Geography

• Ground fires


  • Occur underground and impact top soil and sub-surface vegetation
• Surface fires


  • Occur on the surface of the ground and impact low-lying vegetation
• Crown fires


  • Occur in the crown/canopy of the forest, caused by ember attacks /ladder effect
• Hot fires


  Fires with large fuel loads burn with a higher intensity and radiant heat (e.g. 500kW/m)
• Cool fires


  Lower intensity, easier to manage, impacts ground and understory vegetation
• Factors that contribute to fire behaviour

  • Topography
  • Weather
  • Vegetation
• How topography impacts bushfire behaviour

  1. Slope determines how quickly fire moves

  2. Every 10 degrees of uphill slope, fire will double in speed

  3. Every 10 degrees of downhill slope, fire spread rate will halve

  4. Downhill slopes pre-heat the fuel
• Fuel


  Any material that affects the flammability of fuel, including size, quantity, type, arrangement and fuel moisture content
• Fuel load


  Higher the fuel load, the more intense, hotter and potentially catastrophic the fire
• Fuel compaction


  Loosely compacted fuel will burn faster than heavily compacted/scattered fuel sources
• Weather factors affecting bushfire behaviour

  • Humidity
  • Temperature
  • Rainfall
• Relative humidity is the most used measure of atmospheric moisture. Very low relative humidity can contribute to faster fire spread.
• Spatial distribution of bushfires

  • South America
  • North America
  • Africa
  • Europe & Asia
• Bushfires occur on every continent except Antarctica. Regions that have regular bushfires are often located in drier climates.
• Temporal distribution of bushfires

  • Increased frequency of major fire events in recent years
  • Fire season is extending into Autumn and starting 1-2 months earlier
• Major fires used to occur every 5-6 years, but the risk has increased because of climate change pressure on water sources.
• Natural/physical processes contributing to bushfire risk

  • Hot/dry summers
  • Low humidity
  • Combustible fuel types
  • Climate change and climate processes (Pacific Decadal Oscillation, Indian Ocean Dipole, El Nino, La Nina)
• Human processes contributing to bushfire risk

  • Land clearing methods
  • Agricultural practices (slash and burn)
• Vulnerability

  Assesses the risk level and refers to how a hazard event will affect human life and property
• Factors that increase a community's potential vulnerability to bushfires

  • Proximity to bushfire prone areas
  • High fuel loads
  • Adverse weather conditions
  • Strong winds
  • Little/poor community cohesion
  • Inadequate knowledge
  • Inadequate insurance
  • Inadequate government infrastructure
• Differences in vulnerability between Less Developed Countries (LDCs) and More Developed Countries (MDCs)

  • LDCs: Low GDP, minimal industry, minimal technologies, high agricultural dependence

  MDCs: High GDP, advanced technology
• Physical factors contributing to LDCs' vulnerability to bushfires


  • Geographical location around sub-tropic latitudes
  • Lightning
  • Physical features like mountains, peaks, dense forests
  • Greater climate change impacts due to lack of adaptation strategies
• Human factors contributing to LDCs' vulnerability to bushfires


  • Managing natural vegetation
  • Demographic pressure and living in hazardous areas
  • Lack of building codes
  • Land clearing methods and agricultural practices (slash and burn)
  • Lack of technology, infrastructure, information, knowledge, education, fire brigades
  • Lack of funds to fight and recover from fires, reliance on international assistance