What is the wildland-urban interface?

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Wildland-urban interface (WUI)

Historically we have described the WUI as the line, area, or zone where structures and other human development meet or intermingle with undeveloped wildland or vegetative fuels.

In a wildland urban interface fire; all vegetation (“natural” or “wildland”  and cultivated), buildings (structures), attachments (fences, decks, outbuilding), infrastructure  (bridges, power lines, communications towers, pump stations, etc,) and other items (vehicles, boats, firewood, stored materials, hazardous materials, etc,) are potential fuel for the fire.

For simplicity, these fuels are typically divided into two main categories.


Wildland Fuels

All vegetation (natural and cultivated)

Built Fuels

Man-made structures (buildings and infrastructure)

Combined, these wildland and built fuels result in a WUI fuel complex.

These fuels all have different burning characteristic; and when combined into a WUI fuel complex, they create uniquely complex conditions that affect the ignition and spread of fire that differs from both an isolated structure fire and an isolated wildland fire.

Understanding the complexities of these combined fuels, helps us begin to understand the unique and often overwhelming challenges that a WUI fire presents to suppression resources.

A more accurate definition of the wildland urban interface describes both structures and vegetation as “fuel”, includes the topographic and weather conditions that affect the combustibility of these fuels and recognizes the unique interactions within this “combined fuel complex” that allows for the ignition and spread of fire through it.

Therefore, for the purposes of neighbourhood wildfire planning and WUI regulation development, this definition more accurately describes the WUI:

Any developed area where the combination of human development and vegetation have the potential to result in negative impacts from wildfire on the neighbourhood.