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2025 Hazard Mitigation Plan
<br />Kittitas County, Washington
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<br />Chapter 4: Hazard Identification and Risk Assessment 185
<br />4.6.9. Wildfire
<br />4.6.9.1. Description
<br />Wildfires are unplanned fires that occur in wildlands (e.g., forest, rangelands, or grasslands) and they are
<br />nearly impossible to prevent and difficult to control. These extreme events are common in the western
<br />United States, usually occurring during the summer and fall.235F
<br />235 Free-burning fires can occur whenever
<br />combustible fuel (e.g., grasses, shrubs, trees, dead leaves) in the presence of oxygen at an extremely
<br />high temperature becomes gas (flames are the visual indicator of heated gas). Smoldering fires can occur
<br />with lower temperature heat sources and, over time, can reach ignition temperature when rapid fire
<br />growth occurs. Wildfires can be ignited by natural occurrences (e.g., lightning strike) or by human causes
<br />(e.g., unattended campfire, debris burning, or arson). In 2022, 87% of wildfires in the United States were
<br />ignited by humans; meaning that they could have been prevented.236F
<br />236 However, weather conditions and
<br />topography determine the behavior of wildfire. Wind, high temperatures, and low humidity create a perfect
<br />environment for a wildfire to grow; furthermore, flames burn faster when they are moving uphill versus
<br />downhill.
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<br />Wildfires can be classified in three (3) different classes, listed in Table 4-138, and it is common to have
<br />all three (3) types of fire.237F
<br />237
<br />Table 4-138. Types of Wildfires
<br />Type Description
<br />Ground Fires
<br />Mostly burn in decayed roots below ground and in the duff later which is comprised of
<br />dead plant materials (e.g., leaves, bark, needles, and twigs). Ground fires are sustained
<br />by glowing combustion (without flames) and go undetected for a long period of time
<br />because the produce little to no smoke and spread slowly.
<br />Surface Fires
<br />Burn loose needles, moss, lichen, herbaceous vegetation, shrubs, small trees, and
<br />saplings that are located at or near the surface of the ground, mostly by flaming
<br />combustion. Surface fires can grow in intensity to scorch or consume the forest canopy,
<br />a characteristic that is seen in crown fires depending on the following – amount of
<br />surface fuel (high), fuel moisture content (low), slope and/or wind speed (high), resultant
<br />surface flame length (high), height of the base of tree crowns (small), and density and
<br />compactness of tree crowns (tight).
<br />Crown Fires
<br />Usually ignited by a surface fire, crown fires burn forest canopy fuels, which include live
<br />and dead foliage/ branches, lichens in trees, and tall shrubs that lie well above the
<br />surface fuels. Crown fires can be passive (involving the burning of individual trees or
<br />small groups of trees, often called torching) or active (also referred to as running crown
<br />fires, present a solid wall of flame from the surface through the canopy fuel layers as
<br />seen in the photo below.
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<br />Wildfires are a necessary part of the natural ecosystem, but they become a hazard when they extend out
<br />of control into developed areas, resulting in loss of property, injuries, or the loss of life. The wildfire risk
<br />in the United States has increased in the last few decades with the increasing encroachment of
<br />residences and other structures into the wildland environment and the increasingly large number of
<br />people living in wildland areas.
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<br />235 United States Department of Agriculture. (n.d.). Wildfire. Retrieved from
<br />https://www.climatehubs.usda.gov/taxonomy/term/398.
<br />236 United States Forest Service. (n.d.). About Wildfires. Retrieved from https://smokeybear.com/en/about-
<br />wildland-fire.
<br />237 Northwest Fire Science Consortium. (n.d.). What are Types of Fire? Retrieved from
<br />https://www.nwfirescience.org/sites/default/files/publications/Types%20of%20Fire.pdf .
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