Seminar: Subdivision Design. Bushfire Management Overlay. Focus on applying defendable space. March 2013

Transcription

1 Seminar: Bushfire Management Overlay Subdivision Design Focus on applying defendable space March 2013

2 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 Bushfire Management Overlay; & Clause Bushfire Protection: Planning Requirements

3 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

4 Clause Bushfire Protection: Planning Requirements 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) 4

5 The BMO objectives, standards and mandatory standards (Clause 52.47) 5

6 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.

7 Clause Mandatory Condition for subdivision: 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 Building envelope and defendable space to achieve approved Bushfire Attack Level (BAL). Vegetation management requirements to implement defendable spaces. Access and water supply requirements. 7

8 All development Standard BF3, BF4 & BF5 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) 8

9 Subdivision - Location, Layout & Siting 9

10 Subdivision - Location, Layout & Siting 10

11 Defendable Space & Construction Requirements - Mandatory Standards BF6.1, BF7.1 &

12 Defendable space and construction requirements Must be calculated in accordance with Table 1 or 2 of Clause to limit radiant heat and ember attack 12

13 AS 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)

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15 AS Model

16 Defendable Space Table 1 & 2 of Clause 52.47

17 Bushfire Site Assessment (Example - Single Site)

18 Bushfire Site Assessment (Example - Subdivision) Table Vegetation, Slope, Construction Requirement & Defendable Space

19 Subdivision Defendable space location 19

20 Subdivision - Defendable space location 20

21 Subdivision - Defendable space location 21

22 Subdivision communal (open space) areas 22

23 Subdivision communal (open space) areas 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 23

24 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 24

25 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 25

26 Activity: Subdivision design 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). Subject land 26

27 Activity: Existing subdivision pattern Bushland reserve (Woodland) 27

28 Activity: Existing characteristics 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). 28

29 Activity: Subdivision design 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? 29

30 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. 30

31 Activity: Outcome Establishing the main road network BAL 19 defendable space (37 metres) identified to assist in restructuring the southern perimeter road network. Main and secondary road network identified. Majority of road network to remain unchanged. 31

32 Activity: Outcome Fire Access Tracks Fire Access Tracks added to improve emergency vehicle access adjacent to fire risk. 32

33 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. 33

34 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

35 Activity: Comparison 35

36 Key messages 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. Looking north on neighbouring 2 land 1 36

37 CFA REQUIREMENTS To guide assessment of subdivisions, CFA has published requirements Residential subdivisions must be designed and located to provide ready access for fire trucks and water supply

38 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

39 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

40 WATER SUPPLY REQUIREMENTS

41 Water Supply Requirements

42 WATER SUPPLY REQUIREMENTS Hydrant Location A + B = 120m Maximum 200m A B < 60m

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44 ACCESS REQUIREMENTS 3.2m 8.2m 3.1m Mirror to mirror

45 ACCESS REQUIREMENTS 3.9m 11.8m

46 ACCESS REQUIREMENTS 7m- 7.5m 5.5m In between

47 ACCESS REQUIREMENTS:

48 ACCESS REQUIREMENTS

49 CREATING A SAFER COMMUNITY For more information visit