Knowledge Objectives (3 of 3)

Transcription

1 Wildfire Investigations Knowledge Objectives (1 of 3) Describe the difference among ground fuels, surface fuels, and aerial fuels and their effects on fire spread. Describe the effects of wind, fuels, topography, weather, fire suppression, and other natural mechanisms on fire spread. Knowledge Objectives (2 of 3) Describe indicators a fire leaves behind that can lead the investigator to the origin of the fire. List special safety considerations associated with wildland fire investigation. Describe methods of conducting a wildfire investigation. Knowledge Objectives (3 of 3) Explain fire cause categories used in wildland fire investigation. Identify methods of evidence collection for wildfire investigations. Skills Objectives Employ special safety considerations associated with wildland fire investigation. Protect the general area of origin. Conduct an origin investigation. Conduct a cause investigation. Collect evidence for wildfire investigations. Introduction Wildfire investigations involve special: Techniques Practices Equipment Terminology Understanding of wildfire behavior is necessary Consider enlisting specialized personnel 1

2 Wildfire Fuels Ground fuels All flammable materials lying on or in the ground Surface fuels All flammable materials located just above the ground Aerial fuels All green and dead materials located in the upper forest canopy Fuel Condition Analysis (1 of 2) Physical characteristics of the fuel must be classified by the: Burning characteristics of individual materials Combined effects of these materials Ground fuels Duff is not major influence Roots restrict air supply, but provide avenue for fire spread Fuel Condition Analysis (2 of 2) Surface fuels Coniferous litter Understory vegetation Aerial fuels Crowns Snags Moss ppart/shutterstock, Inc. Fuel Matrix Major fuel groups are: Grass Shrub Timber Litter Logging debris Groups are further classified by species, fuel form, size, arrangement Factors Affecting Fire Spread (1 of 8) Heat transfer Convective heat allows fire to spread upwards Radiant heat spreads fire laterally. Lateral confinement Fire cannot spread laterally because of inflammable terrain Alters speed, intensity, and direction of spread Factors Affecting Fire Spread (2 of 8) Wind Influence Pushes flames ahead and preheats fuel Four types of wind Meteorological Diurnal Fire winds Foehn winds 2

3 Factors Affecting Fire Spread (3 of 8) Fire head, flanks, and heel (rear) Different locations within the fire Head: area of greatest intensity Flanks: either side of head Heel: opposite end from head Factors Affecting Fire Spread (4 of 8) Fuel influence Species and condition of vegetation Solar exposure, weather, geography Roots Surface fuels Crown fuel Factors Affecting Fire Spread (5 of 8) Topography Form of natural and human made earth surfaces Slope: change in elevation over a given distance Aspect: direction the slope faces Factors Affecting Fire Spread (6 of 8) Weather Weather history Description of atmospheric conditions Ambient temperature Air temperature of the surrounding environment Relative humidity Amount of moisture in a given volume of air compared with how much moisture the air could hold at that same temperature Factors Affecting Fire Spread (7 of 8) Fire suppression Fire breaks Natural or humanmade barriers Air drop Courtesy of Michael Rieger/FEMA Aerial application of retardant Firing out Burning fuel between fire break and fire Factors Affecting Fire Spread (8 of 8) Other natural mechanisms of fire spread Wind borne firebrands Spot fires Fire storm Animals and birds 3

4 Indicators of Directional Pattern (1 of 4) Wildfire V shaped patterns Ground surface burn Horizontal Degree of damage Grass stems Brush Trees Indicators of Directional Pattern (2 of 4) Angle of char Pole type fuels Timber type fuels White ash deposit Shows up on objects exposed to greater amounts of heat Cupping Concave or cup shaped char pattern Die out pattern Develops as spread of fire slows Exposed and protected fuels Noncombustible objects shields unexposed side Indicators of Directional Pattern (3 of 4) Staining and sooting Appears on side of object exposed to flames Depth of char Greatest on side facing advancing fire Spalling Appears on side of rock exposed to flames Curling Leaves curl toward heat source; associated with slower moving, lighter burns Foliage freezing Needles or leaves of tree bend in wind direction Indicators of Directional Pattern (4 of 4) Noncombustibles Fire direction was from the opposite side of the protected area Loss of material Can produce lines of demarcation and fire patterns Special Safety Considerations (1 of 3) Keep informed on fire weather conditions and forecasts. Know what your fire is doing at all times. Base all actions on current and expected behavior of the fire. Identify escape routes and safety zones, and make them known. Post lookouts when there is possible danger. Be alert. Keep calm. Think clearly. Act decisively. Special Safety Considerations (2 of 3) Maintain proper communications with forces, the supervisor, and adjoining forces. Give clear instructions, and ensure they are understood. Maintain control of your forces at all times. Fight fire aggressively, having provided for safety first. 4

5 Special Safety Considerations (3 of 3) Also consider: Maintenance of personnel accountability Underground burning hazards Falling or rolling debris Current and changing weather Reburn potential Downed live power lines Hazardous materials Conducting an Origin Investigation Consider wind, topography, fuels Origin is normally close to heel (rear) of fire Interviews can help narrow down area Observations of initial attack crew are very useful Satellite or imaging tools can be used. Consider a vehicle line up. Security of the Area or Point of Origin Integrity of fire scene needs to be preserved Area of origin should be secured Flag off area Restrict access Protect tire tracks, foot prints, potential ignition sources Search Techniques (1 of 4) Walk the exterior of the fire. Look for burn patterns. Identify the general area of origin. Enter the general area of origin. Identify the specific area of origin. Grid the specific area of origin. Identify the origin. Search Techniques (2 of 4) Walk search area twice (opposite directions). Identify clusters or groups of indicators. Reduce the flagged off area, and work to the specific area of origin. If the origin is large, use segment division Search Techniques (3 of 4) Use metal flagging stakes or labeled flags to identify evidence. 5

6 Search Techniques (4 of 4) Loop technique: small areas Approach from the head and work from flank to flank, back and forth, to close in on origin Grid technique: large area with more than one investigator Lane technique: inspecting area in great detail Document your examination with a photographic record sketch. Magnifying glass or reading glasses Magnets Straight edge Probe Comb Search Equipment Hand held lights Air blower (nasal aspirator) Metal detector Sifting screen GPS recorder Fire Cause Determination Establish and confirm cause of fire And determine what did not cause fire Document findings. Recover heat or ignition source, if possible Test hypothesis through use of literature or by live testing under controlled conditions Natural Causes (1 of 2) Many wildfires start from lightning. Lightning maps are available. Lightning strikes can cause fulgurites. Courtesy of the World Meteorological Organization (WMO)/NOAA Natural Causes (2 of 2) Other evidence may include: Bark shredded from trees or shrubs Multiple strikes Holes in the ground Strange burn patterns on the ground Human Causes (1 of 2) Accidental fires are those for which there was not a deliberate human act. Incendiary fires are deliberately ignited by a person who knows that the fire should not be ignited. 6

7 Campfires Smoking Debris burning Incendiary Prescribed fire (controlled burn) Human Causes (2 of 2) Machinery and vehicles Railroad Fire play Fireworks Utilities (1 of 3) Fires can result from equipment failures and from power lines contacting: Wind damaged trees Birds or small animals Balloons Fulgurites or indentations in the ground are often found if wires contact the ground. Utilities (2 of 3) Utilities (3 of 3) Pits are often found where power line contacts tree. Electric fences and oil and gas drilling operations may start also start fires. Miscellaneous Wildfire causes than cannot be classified under other cause groupings Examples Spontaneous heating Sunlight and glass refraction Evidence Collection Procedures Identifying and gathering Contamination Collection Detailed identification Transporting and storage Testing 7

8 Summary (1 of 5) Wildland fire investigations are used to determine the origin and cause of a fire and responsible party of wildfires. Investigators must learn to read the indicators that the wildland fire impresses on the landscape to determine where the fire started. Summary (2 of 5) Investigators must preserve the origin and all evidence correctly, conduct interviews, and prepare professional investigation reports to prepare for cost recovery, where applicable. Summary (3 of 5) Fuels are classified as: Ground fuels, which include all flammable materials lying on or in the ground Surface fuels, which include all flammable materials lying just above the ground Aerial fuels, which include all green and dead materials located in the upper forest canopy Summary (4 of 5) Wind speed and direction are important factors to consider when determining the possible area of fire origin. The origin is normally located close to the heel or rear of the fire. Summary (5 of 5) By back tracking the progress of the fire, the investigator can retrace the path of the fire to the point of origin. Wildfires originate from both natural and human causes. 8