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"C fii. ( I 2.7 Wildfire Hazard Identification A wildfire or wildland fire is any fire occurring on grassland, forest, or prairie, regardless of ignition source, damages or benefits. According to the 2000 National Fire Plan, authorities now consider the wildland fire risk as "the most significant fire service problem of the Century." There are four categories of wildfires that are experienced throughout the United States described below. I . Wildland fires are fueled almost exclusively by natural vegetation. They typically occur in national forests and parks" where Federal agencies are responsible for fire management and suppression. . Interface or intermix fires are urban/wildland fires in which vegetation and the built- environment provide fuel. , . Firestorms are events of such extreme intensity that effective suppression is virtually impossible. Firestorms occur during extreme weather and generally burn until conditions change or the available fuel is exhausted. . Prescribed fires and prescribed natural fires are fires that are intentionally set or selected natural fires that are allowed to bum for beneficial purposes. Fires can be caused by arson, debris burns, lightning strikes, (especially during a seasonal drought). Multiple fires can be started and can quickly become out of control. People are becoming more vulnerable to wildfires by choosing to live in wildland settings. There are three principal factors that have a direct impact on the behavior of wildfires-- topography, fuel and weather; I . Topographv can have a powerful influence on wildfire behavior. The movement of air over the terrain tends to direct a fire's course. Gulches and canyons can funnel air and act as a chimney, intensifying fire behavior and inducing faster rates of spread. Similarly, saddles on ridgetops tend to offer lower resistance to the passage of air and will draw fires. Solar heating of drier, south-facing slopes produces upslope thermal winds that can complicate behavior. . Fuels are classified by weight or volume (fuel loading) and by type. Fuel loading, often expressed in tons per acre, can be used to describe the amount of vegetative material available. If fuel loading doubles, the energy released also can be expected to double. Each fuel type is given a burn index, which is an estimate of the amount of potential energy that may be released, the effort required to contain a fire in a given fuel, and the expected flame length. Different fuels have different burn qualities. Some fuels burn more easily or release more energy than others. Grass, for instance, releases relatively little energy, but can sustain very high rates of spread. Ha~'s counl~', Texas Mitigation Plan 66