Hazards - Wildifres Flashcards
What is a wildfire?
‘An uncontrolled rural fire’
What are the 3 different types of wildfire?
Ground fire
Surface fire
Crown fire
What is a ground fire?
A slow smouldering fire that burns organic matter in the soil such as peat.
Spread slowly
Fairly low temps for long periods of time
May be no flame
What is a surface fire?
The burning of leaf litter and low-lying vegetation.
The most common type of fire.
Can be low or high intensity.
They cool quickly and are relatively easy to control.
What is a crown fire?
A fire that moves rapidly through the canopy.
This type has a dramatic effect on forested areas.
The hottest type of fire.
Very difficult to contain.
What is a ‘fuel ladder’?
A firefighting term for live or dead vegetation that allows a fire to climb up from the landscape or forest floor into the tree canopy.
Common ladder fuels: tall grasses, shrubs, tree branches
How to prevent the ladder effect?
Pruning trees and removing lower hanging branches
What conditions favour wildfires?
Heat - allows fire to spread by evaporating moisture in fuels allowing it to ignite and travel easily.
Oxygen - 16% required, supports oxidation process creating heat and gases
Fuel - gives fire burnable material allowing the fire to advance
What three key elements favour wildfires?
A ready supply of fuel - dry vegetation
An ignition source - can be natural / human
Favourable climatic or weather conditions - eg) dry winds
What fuel characteristics / vegetation types favour wildfires?
Thick undergrowth with closely spaced trees
Lots of fine, dry material - long grasses / twigs
What climate and recent weather conditions favour wildfires?
Sufficient rainfall for vegetation to grow
A distinct dry season
Strong winds - provide oxygen and help spread
Climate events - El Niño
What are the natural causes of wildfire?
Lightning
Volcanic eruptions
Heat transfer
Fire brands
What are the human causes of wildfire?
The wildland-urban interface - zone of transition between wilderness and land developed by human activity
Built environment meets natural environment
Human settlements in the WUI zone are more at risk of catastrophic wildfire
What are some positive effects of wildfires?
May remove dead or dying material from forest floor as well as harmful insects and diseased plants. This encourages new plant growth.
Some species of plant cannot reproduce without fire eg) Douglas fir needs fire to aid seed germination
How can wildfires be managed - preparedness
Households write emergency plan and buy supplies.
Defensible space established around homes in vulnerable areas
Warnings released using TV, social media
Red flag warning used in USA when conditions are perfect for serious fire
How can wildfires be managed - mitigation
Satellites with infrared sensors can deter thermal variation
Back burning - where controlled fires are lit to burn the fuel (vegetation) ahead of fire.
Disaster aid and fire insurance
How can wildfires be managed - prevention
Fire beaters available near recreation spaces so people can put out small fires before they spread.
Public education - Smokey bear mascot to provide info on prevention, with intention of becoming well known so people recognise risks.
Fire bans during high risk times
How can wildfires be managed - adaption
Planning regulations to enforce use of non-flammable building materials used in vulnerable areas.
Fire breaks created in forests to halt fires from spreading. However fires in strong winds can jump fire breaks (Alberta jumped 1km wide river)
The thought that fires are a natural process and should be allowed to run their course .
