After the deadly 2017 fire season, there should be no question that the current wildland fire environment is a very complex and dynamic arena. There are numerous reasons for this complexity, some of which we have control over and many we do not: fire behavior, the modification of the fuels by human activities, the shear potential size of an incident due to the lack of walls keeping fire from spreading across a diverse topography, and the variability and uncontrollable impact that weather has on wildland fire producing at times extreme fire behavior.
When our personal drive for successful fire suppression combines with the human interest factor of structures and the entire associated infrastructure, the pressure on responders is immense. The potential of challenging and high-risk incidents testing our best commanders and company officers and ultimately jeopardizing each and every firefighter responding has never been greater.
At every rank, at every level of supervision, we must recognize that the overwhelming intensity produced by the current wildland fire environment is a condition that at times cannot be beaten, no matter what we commit to that mission. Our collective responsibility to ourselves and to our communities is to maintain our situational awareness when operating in extreme conditions, and know when conditions align that force us to change our tactics—and ultimately get out of the way.
Flow path science
One of the ways we can best protect firefighters operating in these extreme conditions is through the analysis of the wildland flow path. Flow paths can be defined as the movement of heat and smoke from the higher air pressure within the fire area to all other lower air pressure areas both inside and outside of a fire building,
The concept of the wildland flow path is simple and directly related to the concept of flow path in structure fires. Firefighters exposed to flow path are experiencing the physics of thermal buoyancy and the desire of the environment to stabilize areas of high and low pressure. This law of physics on our planet is responsible for large- and small-scale air motion, whether fire is present in the equation or not. Air that is heated by any means becomes less dense through expansion and begins to rise. This lifting is considered a relative low pressure, and air from the surrounding relative high pressure rushes in to replace the more buoyant air rising. High pressure flowing to low pressure is another constant on our planet.
Where things get quite complicated for us in the wildland fire environment is the added dimension of the shape of the terrain influencing the flow or air as it attempts to equalize the pressures. Like water, air will always follow the path of least resistance and, in fact, the two elements behave almost identical while in motion. Air, heat, embers and products of combustion will be focused in certain instances, delivering an intensified path of extreme fire behavior and possible destruction. This is the wildland flow path we have to be cognizant of at all times.
Consider this flow path concept to help explain the well documented tornado-force winds experienced by civilian and firefighters on the Sonoma County, CA, Tubbs Incident in October 2017. Imagine the amount of buoyancy created when an entire neighborhood is burning at once with all of the BTUs being released heating large volumes of air rapidly. The replacement air is racing in, channeled by the shape of the land and pushed by the surface winds that caused the fire to spread so fast—an interaction of high and low atmospheric pressures on a grand scale. These factors create conditions that no individual or aircraft can begin to contain, and can even pick up and throw vehicles a significant distance.
Recognition and avoidance
This potential concentration of energy delivery can be fatal to humans and destructive to structures. When assigned to structure defense, always have a temporary refuge area identified, and recognize if the structure is located in an area of the topography where the energy release of the approaching fire could be focused right on top of you. Don’t be lulled in to a false sense of security just because there is defensible space present. If the structure is located in the flow path and under extreme conditions, the defensible space may not be sufficient to keep the house from burning or create a tenable space for you to tactically operate.
If all firefighters responsible for wildland fire suppression begin the pre-season refresher training by making it a priority to train to improve our skills at identification of the wildland flow path, our collective safety will be improved. By default, planning tactical actions and making assignments after recognition and identification of potential flow path our suppression efforts will be completed with more effectiveness and increased safety.
Simply put, the ingredients of fuels, weather and topography, on any given day, in any given location, combine in a recipe to produce an output. The output of this unique recipe is the observed fire behavior. Change any one of the ingredient’s parameters and the fire behavior will change. Instinctively all firefighters know this interrelationship of ingredients, but applying these instincts, in a timely manner, is the key to safe operations. The interactions of the recipe ingredients changes in complexity over time and space. The ability to process all the variables improves with experience and training, but is unfortunately subject to distraction, fatigue, complacency and a multitude of other factors that erode our effectiveness in this important task.
The concept of recognition and avoidance is simple but vital during the risk-management process. Our challenge is to use our understanding of wildland fire behavior inputs to process and recognize when the fire’s output is too significant to operate in its path. What makes this process challenging during real-time incident conditions is the high-stress, task-saturated and time-compressed environment in which we as firefighters find ourselves. The act of recognition is imperative. Every firefighter needs to actively make safety and effective tactical decisions. Our job is to suppress the fire and protect the lives at risk, but more frequently than ever before, fire conditions force us to step aside.
Crew safety and effectiveness is the number one goal of any firefighter regardless of the type of emergency incident. Whether it is the medical aid, vehicle extrication, rope rescue, structure fire or wildland fire response, the phrase “Everyone Goes Home” should not be just idle lip service. This fundamental guiding principal should be the foundation, the integral part of every thought process, strategic or tactical decision, and ingrained into the mind of any person responsible for commanding personnel in a high-risk environment. Wildland fire suppression is one of those environments, and demands a high level of training, experience and education to safely and effectively engage personnel and equipment resources.
This is a proactive thought process, and when completed accurately, should assist personnel with the critical decision of locating a safe area to operate and a dangerous place to avoid or exit from with a positive safety margin. Furthermore, the identification of wildland flow path conditions will place personnel in the desirable position of being pleasantly surprised, as opposed to tragically surprised, during fire behavior changes.
Call it proactive risk/benefit analysis, worst-case scenario planning or all of the above, but the bottom line is by evaluating the fire environment conditions, energy-release potential and topographic influence on every shift, day or night, firefighters are better situated to determine where the flow path is pointed and where to go to avoid it.
So the next time you find yourself at a wildland fire incident, get your hands on an accurate topographic map, a complete weather forecast, analyze the state of the fuels, and then evaluate the fire’s potential.
Final thoughts
This simple question of how to stay out of the wildland flow path is the most direct application of the complex analysis of fire behavior related to the most important strategic goal at any incident: personnel safety. Although recipes produced by the environment can in some cases present significant challenges to fire suppression operations, a better understanding of the wildland flow path can hopefully position personnel in a safe location when fire behavior intensifies.
