Tecnobosque Wildfire Knowledge Graph · Fire Behaviour
Reference Concept · v1.0Definition → relationship → calculation → evidence context
A head fire is the portion of a fire spreading in the primary forward direction, commonly with the wind and/or upslope, and often exhibiting the highest spread rate and intensity within the same fire perimeter.
What is head fire?
The head is a directional part of a fire, not a separate incident. Its behaviour emerges from the alignment of fuels, wind, slope and fire geometry.
Because many engineering relations use a local rate of spread or intensity, identifying the segment as head fire provides essential context.
Why it matters
Reported wildfire speed often refers implicitly to the head. Stating “head-fire ROS” avoids transferring that value to other parts of the perimeter.
It is the front that is moving most strongly in the dominant spread direction. The sides are flanks and the rear/backing portion behaves differently.
What controls or changes this quantity?
Wind aligned with spread can preheat fuels and increase forward propagation.
Upslope alignment can increase heat transfer to fuels ahead.
Continuous receptive fuel supports sustained forward spread.
Firebrands ahead of the head can create discontinuous growth beyond the main front.
Engineering context
Dominant forward-spreading portion.
Lateral sides of the perimeter.
Portion spreading opposite the dominant direction.
Separate ignition outside the main perimeter, potentially ahead of the head.
How to interpret it correctly
- State the direction and time window when reporting head-fire spread.
- Do not assume head-fire values apply to flanks or rear.
- Distinguish continuous head advance from spot-fire jumps.
- Link head-fire measurements to evidence of wind and slope when reconstructing causation.
Use the calculator as a transparent technical aid and keep its assumptions explicit.Open Rate of Spread Calculator →
Why it matters in wildfire analysis
A mapped perimeter sequence can show a strong elongated head while side and rear growth remains much slower. Using one incident-wide speed would erase that directional behaviour.
Tecnobosque uses head-fire context to connect ROS, fireline intensity, flame length and growth without pretending the entire perimeter shares one value.
Limitations and boundaries
- The dominant spread direction can rotate when wind changes.
- Multiple active heads can develop in complex terrain or multi-lobed fires.
- Remote perimeter observations may not resolve the exact active head at fine time scales.
Head Fire FAQ
What is a head fire?
The portion of a fire spreading in the primary forward direction, commonly with the wind or upslope.
Is the head fire always the fastest part?
It often has the highest forward spread under aligned conditions, but real incidents can be complex and variable.
Is head-fire ROS the same as whole-fire growth?
No. It is a local directional spread rate, not the change in total fire area or perimeter.
Can the head-fire direction change?
Yes. Wind shifts, terrain and fuel changes can rotate or split the dominant forward-spread direction.