Understanding Your Risk
Wildfires are oftentimes an unstoppable force, burning through our natural resources, destroying homes and communities, and causing billions of dollars in damage. Burning wildfires also pose serious health risks to nearby residents, pets, and livestock, including respiratory distress and complications from smoke inhalation.
Anywhere in the country is at risk of a spreading wildfire, including your own backyard. Fires are often started accidentally due to a combination of ideal conditions like lack of rain and the availability of dry grass ignited by a lightning strike. There are also many out of control wildfires that raged after a careless smoker dropped a cigarette on a pile of leaves or the burning fires set intentionally.
Wildfires can move as fast as 14 miles an hour, burning up everything in their path. Wildfires have been responsible for an increasing number of deaths among people in the fire’s path, including many firefighters and volunteers battling to put the fires out. According to National Geographic
, more than 100,000 wildfires occur in the United States each year, clearing 4-5 million acres of land. More recent fires have claimed over 9 million acres.
It is important to understand how wildfires can affect your life, especially if you live in areas of extended drought. By understanding the risks involved in facing a wildfire, you can better prepare your household for such an unexpected event.
Can Wildfires be Predicted?
Fire danger refers to both the consistent and changing factors influencing the start, spread, and control of a wildfire in a specific area. Technologies are used to accurately predict fire danger based on weather patterns, geographical topography, and presence of fuel to reliably determine the potential danger of wildfire risks in certain areas.
According to the United States Department of Agriculture
, emergency management teams and national park managers across the United States use the National Fire Danger Rating System, first implemented in 1972, to receive fire danger information. This allows them to effectively perform a number of tasks including:
- Communicating wildfire watch and warning alerts to the public
- Setting restrictions or closures on public lands
- Preparing equipment and staff to fight fires
- Deciding whether to control fires or allow them to burn under certain conditions
The National Fire Danger Rating System (NFDRS) offers five rating levels to alert the public to potential wildfire danger levels each day since 1974. These levels include:
Green (Low Risk)
Fire conditions are unlikely. In the event of a fire, weather and fuel conditions will result in a slow spreading fire, burning at low intensity and easy to control. Controlled burns can be done with reasonable safety.
Blue (Moderate Risk)
Some wildfires may be expected, with a moderate rate of speed. Control is not difficult. Controlled burns can be done safely but with additional caution.
Yellow (High Risk)
Wildfires are likely. Fires in mature forests, weed fields, and grasslands will be harder to control in windy conditions. Control will be difficult but not impossible. Controlled burning should be restricted to early morning or late evening hours.
Orange (Very High Risk)
Wildfires start easily and can spread quickly in advance of containment. High intensity flames make control difficult. Controlled burning is not recommended.
Red (Extreme Risk)
Wildfires will start and rapidly spread, with a potential to grow large. Erratic fire behavior can be expected. No controlled burns outdoors should occur in any areas under an extreme fire danger alert.
What Factors are Considered with the NFDRS?
A number of factors influence the threat and probability of wildfire ignition and their subsequent spread. These factors include:
Relative Humidity (RH) Levels
RH levels consist of the ratio of the amount of moisture in the air compared to the amount of moisture necessary to saturate the air at the same pressure and temperature. Relative humidity levels are expressed in percentages and are measured by automated weather stations or manually using a psychrometer.
The RH levels are important because the air is always exchanging moisture with dead forest fuels. High humidity levels enable dead forest fuels to take moisture from the air, while low levels allow the air to take moisture from the fuels. As RH levels drop, lighter fuels become drier and increase the risk of wildfire spread. Heavy fuels react to humidity changes more slowly and require more moisture to trigger change.
Fuel moistures are measured for live annual and perennial plants, as well as branches, foliage, and shrubs. Fuel moisture levels are also taken for dead fuel sources. Measurements represent the moisture content of the fuel source, which changes through each growing season and in different climates.
Greenness maps offer a visual representation of live fuel moisture, divided into four categories which use data from satellites to compare areas of wet and dry lands, pinpointing significant changes in the region based on vegetation images.
The Keetch-Byram Drought Index
is used to measure the effects seasonal droughts have on the potential for fire danger. The value offered by the index is an estimation of how much rain is needed in 100ths of inches to saturate the soil. As the value of the index increases, vegetation is suffering from a deficiency of moisture. Higher values indicate living plants will die and become fuel for a potential fire.
The Haines Index is acquired using the morning sounding from Radiosonde Observation stations throughout North America. The index features a stability term, which shows the temperature difference between two atmospheric layers. The moisture term shows the dew point depression at a single atmosphere level. When the index level is low, it correlates with a low potential for wildfire danger. When the index level increases, it corresponds to a higher fire risk due to a dry and unstable atmosphere.
This number relates to the probability a wildfire result is an ignition source introduced into a fine fuel resource. Ignition components range from a 0 when weather is calm, cool, and damp to 100 when weather is windy, and conditions are dry. The closer the temperature a fuel source is to the ignition temperature, the more likely a fire will result, such as in the case of parking a hot vehicle exhaust system over a field of tall, dry grass.
Energy Release Component (ERC)
The Energy Release Component refers to the potential available energy per square foot at the head of a fire, using a BTU measurement. Tables are used for each type of fuel to determine the rate of combustion of a potential fire.
Lightning Ignition Efficiency
Lighting has been the cause of many wildfires. Ignition efficiency for starting a fire is based on the duration of the continuing current of the ground strike and what type of fuel the strike hits. Different fuels require different conditions in order to be set on fire by lightning, including fuel conditions and levels of lightning activity.
Lightning Activity Levels
Lightning Activity Level (LAL) measures the cloud-to-ground lightning activity being observed within a 30-mile radius of the observation site. The NFDRS requires two factors to gauge lightning activity level: Yesterday’s Lightning refers to the data received during the previous day’s observation. Morning Lightning refers to the information observed between 12:00 am and the current observation time.
There are four types of fires recognized by the NFDRS:
Ground fires – burn in natural ground litter, roots, and high organic soil. They are hard to detect and control once started.
Surface fires – burn in grasses and low shrubbery or low branches in trees. These types of fires move quickly, and control depends on the fuel involved in the fire.
Crown fires – these fires burn in the treetops and are hard to control due to wind conditions.
Spotting fires – often produced by crown fires and windy conditions. Large embers are thrown around and ignite other areas of fuel. Once embers fly, fires are very hard to control.
Wildfires are measured by area in the United States, either acres or square miles. The largest fires are typically spread by strong winds and exacerbated by excessively dry land.
How are Wildfires Contained?
Wildfire containment has come a long way thanks to recent technologies, but the unpredictability and power of a wildfire still makes it difficult to contain and snuff out the voracious flames.
Today’s firefighters use a number of resources and techniques to contain fires as fast as possible. As soon as a wildfire is recognized, a dedicated response team mobilizes to douse the flames. Responders include local and regional firefighters with fire trucks and equipment, ground crews, aircraft, and bulldozers.
Firefighters spread out fire hoses along the edge of the fire, with a hose place about every 100 feet. Bulldozers are used to create a fire break, creating a line around the perimeter of the fire and removing all fuel sources including brush and dead grass. When public reports are made indicating the fire is 40% contained, it refers to the circumference of the fire line as it extends around the fire.
Crews may also start a controlled burn to dictate the direction the wildfire will spread. This burn removes fuel sources between the path of the fire and a barrier, like a rock face or road.
Helicopters are often used to drop water or a fire suppressant foam on hot spots within the wildfire. The foam coats unburned fuel sources to prevent them from igniting. Other aircraft are used to drop flame retardant chemicals on the fire to slow its progress.
Danger alerts are issued to the public as fires spread towards neighborhoods. The government’s emergency systems designed to alert homeowners to evacuate are effective, but a number of people still lose their lives because fires move too quickly, leaving no time for an evacuation. During an active wildfire, it is crucial households monitor the fire situation and predictions closely, especially during the night when people are usually asleep.
Communication is often lost between the emergency management teams and the public when the fire consumes critical power lines and other communication resources. A battery-operated weather radio is a good investment to keep up-to-date on emergency orders and the fire’s progress.
How are Wildfires Monitored?
The fire response crew relies on satellite images to track the path of a wildfire. The aircraft deployed to drop water and fire suppressants also monitor the fire activity. Recently, drones have been used to gather information about the fire. Drones allow a closer look at the fires for a longer time period, without risking the health and safety of a human crew.
Data collected by the fire response crew is used to identify potential dangers to important locations, such as power lines, water systems, and gas resources in the path of the fire. The information is also useful in making predictions as to how the fire will spread, and to keep the public alerted to potential dangers and the need for evacuations.
What can be Done to Prevent Wildfires?
Many wildfires are started accidentally, due to the carelessness or inattentiveness of humans. Smokey the Bear has long been a champion of wildfire prevention
, touting his famous “Remember, only you can prevent forest fires” since 1947. The famous bear reminds kids to avoid playing with matches or lighters, and informs them about the responsibilities that go along with having a campfire.
Some of the most significant wildfires were started by human activities, such as:
Cigarettes tossed from a car window or thrown on the ground can ignite a fire quickly. It is important to always put cigarettes out completely by putting them in a cup of water or a contained ashtray.
Campfires first need to be set up properly by creating a fire pit surrounded by rocks. The pit should be at least 10 feet away from any structures or combustibles. A campfire should only contain firewood, as other burning debris can drift off into the trees or grass nearby.
Whenever starting a campfire, it is helpful to have a hose or bucket of water and a shovel handy to douse flames if the fire grows too large and to extinguish the fire when you are ready to go. A common mistake people make after enjoying a campfire is not extinguishing it properly. Fires should be completely out before you leave the area.
Homeowners who are permitted to burn on their property often use fire to quickly get rid of yard waste, like leaves, brush, and tree limbs. In windy conditions, or when other trash is burned, fires can quickly spread. Backyard grasses and trees can catch fire and burn quickly in a dry area. Avoid burning in windy conditions. Watch the weather for upcoming rainy days and plan to burn on damp days.
Hot vehicles parked over dry leaves and grass cause a number of wildfires every year. Vehicles and off-road vehicles need to be parked on rocky areas where there is less vegetation. It’s helpful to carry a jug of water to douse a fire started by your vehicle.
Fireworks have resulted in wildfire ignition in many areas around the country. Many of the fireworks being used were illegal to start with and users traveled to forested areas to avoid getting caught. Fireworks lit in grassy areas are known to ignite grass fires, which can spread quickly. Sparks from fireworks have also been known to catch trees and brush on fire. Ignite approved fireworks only on a flat, vegetation-free surface and ensure all fireworks are completely put out before leaving the area.
Any fire or heat source that can trigger a wildfire needs to be carefully monitored, or avoided, to reduce your risk of starting a wildfire. Even a backyard campfire can quickly turn into a critical emergency situation. Everyone has a responsibility to properly start and extinguish outdoor fires for the protection of the neighborhood, the community, and all residences and businesses contained within.
Households should always be prepared to handle a wildfire emergency, including having access to clean water, non-perishable emergency foods, and an actionable evacuation plan. Fire damaged homes and property can be replaced but human lives cannot.