the heels of Oregon’s most expensive wildfire season ever in 2018, researchers
at Oregon State University are ramping up efforts to better predict how the
blazes behave, including how they generate fire-spreading embers.
team led by David Blunck of OSU’s College of Engineering has been chosen by the
U.S. Department of Defense to spearhead a new $2.1 million effort to study the
burning of live fuels.
will partner with the U.S. Forest Service on a four-year grant awarded through
the DOD’s Strategic Environmental Research Development Program.
DOD is interested in this because they have a lot of land, and it burns,” said
Blunck, an assistant professor of mechanical engineering. “Live fuels are
basically trees that are green and living. These trees are often what torches,
but historically, dead fuels have primarily been studied.”
work will be built around the theory that there are likely just a handful of
factors – such as pyrolysis, the decomposition that results from high
temperatures, and the products of that decomposition – that cause differences
in burning behavior when live fuels burn.
live fuel studies tend to be fuel specific, controlling for variation in
burning behavior based on time of year and moisture content, but with those
results, it’s hard to know how new fuels will burn, or even how the same fuel
will burn outside the conditions that have been studied,” Blunck said. “So it’s
really better to understand what’s driving the sensitivity when you have
different fuels. Our theory is that it’s just a few processes that cause the
differences when you burn different live fuels, and if we can understand what
they are, we can better predict how new species would burn.”
research will provide Department of Defense managers with fire models that can
predict ignition, burning rate and fuel consumption for mixtures of live and
dead fuels, allowing them to more effectively plan prescribed burning as well
as wildfire responses. It will involve a mix of lab work, modeling and field
recent months, Blunck’s group has examined the burning behavior of more than
100 trees representing four different species – Douglas fir, grand fir, western
juniper and ponderosa pine – in the range of 10 to 15 feet tall.
height is not very large for a forest perspective, but for testing for wildfire
purposes this is typically not done, and never for the number of trees that we
have burned,” he said.
wildfire research, Blunck explains, involves either prescribed burns, or work
in a laboratory on samples up to a size of roughly 1 meter.
the lab you can control all the parameters like temperature, size and moisture
content, but how well do the results scale?” he said. “With a prescribed burn,
you’re researching under actual conditions, but with the data you get it’s very
hard to understand cause and effect. There’s so much out of our control that
it’s hard to know what’s driving the various phenomena.
trees that are about 10 feet tall, we can bridge the scales between the
laboratory and prescribed burns,” Blunck said. “We can look at many species and
start to vary the parameters we think are important. Our experiments are on an
intermediate scale but have a replicate size that is not rivaled by any study I
have ever found.”
addition, last December Blunck and other researchers studied the effect of fire
retardant on ember generation and found that under some conditions, trees
coated in the retardant sent off fewer embers that contained enough energy to
start a new fire. This effort was in partnership with an industry sponsor, P N
are wildfires’ most unpredictable modes of causing spread,” Blunck said. “By
understanding how embers form and travel through the air, we can more
accurately predict how fire will spread.”
for studying embers include infrared videography, collecting embers in trays of
water and measuring scorch marks on squares of fire-resistant fabric placed on
the ground at varying distances from the fire.
using fire-resistant fabric to collect embers, in conjunction with trays filled
with water, the fraction of ‘hot’ embers can be determined and used to help
predict spotting,” said Tyler Hudson, a graduate student in the College of
char marks on the fabric are used to estimate how much energy an ember has when
it lands. Trees coated in fire retardant tended to produce bigger embers, but
generally with lower energy.
Oregon last year, the cost of fire suppression for the first time exceeded half
a billion dollars, according to the Northwest Interagency Coordination Center, which
provides logistical support and intelligence for federal and state wildland
fire suppression agencies.
state in 2018 saw 1,880 fires burn 1,322 square miles – more land area than the
state of Rhode Island.