Transparent explanations of wildfire engineering relationships, units, assumptions, sensitivity and model limitations — connected directly to Tecnobosque’s interactive calculation tools.
Measurements, mapped data, documented observations and justified assumptions define the starting point.
Select an equation whose variables, units, purpose and limitations match the question being examined.
Report the result with appropriate units and practical precision rather than false certainty.
Test sensitivity and state what the model can and cannot support before drawing conclusions.
Wildfire behaviour is described through several related but distinct quantities. Understanding the definition of each one matters before using it in an equation or comparison.
Forward movement of a fire front, commonly expressed in m/s or m/min. It depends on the fire segment, fuel conditions, wind and terrain.
Heat-release rate per unit length of active fire front, commonly expressed in kW/m.
A geometric description associated with a defined observation or empirical relationship. Flame length is not simply flame height.
Thermal power received per unit area. Source behaviour, geometry, distance, orientation and atmospheric transmission can affect the estimate.
Fireline intensity combines heat yield, fuel consumed in the flaming zone and rate of spread into a heat-release rate per unit length of fire front.
| Variable | Example | Unit |
|---|---|---|
| Low heat of combustion, H | 18,000 | kJ/kg |
| Fuel consumed in flaming, w | 1.0 | kg/m² |
| Rate of spread, r | 0.02 | m/s |
| Fireline intensity, I | 360 | kW/m |
The arithmetic is straightforward: 18,000 × 1.0 × 0.02 = 360 kJ/(m·s), equivalent to 360 kW/m.
The more difficult question is whether the heat, flaming fuel consumption and rate of spread describe the same fire segment and time with defensible accuracy.
Tecnobosque’s dedicated Fireline Intensity Calculator lets you move each variable in real time, compare scenarios and inspect the resulting intensity.
Open Fireline Intensity Calculator →An engineering calculator can return a highly precise numerical result even when the values entered into it contain substantial uncertainty.
Fuel consumption may be estimated, rate of spread may represent only part of the perimeter, and a weather observation may come from a station some distance from the fire.
Tecnobosque therefore treats assumptions, units, evidence quality and sensitivity as part of the result — not as information to hide beneath it.
There is no single universal wildfire radiation equation. Different simplified relationships represent different source geometries and require different inputs. They should not be mixed without stating the modelling assumptions.
This relationship begins with source emissive power and applies geometric coupling through the view factor together with atmospheric transmissivity.
It is useful for exploring how source behaviour, geometry and transmission influence incident radiant heat flux.
The dedicated Tecnobosque interactive calculator uses this model.
A different screening approach can idealise a fire front as a long line source using fireline intensity, radiant fraction, transmission and perpendicular distance.
This is a different geometric representation and should not be treated as interchangeable with a view-factor model.
Real flames are neither perfect surfaces nor infinite straight line sources.
Change source emissive power, view factor and atmospheric transmissivity and see the calculated incident flux respond.
The calculation itself is often the easiest part. The quality of the result depends on whether the model and inputs actually represent the question being asked.
Confirm that every variable means what the selected relationship requires.
Convert inputs consistently and preserve dimensional compatibility throughout the calculation.
Identify whether an input was measured, mapped, estimated, assumed or taken from literature.
Check whether the relationship is being applied within conditions appropriate to its intended use.
Change uncertain inputs and examine whether the interpretation remains stable.
State whether the result is descriptive, comparative, exploratory or a defined screening estimate.
One preferred scenario can hide how strongly a result depends on uncertain assumptions. Testing a defensible range is often more informative.
Use a defensible lower input set and check whether the conclusion changes under less severe assumptions.
Use the best-supported inputs and document how each value was selected.
Use a defensible upper input set rather than an invented worst case to expose sensitive conclusions.
A useful calculator should expose enough information for another reader to understand what was calculated and where the boundaries of the result lie.