Bushfire Causes
Bushfires can be naturally occurring or man-made, but every bushfire needs fuel to start. Fuel is anything that can burn; this is commonly grass, sticks, leaves, rubbish, shrubs and trees. Houses, sheds and other structures are also considered fuel, along with any other objects that will burn. Temperature, wind speed, slope and moisture are other factors that will determine the intensity of the bushfire. |
Fuel Load and Moisture
The greater the load of fuel there is available for the fire, the greater the fire's intensity and temperature will be. The height of the fuel can also control how high the fire will reach, as the fire will burn to the top of its fuel. Small pieces of fuel (twigs, leaves, etc.) will burn very quickly whereas larger pieces, like tree trunks, will take a lot slower to burn. If this fuel is wet, the chances of it burning at all would be really low, no matter what the size of it is. |
Weather
Weather plays a major part in determining the intensity of a bushfire. Lightning strikes are one of the most common causes of a bushfire. Hot and dry weather make it more likely that a bushfire will start, as the fuel would be completely dry and closer to its ignition point in the heat. Plants will become more flammable in dry weather because they release more of their moisture in low humidity, making it easier for them to ignite and create a more intense fire. Wind and wind speed can alter the direction a bushfire is heading, blow embers into other areas, creating smaller fires, and lead the fire to fresh fuel. The greater the wind speed, the more rapidly a bushfire will spread and start spotting. Wind is also a factor in reducing moisture, which creates a low humidity. |
Slope
The slope of land can change the speed at which the bushfire is moving. Bushfires will move a lot faster going up a slope, and a lot slower going down a slope. Every 10 degree increase in a slope will cause the bushfire to double its speed. This means that on a 20 degree slope, the bushfire would be moving four times faster than it would be if it was moving along flat ground. |
Man-Made Bushfires
Man-made bushfires caused by people accidentally or deliberately. Accidental bushfires could be caused by embers from a bonfire being blown into the bush, causing it to start spotting and quickly get out of control. Machinery and equipment, chainsaws for example, sparking could also potentially cause a bushfire, even if it is just a small one. Unfortunately, people referred to as arsonists will deliberately light a fire in the bush. These deliberate fires can simply be someone lighting a fire with a lighter or something like throwing cigarettes away into the bush carelessly. |