Teaching Sequence

Work through this resource material in the following sequence:

10 minutes	Part A: Where is fire more likely to occur?
25 minutes	Part B: The two fire triangles
25 minutes	Part C: Conduct a risk assessment
05 minutes	Reflection

Part A: Where is fire more likely to occur?

Step 1.

Using this Powerpoint, ask students to determine in which image they think a fire is more likely to occur, and explain their reasoning.

Part B: The two fire triangles

Step 1.

Explain to students that scientifically, a fire requires three things:

A source of heat is required to start and sustain a fire.
A source of fuel is needed to burn.
An adequate supply of oxygen is needed for a burning/chemical reaction.

This is easily summarised by the fire triangle:

Step 2.

Can students explain these three requirements in terms of a wildfire in the bush?

Heat might come from a lightning strike, and the hot weather and conditions would dry out the fuel and keep the fire burning
There would be fuel in the grass, scrub, and trees
There would be oxygen in the air

Step 3.

There is also a second triangle that explains how fires behave after they have started burning.

Elements in this second triangle include:

Topography or terrain is the shape of the land: Interestingly, fire runs faster uphill. Kids will find that fun because they don't run faster uphill! A fire will move faster uphill than across flat ground or downhill, because it has more access to fuel, and the fuel above the fire heats up due to the smoke and rising flames. We might think that a fire spreads as a result of more fuel coming into direct contact with a flame. But radiant heat from a really hot fire can also set nearby fuel alight.

For every 10˚ increase of the slope, the fire will double its speed. For example, if a fire is travelling at five km per hour along flat ground and it hits a 10˚ slope it will double in speed to 10 km per hour up the hill.

The opposite applies to a fire travelling downhill. The flames reach less fuel, and less radiant heat pre-heats the fuel in front of the fire. For every 10˚ of downhill slope, the fire will halve its speed.

Weather: This is closely linked to heat–the drier the vegetation the easier it will burn. Wind also influences the:
- speed at which a fire spreads
- direction in which a fire travels and the size of the fire front
- intensity of a fire – wind provides more oxygen
- likelihood of spotting

Vegetation: This is linked to fuel. If there’s no vegetation, a fire has nothing to burn (like in the sandy desert). However, the type of vegetation also impacts how quickly a fire spreads. Dense, lush vegetation, such as trees or damp grasses, will burn slower for longer. Fire can quickly race over dry grass and twigs.

Step 4.

Watch:

TPWDiscover | How Does Fire Behave? (https://www.youtube.com/watch?v=1yobt6rrz0Y)

Part C: Conduct a risk assessment

Step 1.

Firstly, students draw their own fire triangles and explain, in their own words, their understanding of heat, fuel, oxygen, and vegetation, weather, and terrain/topography.

Step 2.

Using their individual devices, students jump onto Google maps and find a birds-eye view of their local area. If you’re in a larger city or town, you might have to zoom out a bit further to be able to see the bushland on the outskirts.

Step 3.

Using this image and the knowledge they have gained, ask students to conduct a risk assessment of their local area. Where do students think might be most susceptible to a bushfire? Why?

Is there a lot of fuel in a certain area to encourage the fire to spread in a certain direction?
Is there a slope, and does this increase or decrease the chances of the fire spreading?
Is there a local waterway, such as a creek or lake? Do you think this will impact the starting or spreading of a fire in that area?
Is there more or less vegetation, trees or open grasslands in a certain area? Or is there some other kind of highly flammable fuel? How might this affect the spread of the fire?
What is the weather usually like in this area? Are there any times of the year that are more suitable for fires to start and spread?

Provisions for Learning Support - Alternatively, students could work in small groups, taking different areas of the surrounding landscape (for example, north of town, south of town etc.) Students conduct research and report back to the class to share their knowledge.

Reflection

Exit Ticket - Before moving to their next class or an outside break, students purchase their 'exit' with a 'ticket' that demonstrates their understanding of the learning undertaken in this lesson.

You can have students write their responses on a sticky note along with their names, or you can have them line up and verbally communicate their understanding to you at the door as they leave.

Students share one thing they didn’t know at the beginning of this lesson.

Teacher reflection

Take this opportunity to reflect on your own teaching:

What did you learn about your teaching practice today?
What worked well?
What didn't work so well?
What would you share?
Where to next?
How are you going to get there?

Resilient Australia - How Do Fires Behave?

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