Chapter 11: Wildfires

INTRODUCTION
Wildfires are a natural phenomenon that have occurred for many millions of years. While they have many ecosystem benefits, they also pose a threat to human habitation that is increasingly moving into the urban-wildland interface. Human changes to landscapes, including wildfire suppression, have reduced the natural fire cycle and increased the probability of large, hot, and damaging fires that can reduce ecosystem functioning for many years. In this chapter we will explore what controls wildfire spread, how humans can mitigate and prepare for wildfires, and the human and ecosystem impacts of wildfires.
LEARNING OUTCOMES
The goals and objectives of this chapter are to:
  • Describe the causes of wildfire ignition and spread.
  • Explain the positive and negative impacts of wildfires.
  • Describe how mitigation can reduce wildfire risk.
  • Explore the role of wildland firefighters in fire management.

Introduction to Wildfires

TYPES OF WILDFIRES
The three main types of wildfires, as described by the National Park Service are:
Ground fires—which burn organic matter in the soil beneath surface litter and are sustained by glowing combustion.
Surface fires—which spread with a flaming front and burn leaf litter, fallen branches and other fuels located at ground level.
Crown fires—which burn through the top layer of foliage on a tree, known as the canopy or crown fires. Crown fires, the most intense type of fire and often the most difficult to contain, need strong winds, steep slopes and a heavy fuel load to continue burning.
ECOLOGICAL EFFECTS
Read pages 1-3 in the USDA report below about the basic impacts of wildfires and the ecological effects:

The Fire Environment

Picture
FIRE TRIANGLE
The fire triangle contains the three key ingredients for fire ignition and spread:
  • Fuel
  • Oxygen
  • Heat
The combination of these three factors contributes to fire behavior and is related to the environment of the fire. Fuel provides the energy source, oxygen is required for the combustion process, and heat often provides the trigger for the fire. Fire will occur when these three factors combine.
For wildfires, this triangle is sometimes modified to include the specific factors important for fires in wilderness lands namely:
  • Fuel
  • Topography
  • Weather
The fuels in wildfires includes trees, shrubs, and grasses, but also can be dead organic material littering the floor of the wild area. Both living and dead organic material can burn. A key feature of fuels in fuel moisture, which is the amount of water in living or dead fuels. This will be a factor of the type of vegetation, whether it is living or dead, the time of year, and the preceding weather and climate conditions. Fuel type can also impact spread, as some vegetation types, such as junipers and pines, are particularly flammable. Finally vegetation density, will impact the rate and ability of spread of the wildfire.

Topography, while easy to analyze with topographic maps, is a challenging factor for wildfire spread. First, fire, being hot, tend to move upward, and therefore will move up slopes at a much faster speed than down slopes. Additionally, the steepness and aspect of slopes will determine the type and spacing of vegetation growing. Wildfires burning in very complex topography are challenging to forecast and pose a particular danger.
FIRE WEATHER
Weather is critical in forecasting both the likelihood that a wildfire will start, as well as the behavior of a fire once it has started. The key weather variables that impact fire are:
  • Temperature
  • Relative Humidity
  • Wind Speed
  • Wind Direction
  • Cloud Cover
  • Rainfall
  • Chance of Lightning
Meteorologists and firefighting personnel can assess these conditions in the field using existing surface weather stations, with temporary weather stations, and with handheld weather stations. Forecasts of these conditions are created by local offices of the National Weather Service and communicated to firefighters and emergency managers in the field. On large fires, and Incident Meteorologist from the National Weather Service is assigned and sent to the fire location to provide detailed and up to date weather information to personnel in real time.

However, in many cases the fire itself can create different weather conditions. Additionally, the topography around the fire can create weather. These, changes in conditions happen on very small scales and are not able to be forecast by meteorologists. Therefore, it is important for wildland firefighters to have a basic understanding of fire weather, so they can assess changing situations in the field and modify their activities to stay safe.

Impacts of Wildfires

WILDFIRE THREATS
Read the USGS report below to explore the threat of wildfires in the United States:

Fighting Wildfires

MITIGATING THE THREAT
Wildfire mitigation has three main components:
  • Thinning fuels or prescribing small fires to reduce wildfire intensity and decrease the likelihood of crown fires. This activity tries to restore forests and landscapes to a healthier state, and restore the natural fire cycle.
  • Creating fire breaks (roads or other non-vegetated areas) to reduce fire spread, and aid in fire fighting activities.
  • Creating defensible space around homes in the urban-wildland interface.
The Federal Emergency Management Agency (FEMA) recommends the following steps to create defensible space and prepare homes within wildfire hazard areas:
  • Rake leaves, dead limbs and twigs. Clear all flammable vegetation.
  • Remove leaves and rubbish from under structures.
  • Thin a 15-foot space between tree crowns, and remove limbs within 15 feet of the ground.
  • Remove dead branches that extend over the roof.
  • Prune tree branches and shrubs within 15 feet of a stovepipe or chimney outlet.
  • Ask the power company to clear branches from powerlines.
  • Remove vines from the walls of the home.
  • Mow grass regularly.
  • Clear a 10-foot area around propane tanks and the barbecue. Place a screen over the grill - use nonflammable material with mesh no coarser than one-quarter inch.
  • Regularly dispose of newspapers and rubbish at an approved site. Follow local burning regulations.
  • Place stove, fireplace and grill ashes in a metal bucket, soak in water for 2 days; then bury the cold ashes in mineral soil.
  • Store gasoline, oily rags and other flammable materials in approved safety cans. Place cans in a safe location away from the base of buildings.
  • Stack firewood at least 100 feet away and uphill from your home. Clear combustible material within 20 feet. Use only wood-burning devices evaluated by a nationally recognized laboratory, such as Underwriters Laboratories (UL).
  • Review your homeowner's insurance policy and also prepare/update a list of your home's contents.
WILDLAND FIREFIGHTERS
Fighting wildfires is a dangerous and physically demanding job, which requires extensive training. This training has three main facets.
  • Fitness training to ensure firefighters can handle to physical challenges of the job.
  • Fire fighting training to learn the appropriate tools and techniques to use at different fire stages and in different situations.
  • Safety training in order to understand and identify the many hazards of wildfires and how to reduce the risk associated with these hazards.
10 Standard Firefighting Orders
Fire Behavior
1. Keep informed on fire weather conditions and forecasts.
2. Know what your fire is doing at all times.
3. Base all actions on current and expected behavior of the fire.
Fireline Safety
4. Identify escape routes and safety zones and make them known.
5. Post lookouts when there is possible danger.
6. Be alert. Keep calm. Think clearly. Act decisively.
Organizational Control
7. Maintain prompt communications with your forces, your supervisor and adjoining forces.
8. Give clear instructions and be sure they are understood.
9. Maintain control of your forces at all times.
If 1-9 are considered, then...
10. Fight fire agressively, having provided for safety first.
Eighteen Watch Out Situations
  1. Fire not scouted and sized up.
  2. In country not seen in daylight.
  3. Safety zones and escape routes not identified.
  4. Unfamiliar with weather and local factors influencing fire behavior.
  5. Uninformed on strategy, tactics, and hazards.
  6. Instructions and assignments not clear.
  7. No communication link with crew members or supervisor.
  8. Constructing line without safe anchor point.
  9. Building fireline downhill with fire below.
  10. Attempting frontal assault on fire.
  11. Unburned fuel between you and fire.
  12. Cannot see main fire; not in contact with someone who can.
  13. On a hillside where rolling material can ignite fuel below.
  14. Weather becoming hotter and drier.
  15. Wind increases and/or changes direction.
  16. Getting frequent spot fires across line.
  17. Terrain and fuels make escape to safety zones difficult.
  18. Taking a nap near fireline.

Case Studies

YARNELL HILL FIRE
A lightning storm ignited a wildfire on June 28, 2013 in a desert area northwest of Phoenix, AZ. As the fire grew nearby towns were evacuated and the Granite Mountain Hot Shots crew arrived to aid in fire suppression and protection of the nearby towns. On June 30, 2013, while retreating toward the town of Yarnell, 19 of the firefighters were overtaken by the flame front. They deployed their fire shelters, but all 19 succumbed to the heat and flames. The accident was partly caused by outflow winds from a thunderstorm to the northwest, which increased fire movement dramatically and created dangerous fire conditions.
More detailed information and accounts from this tragedy can be explored HERE.
MILFORD FLAT FIRE
The Milford Flat Fire was the largest wildfire in Utah history, 363,000 acres, and started from dry thunderstorms on July 6, 2007. Milford Flat is an area in central Utah north of the town of Milford and west of the I-15 corridor and the towns of Fillmore and Kanosh. While the wildfire itself caused little damage to infrastructure, post-fire rehabilitation desertified the area and created a large source of dust for many years. Strong winds from the south ahead of approaching storm systems lofted dust from the fire scar and transported north to the population centers along the Wasatch Front of Utah and the Wasatch Mountains. These dust storms are a hazard to transportation and human health, but also increase the melt rate of mountain snowpacks, by creating a darker surface, which absorbs more solar radiation.
RESOURCES
Firewise Communities, http://www.firewise.org/
National Interagency Fire Center, https://www.nifc.gov/
Ready.gov: Wildifres, http://www.ready.gov/wildfires
USDA, Wildfire, Wildlands, and People: Understanding and Preparing for Wildfire in the Wildland-Urban Interface, January 2013
http://www.fs.fed.us/openspace/fote/reports/GTR-299.pdf
USGS, Wildfire Hazards--A National Threat, February 2006
http://pubs.usgs.gov/fs/2006/3015/2006-3015.pdf
Utah Fire Info, http://www.utahfireinfo.gov/