Know when to go: a new way to keep firefighters safe from harm

The above figure illustrates the trigger buffer concept for a fire in California. Firefighters are assigned along a road running from north to south, as the fire approaches from the southwest. Morning winds are forecast to be from the northeast between 6.4 and 12.9 kilometers an hour, switching to the southwest between 9.7 and 19.3 kilometers an hour in the afternoon.

A safety zone is set where the road reaches a river at its northern end.

The model calculates fire spread rates based on the predicted wind conditions and the time required for firefighters to evacuate to the safety zone on foot along the road. The buffer is larger on the southern end of the road, because firefighters must leave that area much earlier to reach the safety zone.

Predicting firefighter travel times and fire spread rates also provides information on when not to evacuate. If the fire is too close and the safety zone is too far away, then firefighters may be trapped along their evacuation route.

If the trigger buffer has already been crossed and there is no way to reach a safety zone without risking entrapment, then the best strategy would be to find an area in the immediate vicinity to deploy fire shelters. Having a few additional minutes to find the best area to shelter in place could mean the difference between life and death.

This model does not replace on-the-ground decision-making. Rather, it provides a tool that helps firefighters understand the risk of entrapment under a given set of fuel, terrain, and weather conditions.

There is no replacement for expert decision-making, and the location of the fire still has to be known for a trigger buffer to be effective. Remote sensing, potentially by unmanned aerial vehicles, provides one way to monitor fire location and provide updates to firefighters in the field.

In the more general case, this model can also provide evacuation trigger buffers for communities threatened by bushfire. Termed “WUIVAC” for Wildland Urban Interface eVACuation, modelling of evacuation travel times and fire spread rates can help determine when a household or community should evacuate to a safer location. Factors such as the number of households and potential for traffic incidents can be incorporated into travel times.

For strategic decision making, trigger buffers can be modelled under “worst case” scenarios where wind speed and direction are based on historical maximum values. Communities can use these strategic trigger buffers to plan their bushfire response.

The list of challenges to firefighters continues to grow. Changing climate means that firefighters are facing new fire threats and working under more difficult conditions. Increasing population in the wildland urban interface requires firefighters to protect more lives, property, and resources.

Our hope is that modelling can provide tools to protect the safety of the men and women who keep us safe from fire.

Philip Dennison is Associate Professor, Department of Geography,University of Utah; Tom Cova is Professor, Geography Department,University of Utah;Greg Fryer is Assistant Superintendent of the Bonneville Interagency Hotshot Crew.This storyis published courtesy of The Conversation(under Creative Commons-Attribution/No derivatives).