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Bushfire Hazard Assessment - 11 Senegal Rise
ABN: 74 622 643 421
PO BOX 7044 SIPPY DOWNS QLD 4556
[email protected]
+61 412 788 532
Chris Bentley
BUSHFIRE HAZARD ASSESSMENT
Proposed Dwelling
11 Senegal Rise, Doonan
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TABLE OF CONTENTS
1.0 INTRODUCTION .................................................................................. 1
1.1 PURPOSE ........................................................................................................................................... 1
1.2 NOOSA COUNCIL BUSHFIRE HAZARD OVERLAY .................................................................................... 1
1.3 STATE PLANNING POLICY BUSHFIRE HAZARD OVERLAY ........................................................................ 2
2.0 SITE DESCRIPTION ............................................................................... 3
2.1 SURROUNDING LAND USES ................................................................................................................ 3
2.2 TOPOGRAPHY .................................................................................................................................... 3
2.3 VEGETATION ...................................................................................................................................... 4
3.0 BUSHFIRE HAZARD ASSESSMENT .......................................................... 5
3.1 STATE ASSESSMENT METHODOLOGY .................................................................................................. 5
3.1.1 General .............................................................................................................................. 5
3.1.2 Vegetation Hazard Classes ............................................................................................. 5
3.1.3 Maximum Landscape Slope ............................................................................................ 5
3.1.4 Forest Fire Danger Index................................................................................................. 6
4.0 LOCAL HAZARD MAP ..................................................................... 7
4.1 GENERAL ........................................................................................................................................... 7
4.2 PATCH AND CORRIDOR FILTERING ...................................................................................................... 7
4.3 CALCULATION OF POTENTIAL BUSHFIRE INTENSITY ............................................................................. 7
5.0 SETBACKS .................................................................................... 11
6.0 CONCLUSION ................................................................................ 12
7.0 REFERENCES ............................................................................... 13
LIST OF FIGURES
Figure 1: Noosa Plan 2020 bushfire hazard overlay .............................................................................. 1
Figure 2: State Planning Policy bushfire hazard mapping ..................................................................... 2
Figure 3: Surrounding land uses .......................................................................................................... 3
Figure 4: Open Eucalypt forest vegetation ........................................................................................... 4
Figure 5: Vegetation Hazard Classes .................................................................................................... 8
Figure 6: Sub Unit Map ........................................................................................................................ 9
Figure 7: Local Hazard Map ............................................................................................................... 10
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Job No. 20-052 Bushfire Hazard Assessment – 11 Senegal Rise, Doonan
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Disclaimer This assessment has been prepared by Urban Catalyst 3 Pty Ltd for Chris Bentley (Client) and may only be used and relied upon by the Client and Noosa Council for the purposes set out in Section 1.1 of this report. No responsibility is held to any person other than the Client for any decision or action arising from or in connection with this report. All implied warrantees and conditions are excluded to the extent permitted by law. All opinions and conclusions are based on assumptions detailed in this report and no responsibility is held for any error or omission arising from these assumptions being incorrect. This assessment has been based on site conditions present at the time of preparation and the setbacks and nature of the building proposed, relying on current hazard assessment methodologies as described in this report. These methodologies are not based on assessments of catastrophic bushfire events which may occur from time to time. By their nature, bushfires are unpredictable, and no guarantee is able to be provided or should be assumed that the area will not be affected by bushfire at some time. Property owners and tenants should be aware of the often unpredictable nature of bushfire and potential consequences of such events, and should be responsible for their property and personnel by being prepared for extreme events accordingly. Document Issue This document is the property of Urban Catalyst 3 Pty Ltd. Urban Catalyst 3 Pty Ltd ABN: 74 622 643 421 PO Box 7044 Sippy Downs QLD 4556 [email protected] +61 412 788 532 Revision No. Authorised for Issue Date Final D. Willis 19 July 2021 19 July 2021 Chris Bentley Page: iii Job No. 20-052 Bushfire Hazard Assessment – 11 Senegal Rise, Doonan
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1.0 INTRODUCTION
1.1 PURPOSE
This report documents the outcomes of a bushfire hazard assessment completed for land located
at 11 Senegal Rise for a proposed primary dwelling to be constructed within the site.
Particulars relating to the lot are as follows:
Real Property Description: Lot 120 on RP887986
Address: 11 Senegal Rise, Doonan
Area: 1.056ha
Tenure: Freehold
Owner: Chris Bentley
Improvements: The site is currently unimproved
1.2 NOOSA COUNCIL BUSHFIRE HAZARD OVERLAY
The application is for a material change of use development permit for construction of a primary
dwelling within the eastern extent of the site. The vegetated areas within the subject land are
mapped within a High Bushfire Hazard area under the Noosa Plan 2020. An associated Potential
Impact Buffer area extends 100m from the mapped hazard area and is mapped across the existing
cleared areas within the site in which the dwelling is proposed (refer Figure 1).
Figure 1: Noosa Plan 2020 bushfire hazard overlay
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1.3 STATE PLANNING POLICY BUSHFIRE HAZARD OVERLAY
The vegetated areas within the subject land are mapped within a Very High Bushfire Hazard area
under the State Planning Policy (SPP) bushfire hazard mapping. An associated Potential Impact
Buffer area extends 100m from the mapped hazard area and is mapped across the existing cleared
areas within the site in which the dwelling is proposed (refer Figure 2).
Figure 2: State Planning Policy bushfire hazard mapping
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2.0 SITE DESCRIPTION
2.1 SURROUNDING LAND USES
The subject land is located within a rural-residential landscape characterised by a mosaic of
cleared and vegetated areas. The largest patches of hazardous vegetation present within the
wider landscape consists of remnant vegetation contained within Livistona Park to the immediate
west of the subject land and the Tewantin section of Noosa National Park approximately 200m to
the north of the subject land. Semi vegetated rural-residential properties are located immediately
adjoining the subject site to the east and north. A plan showing surrounding land uses is included
as Figure 3.
Figure 3: Surrounding land uses
2.2 TOPOGRAPHY
The subject site is located on the mid to upper slope of a roughly north-westerly to south- easterly
aligned ridgeline. The dwelling is proposed on relatively flat land on the crest of the ridge, with
onsite vegetation located on moderate to steep southerly to south-westerly facing slopes
averaging 16-18 degrees. The site ranges from approximately 76m AHD in the north-east and
declines to approximately 33m AHD in the south.
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2.3 VEGETATION
The vegetation within the subject site consists of an open eucalypt forest with shrubby
understorey. Figure 4 depicts typical vegetation conditions within the assessment area.
Figure 4: Open eucalypt forest vegetation
A site assessment was undertaken on 6 July 2021. The open eucalypt forest vegetation unit was
observed to be approximately 30m high and dominated by species such as Eucalyptus microcorys
(tallow wood), E. propinqua (small-fruited grey gum), E. siderophloia (grey iron bark) and
Syncarpia glomulifera (turpentine) in the canopy. The mid-storey contained juvenile canopy as
well as species such as Lophostemon confertus (brush box), Allocasuarina littoralis (black she-oak)
and Alphitonia excelsa (red ash). A tall shrub/small tree layer was also observed and included
species such as Backhousia myrtifolia (grey myrtle), Acronychia laevis (glossy Acronychia) and
various Acacia species. The understorey contained a diverse range of native grasses, sedge and
fern species.
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3.0 BUSHFIRE HAZARD ASSESSMENT
3.1 STATE ASSESSMENT METHODOLOGY
3.1.1 General
The Noosa Plan 2020 requires a site-specific bushfire hazard assessment to be undertaken when
a development site is located within a mapped Bushfire Hazard Area. Chapter 2, Part 1, Section 8,
Item 4(a) of the Planning Act 2016 states that where there is an inconsistency between a State
Planning Policy and a local government planning instrument, a State Planning policy applies
instead of a local planning instrument. While Council’s Bushfire hazard overlay mapping ascribes
a high risk to the vegetation, the SPP nominates the area as a very high bushfire hazard. The SPP
mapping is therefore used as the trigger for assessment under Council’s Bushfire hazard overlay
code. Furthermore, the site-specific hazard mapping required by the Bushfire hazard overlay code
is to be prepared consistent with the more recent methodology adopted to prepare the SPP
mapping.
The State government have described the methodology used to prepare the SPP mapping in the
following publications:
• Natural Hazards, Risk and Resilience –– Bushfire State Planning Policy – state interest guidance
material (The Department of Infrastructure, Local Government and Planning, 2019)
• Bushfire Resilient Communities. Technical Reference Guide for the State Planning Policy State
Interest ‘Natural Hazards, Risk and Resilience - Bushfire’ (Queensland Fire and Emergency
Services, 2019).
The preparation of a Local Hazard Area Map has been undertaken for the site in accordance with
the methodology described in the above referenced documents. The input parameters used to
determine the bushfire hazard acting on the site are detailed in the sections below.
3.1.2 Vegetation Hazard Classes
Fuel loads need to be determined when preparing a bushfire hazard assessment. The Queensland
Fire and Emergency Services (QFES) refers to the process for identifying, classifying and mapping
vegetation hazard classes as a Vegetation Hazard Class Assessment. In accordance with the
methodology outlined in Section 6 of the Bushfire Resilient Communities (QFES (2019), the
following vegetation hazard classes (VHC) were identified within the assessment area (which
includes a 150m buffer surrounding the location of the subject site):
• VHC 9.1 – Moist to dry eucalypt open forests on coastal lowlands and ranges; and
• Vegetation Hazard Class 40.4 – Continuous low grass or tree cover.
3.1.3 Maximum Landscape Slope
The slope of land underlying the surrounding vegetation is generally steep and falling to the south
and south-west.
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3.1.4 Forest Fire Danger Index
The Queensland government produce a publicly available data package which includes selected
inputs and information used by the CSIRO in conjunction with the QFES to prepare the State-wide
Bushfire Hazard Area (Bushfire Prone Area) mapping (July 2014). The data includes Fire Weather
Severity (Fire Danger Index - FDI). A review of the dataset for the subject site indicates that the
site is located within a band of FDI 48.
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4.0 LOCAL HAZARD MAP 4.1 GENERAL The SPP reference documentation sets out the following methodology for preparing a Local Hazard Area Map: • Categorising the vegetation within the site in accordance with the vegetation hazard classes derived from QFES (2019) • Using the patch and corridor filtering process to remove narrow corridors and small patches of hazardous vegetation • Subdividing the identified vegetation hazard classes into bushfire hazard sub-units based on slope differences and vegetation hazard classes • Assigning SPP Potential Bushfire Intensity classes to the sub-units • Application of 100m Potential Impact Buffers to the amended sub-units to derive an overall Local Hazard Map. 4.2 PATCH AND CORRIDOR FILTERING Section 4.2.6 of Bushfire Resilient Communities (QFES (2019) outlines the patch and corridor filtering process to modify potential intensity of small patches and corridors (based on Leonard et. al. 2017). The process involves the following three stages: • Merging small patches of a single Vegetation Hazard Class less than 0.5 ha; • Merging small Vegetation Hazard Class patches between 0.5 and 1 ha with higher or moderate fuel loads (greater than 8 tonnes/ha); and • Removing narrow corridors of vegetation less than 50m wide through a process of patch erosion and dilation. These small patches are merged with surrounding vegetation by allocating a patch to the Vegetation Hazard Class that is most common to the patch boundary (Leonard et al., 2017). 4.3 CALCULATION OF POTENTIAL BUSHFIRE INTENSITY Potential Bushfire Intensity is calculated by inputting the site-specific input parameters discussed in Section 3.1 into the FLAMESOL computer model. FLAMESOL uses industry standard bushfire equations and allows numerous input variables to be adjusted including fuel loads, fire danger index, site slope and distance to vegetation. The table below details the Potential Bushfire Intensity classes and their corresponding potential fire-line intensity (KW/m) values as prescribed within Leonard et. al. 2017. POTENTIAL BUSHFIRE INTENSITY POTENTIAL FIRELINE INTENSITY Very High >40,000 kW/m High 20,000-39,999 kW/m Medium 4,000 – 19,999 kW/m Figures 5-7 are presented below and have been prepared as per the above referenced methodology. 19 July 2021 Chris Bentley Page: 7 Job No. 20-052 Bushfire Hazard Assessment – 11 Senegal Rise, Doonan
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LEGEND | SUBJECT SITE ccc" 1 ‘T 150m ASSESSMENT BUFFER L---4 [ VHC 8.1 - MOIST TO DRY EUCLAYPT OPEN FOREST [| VHC 40.4 - CONTINUOUS LOW GRASS OR TREE COVER (ZA VEGETATION REMOVED VIA PATCH AND CORRIDOR FILTERING URB AN C AT A LYST BUSHFIRE HAZARD ASSESSMENT a PRENER 90 T—— Ll a FIGURE 5 11 SENEGAL RISE, DOONAN VEGETATION HAZARD CLASSES
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Sub Unit 1 - Slope assessed as 1 degree due to Sub Unit being located uplsope or across slope relevant to the development area.
Combined | 5
Maximum | Potential .
Surface and ; ee Potential
| Total Fuel | Fire Weather | Landscape | Fireline .
Vegetation Hazard Class_| Near Surface . | Bushfire
Load (t/ha) | Severity (FDI) Slope Intensity .
Fuel Load (degrees) | (kav/m) Intensity
(t/ha)
VHC 40.4 - Continuous low ais 7 an a a raw.
grass or tree cover
Sub Unit 2
Combined . .
Maximum | Potential “
Surface and . Potential
| Total Fuel | Fire Weather | Landscape | Fireline ‘
Vegetation Hazard Class _| Near Surface . "| Bushfire
Load (t/ha) | Severity (FDI) Slope Intensity .
Fuel Load (Coreen meern| Intensity
(t/ha)
VHC 40.4 - Continuous low ag ie a 18 2,318 tow
grass or tree cover
Sub Unit 3
Combined | |
Maximum | Potential .
Surface and ; ee Potential
| Total Fuel | Fire Weather | Landscape | Fireline .
Vegetation Hazard Class _| Near Surface : | Bushfire
Load (t/ha) | Severity (FDI) Slope Intensity .
Fuel Load td y | tkw/m) Intensity
legrees) w/m
(t/ha) 5
IVHC 9.1 - Moist to dry
eucalypt open forests/oni 21 24.2 48 18 52,367 | Very High
coastal lowlands and
ranges
Sub Unit 4 - slope assessed as 1 degree due to Sub Unit being located uplsope or across slope relevant to the development area.
Combined Maxi ar
Surface and | at | cine weather | a x in '2"| Potential
Vegetation Hazard Class | Near Surface) US | Tite Nveainer | Landscape | rirelin€ | a hfire
Load (t/ha) | Severity (FDI) Slope Intensity i"
Fuel Load (a 1») tkw/m) Intensity
legrees w/m
(t/ha) s
VHC 9.1 - Moist to dry
eucalypt open forests on 7
21 24.2 48 4. 16,204 Medium
coastal lowlands and
ranges
LEGEND
[_] sussect site
{ "1 150m ASSESSMENT BUFFER
L---4
[___] Low POTENTIAL BUSHFIRE INTENSITY AREA
| MEDIUM POTENTIAL BUSHFIRE INTENSITY AREA
[7] VERY HIGH POTENTIAL BUSHFIRE INTENSITY AREA
URBAN CATALYST 3 firsenesarnise, DOONAN ee ®
L
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L.--4 [ LOW POTENTIAL BUSHFIRE INTENSITY AREA LJ MEDIUM POTENTIAL BUSHFIRE INTENSITY AREA LT VERY HIGH POTENTIAL BUSHFIRE INTENSITY AREA QQ) POTENTIAL IMPACT BUFFER AREA U R B A N Cc AT A LY I) BUSHFIRE HAZARD ASSESSMENT —— = 7 PREUIINARY Bora WT FIGURE 7 11 SENEGAL RISE, DOONAN —_—_— LOCAL HAZARD MAP
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5.0 SETBACKS
Modelling has been undertaken to determine the setbacks required for a new dwelling to be
constructed in the building envelope proposed adjacent to the existing cleared area of the site.
The setbacks detailed below correspond to the varying construction standards under AS3959
(Australian Standard 3959 (2018) Construction of buildings in bushfire-prone areas). The
vegetation to the south-east of the block has been merged with the cleared land on the adjacent
land given its separation from the balance of the vegetation to the west. To summarise the table
below, the new dwelling will require a minimum of 20.9m separation from the retained
vegetation within the site to achieve a BAL 40 construction standard, a minimum of 28m
separation to achieve a BAL 29 construction standard etc.
BAL
Setback Distance Required from Edge of Assessable Vegetation
Construction
Standard
BAL Flame 10 - <20.9m
Zone
20.9 – 28m
BAL 40
BAL 29 28 – 39.6m
BAL 19 39.6 – 53.5m
BAL 12.5 53.5 - 100m
All queries regarding building materials should be discussed with the architect and/or building
designer and confirmed to be compliant with the requirements of the AS 3959:2018 by a
registered building certifier.
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Job No. 20-052 Bushfire Hazard Assessment – 11 Senegal Rise, Doonan
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6.0 CONCLUSION
The Bushfire Hazard Assessment undertaken for Lot 120 on RP887986 located at 11 Sengal Rise,
Doonan has been prepared to assess the degree of bushfire hazard and potential bushfire risk
acting on the proposed construction of a primary dwelling within the north-east of the site. A
Local Hazard Map has been prepared for the site consistent with the State Planning Policy –
Natural Hazards, Risk and Resilience – Technical Manual. The Local Hazard Map has identified that
the proposed construction area is within a Potential Impact Buffer Area associated with the
adjacent Very High Potential Bushfire Intensity area.
Additional vegetation clearing is likely to be required to facilitate an acceptable BAL construction
standard under AS3959:2018, with vegetation clearing predominantly occurring to the west.
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7.0 REFERENCES
Leonard, J., Opie, K. (2017). Estimating the potential bushfire hazard of vegetation patches and
corridors. An enhancement of Queensland’s methodology for State-wide mapping of bushfire
prone areas. CSIRO Land & Water, Australia.
Queensland Fire and Emergency Services. (2019). Bushfire Resilient Communities - Technical
Reference Guide for the State Planning Policy - State Interest Guideline - Natural Hazards, Risk and
Resilience 2- Bushfire.
The State of Queensland, Department of State Development, Manufacturing, Infrastructure and
Planning (2019). Natural hazards, risk and resilience - Bushfire State Planning Policy – state
interest guidance material.
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Job No. 20-052 Bushfire Hazard Assessment – 11 Senegal Rise, Doonan