Wildfires

Biological hazard

-An uncontrolled fire fueled by natural vegetation

-Often start in rural wilderness areas, but migrate to rural urban fringes, affecting populations

-Fuel (vegetation to burn)

-Oxygen (air)

-Heat (to bring fuel up to ignition temperature)

-The temperature at which it will burst into flames

-For wood it’s 300 degrees (at this temp, it releases hydrocarbon gases that mix with oxygen in the air, combust and create a fire)

300 degrees (at this temp, it releases hydrocarbon gases that mix with oxygen in the air, combust and create a fire)

-Natural

-Human

Lightning

(climate of low rainfall = dry vegetation = captures fire easier)

-Discarded cigarettes

-Children playing with matches

-Camp and agricultural fires getting out of hand

-Arson

(fires have increasingly been caused by humans)

-Fuel is vegetation

-Has to be of sufficient quantity and dry enough to burn

-Affects frequency and duration of droughts (vegetation and litter can accumulate and dry out)

-Affects type of vegetation that grows in an area

-Affects rate at which litter can be produced

Vegetation

Leaves

-Surface

-Ground

-Crown

-Only burn surface litter

-Easiest fires to put out

-Cause least damage to forest

-Underground in deep accumulations of humus, peat and dead vegetation

-Move very slowly

-Difficult to fully put out

-Burn trees up their entire length

-Most intense and dangerous

The manner in which fuel ignites, the flame develops and fire spreads

-Vegetation type (trees, shrubs etc) and density

-Fuel characteristics (amount and thickness)

-Climate (rainfall and temp of an area)

-Recent weather (temp, wind direction, speed, rain)

-Fire behaviour (how it burns)

-Thick undergrowth, closely spaced trees allow fire to spread more easily (surface and crown fires)

-Some trees naturally contain alot of oil, and so burn easier

-Vegetation with needles/loose papery bark ignite easier

-Fine dry material burns most easily

-Large amounts of fuel that form a continuous cover help fire burn for longer and spread more intense

-Semi arid with distinct dry seasons are more prone to fires

-Needs to be some rainfall for vegetation to grow in the first place though

-Over periods of time, area lacks precipitation, have low humidity and high temps giving rise to more intense fires as the fuel dries out (harder to stop once ignited)

-Stronger winds = faster spread of fire

-Wind can transfer embers that can ignite new areas = expanded spread

-Drought conditions = dried out veg = more flammable

-Crown fires are more intense as they burn trees up their entire length

-Surface fires are less intense as they only burn surface litter

-Creeping fires move across ground surface slowly

-Running fires spread rapidly

-A rural hazard

-Can occur in most environments

-With continued expansion of humans, fires can occur within boundaries of substantial settlements

-Log Angeles Basin, California

-Much of the area is covered by drought resistant chaparral (area too dry for much tree growth)

-Santa Ana dry wind increases vegetation dryness massively and increases fire spread

Physical: fires, air pollution

Human: death, building and vegetation destruction

Physical: flooding

Human: health issues, homelessness, loss of crops and tourism

-People may be killed or injured if they don’t evacuate in time

-Homes are burnt and destroyed so people become homeless

-Power lines can be burnt, leaving people without electricity

-Health problems (inhaling smoke)

-Release of toxic gases = air pollution

-Plants and wildlife are killed

-Habitats burnt and destroyed

-Soil are damaged due to removal of organic matter

-Businesses are destroyed = loss of jobs and income

-Insurance increases after fire

-Cost of fighting the fire is huge

-Tourist numbers may decline after

-Governments can face criticism for their management if the fire has severe impacts

-Governments may have to change their forest management practices

-Vegetation type and density

-Fuel characteristics

-Climate (rain, humidity, temp)

-Recent weather

-Type of fire (surface, ground, crown)

-Magnitude of fire

-Wind speed and direction

-Number of fires

-Level of development

-Level of preparedness

-Population density

-Type of infrastructure

-Human response

-Proximity of urban areas to rural areas

Yes

-Education (on risk factors and how to avoid starting them)

-Fire breaks (remove fuel from a section of land)

-Controlled burning (dry litter on ground is burnt and removed to reduce fuel available for surface fires)

Removing a line of vegetation to stop a fire spreading

Dry litter on the ground is purposefully burnt and removed to reduce fuel available for surface fires

-Managing vegetation (controlled burning and fire breaks in advance)

-Managing built environment (increase the gap between houses and vegetation)

-Hazard mapping (identify areas at higher risk of fires and prevent building there)

-Fire breaks

-Controlled burning

-Fire resistant materials (using stone and brick rather than wood in buildings)

-Education (on risk factors and how to avoid starting fires)

-GIS modelling (used to study ways fire behaves to predict fires behaviour)

-Insurance (expensive in fire prone areas)

-Warning systems (establish lookout towers/air patrols)

-Emergency plans and kits in households

-Shelter (created in emergency)

-Supplies of retardants (slow the spread of fires)

-Evacuations

-Stage 1: create fire breaks, building using fire resistant materials, controlled burning, hazard mapping

-Stage 2: put out fire with firefighters and retardants, evacuation, firebreaks to limit spread

-Stage 3: search and rescue for survivors, treat injured

-Stage 4: emergency aid provided, temporary structure built

-Stage 5: long term aid, permanant infrastructure

-Prevention/mitigation: create fire breaks, carry out controlled burning, use fire resistant materials for building, hazard mapping

-Preparation: educate people, train emergency services, put warning systems in place, create emergency plan

-Response: order evacuations, put out fire with firefighters and retardants, fire breaks, controlled burning, treat injured, search and rescue for survivors

-Recovery: infrastructure rebuilt, long term aid given, replant vegetation stripped from fire