Article 9: ECUFPA: Understanding fire management when burning fire breaks and managing fires
Fire management involves fire protection and using fire for land management purposes such as stubble burning, weed control or the management of native / indigenous vegetation. Fire behaviour is how fire spreads and burns given differences in fuel, weather and topography (shape of the land). This section provides general information that may be useful when considering and planning fire management.
Fire spread: Fire spreads in three main ways:
direct flame contact,
heat transfer – Heat is transferred through hot air currents and as radiant heat.
from embers – Embers can be carried forward by wind and air currents. These start new spot fires well ahead of the main fire front (spotting
Drought conditions: When planning fire management, consider the impact of drought and dry conditions. While grass paddocks tend to be heavily grazed in these situations, fire management still needs to be undertaken as fire can still travel across paddocks with very short grass.
Fire behaviour: Fire behaviour is influenced by three main factors. These are fuel, weather and topography. How hot a fire burns and how quickly it spreads depend on the size, quantity, type, arrangement and moisture content of the fuel being burnt.
Fuel load & Fuel size: The fuel load is the quantity of fuel per unit area. It is commonly expressed as tons per hectare. Reducing fuel loads can help to protect assets from fire and make fires easier to suppress. Fine fuels, such as leaves, twigs, grass and bark, dry out rapidly and burn quickly. Consequently, minimize the quantities of fine fuels near key assets to minimize the risk of radiant heat and direct flame contact. Heavier fuels like branches and logs can also provide fuel for fires, however, they are slower to ignite than fine fuels and give off heat more slowly.
Weather: Weather is a major factor in the ignition and spread of fire. Preparing for common weather patterns, as well as unusual weather events, will assist landowners to minimize fire risk.
o Temperature and humidity: Temperature and humidity impact on fire fuels, especially fine fuels. The higher the air temperature and the lower the humidity the more easily fuel will burn.
o Wind speed: Wind influences fire behaviour significantly.
o Wind direction: In certain areas of the Eastern Cape, hot dry winds often come from the north and northwest and are often followed by a easterly and south-easterly wind changes. In this situation the side of the fire can quickly become a much larger fire front (head of the fire).
Topography: The shape of the land needs to be considered when planning fire management. Fire travels faster upslope than down-slope because when it is moving upslope the flames are closer to the unburnt fuel. This preheats the fuels, making them easier to ignite. The rate of fire spread upslope approximately doubles for every 10 degrees of slope.
Topography can also influence how the wind behaves. As wind passes over an object, such as a hill or windbreak, the wind can tumble, creating turbulence. Wind turbulence produces erratic winds, causing unpredictable fire behaviour.
Valleys and gullies can channel and strengthen winds, increasing the rate of spread of a fire and its intensity. Be aware of local wind conditions. New landowners should ask neighbours and previous owners about local winds when planning fi re management on their property.
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