Very often, people don’t have much of an idea of the complexity of the effort that goes in to contain a large forest fire. It is a lot more than just putting a bunch of men and women near the fire to try to prevent it from spreading It is also normally a great deal more than simply dropping water on it from helicopters and planes or squirting it with water from fire engines, though air and fire tanker support is quite important. Here are some of the aspects that go into fighting a large forest fire. Note that we are defining a ‘large fire’ as one of more than 1,000 acres. Many wildfires greatly exceed this.
Though personnel are usually assigned to start fighting the fire soon after it is detected, one of the important processes is to map the blaze. This has many purposes, not the least of which is to know which direction the fire is moving. This isn’t as silly as it sounds, because the dense smoke can hide the true movement of the fire and since the wind direction at ground level can be totally different than the wind direction at tree top level, the smoke seen from a distance or from above can make it seem like the fire is moving one direction when it is really moving in the opposite direction.
For fire mapping, on the ground observation is important and the Forest Service has something else at their disposal; Infrared Thermal Mapping. Maps made from both airplanes with special equipment and satellites that utilize the infrared spectrum to show where the hottest places in the fire are. With this information and the on the ground observation, the constantly changing fire direction can be ascertained. While smoke can obscure the visual mapping of a fire, infrared can see right through smoke, since it views heat as brighter areas.
Reading the Thermal Map
Being able to read the thermal fire map is far more difficult than it sounds. An infrared technician, who is highly trained in his or her job, must be able to tell not just where the hottest areas are, but also must know what the terrain is and how it is likely to affect the fire. For instance, a fire can often move up a slope far faster than a man can run over level ground. At the same time, it tends to move around obstacles like rocky out-crops, rather than moving over them. An infrared technician is normally well versed in fire behavior, too, and they are appraised of weather conditions, including wind direction, air speed and humidity. All of these affect how the fire is going to behave.
Why Mapping is Important
One of the initial goals of forest fire fighting is to prevent the spread of the fire. This is done by creating natural and man-made fire lines around the fire. This needs to be done near enough to the fire to save as much timber as possible and yet far enough away that the fire fighters don’t get overwhelmed and overtaken by the fire. Part of this is educated guesswork, since conditions can change rapidly. If the educated guess is wrong, fire fighters can sometimes die in the fire. This does happen once in a while, unfortunately.
An accurate fire map is a very valuable tool because it shows in what directions the fire is rapidly advancing and in which directions it is remaining fairly stationary, as well as other aspects of the fire. The bulk of the personnel and equipment can work in the areas where the fire is advancing the most rapidly and if the maps are accurate, the Forest Service has a good idea of where they can put people safely. This should make sense if you consider that if the fire is moving to the east, it would make little sense to put most of the man-power and equipment to the west of the fire.
All of this is greatly simplified and the process is much more complex, but this is an aspect of fighting wildfires that is often not thought about. As we begin to understand more about what goes into containing forest fires, we can get a greater appreciation for the work that people do to fight forest fire. This includes people inside and outside of the US Forest Service. It also explains why wildfire suppression is so expensive.