Heatrequired to reduce moisture to cause combustion
Slope
Wind speed
Fuel compactness
Fuel arrangement
Extreme fire behaviour
Results from combination of environmental factors
Available fuels
Wind
Low fuel moisture
Stability
Weather
Extreme fire behaviour
1. High spread rate
2. Intense burning
3. Crown fires
4. Spotting
Crown fire development
Crownclosure
Stagnation of smoke
Torching
Spotting
Smokecolumns
Wind driven fire
Unpredictable spread in all directions
Highspreadrate
Short range spotting
Sheared smoke columns
Long range spotting
Smokerises up
Smoke colour
White smoke - dry fuel
Black smoke - living fuel
Park smoke - fast spreading fire
Analyzing extreme fire behaviour
1. Analyzingsearingexternal
2. Fuel bed
3. Type of embers
4. Number of embers
5. Gusty wind
6. Atmospheric instability
7. Vortices
8. Intense heat from fire
Wind driven fire
Spotting occurs in front of the fire
Fire spread can be predicted
Plumedrivenfire
Updraftwindforces are stronger than windforce
Firedevelopment is unpredictable, spottingoccurs in all directions
Aspect
Southernaspect has lower temperature, lowest rate of spread
Northernaspect has highertemperature, faster rate of spread
Easterly aspect fuels are transitional, first to cool in afternoon
Westerly aspect fuels are transitional, last to cool in afternoon
Slope contributes to pre-heating and ignition by presenting the fuels to the flame front
Fire will movequickeruphill, slower downhill
Topographyinfluence on firebehaviour
Affects local wind patterns
Certainlandformsattractlightningignition
Slopeaffects fuel pre-heating and rate/direction of spread
Elevationaffectsfueltypes, loading, curing, and length of fire season
Slope is the onefactor that contributes to runaway fires that wecanmanage
Slope positions
More fires at base of slope and mid-slope than on top of ridges
Rate of spread decreases on the downslope
Ridges are the best place to construct a break in steep terrain
Narrow valleys
Tend to funnel and acceleratewind on hotdays
Boxcanyonsandchutedvalleys
Steepnarrowvalleysthatfunnel and accelerate wind, creating a chimney effect
Barrier
Any landscape feature that will obstruct the spread of fire, includingbreaks in fuel, changes in fueltype, fuel moisture, density, and natural or man-madefeatures
Influence of aspect on fuelmoisture
North slope has lowest fuelmoisture during the hottestpart of the day
Southslopereceivesless solar radiation, has higher fuel moisture
Influence of elevation on fuelmoisture
As elevationdecreases, temperatureincreases, relative humidity decreases, and fuel moisture decreases