeterminepotentialfirelineintensityandradiantheatflux.Userscanonlyselectfromoneofthelevel2VHCsdescribedinFigure14.
2. ‘Slopetype’isaBooleanoperatorforeffectiveslope,namelywhethertheeffectiveslopeunderhazardousvegetationisupslopeordownslopeofthesite.
3. Effectivefireslopeinputsarelimitedtovaluesbetween1and20degreesfordownslopeand15degreesforupslope.Siteslopeinputsarelimitedtovaluesbetween1and20degrees.Firelineintensityandradiantheatcalculationsforlocationswithaneffectiveslopeofgreaterthan20degrees(downslope)or15degrees(upslope)maybeunreliable.Intheselocations,specialistassessmentiswarranted.Landwheretheeffectiveorsiteslopeis‘flat’musthaveaminimumslopeof1degree.
4. Bushfireattacklevelisnotcalculatedwheredistanceofthesitefromhazardousvegetationisgreaterthan100metresinaccordancewithAS3959–2018andLeonardetal.(2014).63
5. Firelineintensity,radiantheatfluxandbushfireattacklevelarenotcalculatedfornon-bushfireproneVHCs(grassfireproneVHCs[pronetype=2]orlowhazardVHCs[pronetype=3]).RefertotheVHC_DatasheetofthecalculatorspreadsheetforalistofpronetypesforeachVHCaccordingremnantstatus.
6. ThecalculatordealsonlywithdiscreteVHCs.RadiantheatfluxandassetprotectionzonewidthsformixedorheterogeneousVHCscannotbecalculatedusing
thetool.ManualcalculationsarerequiredwhereVHCsareheterogeneousormixed,e.g.VHC9.1/VHC16.1(60%/40%).
Thecalculator’sinbuiltparameterrulesprevententryofinappropriatevaluesandmanipulationofunderlyingdataandassumptions,suchasmodelconstantsandmodelequations.Thisensuresquality,consistencyandreliabilityofmodeloutputs.
Method2ofAS3959–2018alsoincludesseveralconstantsandassumptionsforwhichdefaultparametersaresuggested.Forthepurposesofproducingafit-for-purposetool,thecalculatoradoptsthefollowingdefaultvalues:
• Ambienttemperature(Ta):308K(35oC)
• Heatofcombustion:18,600kJ/kg
• Flametemperature(T):1200K64
• Flameemissivity( ):0.95
• Flamewidth(Wf):100m
• Windspeed(V):45km/hr(forshrubandheathVHCsonly)
• Vegetationheight(H):8m65(forshrubandheathVHCsonly).
Theabovevaluesarenotvisibletousersandcannotbeedited.
7.7 Bushfire asset protection zone width calculator software and hardware requirements
ThecalculatorrequiresuserstohaveinstalledacopyofMicrosoftExcel2007orlater.Usersmusthavesufficientsecurityprivilegestoenabletheuseofmacrosfromwithintheprogram.
Procedureforfirsttimeuse:
1. Savethefiletoalocalharddriveoranetworklocation.
2. Whenthecalculatorisopenedforthefirsttime,asecuritywarningwillappear.Selecttheenable content button to turn the calculator on.
3. Iftheenable contentbuttonisnotvisible,trust centre settingsmayneedadjustment.Todothis:
a.gotofile > optionsandselecttrust centre
b. in trust centreselectthetrust centre settings button andonthenextscreennavigatetomacro settings
c. under the macro settingsmenu,checkdisable all macros with notification
d. click OKtoconfirmthissetting
e.closethecalculatorandreopenittoapplythischange– the enable contentbuttonshouldappearatthetopoftheworksheetasperstep1.
4. Tosavethecalculator,theautomaticrecalculationofthecalculatorwillneedtobedisabled.Todothis:
a. gotofile > optionsandselectformulas
b. checkthatworkbookcalculationischeckedtomanual and that recalculate workbook before savingisunchecked.
63 Leonard, J, Opie, K et al. (2014), A new methodology for State-wide mapping of bushfire-prone areas in Queensland. 64 Sullivan, AL et al. (2003), A review of radiant heat flux models used in bushfire applications. 65 Upper estimate of vegetation height of shrub and heath VHCs based on available CORVEG data: Queensland Herbarium (2012). Queensland CORVEG Database, Version 4/2017. State of Queensland (Department
of Science Information Technology and Innovation). Brisbane, Queensland Government Data Portal <https://data.qld.gov.au/>, accessed August 2019.
43
Figure18:SPPBushfireassetprotectionzonewidthcalculatoroutputvaluesandsampleresults.Source:QFES,2019.
7.9 Bushfire asset protection zone width calculator results
Thecalculatorallowsuserstoiterativelyassesstheeffectofchangestoinputvalues.Inparticular,theeffectofchangesinassetprotectionzonewidthonradiantheatfluxandbushfireattacklevel.
Reportedresultsinclude:
• Surfacefuelload(t/ha)
• Near-surfacefuelload(t/ha)
• Barkfuelload(t/ha)
• Elevatedfuelload(t/ha)
• Totaloverallfuelload(W)(t/ha)
• Totalsurfacefuelload66(w)(t/ha)
• Potentialfirelineintensity(kW/m)
• Radiantheatflux(kW/m2)
• Bushfireattacklevel,inaccordancewithAS3959–2018.
Modeloutputvaluesaredynamicandnotstored.Eachtimeauseraltersorentersnewinputvalues,resultswillneedtobere-calculatedbypressingthe‘Calculate’button.Userscanselect‘Copy Results’tocopytheinputsandresultsfordisplayinaBushfireManagementPlan(BMP)andtoassistindemonstratingcompliancewithassetprotectionzonewidthoutcomes.
Figure19showsanextractusingthe‘Copy Results’ button withinthetool.Copiedresultscanbeplaced/pasteddirectlyintoaBMPorequivalenttoexpediteassessmentoftheapplication.
66 Used to calculate the forward rate of spread for woodland and forest VHCs with fuel continuity.
7.8 Using the Bushfire asset protection zone width calculator
Thecalculatorrequiresseveninputsasdescribedinsection7.5:
1. Fireweatherseverity/FFDI(5%AEPfireweatherevent)–(CELLREF:D4)
2. Vegetationhazardclass(VHC)–(CELLREF:D5)
3. Remnantstatus–(CELLREF:D6)
4. Slopetype–(CELLREF:D7)
5. Effectivefireslope(eslope,degrees)–(CELLREF:D8)
6. Siteslope( ,degrees)–(CELLREF:D9)
7. Distancefromhazardousvegetation(d,metres)–(CELLREF:D10)
Figure18showsanexampleofthecalculatorinputscreenandexampledatainputs.
Oncethedatahasbeenentered,press‘Calculate’toassesswhethertheproposedseparationcomplieswiththeseparationoutcomessoughtbytheexampleplanningschemeprovisionsfoundintheSPPGuidanceMaterialforBushfire.N.B.Usersshouldusethe‘Calculate’buttonprovidedinthecalculatorsheetandnotMicrosoftExcel’scalculatebuttons.
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Bushfire Resilient Communities – October 2019
7.10 Default asset protection zone width formula
ThemodelprovisionswithinSPPguidancecontainadefaultseparationdistancetabletemplatethatcanbedevelopeduponrequesttoQueenslandFireandEmergencyServices(QFES).Thistablemaybeincludedwherealocalgovernmentseekstoprovideaquantifiableacceptableoutcomeforapplicantsthatremovestheneedtodetermineradiantheatfluxlevels.
APZwidthsarecalculatedusingamodifiedMethod2bushfireattacklevelassessmentfromAS3959-2018,usingconservativeinputs.WidthoutputsusethehighestFFDIandVHCfuelloadsforeachpotentialbushfireintensitycategorywithinthelocalgovernmentarea.Thisprocessandformulaaredescribedbelow:
1. Pre-treatmentoftheVHCdata.
AlldatashouldbeginassnappedtothesloperasterandprojectedinGDA1994AustraliaEqualAlbersprojection.
a. TheVHClayerasproducedisarasterdatasetwithanattachedlookuptable.ThetwocolumnsofinterestareVHC_NIBBLE,andFUELLOAD_NIB.Thesecolumnsaresplitusingthe‘ExtractbyAttributes’tool.Thisallowsthesetwofieldstobeusedwiththe‘Combine’tooltoproduceafastlookuptable.
b. TheBPAexistsasvectordata,butmustfirstbeconvertedtoraster.Using‘PolygontoRaster’,andselecting‘CLASS’asthevaluefield,withacellsizeof25,andsettingtheenvironmentvariable‘ProcessingExtent,Snapraster’tothe25mslopegrid,outputtoBPA_Mergedinageodatabase.
c. Theslopelayershouldbetreatedasthesnaprasterandclippedtotheareaofinterestforperformantoperationasitistypicallyawholeofstatedataset.
2. Combineusingthe‘Combine’tool.
a. Thefollowingshouldbecombinedandsavedinageodatabase:
> FFDI> Slope> FUELLOAD_NIB> VHC_NIBBLE> BPA_Merged.
ThiswillforcetherastertobesavedintheEsrigridformatandautomaticallyassociatealookuptablepreservingallvaluesfromtheinputraster.Thisinturnallowsfieldcalculationsbetweencolumns.Thisrasterwasnamed‘Combined_BPA_Slope_FFDI_VHC_Fuel’.
3. AddField.
a. Addafieldnamed‘Category’to‘Combined_BPA_Slope_FFDI_VHC_Fuel’.
4. CalculateFieldusingPython.
a. Thisprocesswillassignoneof12predefined categoriestoeachcellintherasterbasedonacombinationofslopeandBPA.FieldName‘Category’ExpressioncompareCalc(!slope_clipped!,!BPA_Merged!)
defcompareCalc(slope,bpa):
ifint(slope)<=4.9andint(bpa)==4:
return‘1’elif5.0<=int(slope)<=9.9andint(bpa)==4:return‘2’elif10<=int(slope)<=90andint(bpa)==4:return‘3’elifint(slope)<=4.9andint(bpa)==3:return‘4’elif5.0<=int(slope)<=9.9andint(bpa)==3:return‘5’elif10<=int(slope)<=90andint(bpa)==3:return‘6’elifint(slope)<=4.9andint(bpa)==2:return‘7’elif5.0<=int(slope)<=9.9andint(bpa)==2:return‘8’elif10<=int(slope)<=90andint(bpa)==2:return‘9’elifint(slope)<=4.9andint(bpa)==1:return‘10’elif5.0<=int(slope)<=9.9andint(bpa)==1:return‘11’elif10<=int(slope)<=90andint(bpa)==1:return‘12’else:return‘0’
5. Thetablemaybeexportedandinterrogated.
6. Shouldindividualcategorieswishtobequeried(e.g.a‘VeryHighBPA’and‘Highslope’),the‘ExtractbyAttributes’toolmaybeusedwithaSQLcommandofWhere‘Category=3’.
7. Thestepsfrom2onwardscanbesimplyandeasilymodelledtotheVHCorBPAtofacilitaterapidassessmentofanarea.
Figure19:Bushfireassetprotectionzonewidthcalculatoroutputvaluesandsampleresults.Source:QFES
45
8. PROCESS FOR PREPARING A BUSHFIRE MANAGEMENT, VEGETATION MANAGEMENT OR LANDSCAPE
MAINTENANCE PLANS
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Bushfire Resilient Communities – October 2019
8. Process for preparing a Bushfire Management, Vegetation Management or Landscape Maintenance Plans
8.1 Introduction
Thissectionisapplicablewherealocalgovernment’splanningschemecontainsprovisionsthatenableanapplicanttoprepareaBushfireManagementPlan(BMP)todemonstrateachievementoftheoutcomescontainedintheplanningscheme,forexample:
• reportingontheoutcomesofaBushfireHazardAssessment(BHA),or
• proposingdesignandmanagementmeasuresthatavoid,minimiseormitigatebushfireattackrisktoanacceptableortolerablelevel,or
• proposingmitigationstrategiesincludingvegetationmanagementorlandscapemanagement.
Assuch,aplanningschememayalsoincludeprovisionsforthepreparationofaVegetationManagementPlan(VMP)orLandscapeManagementPlan(LMP).
AlocalgovernmentmaywishtoeitherreferapplicantstothistechnicalguidancedocumentorprovideinformationaboutpreparingaBMP,VMPorLMPinitsplanningscheme(asaplanningschemepolicy,forexample).
8.2 Management plan reporting
Thefollowinginformationshouldbeincludedaspartofallmanagementplans:
• sitedetails,suchasrealpropertydescriptionandstreetaddress
• descriptionoftheproposeddevelopment
• detailsofanyrelevantpreviousapprovals.
8.3 Bushfire hazard reports and Bushfire Management Plans
Abushfirehazardreport–typicallycontainingtheresultsofaBHA–isoftenakeycomponentofaBMP.Thisbushfirehazardreport,ortheBMP,istoincludemapsandplansthatshow:
• vegetationhazardclass(VHC)surveylocationswithinthesiteassessmentarea
• theextentandconfigurationofVHCswithinthesiteassessmentareabeforeandafterdevelopment,includinganyvegetationtoberetained,revegetationareasand/orenvironmentaloffsets
• theextentofbushfireproneareas(firelineintensity)andpotentialimpactbuffer,potentialflamelengthandpotentialrateofspreadinrelationtothedevelopment.
AbushfirehazardreportshoulddetailtheassessmentmethodsandoutcomesofanyBHAthathasbeenundertakeninaccordancewiththehazardassessmentguidanceinsection5.4andistodocumenttheresultsofthatBHA,including:
• resultsofanyreliabilityassessment
• potentialfirelineintensity,potentialflamelength,potentialrateofspreadandradiantheatflux.
ABMPalsowillincludedetailsoftheproposedbushfireprotectionmeasures,suchas:
• separation,includingrecommendedassetprotectionzone,suchasdimensions
• siting,includingbuildingenvelopes
• landscapedesignandmanagement,andvegetationmanagementincludingfuelmanagementareas/zones
• accessandevacuationroutes
• watersupply.
8.4 Vegetation Management Plans
ThepreparationofaVMPmayincludemeasuresforthelong-termmanagementofvegetationinrehabilitationorrevegetationareasorofvaluablevegetation(forexample,whereclearingistobeminimised)toreducetheongoingriskofbushfiresonthesiteandinsurroundingareas.
Fuelmanagementdoesnotnecessitatetheremovalofallvegetation.Vegetationmanagementstrategiesmayinclude:
• retainingtreesaswidelyspacedindividualsorinclumpsthatcontributetolandscapedesignoutcomes,withoutsignificantlyincreasingfuelloadsortheseverityofbushfirehazard
• selectiveremovalofvegetationwhichfacilitatesemberattack,selectiveclearingofnativeunderstoreyvegetationandreplacementwithlow-flammabilityspecies(referFigure20).
8.5 Landscape Management Plans
ThepreparationofanLMPmayincludemeasuresforthedesignandlong-termmanagementoflandscapingwithinbushfireassetprotectionzones(APZs)tominimisethelevelofbushfireriskormechanismsofbushfireattack,providingareducedfuelareawhichiscompatiblewiththeassetprotectionzone.
Thesemeasuresmayinclude:
• landscapedesignthatreducesvulnerabilitytobushfireattack
• plantselectionthatavoidsorminimisesopportunitiesforignitionoflandscapingfeatures
• long-termlandscapemanagementarrangementsthatreduceexposuretobushfireattack.
Inaddition,theuseofbarriersthatlimittheimpactofdirectflamecontact,radiantheat,emberattackandwindcansupplementmeasurestargetingvegetationandfuelmanagement.
Strategiesthatsupporteachofthesemeasuresaredetailedbelow.
8.5.1 Landscape design
• Establishingaminimalfuelaroundbuildingsofanominal10metres.
• Ensuringflammablematerialsarenottouchingorclosetovulnerablepartsofbuildingssuchaswindows,decksandeaves.Thesematerialsinclude:
47
> flammableshrubsandtrees
> flammablemulchesorfences
> treeswherethecanopyoverhangsthebuilding
> climbingplantsorvinesincontactwithexternaltimberfascia,pergolas,posts,beamsand/ortrellis.
• Establishingnon-flammablefeaturessuchastenniscourts,swimmingpools,dams,maintainedlawns,drivewaysorpaths.
• Usingpathsanddrivewaysmadeofnon-combustiblematerialssuchasclay,concrete,gravelandpebbles.
• Ensuringpotentialhazardousfeaturesandout-buildingssuchassheds,coopsandmachinerystoragesaresitedwellawayfromthedevelopmentandpreferablyshieldedfrombushfireattackbyotherbuildingssotheyarenotconsumedandcontributetohazard.
• Ensuringthelayoutofgardenbeds,lawnsanddrivewaysorpathsareconfiguredtoavertthecontinuityoffuelloadswithinAPZs.ContinuousvegetationwithinAPZsassiststhespreadoffire.Byseparatinggardenbedsandclumpsoftreesorshrubswithareasoflowfuel,fuelcontinuityisbrokenup,reducingthepotentialrateofspreadandfireintensity.Examplesincludeplacingmaintainedlawns,pathwaysorpondsbetweenclumpsoftreesorshrubsandgardenbeds.
• Creatinggapsincanopytreesthroughselectiveclearingofexistingvegetationorplantinglayoutorensuringtreecanopiesdonotoverlap.Thismeasurereducesthepotentialspreadofcrownfires.
• Establishinglawnsubstitutesincludingnon-flammablegroundcoverssuchasdecorativestoneorgravel.
8.5.2 Plant selection
• Plantingormaintainingplantspecieswhichminimiseleaflitterdroptoreducetheaccumulationofsurfacefuel(e.g.persistentleaflitter).
• Plantingormaintaininglow-flammabilityspecies(e.g.appropriatelocalnatives)thatarealsoadaptedtolocalconditionsandenhancehabitatvaluesforwildlife.
Note–Environmentalweedsareoftengardenescapeesandcontributetofuelloads,increasingbushfirehazard.Examplesofthisinclude,lantana(Lantanacamara)andgambagrass(Andropogongayanus).
• Plantingormaintainingspecieswithattributes(suchasavoidingspecieswithfibrousbark)whichreducetheeaseofcombustion,minimisecontributiontopotentialfuelloadoractasapotentialbarrier,reducingtherateoffirespread.
• Figure20indicatesthecharacteristicsoflowflammabilityspeciesandtheeffectofplantattributesontheirperformanceinbushfiresituations.67
67 Ramsay, GC, and Rudolph, LS (2003), Landscape and building design for bushfire areas.68 Middlemann, MH (ed.) (2007), Natural hazards in Australia: Identifying risk analysis requirements.69 Neldner, VJ, Niehus, RE et al. (2015), The vegetation of Queensland: Descriptions of broad vegetation groups.
Version 2.0.
Plant attribute Effect Design measure
Foliagemoisturecontent Leaveswithhighermoisturecontentretardignitionandslowtherateofcombustion
Selectspecieswithhighleafmoisturecontent(e.g.rainforestspecies,succu-lentsandsemi-succulents)
Foliagevolatileoilcontent Foliagewithhighervolatileoilcontentignitemorereadilyandenhanceignitionofsurroundingvegetation,eventhoughvolatileoilsthemselvesdonotcontributesignificant-lytototalradiantheat
Selectspecieswithlowervolatileoilcontent68,69
Foliagemineralcontent Foliagewithhighermineralcontenttendtobelessflammable(e.g.Amyemasppmistle-toes)
Speciesselectionshouldfavourspecieswithhigherleafmineralcontent
Leaffineness Theratioofarea-to-volumeofleavesisoneofthemainfactorsaffectingeaseofignitionandintensityofburning.Finerleaves(greaterareatovolumeratio)tendtoigniteandburnmoreeasilythanbroaderleaves
Speciesselectionshouldfavourbroad-leafedspecies
Densityoffoliageandcontinuityofplantform
Specieswithcontinuous,denserfoliagecanactasabarriertowind-borneembersandradiantheat;however,increaseddensitycanincreaseflammability.Specieswithopenbranchingandlowfoliagedensityarelesseffectiveasabarrier,thoughcanbelessflammable
Selectspeciesonacase-by-casebasis
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Bushfire Resilient Communities – October 2019
Plant attribute Effect Design measure
Heightoflowestfoliage Shrubandtreespecieswithpersistentlowheightfoliagearemorelikelytobeignitedbysurfacefires,allowingthespreadoffiresintothecanopyabove
Speciesselectionshouldfavourspecieswhichcanbemaintainedorprunedtoreducepersistent,near-groundfoliage
Sizeofplant(volumeandspread) Theeffectofplantsizevariesaccordingtovolumeorspread.Specieswithagreaterspreadtendtobemoreeffectiveasabarriertothediffusionofradiantheatthannarrowertreeswiththesamevolume.Specieswithagreatervolumecanresultinincreasedemberattack,radiationandflameifignited.Forexample,narrowcolumnartreesarelesseffectiveasabarrierthanwidertreeswiththesameoverallvolume
Speciesselectionshouldensureplantsize(volumeandspread)doesnotincreaseignitionlikelihood
Deadfoliageonplant Persistentdeadleavesandwoodytwigsincreaseflammability
Speciesselectionshouldfavourspecieswhichhavealowvolumeofpersistentdeadleavesandwoodymaterialorcanbemaintainedorprunedtoreduce persistent,deadleavesandwoodymaterial
Barktexture Loose,flaky,stringy,paperyorribbon-likebarkcontributetoladderfuelswhich:• cancontributetodestructivecrownfires• actasapotentialsourceofflame,radiantheatandemberattack
Avoidspecieswithpersistentloose,flaky,stringy,paperyorribbon-likebark.Speciesselectionshouldfavoursmooth-barkedandtightly-heldbarkspecies
Potentialavailablesurfacefuel Theavailabilityofsurfacefuelisafunctionofvolume(quantity)andfineness.Thefirelineintensityincreasesinproportiontoavailablefinefuelquantity.Finefuelincludesdeadfallenmaterialsuchasleaves,bark,twigsandbranchesupto6mmindiameter(forest)andgrassgreaterthan5cminheight(grass-lands).Coarsefueligniteslessreadilybutmayburnforlonger
Speciesselectionshouldfavourspecieswhichdonotcontributesignificantlytopersistent,finegroundfuel
Figure20:Characteristicsoflowflammabilityspeciesandeffectonperformanceinbushfiresituations.Source:Ramsay, GC, and Rudolph, LS (2003), Landscape and building design for bushfire areas. (Same as footnote 67)
8.5.3 Landscape management
• Ensuringstreetandroadvergesandnaturestripscontaininghazardousvegetationareregularlypruned,mownorgrazed.
• Removingaccumulatedleaflitterandwoodydebrisatregularintervals.
• Keepingareasbeneathretainedorplantedtreesandshrubclearedoffuel.Thismayincludevegetationmanagementmeasuressuchas:
> canopyliftingtoreducenear-surfaceorladderfuelloadsandreduceflameheights
> clearingofunderstoreyvegetation
> removalofaccumulatedlitterandwoodydebris
> removalofloosebarkanddeadlimbsfromstandingtrees.
• Regularmowingorslashingofgrasstolessthan10centimetresinheight.
• Availabilityofreliableandsufficientwaterandinstallationofirrigationandsprinklersystemstocreateawell-wateredlandscape.
8.5.4 Barriers
• Selectionoflow-flammabilitytreesandshrubswithgoodbarrier-formingattributes,suchasrainforestspecies.
• Useofnon-combustiblefencesandretainingwalls,suchasstonewalls.
• Positioningnon-combustiblewatertanksatkeylocationstoactasradiantheatbarriers.
• Positioningbarrierplantingswheretheyarelikelytobemosteffective.Vegetationbarriersshouldbelocatedatasuitabledistancefrombuildingsorflammableobjects(suchasfences)sothat,ifignited,theflamescannotcomeintocontactwiththeseelements.
499. INFORMATION THAT MAY INFORM
DEVELOPMENT CONDITIONS
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Bushfire Resilient Communities – October 2019
9. Information that may inform development conditions
9.1 Static water supply
Whereaplanningschemecontainsanassessmentbenchmarkfortheprovisionofanappropriatestaticwatersupply,adevelopmentconditionmayspecifyhowthisistobeprovided.
Anappropriatestaticwatersupply(inbushfireproneareaswherereticulatedsupplyisnotprovided)tosupporteffectiveemergencyservicesresponseincludesawatertankthatisavailablesolelyforfirefightingpurposesandcanbeaccessedbyfirefightingappliances.Thewatertankistobeprovidedwithin10metresofeachbuilding(otherthanaclass10building),which:
a) iseitherbelowgroundlevelorofnon-flammableconstruction
b) hasatake-offconnectionatalevelthatallowsthefollowingdedicated,staticwatersupplytobeleftavailableforaccessbyfirefighters:
i. 10,000litresforresidentialbuildings
ii. forindustrial,commercialandotherbuildings,avolumespecifiedinAS2304–2011Waterstoragetanksforfireprotectionsystems
c) isprotectedfrombushfireattack,includingshieldingoftanksandpumpsinaccordancewithAS2304–2011Waterstoragetanksforfireprotectionsystems
d) allowsmediumrigidvehicle(15tonnefireappliance)clearaccesswithinsixmetresofthetank
e) ifservicedbyaruralfirebrigade,isprovidedwithruralfirebrigadetankfittingsofa50millimetreballvalveandmalecamlockcouplingand,ifunderground,anaccessholeof200millimetres(minimum)toaccommodatesuctionlines
f) isclearlyidentifiedbydirectionalsignageatthestreetfrontage.
9.2 Assembly and evacuation areas
Whereaplanningschemecontainsanassessmentbenchmarkfortheprovisionofasafeassemblyorevacuationarea,adevelopmentconditionmayarticulatehowthiscouldbeachieved.
Asafeassemblyorevacuationareamaybeasuitablealternativetoanevacuationroute,wherethesiteisinanisolatedlocation,andanyevacuationroutewouldbelongorpassthroughthebushfirepronearea.Asafeassemblyorevacuationareawouldinvolve:
• Establishingthesafeassemblyorevacuationareawithinthedevelopmentsiteandoutsidetheidentifiedbushfireprone area.
• Directroute/stothedesignatedareaaredesignedtoensure:
> roadshavesufficientcapacityfortheevacuatingpopulation
> occupantsaredirectedawayfromratherthantowardsorthroughareaswithagreaterpotentialbushfireintensity
> minimisingthelengthofroutethroughbushfireproneareas
> compliancewithAS3745–2010Planningforemergenciesinfacilitieswheredeemedappropriateforisolateddevelopments.
9.3 Protective landscape treatments
Developmentsshoulddemonstratethatlandscapingandopenspaceshaveapotentialavailablefuelloadoflessthan8tonnes/hectareonaggregate,andfuelstructurethatremainsdiscontinuous.Theserequirementsmaybeincludedinaplanningschemewherelandscapingandopenspacesaretocompriseprotectivelandscapetreatments.
9.4 Asset protection zones for vulnerable uses, storage or manufacture of materials that are hazardous and community infrastructure for essential services
SiteplanningwillformparttheriskmitigationapproachwherethesedevelopmentsareunavoidableinaBushfireProneArea,andconditionsunderPolicies6,7and8ofthisdocumentaremet.SiteplanningmayincorporateAPZsaspartofselectedriskmitigationtreatments.Thismayincludeadevelopmentfootprintplanthatisseparatedfromtheclosestedgetotheadjacentmappedmedium,highorveryhighpotentialbushfireintensityareabyadistance(APZwidth)thatachievesaradiantheatfluxlevelof10kW/m2orlessatalldevelopmentfootprintboundaries.
Section7inthisdocumentprovidesguidanceregardingtheprocessforcalculatingassetprotectionzones.
Note–Inadditiontothisguidance,theWorkHealthandSafetyAct2011andassociatedRegulationandGuidelines,theEnvironmentalProtectionAct1994andtherelevantbuildingassessmentprovisionsundertheBuildingAct1975containrequirementsforthemanufactureandstorageofhazardoussubstances.InformationisprovidedbyBusinessQueenslandontherequirementsforstoringandtransportinghazardouschemicals,availableat:www.business.qld.gov.au/running-business/protecting-business/risk-management/hazardous-chemicals/storing-transporting
Note–Existingclearedareasexternaltothesitemayonlybeusedincalculatingnecessaryseparationwheretenureensuresthatthelandwillremainclearedofhazardousvegetation(forexamplethelandisaroad,watercourseorhighlymanagedparkinpublicownership).
5110. EXPERTISE
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Bushfire Resilient Communities – October 2019
10. Expertise
10.1 Introduction
Thissectionisapplicablewherealocalgovernment:
• proposestoundertakeareviewofstatewideStatePlanningPolicyInteractiveMappingSystem(SPPIMS)bushfireproneareamappingaspartofplanning
• proposestoundertakeariskassessmentforbushfireinaccordancewithAS/NZ31000-2018Riskmanagement-guidelines,or
• containsprovisionsinaplanningschemefortheundertakingofaBHA,VegetationHazardClassAssessmentorBMPandpreparationofaBushfireHazardReportaspartofadevelopmentapplication.
10.2 Suitably qualified and experienced
Thepreparationoftheseplanningschemeprovisionsorapplicant-initiatedassessmentsandreportsshouldbeprepared(orpeer-reviewed)bysuitablyqualifiedandexperiencedpeople.Thesepeopleshouldhavethefollowingqualificationsandexperienceasastartingpoint:
• degree(AQFlevel8)qualificationsinenvironmentalscience,environmentalmanagement(orequivalentdiscipline)
• demonstratedexperienceinbotanicalsurveyandspatialanalysismethods,includinguseofgeographicinformationsystems(GIS)software
• demonstratedexperienceintheassessmentofbushfirehazardandrisksortechnicalqualificationsinenvironmentalscience,environmentalmanagement(oranequivalentdiscipline)
• demonstratedrelevantindustryexperienceintheassessmentofbushfirehazardandrisksforaminimumfiveyears.
Wherealocalgovernmentproposestoincludeadviceabouttheprocessforpreparationofapplicant-initiatedassessmentsinitsplanningscheme(asaplanningschemepolicy,forexample),itisrecommendedthatadviceonthenecessaryexpertisealsobeincluded.
53
11. Acronyms and abbreviations
APZ Assetprotectionzone
AEP Annualexceedanceprobability
AS3959–2018AustralianStandard3959–2018Constructionofbuildingsinbushfire-proneareas
BPA Bushfirepronearea
BMP BushfireManagementPlan
BVG Broadvegetationgroup
FDI FireDangerIndex
FFDI ForestFireDangerIndex
FWS Fireweatherseverity
IMS Interactivemappingsystem
LMP LandscapeManagementPlan
MCU Materialchangeofuse
NCC NationalConstructionCode
QFES QueenslandFireandEmergencyServices
RH Relativehumidity
RAL/ROL Reconfigurealot/reconfigurationoflot
SPP StatePlanningPolicy
SPPmap Statewidemapofbushfireproneareas(availableviatheSPPIMS)
SPPmapinputdataStatewidemapofbushfireproneareasinputdatae.g.FFDI(5%AEP),maximumlandscapeslopeandvegetationhazardclass
VHC Vegetationhazardclass
VMP VegetationManagementPlan
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Bushfire Resilient Communities – October 2019
12. Glossary
Asset Protection Zone (APZ)–aspecifiedareaoflandthatenablesemergencyaccessandoperationalspaceforfirefighting.VegetationismodifiedandmaintainedwithintheAPZtoreducefuelloadandmechanismsofbushfireattacksuchasflameandradiantheat.Thezonemayincludeacombinationofelementssuchasperimeterroad,firetrailandworkingareaandopenspacewherevegetationismanaged.
Note–Theassetprotectionzoneneednotbemaintained‘fuelfree’.Sensiblelandscapedesigncanensureabalancebetweenlandscapedesignoutcomesandminimisingthevulnerabilitytobushfireattack.Refertosection8.5inthisdocumentforguidanceonlandscapedesignandvegetationmanagement.
Note–Theassetprotectionzoneconsideredaspartofaplanningdevelopmentapplicationisdifferentfromthesitingofabuildingaspartofdesigningandconstructingthebuildingtoreducetheriskofignitionfromabushfire,appropriatetotheintensityofthebushfireattackonthebuildingandtheassociatedrequirementsprescribedinAS3959–2018Constructionofbuildingsinbushfireproneareasaspartofabuilding
developmentapplication.
Bushfire–agenericAustraliantermforanunplannedvegetationfirewhichincludesgrassfires,forestfiresandscrubfires.Bushfiresaresynonymouswiththeterms‘wildfire’(NorthAmerica,Asia,Europe,NewZealand)and‘veldtfire’(SouthAfrica).
Bushfire hazard–ahazardcanbedefinedasaconditionevent,orcircumstancethatcouldleadtoorcontributetoanunplannedorundesirableevent.Inthecontextofbushfires,hazardsincludesmoke,radiation,hotgases,airborneparticles,burningembers,fire-inducedwindsandflames.
Bushfire prone area–definedintheStatePlanningPolicy(SPP)asthespatialrepresentationofthenaturalhazardareaofbushfire,towhichthe‘Naturalhazards,riskandresiliencestateinterest’applies.Abushfireproneareaissometimesreferredtoasthebushfirehazardoverlay,
Note–A‘designatedbushfirepronearea’forapplicationofthebushfirebuildingcodesisdifferentfromthe‘bushfirepronearea’usedforlanduseplanningpurposes.However,itiscommonforlocalgovernmentsto
adoptthe‘bushfirepronearea’asthe‘designatedbushfirepronearea’.
A‘designatedbushfirepronearea’isdefinedbytheAustralianBuildingCodesBoardasanareadesignatedunderastatutorymechanismasbeingsubjectto,orlikelytobesubjectto,bushfires.Thedeclarationtypicallyoccursthroughstatebuildinglegislation.InQueensland,section12oftheBuildingRegulation2006(QLD)identifiesthatalocalgovernmentmay,inalocalplanninginstrument,designateallorpartofitsareaasadesignatedbushfireproneareafortheBuildingCodeofAustralia(BCA)orQueenslandDevelopmentCode(QDC).
BuildingdevelopmentapplicationsinadesignatedbushfireproneareaarerequiredtomeetthemandatorybushfireprovisionsintheNationalConstructionCode(NCC)series(BCA)andinAS3959–2018Constructionofbuildingsinbushfire-proneareas.BushfireprotectionprovisionsintheNCCapplytoClass1,2and3residentialbuildingsandaccommodationbuildingsandassociatedClass10astructuressuchasgarages,shedsandcarports.
TheNCCperformancerequirementisthat“abuildingthatisconstructedinadesignatedbushfirepronearea,musttothedegreenecessary,bedesignedandconstructedtoreducetheriskofignitionfromabushfire,appropriatetothepotentialforignitioncausedbyburningembers,radiantheatorflamegeneratedbybushfire;andintensityofthebushfireattackonthebuilding.”
TheNCCperformancerequirementisdeemedtobemetwherethebuildingcomplieswithAS3959–2018.AS3959–2018containsprovisionswhichcanbeusedinconstructiontoresistbushfires,toreducetherisktolifeandminimisetheriskofpropertyloss.Theseprovisionsincluderequirementsforburningdebrisandemberprotection,controlsonthecombustibilityofexteriormaterial,andtheprotectionofopenings,suchaswindowsanddoors.
AlocalplanninginstrumentdoesnototherwisedealwithbuildingmatterscoveredbyAS3959–2018.
Effective slope–theslopeundervegetationthatcontributestobushfirehazardinrelationtotheproposeddevelopmentorsiteboundary.Wheremultipleslopesoccurinrelationtoaproposeddevelopmentorsiteboundary,themaximumslopeunderhazardousvegetationisused.
Exposure–theelementswithinagivenareathathavebeen,orcouldbe,subjecttotheimpactofaparticularhazard.Exposureisalsosometimesreferredtoasthe‘elementsatrisk’andcouldincludethenumberandcharacteristicsofthevaluesorassetsexposed,wherethevaluesorassetscouldbetangibleorintangibleaspectsofenvironmental,social,cultural,economicorpolitical/reputationaldimensions.
Fine fuel–thatcomponentofthefuelthatburnsintheflamingzoneofabushfire.Practically,thisincludesdeadplantmaterialsuchasgrass,leaves,barkandtwigslessthan6millimetresthickandliveplantmateriallessthan2millimetresthick.Finefuelsaretypicallydescribedinstrataassurface,near-surface,elevated,bark(ontreeboles)andcanopyfinefuels.Thisdocumentonlyreferstofinefuel,soanyreferencetofuelshouldbetakentomeanfinefuel.
Fire weather severity–isequivalenttotheForestFireDangerIndex(FFDI),asdefinedinAS3959–2018,ascalibratedbythedocument‘AnewmethodologyforState-widemappingofbushfireproneareasinQueensland’.Itisbasedonathree-hourly,83kilometregriddedpredictionoftheFFDIfromlong-termspatialweatherproductsproducedbytheAustralianBureauofMeteorology(BoM).
FFDI–ForestFireDangerIndex.TheFFDIisameasureofthefrequencyofbushfireweathereventsthatinfluencethenatureofbushfirebehaviour.Theycanbemitigatedthroughlanduseplanning.TheFFDIisequivalenttoa5%annualexceedanceprobability(i.e.5%chanceofoccurringinanygivenyear).Theindexintegratesthecombinedeffectofarangeofweathervariablesincludinglong-termdryness,recentprecipitation,currentwindspeed,relativehumidityandtemperature.TheFFDI(5%AEP)indexhasbeencalculatedusingadjustedweatherdatatoreflectprojectedchangestoclimateby2050.
55
Hazard–aprocess,phenomenonorhumanactivitythatmaycauselossoflife,injuryorotherhealthimpacts,propertydamage,socialandeconomicdisruptionorenvironmentaldegradation.72Inthecontextofbushfires,hazardsincludesmoke,radiation,hotgases,airborneparticles,burningembers,fire-inducedwindsandflames.
Hazardous vegetation–vegetationthatcontributestofinefuelsandresultsinabushfirehazardwhenburnt.Areasthataremappedaseitherveryhigh,highormediumpotentialbushfireintensityincludepotentiallyhazardousvegetationthatcouldsupportasignificantbushfire.Thisvegetationisclassifiedandmappedashavingavegetationhazardclass.
Head fire–thepartofafireperimeterwheretherateofspread,flameheightandintensityaregreatest,usuallythepartofthefireperimetermostdownwindorupslope.
Maximum landscape slope–themaximumpotentialslopeofthelandscape,overa25metredistance,thatcouldinfluencetherateoffirespread.Thistermissynonymouswith‘effectiveslope’inthisdocument.
Mitigation–measurestakeninadvanceofabushfireeventthataimtodecreaseoreliminatethebushfire’simpactonsocietyandtheenvironment.
Potential fireline intensity–therateofenergyreleaseperunitlengthoffirefront,regardlessofitsdepth.Severalassumptionsunderpintheinputsforcalculatingthepotentialfirelineintensity,including:
• thefireignitionmustoccurinasuitabletimeandplace
• thefiremustarrivefullydevelopedatthetimeofthemaximumdailyFFDI
• theslopeintheadjacentgridmustbeatthemaximum
• thewinddirectionmustalignwiththeslope
• thefuelloadatthetimeofthefiremustmatchthepotential fuel load
Therefore,whilethefireweatherseverityis5%AEPlikelihood,whencombinedwiththeabovefactors,theactuallikelihoodislessbyanorderofmagnitude.
Potential impact buffer–thespatialrepresentationoftheportionsofabushfireproneareathatcompriselandsatriskofsignificantbushfireattackfromembers,flamesorradiantheat.Thepotentialimpactbuffersurroundsareasmappedaseitherveryhigh,highormediumpotentialbushfireintensity.
Risk assessment–theprocessofriskidentification,riskanalysisandriskevaluationdefinedinAS/NZSISO31000:2018andtheQueenslandEmergencyRiskManagementFramework(QERMF).
Site slope–theaverageslopeofthegroundbetweentheedgeoftheproposeddevelopmentorsiteboundaryandtheedgeofhazardousvegetation.
Vegetation hazard class–thevegetationthatcontributestobushfirehazardandisclassifiedaccordingtoamodifiedversionofQueensland’sbroadvegetationgroups.
Vegetation hazard area–tree,shrub,grassorcultivatedvegetationthatrepresentsapotentialfirehazard,andincludeshazardousvegetationandgrassfireproneareas.
Vulnerability–thecharacteristicsandcircumstancesofacommunity,systemorassetthatmakeitsusceptibletothedamagingeffectsofahazard.
70 Australian Emergency Management Institute (2015), National Emergency Risk Assessment Guidelines.71 Leonard, J., Newnham, G, et al. (2014), A new methodology for State-wide mapping of bushfire prone areas in
Queensland.72 United Nations Office for Disaster Risk Reduction (2017).
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Bushfire Resilient Communities – October 2019
13. Figures
Figure1:TherelationshipbetweentheStatePlanningPolicy(SPP)andtheSPPnaturalhazardsguidancematerial
Figure2: Overviewofbushfireplanningandassessmentprocesses
Figure3:Exampleofamappedbushfirepronearea,includingthepotentialimpactbuffer(landwithin100linearmetresofmappedvegetationofgreaterthan4,000k/Wmfirelineintensity)
Figure4: Methodforcalculationofpotentialfirelineintensity
Figure5: Potentialeffectsofradiantheat
Figure6:Vegetationhazardclass(VHC)codecomponents:broadvegetationgroupandvegetationstructureclass
Figure7. Characteristicsofappropriatesub-hectarearearemoval
Figure8: Characteristicsofeffectivefuelloaddowngradesforsmallpatches
Figure9. Characteristicsoftheeffectiveremovalofnarrowcorridors
Figure10. Characteristicsofeffectivesmallfragmentremoval
Figure11: AnoverviewoftheBushfireHazardAssessment(BHA)process
Figure12:Statewidemapofvegetationhazardclass(VHC)(left)andexampleofagroundtruthedmapofobservedVHCs(right)
Figure13:Fuelloadbasedonstatewidemapofvegetationhazardclass(VHC)(left)andexampleofafuelloadrasterbasedonobservedVHCs(right)
Figure14:Vegetationhazardclassdescriptionsand80thpercentilepotentialfuelload
Figure15: Lifeform,heightandrelativedensityofvegetationstructuralclasses.
Figure16: Vegetationstructuralclasses
Figure17: Bushfireassetprotectionzonewidthcalculatortoolstartscreen
Figure18:Bushfireassetprotectionzonecalculatordatainputvaluesandexampledatainputs
Figure19:Bushfireassetprotectionzonewidthcalculatoroutputvaluesandsampleresults
Figure20:Characteristicsoflowflammabilityspeciesandeffectonperformanceinbushfiresituations
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