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NIST Study Offers First Detailed Look at the
Progress of a Wildland-Urban Fire
National Institute of Standards and Technology
June 16, 2009
A
wildfire rages across southern California wildlands
towards residential communities, endangering
residents and firefighters and sending property up
in smoke. This is an increasingly common story,
occurring several times a summer. To better
understand these Wildland-Urban Interface (WUI)
fires and how best to prevent or fight them,
researchers at the National Institute of Standards
and Technology (NIST) have issued an in-depth study
on fire behavior and defensive actions taken in a
community during such a fire.
WUI fires are becoming more prevalent as housing
developments push into former wilderness areas.
Drought is believed to also be a major contributor
to larger wildfires. In addition to southern
California, WUI fires also burn across the southern
United States and in countries such as Australia,
Greece, Italy and Spain. Little research has been
conducted on understanding WUI fire behavior and on
the effectiveness of current risk mitigation
strategies.
The new NIST study examines in detail the events in
one representative community during the Oct. 21-22,
2007 “Witch Fire” north of San Diego, Calif. The
Witch Fire was the largest of the 2007 California
fire storm. The fire burned 197,990 acres (80,124
hectares) and destroyed more than 1,100 homes. Fire
damage was estimated at $1.8 billion and suppression
costs were $18 million.
For their study, fire researchers Alex Maranghides
and Ruddy Mell tracked down every fire captain who
worked in the fire at The Trails housing development
in Rancho Bernardo to follow the fire’s evolution.
The NIST researchers, with the support of The Trails
Homeowners Association, also collected event
timeline information from homeowners. Of the 274
homes in The Trails neighborhood, 245 were within
the fire’s perimeter. Of those, 74 homes were
completely destroyed and 16 were partly damaged.
The data collection tracked the fire’s approach from
the wildlands, the effects of the fire in the
community and defensive actions taken by owners and
first responders. Researchers documented the
construction characteristics of the destroyed homes
and the wildland and residential vegetation damage
immediately after the fire.
The study revealed that two-thirds of all the homes
destroyed were ignited either directly or indirectly
by embers. “This is an important finding because
current guidelines to make structures more fire
resistant offer little guidance on how to make
structures more resistant to an ember attack,” fire
researcher Alex Maranghides explains. Researchers
also learned that one-third of all structures within
the fire perimeter were defended by first responders
and/or homeowners.
The NIST report is the first in a series of three
publications to understand WUI fire behavior. The
second publication, in progress, will examine the
role of construction and landscaping on the
probability of a structure’s survival. A third
report will describe a study that uses the data to
build a computer-generated virtual community to test
the fire behavior predicted by different fire models
and compare the results to the observed fire
behavior and structural response.
This study is part of NIST’s Reduced Risk of Fire
Spread in Wildland-Urban Interface Communities
research within its Building and Fire Research
Laboratory, a program to develop first-generation
tools by 2013 for improved risk assessment and
mitigation in WUI communities at risk from
wildfires.
“A Case Study of a Community Affected by the Witch
and Guejito Fires,” report may be found
here. |
