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Unit 12 Part 1

Gauging Fire Behavior & Guiding Fireline Decisions12-#-S290-EPGauging Fire Behavior and Guiding Fireline DecisionsUnit 12Part 1Unit 12 ObjectivesDescribe how to apply fire behavior information to safety and suppression decisions.

Demonstrate how to calculate the size of safety zones.

Identify the importance of changes in fire behavior to firefighter safety. 12-#-S290-EPGauging Fire Behavior and Guiding Fireline DecisionsUnit 12Part 124.Discuss what drives large changes and identify the next big change.

5.Demonstrate a simple but systematic method for gauging change and estimating fire spread time.

6.Identify other fire behavior prediction tools.Unit 12 Objectives12-#-S290-EPGauging Fire Behavior and Guiding Fireline DecisionsUnit 12Part 13Fire Behavior Affects Safety and Suppression Decisions12-#-S290-EPGauging Fire Behavior and Guiding Fireline DecisionsUnit 12Part 1Add pictureBasic Fire Behavior MeasuresFlame Length (FL)a measure of how fast energy is being released at the flaming front.

Rate-of-Spread (ROS)a measure of how fast the fire front is moving.12-#-S290-EPGauging Fire Behavior and Guiding Fireline DecisionsUnit 12Part 1The distance from the middle of the flaming zone to the average flame tip.Flame Length 12-#-S290-EPGauging Fire Behavior and Guiding Fireline DecisionsUnit 12Part 112-7-S290-EP

Flame Length12-7-S290-EP12-#-S290-EPGauging Fire Behavior and Guiding Fireline DecisionsUnit 12Part 1Applying Flame Length Flame length affects choice of fire suppression tactics and methods.

Dictates the dimensions of safe zones.12-#-S290-EPGauging Fire Behavior and Guiding Fireline DecisionsUnit 12Part 1Fire Suppression LimitationsFires can generally be attacked at the head or flanks by persons using hand tools. Handline should hold the fire.

Fires are too intense for direct attack on the head by persons using hand tools. Handline cannot be relied on to hold the fire.

Fires may present serious control problems; torching out, crowning and spotting. Control efforts at the head will probably be ineffective.

Crowning, spotting and major fire runs are probable. Control efforts at the head of the fire are ineffective.Flame Length0 - 4 ft.

4 - 8 ft.

8 - 11 ft.

>11ft.12-#-S290-EPGauging Fire Behavior and Guiding Fireline DecisionsUnit 12Part 1

Fire Characteristics Chart

(light fuels)12-10-S290-EP12-#-S290-EPGauging Fire Behavior and Guiding Fireline DecisionsUnit 12Part 1Change VG format to EP in slide numbering10

Fire Characteristics Chart(heavy fuels)FIRE BEHAVIORFire Characteristics Chart(scale for heavy fuels)12-11-S290-EP12-#-S290-EPGauging Fire Behavior and Guiding Fireline DecisionsUnit 12Part 1Safety Zone Calculations12-#-S290-EPGauging Fire Behavior and Guiding Fireline DecisionsUnit 12Part 1Add instructor note for instructor not to let topic stray into fire shelter dos and don'ts discussion from refresher training, stay to calculations for safety zone size calculation.12Definition of a Safety Zone An area cleared of flammable materials used for escape in the event the line is outflanked or in case a spot fire causes fuels outside the control line to render the line unsafe. They are greatly enlarged areas which can be used with relative safety by firefighters and their equipment in the event of blowup in the vicinity. 12-#-S290-EPGauging Fire Behavior and Guiding Fireline DecisionsUnit 12Part 113 used when fire conditions are such that escape routes and safety zones have been compromised. Deployment zones are the last ditch areas where fire shelters must be deployed to ensure firefighter survival due to the available space and/or fire behavior conditions at the deployment zone location. Definition of a Deployment Zone12-#-S290-EPGauging Fire Behavior and Guiding Fireline DecisionsUnit 12Part 1

Safety Zone GuidelinesAvoid locations that are: downwind from firein chimneys, saddles, narrow canyons

Take advantage of heat barriers

Burn out safety zones prior to flame front approach12-#-S290-EPGauging Fire Behavior and Guiding Fireline DecisionsUnit 12Part 1AssumptionsSafety Zone size calculations are made on the worst case scenario.

All sides of the safety zone will receive the same heat flux.

Based on an crew of 3.12-#-S290-EPGauging Fire Behavior and Guiding Fireline DecisionsUnit 12Part 1

Fire surrounding a circular shaped safety zone gives the worst case (most radiant heat transfer).Fire and safety zone edge more closely resemble a straight line. Radiant heat transfer from the sides is low.x feetx feet12-#-S290-EPGauging Fire Behavior and Guiding Fireline DecisionsUnit 12Part 1AssumptionsFlame Length = Flame HeightSafe separation is a straight line from the heat source to the firefighter 12-#-S290-EPGauging Fire Behavior and Guiding Fireline DecisionsUnit 12Part 1

USDA Forest Service, Fire Behavior Research Firefighter Safety ZonesDistanceSeparationFirefighterFlaming FrontFlame Height

12-#-S290-EPGauging Fire Behavior and Guiding Fireline DecisionsUnit 12Part 119Inputs for the mathematical model include flame height, and distance between the firefighter and flame (the safety zone radius).Safety Zone EquationsFlame Height Input: 4 x flame height

Consider increasing the distance separation when more than 3 people and 1 engine will occupy the safety zone.12-#-S290-EPGauging Fire Behavior and Guiding Fireline DecisionsUnit 12Part 120Circle Safety Zone-Example Distance Separation = the radius of the circle.Flame Height = 20 feet 20 x 4 = 80 radius

Distance separation = 80 feetDiameter of circle = 80 X 2 = 160

12-#-S290-EPGauging Fire Behavior and Guiding Fireline DecisionsUnit 12Part 1Safety Zone Size Assuming no Slope and no WindFlameDistanceArea inHeightSeparationAcres10 ft40 ft1/10 acre20 ft80 ft1/2 acre50 ft200 ft3 acres75 ft300 ft7 acres100 ft400 ft12 acres200 ft800 ft50 acres12-#-S290-EPGauging Fire Behavior and Guiding Fireline DecisionsUnit 12Part 122More than 3 people and 1 engine will increase the distance requirement.

Convective heat from wind or terrain will increase the distance separations requirement.

12-#-S290-EPGauging Fire Behavior and Guiding Fireline DecisionsUnit 12Part 1Rate of Spread (ROS)Rate of advance of the flame frontCan be given in absolute terms, such as feet-per-minute (ft/min)

Can be given in relative terms, such as twice as fast as before (2X)Spread Time:The time it will take the fire to move a given distance; it can be determined from ROS.12-#-S290-EPGauging Fire Behavior and Guiding Fireline DecisionsUnit 12Part 1ROS is a key safety factorif a fire can catch you it can hurt you!

Rate of Spread12-#-S290-EPGauging Fire Behavior and Guiding Fireline DecisionsUnit 12Part 1Changes in ROS are very important to safety and suppression.

A universal factor in fireline accidents is a rapid change in ROS.

Rate of Spread12-#-S290-EPGauging Fire Behavior and Guiding Fireline DecisionsUnit 12Part 126ROS can also be used to express how fire spread rate will changeCompare the ROS before with the ROS after a changehow much faster or slower will the fire move?

ROS-ratio=(bigger ROS)/(smaller ROS)Example: ROS changes from 10 to 60 (or 60 to 10), ROS-ratio = 60/10 = 6X 12-#-S290-EPGauging Fire Behavior and Guiding Fireline DecisionsUnit 12Part 127ROS Ratio Example= 6XDIVIDED BY12-#-S290-EPGauging Fire Behavior and Guiding Fireline DecisionsUnit 12Part 128ROS-ratio can indicate the degree of coming danger, and can be used to predict future fire spread time.Rate of Spread Ratio12-#-S290-EPGauging Fire Behavior and Guiding Fireline DecisionsUnit 12Part 1

The idea of predicting fire spread in the future, using the complete application of FLAMEThe next big change30 minutes30 more min.If fire moves 3X faster onthe slope, it will take 1/3 of 30, or about 10 min. to spread up the slopeobservepredictprojectThe slope is about as long as the 30-min. spread on the flats.Note: these are spread times, rather than spread rates, and are very practical for use onthe firelinehow long will it takethe fire to go from here to there? 12-30-S290-EP12-#-S290-EPGauging Fire Behavior and Guiding Fireline DecisionsUnit 12Part 130What a Change in ROS Can MeanROS changes ranging from 60x to 500x have accompanied fireline fatalities.

ROS-ratio of 60x means that fire spread that has taken place over hours can suddenly take place in minutes.

If walking-pace represents slow ROS, an increase of 500x would be the equivalent of twice the speed of sounda huge relative change.

Changes are not instantaneous, and can involve a transition over time (often minutes to 10s of minutes) But always be aware, change is coming!12-#-S290-EPGauging Fire Behavior and Guiding Fireline DecisionsUnit 12Part 131First Consider Current Fire BehaviorCurrent fire behavior demonstrates the effects of current fuels, terrain and weather, and provides a baseline.

Factors such as live fuel moisture or 10-hour FM do not change rapidlythey are important overall, but vary over longer time scales.12-#-S290-EPGauging Fire Behavior and Guiding Fireline DecisionsUnit 12Part 132Unforeseen Changes Kill FirefightersRapid, large increase in fire ROS is a common denominator in fatality fires.ROS increases of 60x and more have been associated with fatality incidents.

To be safe requires firefighters:foresee changes well aheadhave a sense of the size of the changeunderstand both current and expected fire behavior12-#-S290-EPGauging Fire Behavior and Guiding Fireline DecisionsUnit 12Part 133Quotes from Fatality-Fire Reportsbenign appearance of fireno appreciable wind during decision makingLook what its doing now.; the fire didnt look that bad assuming they would see the fire coming at the same rate they had all day.right flank was backing into a light up-canyon wind. numerous observers reported that the wind had remained light and steady intensity and rate-of-spread were much greater than had been anticipated burnout was conditioned upon light upslope winds holdingRevealing a reliance on impressions of current behavior, a tendency to not foresee the coming dangerous fire behavior. 12-#-S290-EPGauging Fire Behavior and Guiding Fireline DecisionsUnit 12Part 1Foreseeing Changes in Fire Behavior12-#-S290-EPGauging Fire Behavior and Guiding Fireline DecisionsUnit 12Part 1It is critical for a firefighter to anticipate the next big change in plenty of time to confront it.Look ahead at the factors that cause big changes.12-#-S290-EPGauging Fire Behavior and Guiding Fireline DecisionsUnit 12Part 136Anticipating the ChangeSupports LCESLookouts-What to be looking for, and using the most appropriate lookout locations Communications-What key things to communicate and how oftenEscape routes-Where and how long Safety zones- Close enough and big enough12-#-S290-EPGauging Fire Behavior and Guiding Fireline DecisionsUnit 12Part 13712-38-S290-EP

Dominant Change-MakersLitterCrowns (timber & brush)GrassFUEL TYPE is a significant contributor to big changes, changes of 15X or more.WIND (effective wind, which includes slope) is the biggest change-maker, ROS changes of 200X or more.12-38-S290-EP12-#-S290-EPGauging Fire Behavior and Guiding Fireline DecisionsUnit 12Part 13812-39-S290-EP

Another Important Factor 1-hour FM can change fairly rapidly and can cause changes up to 1.6x or so (usually less), but it is a minor change-maker compared to fuel-type or wind.Very important:1-hour FM is a key factor in the potential for crown fire.

12-39-S290-EP12-#-S290-EPGauging Fire Behavior and Guiding Fireline DecisionsUnit 12Part 139Typical Big Change EventsBy drawing in the simple pictures both current and expected fire behavior must be consider.

If either picture is blank, your evaluation of the fire behavior is incomplete.12-#-S290-EPGauging Fire Behavior and Guiding Fireline DecisionsUnit 12Part 14012-41-S290-EP

Sudden Wind Change Current conditions - Light winds

Expected conditions - Strong winds, direction changeWhat are some examples of wind change?12-41-S290-EP12-#-S290-EPGauging Fire Behavior and Guiding Fireline DecisionsUnit 12Part 141

Change in Fuel Type Current conditions - Litter fire Expected conditions - Crown fire12-42-S290-EP12-#-S290-EPGauging Fire Behavior and Guiding Fireline DecisionsUnit 12Part 142

Slope Reversal a major change, often in both fuel and wind Current conditions - Upslope crown fire - Wind-exposed

Expected conditions - Downslope litter fire - Wind-shelteredFavorable change12-43-S290-EP12-#-S290-EPGauging Fire Behavior and Guiding Fireline DecisionsUnit 12Part 14312-44-S290-EP

Current conditions - Downslope litter fire - Wind-sheltered

Expected conditions - Upslope crown fire - Wind-exposedDangerous change12-44-S290-EPSlope Reversal12-#-S290-EPGauging Fire Behavior and Guiding Fireline DecisionsUnit 12Part 144Gauging the Changes in Fire Behavior12-#-S290-EPGauging Fire Behavior and Guiding Fireline DecisionsUnit 12Part 1How much does ROS change as fuel factors, wind, and slope change? Well look at each factor, to develop our sense of change, and eventually learn to apply guidelines to assess changes in fire behavior.12-#-S290-EPGauging Fire Behavior and Guiding Fireline DecisionsUnit 12Part 1A scaled diagram can help develop a sense of change to expect as conditions change.

Specific guidelines will allow us to consider any change in:

- fuel type - wind - slope12-#-S290-EPGauging Fire Behavior and Guiding Fireline DecisionsUnit 12Part 1Consider first the effects of changing fine dead fuel moisture (FDFM), a fairly large change, equivalent to a substantial change in relative humidity.

Later well introduce a guideline for gauging the effect of FDFM on ROS. 12-#-S290-EPGauging Fire Behavior and Guiding Fireline DecisionsUnit 12Part 148

FDFM: Timber Litter1-hour fine dead fuel moisture = 2%ROS = 6 ch/hFL = 3 ft.1-hour fine dead fuel moisture = 10%ROS = 3 ch/hFL = 2 ft.12-49-S290-EP12-#-S290-EPGauging Fire Behavior and Guiding Fireline DecisionsUnit 12Part 1Check all alignments of these kinds of slides

FDFM: Logging Slash1-hour fine dead fuel moisture = 2%ROS = 13 ch/hFL = 9 ft.1-hour fine dead fuel moisture = 10%ROS = 7 ch/hFL = 6 ft.12-50-S290-EP12-#-S290-EPGauging Fire Behavior and Guiding Fireline DecisionsUnit 12Part 1

FDFM: Short Grass1-hour fine dead fuel moisture = 2%ROS = 53 ch/hFL = 4 ft.1-hour fine dead fuel moisture = 10%ROS = 20 ch/hFL = 2 ft.12-51-S290-EP12-#-S290-EPGauging Fire Behavior and Guiding Fireline DecisionsUnit 12Part 1

FDFM: Tall Grass1-hour fine dead fuel moisture = 6%ROS = 96 ch/hFL = 14 ft.1-hour fine dead fuel moisture = 10%ROS = 49 ch/hFL = 9 ft.12-52-S290-EP12-#-S290-EPGauging Fire Behavior and Guiding Fireline DecisionsUnit 12Part 1

FDFM: Shrub1-hour fine dead fuel moisture = 2%ROS = 63 ch/hFL = 20 ft.1-hour fine dead fuel moisture = 10%ROS = 44 ch/hFL = 15 ft.12-53-S290-EP12-#-S290-EPGauging Fire Behavior and Guiding Fireline DecisionsUnit 12Part 1Changes in Fuel Type Produce Large Changes in Fire Behavior12-#-S290-EPGauging Fire Behavior and Guiding Fireline DecisionsUnit 12Part 15412-55-S290-EP

Fuels are grouped into fuel-types based on their similarities in ROS.

Litter is a dead, compact,horizontal fuel

Crown foliage is a live,vertically arranged, open fuel

Grass is a dead, verticallyarranged, open fuelslowestfastest12-55-S290-EP12-#-S290-EPGauging Fire Behavior and Guiding Fireline DecisionsUnit 12Part 155

Effect of Fuel-type on Relative Rate-of-SpreadLitter1xROS in crown fuels about4x faster than in litterROS in grass fuels about3x or 4x faster than in crownsOther factors being equalThis is only about fuel-types

Crown4xGrass15x12-56-S290-EP12-#-S290-EPGauging Fire Behavior and Guiding Fireline DecisionsUnit 12Part 156Fuel-Types often Change with Aspect

SN

SN

SN12-#-S290-EPGauging Fire Behavior and Guiding Fireline DecisionsUnit 12Part 157Transition Fire Behavior:an Important Change in Fuel-Type

Can become crown fireSuch changes between fuel beds that are stacked vertically can be very rapid and may be difficult to foresee.

Surface fire (litter or grass)12-#-S290-EPGauging Fire Behavior and Guiding Fireline DecisionsUnit 12Part 158Indicators of Crown-Fire PotentialSeasonal drought period prevailsOverall drought makes matters worseRecent crown fire Relative Humidity 35%-20%, or lessBacking fire produces torchingFire moving up ladder fuelsTorching and short crown runs

12-#-S290-EPGauging Fire Behavior and Guiding Fireline DecisionsUnit 12Part 1Effective Wind Speed (EWS)

Combines the effects of wind and slope. Think of EWS as the midflame wind speed (MFWS).

It is a huge driver of change!12-#-S290-EPGauging Fire Behavior and Guiding Fireline DecisionsUnit 12Part 160Key QuestionsHow does wind vary from place to place?How does wind at flame level vary with fuel type?How do we account for slope?12-#-S290-EPGauging Fire Behavior and Guiding Fireline DecisionsUnit 12Part 16112-62-S290-EP

Wind speed is the component of the wind that is pushing the fire ahead into new fuels.Across the heel, wind has least effect on fire spreadAcross the flank, wind parallels the flame front; little net wind influenceAcross the head, full wind effectMidflame wind speedMost of the time well consider either head fire or backing/flanking fire.12-62-S290-EP12-#-S290-EPGauging Fire Behavior and Guiding Fireline DecisionsUnit 12Part 162Change arrow colorchange color of bottom of slide

Check with jim on this slide12-63-S290-EP

How We Express Changes in Effective Wind Speed As the ratio of the bigger to the smaller wind speed(very much like the ROS-ratio)For example: 6 mi/hrThe bigger wind speedex: 2 mi/hrThe smaller wind speed= 3x in our example; (i.e. the wind speed will triple)The ratio of the wind speeds, the EWS-ratio.=Divided by12-63-S290-EP12-#-S290-EPGauging Fire Behavior and Guiding Fireline DecisionsUnit 12Part 163

Calculating EWS-RatioSmaller EWS Larger EWS In this example, the bigger wind is 6 and the smaller wind is 2 a tripling of EWS.12-64-S290-EP12-#-S290-EPGauging Fire Behavior and Guiding Fireline DecisionsUnit 12Part 164Effects of Doubling the Wind Speed on ROS and FL12-#-S290-EPGauging Fire Behavior and Guiding Fireline DecisionsUnit 12Part 165

Midflame Wind: Timber litterMidflame Wind = 4 m.p.h.ROS = 6 ch/hFL = 3 ft.Midflame Wind = 2 m.p.h.ROS = 2 ch/hFL = 2 ft.12-66-S290-EP12-#-S290-EPGauging Fire Behavior and Guiding Fireline DecisionsUnit 12Part 1

Midflame Wind: Logging SlashMidflame Wind = 4 m.p.h.ROS = 11 ch/hFL = 7 ft.Midflame Wind = 2 m.p.h.ROS = 6 ch/hFL = 5 ft.12-67-S290-EP12-#-S290-EPGauging Fire Behavior and Guiding Fireline DecisionsUnit 12Part 1

Midflame Wind: Short GrassMidflame Wind = 4 m.p.h.ROS = 61 ch/hFL = 4 ft.Midflame Wind = 2 m.p.h.ROS = 18 ch/hFL = 2 ft.12-68-S290-EP12-#-S290-EPGauging Fire Behavior and Guiding Fireline DecisionsUnit 12Part 1

Midflame Wind: Tall GrassMidflame Wind = 4 m.p.h.ROS = 89 ch/hFL = 12 ft.Midflame Wind = 2 m.p.h.ROS = 39 ch/hFL = 8 ft.12-69-S290-EP12-#-S290-EPGauging Fire Behavior and Guiding Fireline DecisionsUnit 12Part 1

Midflame Wind: ShrubMidflame Wind = 4 m.p.h.ROS = 72 ch/hFL = 20 ft.Midflame Wind = 2 m.p.h.ROS = 30 ch/hFL = 13 ft.12-70-S290-EP12-#-S290-EPGauging Fire Behavior and Guiding Fireline DecisionsUnit 12Part 1Effects of Slope Alone(from Gentle to Steep)12-#-S290-EPGauging Fire Behavior and Guiding Fireline DecisionsUnit 12Part 171

Slope: Timber LitterSlope = 8%ROS = 1 ch/hFL = 1 ft.Slope = 24%ROS = 2 ch/hFL = 2 ft.Slope = 72%ROS = 8 ch/hFL = 3 ft.12-72-S290-EP12-#-S290-EPGauging Fire Behavior and Guiding Fireline DecisionsUnit 12Part 1

Slope: Logging SlashSlope = 8%ROS = 2 ch/hFL = 3 ft.Slope = 24%ROS = 3 ch/hFL = 4 ft.Slope = 72%ROS = 13 ch/hFL = 8 ft.12-73-S290-EP12-#-S290-EPGauging Fire Behavior and Guiding Fireline DecisionsUnit 12Part 1

Slope: Short GrassSlope = 8%ROS = 5 ch/hFL = 1 ft.Slope = 24%ROS = 14 ch/hFL = 2 ft.12-74-S290-EP12-#-S290-EPGauging Fire Behavior and Guiding Fireline DecisionsUnit 12Part 1

Slope: Tall GrassSlope = 8%ROS = 6 ch/hFL = 3 ft.Slope = 24%ROS = 14 ch/hFL = 5 ft.12-75-S290-EP12-#-S290-EPGauging Fire Behavior and Guiding Fireline DecisionsUnit 12Part 1

Slope: ShrubSlope = 8%ROS = 6 ch/hFL = 6 ft.Slope = 24%ROS = 14 ch/hFL = 9 ft.12-76-S290-EP12-#-S290-EPGauging Fire Behavior and Guiding Fireline DecisionsUnit 12Part 1Add the Influence of Slope to the Wind to Get the Effective Wind SpeedSlope acts like a little more upslope wind, increasing the efficiency of heat transfer to new fuel.

As a guideline, add a little bit to the upslope wind speed to account for slope (mostly on upslope fires).12-#-S290-EPGauging Fire Behavior and Guiding Fireline DecisionsUnit 12Part 1

Effective Wind, the Slope Contribution20%40%80%60%Less than 20%, no adjustment 1 mph20% to 40%, add 1 mph 2 mph40% to 60%, add 2 mph 3 mph60% to 80%, add 3 mph Add the contribution for slopeto the upslope wind component 5 mphOver 80%, add 5 mph 12-78-S290-EP12-#-S290-EPGauging Fire Behavior and Guiding Fireline DecisionsUnit 12Part 178Add graph to sw

Combine Slope Contribution and Mid-Flame Wind in EWSWind Blows UPSLOPE: Add6MFWS2+slope=8EWSWind Blows DOWNSLOPE: Subtract6MFWS-slope2=EWS4NEVER USE EWS < For fires backing upslope into the wind set EWS = 12-79-S290-EP12-#-S290-EPGauging Fire Behavior and Guiding Fireline DecisionsUnit 12Part 1Add line art graphic to sw79Potential Magnitude of Fuel and Wind Effects on Short-Term Changes in ROSFM in large and live fuels~ 1.2xFM in fine fuels~ 1.6xFuel type (litter, crown, grass)~ 15xEffective Wind Speed~ 200x It is clear that fuel type and effective wind speed dominate changes in ROS. The FireLine Assessment MEthod, FLAME concentrates on those factors. 12-#-S290-EPGauging Fire Behavior and Guiding Fireline DecisionsUnit 12Part 1End of Unit 12 - Part 112-#-S290-EPGauging Fire Behavior and Guiding Fireline DecisionsUnit 12Part 181