Fire Barriers in Forests

A forest fire can be a manmade disaster, or a natural part of a forest's life cycle (e.g., as a result of lightning strikes, or falling rocks that create sparks). Firebreaks are natural or manmade areas that lack fuel, and can therefore slow, stop or divert forest fires. Although firebreaks can arrest smaller fires, they generally do little to stop the progress of an out-of-control fire. The U.S. Forest Service identifies natural firebreaks when planning fire containment strategies, and can also create firebreaks using heavy equipment or hand tools.

Rivers and Lakes

• Water serves as a natural firebreak. Lakes and rivers can provide an effective barrier if they are wide enough. However, when a fire "crowns" (i.e., the tops of the trees burn), wind can easily carry burning embers across rivers and streams. Hot, fast-burning fires can create their own strong winds, even if the weather is otherwise calm.

Roads

• Roads and highways can act as a firebreak, and may buy valuable time for firefighters who are working to contain a forest fire. However, roads did little to contain the massive Rodeo-Chediski forest fire in the White Mountains of Arizona. This fire burned from June 18 to July 7 of 2002, consuming nearly 470,000 acres of forest and burning approximately 500 homes. Public agencies like the Forest Service and Highway Patrol typically close roads during forest fires, partly because the smoke results in poor visibility and partly because firefighters need them for vehicles and equipment.

Chemical Barriers

• Landowners and firefighters often use chemical barriers to retard or stop forest fires. These chemicals can create a firebreak around valuable buildings or property. Some of these products dry clear, while others foam. The Forest Service tests the effectiveness of new chemical barriers in its Wildland Fire Chemicals Systems (WFCS).

Manmade Breaks

• The Forest Service may use heavy equipment to create firebreaks in hopes of protecting property and habitat. Firefighters use bulldozers to plow down vegetation and expose dirt, which slows the fire's progress. Ground crews can also use hand tools and chainsaws to create firebreaks in terrain that bulldozers can't reach. To create firebreaks in remote areas, "hotshot" crews and firefighters may need to parachute from a helicopter or airplane.