The Woodsman's Journal Online: Surviving a Wildfire! Part One©

Forest fires, wildfires, brushfires, conflagrations, infernos, global cataclysms! It doesn’t matter what you called them, but it seems like everyone was talking about them on June 7^th, as the smoke from the Canadian wildfires drifted down the East Coast of the United States, negatively effecting air quality on a continental scale.

This week we will talk about what causes a wildfire to become an inferno, and next week we will talk about how to survive a wildfire in the wilderness, if you get caught up in one!

Wildfire!

What turns an ordinary small and controllable flame into an uncontrollable inferno?

Wildfires, just like small campfires, need three ingredients to sustain combustion; fuel, oxygen, and heat source to ignite the fuel. The heat from a wildfire is radiated, conducted, or transferred by convention to other nearby fuels and the fire grows and grows.

Besides fuel, there are two other conditions, weather, and topography, which when combined change a controllable fire into a monster conflagration, out of control.

Fuel

Wildfire fuels are typically the remains of plants, however the quality of the fuel, its ability to easily combust, depends on its surface area and the amount of moisture that it has absorbed from the environment around it.

The smaller and finer the fuel, the easier it catches fire and the faster it burns, because of its greater surface, than larger, thicker fuel.

Conversely, the greater the surface area, the faster the fuel can absorb
moisture from the environment. When the moisture content of the fuel is high, it is difficult to ignite, and it will burn poorly, if at all. When moisture in the fuel is low, it will ignite quickly, and will burn well.

Weather

Wind and amount of moisture in the fuel are the two most important weather related conditions affecting wildfires and of the two, wind is the least predictable and most changeable. Winds are affected both by the large scale weather patterns and the topography of the land over which they blow. Winds affect wildfires by drying forest fuels and by aiding initial ignition and combustion, by increasing the oxygen available to the fire. Wind also aids the spread of wildfires by carrying heat and burning embers to new fuels and by bending the flames closer to the ground and the unburnt fuels, ahead of the flames.

Topography

Topography, the shape of the land’s surface, has a major effect on how fast a fire moves and where it moves to. Fires run uphill surprisingly fast, particularly on steep slopes, and in gullies, which funnel the wind.

A fire blazing uphill resembles a fire burning before a wind. The speed of burning will usually increase as the slope increases. Not only are the flames closer to the ground on a steep slope, but the upwardly moving heated air is more likely to carry firebrands and start spot fires. All things staying the same, a fire burning on level ground (a slope up to a 5% or 3^o) will spread twice as fast when it reaches a 30% or 17^o slope. This rate of spread will double again when the slope reaches 55% or 29^o.

Don’t forget to come back next week and read “Surviving a Wildfire! Part One©”, where we will talk about how to survive a wildfire in the wilderness if you get caught up in one!

I hope that you continue to enjoy The Woodsman’s Journal Online and look for me on YouTube at BandanaMan Productions for other related videos, HERE. Don’t forget to follow me on both The Woodsman’s Journal Online, HERE, and subscribe to BandanaMan Productions on YouTube. If you have questions, as always, feel free to leave a comment on either site. I announce new articles on Facebook at Eric Reynolds, on Instagram at bandanamanaproductions, and on VK at Eric Reynolds, so watch for me.

That is all for now, and as always, until next time, Happy Trails!

Sources

Countryman, Clive M.; Heat-Its Role in Wildland Fire- Part 1, [U.S. Department of Agriculture, Forest Service, Pacific Northwest, 1975], https://books.google.com/books?id=9-4TAAAAYAAJ&printsec=frontcover&dq=Fuels+for+Radiation+and+Wildland+Fire&hl=en&newbks=1&newbks_redir=0&sa=X&ved=2ahUKEwiH_eO1vsH_AhVSFVkFHXwmAuQQ6AF6BAgDEAI#v=onepage&q=Fuels%20for%20Radiation%20and%20Wildland%20Fire&f=false, accessed June 13, 2023

Schroeder, Mark J., and Buck, Charles C.; Fire Weather: Agricultural Handbook 360, [U.S. Department of Agriculture, Forest Service, Broomall, PA, May 1970], https://books.google.com/books?id=j4f_lBHsSKEC&pg=PA88-IA2&dq=%22smoke+columns%22+wind+direction&hl=en&newbks=1&newbks_redir=0&sa=X&ved=2ahUKEwjI6r_dzsH_AhX4EWIAHYqwCwgQ6AF6BAgHEAI#v=onepage&q=%22smoke%20columns%22%20wind%20direction&f=false, accessed June 13, 2023

Wilson, Carl C., and Sorenson, James C.; Some common denominators of fire behavior, [U.S. Department of Agriculture, Forest Service, Broomall, PA, December 1978], https://books.google.com/books?id=w_tq7y2v8I4C&printsec=frontcover&dq=smoke+wind+direction+wildfire&hl=en&newbks=1&newbks_redir=0&sa=X&ved=2ahUKEwi78oTswcH_AhUxMVkFHSE_Dd04ChDoAXoECAkQAg#v=onepage&q&f=false, accessed June 13, 2023