Fire at the Wildland Urban Interface

CarolinaFireJournal - Dale Wade
Dale Wade
10/14/2011 -

(This is part one of a two-part series.)

What are the differences in fire behavior and control between structural and wildland fires? What are a few possible misconceptions some of you may have? The purpose of this article is to pass on a few facts and suggestions that you might find useful. I did call on a number of folks that are much more knowledgeable about the brushfire capabilities of VFDs and RFDs than I am, but the following is my assessment and I take full responsibility for what I say. I welcome any feedback, both positive and negative, and will try to answer any wildland fire questions you might have. I begin with some general comments and break the remainder into four broad wildland fire topics:

  • Wildland Urban Interface (WUI)
  • Fire behavior,
  • Fire suppression,
  • Training.

I weave safety into each rather than discussing it as a separate topic, but safety should always be your first consideration. Those trying to get a fire under control don’t need to have their priorities redirected by a medical emergency.

General Comments

My guess is that many of you my age are good old boys and gals who as children learned the value of burning the woods from older family members. Today, this is pretty much a lost art in the mountains of western North Carolina where I reside, but even though it is gaining wide acceptance in some places, it is now much more complicated because of smoke management issues and the unprecedented live and dead fuel loads that have accumulated as the direct result of a misguided Bear named Smokey.

Thankfully, the failed national policy of fire exclusion has been reversed and our native plant communities and wildlife will recover given the proper fire regime, but the process will take many decades and in the meantime we will continue to be faced with the fallout from this debacle. Don’t get me wrong — Smokey now has a message which I enthusiastically embrace: “Be Careful With Fire,” but during the second half of the past century he did more to ruin the ecological balance of our nations ecosystems than any other single factor, and in the process left us with the formidable task of having to cope with much more dangerous wildfires. Moreover, your personal view on global warming notwithstanding, the wildland fire season has been getting longer over the past several decades. Couple this with the incredible and often unregulated proliferation of single-family dwellings in “rural” settings, and one has a good recipe for disaster.

To make matters worse, municipal and state agency budgets have taken big hits in the past few years and more are likely to come. Many of you may now be having to drive further to your place of employment or even working two jobs in an effort to cobble together a living, which might mean it takes you longer to individually respond to a call. Funding for training is now harder to come by and you may also now have less time available for this all-important subject.

At the state level, open positions may not be filled and the assigned duties transferred to others, often in a different county, and equipment is not being replaced as scheduled. For example, the North Carolina Forest Service has gotten rid of its fixed wing air tankers although they still have three helicopters, one stationed in each region. That’s great if your fire is in that locality, but it can also mean better than a long two-hour wait for the ship to arrive once requested.

As the state’s response time to multiple wildland fires deteriorates and the resources immediately available dwindle, it means local fire departments and county units will try to pick up the slack. But their primary responsibility is protecting people and homes, not wildland fire suppression. It thus makes good sense to spend any available funds on those priorities first. I know I am preaching to the choir, but the bottom line is that we are being asked to do more with less, and in the case of wildland fire suppression, all too often without the needed training and equipment that would make your task safer and more efficient.

The N.C. Forest Service has the statutory responsibility for wildland fire suppression throughout the state, except on federal lands, and in many counties the ranger will not let local department personnel go past the end of a live reel unless they have had basic wildland fire training — which I think is a smart decision.

There are still local departments trying to do their job with 40-year-old engines and outdated worn-out equipment that they somehow keep running. Most states have grant programs available for specific purposes, but they are usually on a 50/50 cost basis and thus still beyond reach of some hard-pressed departments. One caveat is that the states I am familiar with put the most needy departments at the top of the list. This means that you might be aware of a surplus piece of equipment in your vicinity that you have told the state forestry agency you would like, but watch it go to another department clear across the state.

Another problem is clothing. You don’t want to be wearing full bunker gear and rubber boots on a wildland fire for a number of reasons. Your energy will be rapidly sapped regardless of your physical condition. If you know you are responding to a wildland fire rather than a structure fire, I urge you to dress in fire-resistant long sleeve shirts and pants, leather lace-up boots, gloves and hardhat. A fire shelter is a luxury item that I encourage you to wear if you have one and have been trained in its deployment. Although I never needed mine, I always wore it case I found myself in an untenable situation, it would have been too late to go back to the truck and get it!

If you ever do find yourself at your vehicle in an “oh crap” situation, wet down surrounding vegetation, yourselves and the vehicle if you have time, then get in it, inform dispatch of the situation giving them your exact location as best you can, turn off the ignition, shut all windows tightly, close the vents and hunker down, putting a blanket — wet is even better than dry — over you if handy. It takes more heat energy to heat a cool wet object up to ignition temperature and lots more heat to change liquid moisture into steam. I have been involved in the aftermath of too many incidents where folks panicked and either tried to outrun a fire on foot or drive to safety under zero visibility conditions with disastrous results. The exterior paint may bubble, the tires may ignite and it will get uncomfortably hot, but your chances of survival are excellent, and you can exit very soon after the flame front has passed and perhaps even extinguish the tires with the onboard fire-extinguisher and/or with dirt.

Wildland Urban Interface

The statistics I looked at show North Carolina ranked No. 1 in the country in area classed as Wildland Urban Interface (WUI) and No. 5 in the number of homes in the WUI. In fact, 41 percent of all homes in North Carolina are located in the WUI. Most of these new arrivals have no idea they are now living in a fire-dependent ecosystem that will burn sooner or later. The Firewise program is strongly endorsed by most state and federal agencies as well as by many VFDs and RFDs, but it is hard to convince folks that they are living amidst a tinderbox until they see catastrophic fire in their own backyard.

I urge each of you to set an example on your own property and to encourage your neighbors to follow suit; guidelines that will dramatically improve the chances of a home surviving the inevitable wildland fire should be readily available at your station as well as at the local state forest agency office. It isn’t rocket science to recognize that the prudent homeowner should keep gutters, roofs and porches clear of debris, not stack firewood on or under the porch, and to thin dense underbrush and trees — especially conifers — from around the house and out-buildings.

Beware of discarded 55 gallon drums, propane tanks, and large items that are often hidden in the vegetation surrounding a home; the current occupant might not even know they are there. Keep a sharp eye out so you can deal with the unexpected before whatever it is gets bathed in flame. If you have your cell phone on you, use it to snap a quick picture of abandoned cars and boats that are overgrown with vegetation as that piece of junk can miraculously become worth thousands of dollars after being consumed in a fire.

Fire Behavior

All fires require heat, oxygen and fuel — remove one and the fire will go out. But that said, wildland fire behavior differs substantially from structural fire behavior and is determined by different factors. Methods of attack will thus also differ.

House fires can be thought of as burning in a closed environment within the structure footprint while brush and grass fires burn in an open environment and run with the wind or upslope. Lots of water is usually necessary to completely extinguish structure fires because the burning fuels are relatively large and likely to re-ignite if not thoroughly drenched.

Grass and brush fires, on the other hand, although a moving target, take less water under most weather conditions because the fuels spreading the fire are smaller in size — usually dead foliage, cured grass and small branches — and thus much easier to saturate with water. That is why you rarely see a wildland fire during, or just after a rain, but often fight structure fires in such weather.

A spray is more effective in most cases and conserves water. Aim just above the base of the flames and don’t waste water shooting it high into the flames — it will just evaporate with little affect on the fire. When large diameter logs or burning stump holes are encountered, a stream of water is, however, often the answer.

On level ground, a free burning fire will burn in the direction the wind is blowing, its rate of spread determined by the speed of the wind. You need to be aware of the imminent passage of a cold front as it will change the wind direction to a northerly direction — WNW to NE depending upon the angle of approach. If you are near the ocean or a large lake, differential heating will also cause a sea breeze or lake breeze to develop most days which can cause a 180 degree change in wind direction; local knowledge is indispensible in such locations.

Also be alert to any approaching thunderstorms; although they may bring rain, they also produce dangerous downdrafts which hit the ground and blow out in all directions which means wind direction will continue to change as the storm passes by.

Heated air rises, which means that air movement will be uphill on a sunny day and conversely, downhill at night. In the mountains, the direction of fire spread at night will depend upon fire intensity. A cool fire with flame heights of only a few inches is likely to move downhill along with the smoke produced while a more actively burning fire will overpower the downslope flow of air.

In hilly terrain, fire rate of spread will roughly double with each 10 percent increase in slope. Not only are the flames bent closer to the ground by wind which increases radiant and convective preheating of the fuel, but also because the slope puts the flames and smoke closer to the unburned fuel ahead of the fire.

Spotting is another factor one has to deal with. A multitude of embers are continually landing ahead of any fire. They will ignite adjacent fuel depending upon the size of the ember and the moisture content of the fuelbed they land in. Small diameter fuels ignite the quickest and they also dry or dampen the quickest. Changes in the relative humidity (RH) will change fine fuel moisture very rapidly. As the RH drops below about 35 percent, an increase in spotfires will take place and as the RH drops below about 25 percent you can expect lots of problems from short distance spotting ahead of a fire. As a fire’s intensity increases, the size of burning embers lofted above the fire also increases and these larger burning fuels such as pinecones and bark can result in spotfires at much greater downwind distances — up to several miles under worst case situations — ahead of the main fire.

If trees are torching out, be careful as the fire may be getting ready to blowup. If the fire is crowning in timber, don’t even think about direct attack. Warn people ahead of the fire and make sure reinforcements are on the way.

You will have a good idea of when and where the last rain occurred in your area as well as its duration and the amount that fell. The damper the fuel, the harder it is for a fire to sustain itself, and the easier it is to control.  At the other end of the spectrum, when you are in an extended drought, any ignition source is more likely to ignite the adjacent fuel and the resulting fire will burn hotter, deeper into the forest floor and be more difficult to suppress. Larger diameter fuels will also ignite more easily, especially rotten logs.

In part two we will discuss fire supression and training.

Dale Wade has over 50 years of wildland fire experience ranging from straw boss on a Southern California Hot Shot crew to USFS Prescribed Fire Research Project Leader in Georgia. He was a certified prescribed burner in five southern states and was lucky enough to ply his trade wordwide working across the full spectrum from small landowners to National leaders.He decided to semi-retire in 2003 spending his time now by passing on the knowledge he has picked up over his career. He can be reached at [email protected].
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