Wildland Fire behavior-Chapter 4 {(*)Highlights & (-)Red Notes}
Wildland Fire behavior (Highlights & Red Notes) * Highlight - Note Chapter 4
* Smoke column- one of the best indicators of fire behavior is the smoke column. Lean= wind drive, short range spotting. Sheared=rises, winds aloft may cause long range spotting, columns is sheared off by strong winds aloft. Well-developed= intense burning, unpredictable fire spread in all directions, look for capped top. Changing smoke column-beware when change color or rotates. Collapsing smoke column- beware when column begins to collapse, down draft winds can cause fire to run in all directions. Rotating or split fire column- beware this is indicator of very unstable air. *Firewhirls-indicator of unstable air, fire is going vertical. *Increasing spot fires- sign conditions are deteriorating rapidly. *Burning characteristics based on time of day: 1000-1800- all factors of fire intensity are at their highest 1800-0400- factors favorable for fire control 0400-0600- time of day when fire can be most easily controlled. 0600-1000- fire intensity begins to increase -The higher the dead-to-live ratio the higher the chance of a crown fire. -Wood shingles make the worst kind of firebrands. *Win driven fire- more predictable, increase rate of spread, long range spotting. *Plum driven fire-less predictable, spotting occurs in all directions, downdrafts should be a major concern.
Wildland Fire behavior (Highlights & Red Notes) * Highlight - Note Chapter 4
* The most important weather components are wind, temperature, & RH. Weather being the most important factor. *The most important topography components are steepness of slope & aspects. *The most important fuel components are fuel moisture & temperature. -Fire behavior is three dimensional. A change in one factor causes all of the relationships of the others to shift. *Size & shape of fuels: The smaller/finer they are the easier they ignite. *Compactness & arrangement of fuels: If they are loose & open they will ignite easier. *Fuel moisture content: The drier they are the easier they ignite. *Fuel temperature: The warmer the fuel the less heat it takes to reach ignition easier. *Firebrands are lifted by convective heating & dropped some distance away. -In steep terrain, rolling pine cones & logs can carry fire across firelines *Spread- movement of fire/rate of spread. Chain= 66ft in length. *Smoldering-Fire burning w/o flame & spreading slowly *Creeping- Fire burning w/ low flame & spreading slowly. *Running- Fire spreading rapidly with a well defined head. *Backing- Fire moving away from the head, down hill, or against the wind.
Wildland Fire behavior (Highlights & Red Notes) * Highlight - Note Chapter 4
*Torching- surface burning with occasinoal igniting of crown of tree/brushes. *Spotting- sparks/embers produced by mian fire carried by winds across control lines. *Crowning-Fire that advances accross tops of trees.Independent of surface fuels/very fast/ dangerous *Blowup-sudden increase in fire intensity of rate of spead-changes supression plans *Fuel Loading-type/amount of fuel available to burn *Compactness of arrangement of fuels- tightly arranged fuels with little space for air/heat to burn and less intense *Fuel moisture content-if increase heat is needed to decrease fuel moisture level a fire will have decrease intensity. *Slope & wind speed- Fire burn more intensely moving upslope & downwind because of convective heat. *Fire intensity- increase intensity increases heat generation & rate of speed. *Wind Speed- increase wind puts more lean of fire & the faster the rate of spread. *slope- increase slope the closer the flame/convective column are to fuel= increase spread. *Fuel type changes- change of rate of spread & burn pattern. *Natural man made barriers- that sop/slow spread-roads, streams, lakes change/affect burn pattern *Spotting- if fire is generating spot fires ahead of or below fire the burn pattern will change. *Fire intensity- fire heats air causing it to rise through atmosphere-hotter=higher *Stability of air-major factors in the vertical dimension of the fire
Wildland Fire behavior (Highlights & Red Notes) * Highlight - Note Chapter 4
*Winds aloft- strong upper level winds tend to limit the vertical development of fire. *Fire behavior characteristics determine how/where you should fight the fire. *Fire suppression interpretations from the flame length: - <4 feet- fires can be attacked on head/flanks by FF with hand tools. - 4-8 feet- no direct attack on head with hand tools. Need bulldozers engines, air drops of retardant. - 8-11 feet- serious control problems-torching/crowning & spotting. Control efforts at the head will probably be effective. - Over 11 feet- Crowning, spotting, & major fire runs. Control efforts at the head are ineffective. -80% of energy release on Wildland Fire goes into the atmosphere. -20% of heat energy/radiation heats unburned fuels. *7 Fire environment indicators: Fuel characteristics, fuel moisture, fuel temperature, topography/aspect, wind, atmospheric stability, fire behavior. * Fine Fuels are involved with the spread of most wildland fires. Continuous fine fuels provide provide potential for rapid rates of spread-most common with fatal fire. -Stay away from chutes, saddles & narrow canyons. *Steep slopes- allow fire to move quickly uphill/burning material to roll downhill, common in fatal fires. *Box canyons/chutes can act like a chimney channeling both wind & fire. *Saddles- cause a channeling effect/rapid rate of spread. *Narrow Canyons- allow for preheating, other slopes, increase spotting & jeopardize safety at canyon floor.
Wildland Fire behavior (Highlights & Red Notes) * Highlight - Note Chapter 4
-The fire environment controls the level of fire behavior. -There are 18 primary factors that influence how wildland fire will burn: Fuel--loading size and shape, compactness, horizontal continuity, vertical continuity, chemical content, fuel moisture, fuel temperature. Weather--temperature, RH, atmospheric stability, wind speed & direction, precipitation. Topography--elevation, position on the slope, aspect, shape of terrain, steepness fo the slope.
