Wildland Fire Behavior

Component 1 Fuel-grass, shrub, timber litter, logging slash 01-02-S390-VG

Less than 30, treat as a dead fuel. LIVE FUEL MOISTURE STAGE OF VEGETATIVE DEVELOPMENT ________________________________________ Fresh foliage, annuals developing early in growing cycle. Maturing foliage, still developing with full turgor. Mature foliage, new growth complete and comparable to older perennial foliage. Entering dormancy, coloration starting, some leaves may have dropped from stem. Completely cured. MOISTURE CONTENT Percent 300 200 100 50 Less than 30, treat as a dead fuel. 01-10-S390-VG

PROBABILITY OF IGNITION A rating of the probability that a glowing firebrand will cause a fire. 01-11-S390-VG

Wind 20 mi/h 20 mi/h 10 mi/h 3 mi/h 01-13-S390-VG

Fuel exposure to wind Unsheltered (ridgetops) Wind Partly sheltered (under timber midslope, wind on slope) Partly sheltered (patchy timber) Fully sheltered (under timber, flat or gentle slope, near base of steep mtn.) Unsheltered (no foliage, near clearings) 01-14-S390-VG

PERCENT SLOPE X 100 % RISE IN FEET % SLOPE = RUN IN FEET RISE RUN 01-16-S390-VG

A MATHEMATICAL MODEL IS A SET OF EQUATIONS 02-04-S390-VG

ASSUMPTIONS OF THE FIRE SPREAD MODEL 1. Fire is spreading at the flame front. 2. Fire is free burning. 3. Fine fuels control rate of spread. 4. Uniform and continuous fuels. 5. Surface fire. 6. Uniform weather and topography. 02-05-S390-VG

RATE OF SPREAD DISTANCE/TIME ENDING TIME STARTING TIME DISTANCE RATE OF SPREAD DISTANCE/TIME 02-09-S390-VG

FLAME LENGTH FEET 02-12-S390-VG

POINT SOURCE Point source model is designated for fires burning on flat ground or where the wind is blowing in the direction of the slope plus or minus 30°. upslope max slope ± 30º 02-15-S390-VG

SPREAD CALCULATION SD=PT X ROS SD = SPREAD DISTANCE PT= PROJECTION TIME ROS = RATE OF SPREAD 02-16-S390-VG

SPREAD DIRECTION NO WIND WIND WIND WIND UP SLOPE UP SLOPE UP SLOPE DOWN SLOPE DOWN SLOPE DOWN SLOPE 02-18-S390-VG

POINT SOURCE PREDICTION LIMITATIONS Calculations with windspeeds less than 2.5 miles per hour are generally too low. Better predictions result with windspeeds greater than 2.5 miles per hour. 02-21-S390-VG

FIRE PERIMETER AND SHAPES Fire perimeter and shapes are based on smooth ellipses - actual perimeter of the fire edge would likely be greater length and follow topographic relief. 02-23-S390-VG

APPROXIMATE FIRE SHAPES ASSOCIATED WITH MIDFLAME WINDSPEEDS OF….. Wind Direction Fire Start 7.5 mi/h 2.5 mi/h 10 mi/h 15 mi/h 5 mi/h 02-24-S390-VG

AREAS OF USE SUPPRESSION Determination of locations to place crews, equipment, helicopters and fuel breaks. Development of the wildland fire situation analysis. 02-25-S390-VG

PRESCRIBED BURNING Distance between spot fires to accomplish an objective. Calculating timing of ignition to take advantage of diurnal weather patterns. Managing wilderness fires. Development of escaped fire contingency planning. 02-27-S390-VG

EFFECTIVE WINDSPEED The midflame adjusted for the effect of slope on uphill fire spread. 02-37-S390-VG

EXAMPLES OF EFFECTIVE WINDSPEED 3 mi/h EFFECTIVE WINDSPEED IS 5 mi/h 60% 5 mi/h 02-38-S390-VG

MAXIMUM SPOTTING DISTANCE When torching trees, piles or wind- driven surface fires loft firebrands, which are then carried by the prevailing wind. 02-43-S390-VG

SOURCES OF FIREBRAND Torching trees Burning pile Spreading surface fire 02-44-S390-VG

FACTORS RELATING TO THE SPOTTING PROBLEM Probability of production of firebrands. Windspeed. Fire intensity. Number of firebrands 02-45-S390-VG

Dispatching Priorities FUELS WEATHER TOPOGRAPHY 03-05-S390-VG

Predicting “Real Time” Fire Behavior Running Surface Fire Wildland Fire Situation Analysis(WFSA) 03-06-S390-VG

Prescribed Burning Estimate the behavior of escapes or spots. Assess fuel and weather conditions at burn time. Develop burn prescriptions. Develop containment and control plans. 03-07-S390-VG

FIRE PLANNING Preattack Describing consequences Environmental documents 03-09-S390-VG

Spread Distance Elapsed Time Rate of Spread = 03-28-S390-VG

FLAME LENGTH* Indicator of intensity Observable *Remember flame length is not equal to flame height. 03-30-S390-VG