Wildfires can be extremely destructive and dangerous, and a lot of effort goes into combating them when they break out. There are many techniques for fire fighting, including the use of water-bombing aircraft and fire retardant sprays, but one of the most common and effective is the creation of a firebreak. A firebreak is a line of ground which has been stripped of fuel; the fire can burn up to it, but will stop there and won’t be able to spread to the other side.
Many forest plantations have ready-made firebreaks in them, and keeping these clear is part of the job of forestry services. Often, though, they have to be created in a hurry when a fire is already burning. Maybe the most dramatic (and expensive) firebreak in history was created in 1906, when most of San Francisco’s Van Ness Avenue was dynamited to prevent the fire that followed the great earthquake from spreading. Firebreaks are also known as control lines, and are often created using heavy machinery; this is usually called a dozer line. One of the most flexible but difficult methods, though, is what’s known as a hand line.
Hand lines are made by fire-fighters using hand tools. The difficulty is in the amount of material that has to be cut and moved; a control line has to be wide enough that the fire can’t be driven right across it by the wind, and it has to be cleared thoroughly enough that there isn’t enough fuel in it to keep the fire going. In some forests this might mean clearing a line wider than the height of the trees to prevent a burning tree falling across the break and spreading the fire into the protected area, and that means a lot of work. The benefit, though, is that hand lines can be created in places where heavy machinery can’t reach; fire-fighters can get there by helicopter, in light vehicles or even on foot and stop the fire where it needs to be stopped.
Two things have to be done to create an effective hand line; cut down any trees and clear vegetation, dry grass and dead leaves from the ground. Both of these need a range of tools, some standard ones and a few more specialised bits of equipment.
Trees can be felled quickly with chainsaws or axes. Standard felling axes can be used, or a special tool called a pulaski; this has an axe head with a mattock on the back of it. The axe can be used for chopping down trees and the mattock for digging. Hauling tackle is often needed to remove felled trees from the line, otherwise they can become fuel lying on the ground. Sometimes chopping away branches is enough if the fire isn’t intense enough to set the trunks on fire, but often the whole thing has to go.
Undergrowth is very flammable and needs to be cleared to create an effective break. Machetes and hand-held trimmers can be used for this, or for smaller plants a drag chain can be pulled over the ground to uproot them and haul them away.
If the ground is bare earth with dead leaves on it these can be raked away. Sometimes the ground needs to be dug over though, often because there’s thick grass on it. For this spades and pickaxes are often used, and the mattock on the back of a pulaski is also great for loosening and turning over hard ground. Another way to clear away grass and undergrowth is by carrying out a controlled burn, often known as a back burn. This involves lighting one or more small fires to clear away potential fuel, but keeping them small enough that they can be kept under control and either extinguished when the fuel is gone or directed into the path of the wildfire. Back burns can be lit with magnesium flares or a device called a driptorch, which drips a burning diesel mix under control. A series of small, easily controlled fires can quickly create a strip of ground with nothing for the wildfire to burn.
Once a line has been created it needs to be observed; high winds can carry burning scraps across the line, and fire-fighters need to be ready to move behind the line to put out any fires before they can get established. A good firebreak is one of the best ways to bring an out of control fire to a stop, though, and hand lines remain an important way of making them.