Seminar:

Bushfire Management Overlay

Subdivision Design

Focus on applying defendable space

March 2013

Bushfire Management Overlay (BMO)

• The BMO mapping is applied to the areas that have

the highest bushfire risk.

• A planning permit is required to subdivide land,

construct a building or construction or carry out

works.

• Applications in a BMO must meet the planning

provisions contained in:

Clause 44.06 – Bushfire Management Overlay; &

Clause 52.47 – Bushfire Protection: Planning

Requirements

Specific application requirements for subdivision

Locality and Site Description• Locality (Site) Plan

Bushfire management statement• Report

• Bushfire Site Assessment

• BMO Subdivision Plan

• Vegetation Management Plan

Relevant standards to address:

Subdivision

• BF1 (General requirements)

• BF2 (Residential lots)

All development

• BF3 (Location)

• BF4 (Siting and layout)

• BF5 (Bushfire protection measures)

Buildings and works

• BF6 (Defendable space for dwellings)

• BF7 (Defendable space for industry, office and retail)

• BF8 (Defendable space for other occupied buildings)

• BF9 (Defendable space location)

• BF10 (Water supply and access)

Clause 52.47 - Bushfire Protection: Planning Requirements

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The BMO objectives, standards and mandatory standards

(Clause 52.47)

Subdivision objective – Standard BF1 & BF2

Ensure that subdivision of land that would result in unacceptable risk

to human life is not permitted.

Standard BF1 (general – All lots to be created):

• Ensure all lots created are capable of providing bushfire protection measures

• For ten lots or more, consider need for perimeter road adjoining bushfire

hazard

Standard BF2 (Residential lots):

• Static water supply and access/egress that meet the needs of the relevant fire

authority.

• For ten lots or more, defendable space of a single dwelling to be BAL 19 or less.

• For less than ten lots, defendable space of a single dwelling to be BAL 29 or less.

Permit for a residential lot requires a section 173

agreement that sets out:

• Exemption from planning permit requirement for building and

works (i.e. construction of a dwelling) under Clause 44.06-1.

• Building envelope and defendable space to achieve approved

Bushfire Attack Level (BAL).

• Vegetation management requirements to implement defendable

spaces.

• Access and water supply requirements.

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Clause 44.06-4 Mandatory Condition for subdivision:

All development – Standard BF3, BF4 & BF5

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Essential that bushfire be considered early in the design process.

• Location objective - landscape scale (Standard BF3).

• Siting and layout objective (Standard BF4)

• Bushfire protection measures objective (Standard BF5)

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Subdivision - Location, Layout & Siting

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Subdivision - Location, Layout & Siting

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Defendable Space & Construction Requirements

- Mandatory Standards BF6.1, BF7.1 & 8.1

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Defendable space and construction requirements

• Must be calculated in accordance with Table 1 or 2 of

Clause 52.47 to limit radiant heat and ember attack

AS 3959-2009 Model

• In essence the calculation of radiant heat

under AS 3959 methodology determine:

• How a fire is likely to move across the landscape

• The flame length, and

• How this flame will emit radiation and how that

energy will be received by a structure

(Radiant heat exposure)

AS 3959-2009 Model

Defendable Space Table 1 & 2 of Clause 52.47

Bushfire Site Assessment (Example - Single Site)

Bushfire Site Assessment (Example - Subdivision)

Table – Vegetation, Slope, Construction Requirement & Defendable Space

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Subdivision – Defendable space location

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Subdivision - Defendable space location

Subdivision - Defendable space location

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Subdivision – communal (open space) areas

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Subdivisions that create public open space or communal land

• Management agreement to implement defendable space

- Agreement to be provided from responsible party

- Outline defendable space prescriptions

- To be applied in perpetuity

- Section 173 agreement where land is privately owned

• Management agreement to be implemented prior to

Statement of Compliance

Subdivision – communal (open space) areas

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Standard BF1 & BF2 – additional matters

• BF 1 subdivisions- defendable space should

adequately reflect the use of the land

- E.g. Rural land BAL 12.5 defendable space

- Siting constraints, landscape risk and

surrounding density of development may allow

for less defendable space than 12.5

• May consider a section 173 agreement for all

subdivisions (i.e. including rural land) for the

purpose of dwelling permit exemption, if

appropriate.

• Defendable space to be implemented prior to

Statement of Compliance

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Subdivision containing Existing Development

• Subdivision should not create a lot that would not

get a future permit to develop the land in line with

its zoning

• Existing buildings BAL defendable space

commensurate to existing construction standard

• Where BAL 12.5 defendable space is not being

achieved should demonstrate subdivision will not

increase the risk

• Defendable space on the allotment rather than

relying on a 173 Agreement

Proposal:

• Subdivision.

• Some lots are at significant

fire risk (possible flame

contact) and cannot achieve

BAL 40.

• Residential 1 (adjoining PUZ

– bushland reserve to the

south).

• Overlays: SLO, BMO, DPO,

ESO (Part).

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Subject land

Activity: Subdivision design

Activity: Existing subdivision pattern

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Bushland reserve (Woodland)

• Subject land located adjacent to

other residential estates (North,

East, and West).

• Predominately large lots

designed for single dwellings.

• Southern most lots exposed to

abutting bushland reserve

(significant fire risk – possible

flame contact).

• Lack of connectivity and

circulation to the south (poor

emergency access).

Activity: Existing characteristics

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• Some lots are at significant fire risk (possible flame

contact).

• If we had our time again, what subdivision design changes

could be made to achieve BAL 19?

Activity: Subdivision design

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Activity: Outcome of design review

• Southern-most lots exposed to

bushland reserve (significant fire

risk – possible flame contact).

• Remainder of subdivision has a

reduced fire risk.

• Full re-design not required.

• Re-design should consider the

risks posed to southern lots with a

view to redesigning these lots.

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Activity: Outcome – Establishing the main road network

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• Main and secondary

road network

identified.

• Majority of road

network to remain

unchanged.

• BAL 19 defendable

space (37 metres)

identified to assist in

restructuring the

southern perimeter

road network.

Activity: Outcome – Fire Access Tracks

• Fire Access

Tracks added to

improve

emergency

vehicle access

adjacent to fire

risk.

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Activity: Outcome – Perimeter roads

• Cul-de-sacs

adjacent to

bushland reserve

re-considered.

• Perimeter roads

introduced adjacent

to fire risk:

- Improved

circulation for

residents and

emergency

vehicles.

- Provides a buffer

between

residential lots

and major fire

risk.

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Activity: Outcome – Lot re-design

• Lots adjacent to

fire risk reduced,

re-designed, and

re-orientated so as

to achieve

defendable space

requirements.

• Building envelopes

located outside of

37 metre

defendable space

distance to achieve

BAL 19.

• Building and

population density

increased away

from fire risk.

- Additional lots

created.34

Activity: Comparison

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Key messages

1

2Looking north on neighbouring land

• Identifying the bushfire risk and defendable space requirements up front is

critical.

• In this instance, a response requiring re-design of whole subdivision was

not required.

• Small design changes led to significant reduction of bushfire risk through:

• Minor Lot reconfiguration (predominately along the southern

boundary),

• Fire Access Tracks,

• Perimeter Road.

• Minor increase in road space / easements.

• Major benefits:

• Provisions facilitated the development of a potentially “stuck site”.

• No net loss of dwellings.

• No reliance on reaching land management agreement on adjoining

land.

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CFA REQUIREMENTSTo guide assessment of subdivisions,

CFA has published requirements

www.cfa.vic.gov.au

Residential subdivisions must be designed and located to

provide ready access for fire trucks and water supply

CFA REQUIREMENTS

Pretty simple really

• Fire trucks need water for firefighting

• Fire trucks need to access the water source and the

residence

• The response to a fire is time critical, delays must be

avoided.

• Firefighters must be able to access equipment on their

vehicle efficiently and effectively

CFA REQUIREMENTS

INAPPROPRIATELY DESIGNED AND SITED SUBDIVISIONS

RISKS

• Emergency vehicles can not access incident

• Insufficient water supply to adequately fight fire and provide

protection for fire fighters

WATER SUPPLY REQUIREMENTS

Water Supply Requirements

WATER SUPPLY REQUIREMENTS

Hydrant Location

200m

< 60m

A

B

A + B = 120m Maximum

ACCESS REQUIREMENTS

8.2m

3.2m

3.1mMirror to mirror

ACCESS REQUIREMENTS

11.8m

3.9m

ACCESS REQUIREMENTS

7m- 7.5m 5.5m In between

ACCESS

REQUIREMENTS:

ACCESS REQUIREMENTS

‘CREATING A SAFER

COMMUNITY’For more information visit

www.cfa.vic.gov.au