Bush%20fire%20building%20safety%20advice

1
Bush fire building safety advice

• Ralph Smith
• Fire Emergency Services Authority

2
(No Transcript)
3
People and Bush Fires

• Greatest threat to people is radiant heat
• Critical to protect people and buildings from
  radiant heat and direct flame contact
• Most bush fires are started by people

4
Buildings and Bush Fires

• Buildings are affected by three main factors
• Burning debris embers
• Radiant heat
• Direct flame contact
• Most homes are lost to ember attack

5
Limiting Vulnerability

• FESA and local governments publish information on
  fire risk
• Limiting the fuel quantity around communities and
  buildings
• Limiting extremes in fire behaviour by the
  appropriate placement of building slope
• Limiting ember attack through materials and
  building design
• Water supplies

6
(No Transcript)
7
Limiting Vulnerability

• Ember attack Jarrah forest type fuels
• Spotting distances associated with the Jarrah
  forest
• Fibrous bark main source of firebrand
• More embers are generated from the older fuels
  around double the number of embers between the 5
  year old fuel and the 22 year old fuel

8
Fuel Age- years since last fire Moving fires Reaching the break Long Distance spotting
2 (4 t/ha) 5m lt10m 0
5 (8 t/ha) 20m 40-50 m 200
22 (18 t/ha) 50m 50-60 m 360
9
Limiting Vulnerability - Slope

• Fire rates of spread (RoS) increase upslope

Ros multiplier
5 1.4
10 2
15 3
20 4
10
Radiant heat and flame contact

• By maintaining the building protection zone (BPZ)
  and hazard separation zone (HSZ) will reduce the
  potential for radiant heat and direct flame
  contact
• As a general guide when planting shrubs determine
  the height they will grow and then double it to
  get the planting distance from the house

11
Radiant heat and flame contact

• Try and maintain a gap of between 10 15 metres
  between trees
• Be careful not to place plants that may
  compromise the integrity of the building
  windows can be a weak point and allow embers to
  enter

12
Intensity kW/m Flame Height (m) RoS Fuel Type
Indirect unlikely to succeed gt 3,000 gt 8,000 gt 8 gt 5 gt1250 m/hr Forest Shrubland grassland
Direct attack not possible or unlikely to succeed gt 2,000 gt 2,000 gt 5,000 gt 6 gt 2 gt 2 gt 400 m/hr gt 1,000 m/hr gt 6,500 m/hr Forest Shrubland Grassland
Machine and tanker attack possible lt 2,000 lt 2,000 lt 5,000 lt 6 lt 2 lt 2 lt 400 m/hr lt 1,000 m/hr lt 6,500 m/hr Forest Shrubland Grassland
Hand tool attack possible lt 800 lt 800 lt 800 lt 140 m/hr lt 140 m/hr lt 300 m/hr Forest Shrubland Grassland
Readily suppressed lt 300 lt 60 m/hr All fuels
13
BPZ HSZ
14
Low Bush Fire Hazard

• Include
• Areas devoid of scrub vegetation thinned
  overstorey
• Areas due to climatic conditions do not
  experience bush fires

15
(No Transcript)
16
(No Transcript)
17
Reducing the Hazard

• Choose a method that you know you can apply for
  the long term
• It may be
• Burning
• Slashing
• Parkland clearing

18
Hazard Separation Zone

• To achieve a fire of intensity of around 2000
  kW/m requires a fuel load of less than 5 t/ha
  when the FFDI - 80
• This equates to a parkland type of vegetative
  cover

19
Hazard Separation Zone

• Research undertaken by McArthur from the CSIRO
  indicates that a fuel load of less than 8 t/ha
  will not support a crown fire

20
Building Protection Zone

• To achieve a fire of intensity less than 800 kW/m
  requires a fuel load of around 2 t/ha when the
  FFDI - 80
• This does not equate to a cleared area, but a
  managed area with appropriate vegetative cover

21
Building Protection Zone

• Have a 2 m gap between trees and houses no
  overhanging limbs
• Prune the low limbs of trees to 2 m
• Cut the long grass and dense scrub
• Rake up the leaves and twigs
• Plant shrubs singularly
• Prune the dead material from the shrubs

22
(No Transcript)
23
Scorch in the crown
Low intensity fire near to the house
24
Tree crowns
Burnt shed
25
(No Transcript)
26
House damage low intensity fire ember attack
27
(No Transcript)
28
How to Assess your Hazard

• Determine the vegetation type and class
• Determine the slope
• Determine the distance between predominant
  vegetation class and the site

29
(No Transcript)
30
Hazard AS 3959
Hazard Application of AS 3959
Extreme Do not build
High Level 2
Medium Level 1
Low Standard construction
31
Hazard Separation Zone

• The distance between the predominant vegetation
  and the building is critical in determining the
  level of protection required from the
• Potential ember attack
• Flame contact
• Radiant heat

32
HSZ AS 3959

• As the distance between the predominant
  vegetation reduces the construction standard
  increases ( BPZ)
• Forest gt100m no increased construction
• Forest 60 100m (medium) level 1
• Forest 35 60m (high) level 2
• Forest lt 35m (extreme) do not build

33
Fuel levels

• At an FFDI of 80
• HSZ To achieve a fire of intensity of around
  2000 kW/m requires a fuel load of less than 5
  t/ha
• BPZ - To achieve a fire of intensity less than
  800 kW/m requires a fuel load of around 2 t/ha

34
Thank you