As the nation’s wildfire risk grows, even in densely populated areas, and as building construction continues to branch out into wildfire-prone locations, more and more firefighters will face the dangers posed by tree fires.
Many departments respond to wildland-urban interface (WUI) fires where trees, grass or open fields may catch fire and spread to adjacent urban areas or buildings. This past year has seen an increase in these types of fires where, at times, entire towns have been destroyed.
In our video example this month, firefighters respond to a scene where two tall cypress trees have caught fire and spread to a nearby building.
Tree or grass fires can ignite due to natural occurrences, like a lighting strike, or as a result of human-caused actions, like a discarded cigarette. Regardless of the reason why the fire began, the fuel types and loads will vary based upon the environmental conditions.
A fuel load that is dry will be more dangerous than a fuel load that is wet or full of moisture. The fire spread factor will be intensified by a drier fuel load, particularly if accompanied by a low or moderate wind to assist with driving the fire toward adjacent buildings.
Certain types of trees, like those in the above video, that are tall will burn upward very quickly and will also allow the fire to spread vertically at that height to an adjacent building, as opposed to a fire starting low in the building and then burning upward. Right away, the fire department will be facing a fire that may be located several stories above the ground.
Due to the potential height of tree fires, electrical supply lines may be located nearby or directly above the fuel load. This could compound the situation as the electrical wires could fall and ignite additional fires or pose an electrical hazard for responding personnel on scene.
In some buildings, there are green spaces situated on top of the roof where shrubbery, grass and trees will be located. These spaces also present the same WUI problems as described above with the exception that the interface is located several stories above the ground. The fire spread factor will depend upon what exposures are located nearby and above the roof area.
Creating different tactics to approach these types of fires will assist crews in dealing with special situations like green spaces on rooftops or even with the tree fire that we have in our video example.
Training time
After watching this video, departments can work to prepare for the hazards of tree fires by:
- Identifying which buildings in your response district have green spaces located on the roof, if any.
- Plan a drive around your response area to identify where WUI areas may be located. From this, determine which tactics will work best to deal with such fires should they occur.
