Wildfire Protection in the
Wildland-Urban Interface
Ross W. Gorte
Specialist in Natural Resources Policy
Kelsi Bracmort
Specialist in Agricultural Conservation and Natural Resources Policy
January 23, 2012
Congressional Research Service
7-5700
www.crs.gov
RS21880
CRS Report for Congress
Pr
epared for Members and Committees of Congress
Wildfire Protection in the Wildland-Urban Interface
Summary
Congressional interest in funding to protect against wildfire threats has focused on communities
in and near forests, an area known as the wildland-urban interface (WUI). The WUI is expanding
in size and population, leading to increased concern for life and property that could potentially be
damaged by wildfires. Approximately 9% of all land in the lower 48 states is classified as WUI. A
significant concentration lies along the East Coast, although western states have the highest
proportions of homes in the WUI.
Federal funding for wildfire protection has increased significantly over the last decade. The U.S.
Forest Service (USFS) and the Department of the Interior (DOI) receive the bulk of funding to
prevent and suppress wildfires. Nearly half of the USFS budget in 2010 was allocated for wildfire
funding. A portion of this funding is spent on WUI efforts.
Wildfire, whether in a WUI community or not, occurs primarily as a surface fire or a crown fire.
A surface fire burns the needles or leaves, grass, and other small biomass within a foot or so of
the ground and quickly moves on. A crown fire burns biomass at all levels, from the surface
through the tops of the trees.
Wildfire suppression involves removing one of the three elements that cause fire—fuel, heat, or
oxygen. A variety of WUI wildfire control efforts may be used for structures, including building
structures to meet protective standards. Some standards vary by state, and many are voluntary,
such as removing burnable materials in proximity of a structure (i.e., defensible space). Control
efforts for protecting wildlands include fuel reduction, or allowing the fire to burn if the
ecosystem is able to adapt to and recover from periodic burning.
Programs and other options exist to address wildfires in the WUI. However, these programs could
be refined to better address the current situation, and new initiatives and funding could be applied
towards WUI issues not yet addressed. For example, programs could be expanded to educate
homeowners, state and local governments, and the insurance industry about the ways to protect
homes through actions, planning, and zoning and building regulations. Congress could consider
expanding protection for defensible space beyond the home ignition zone to a community
protection zone. Congress could also consider appropriating additional funds through the states
for fuel reduction on private lands in the WUI where the treatments would be effective.
Additionally, Congress could consider expanded compensation for landowners who suffer
resource losses from wildfires.
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Wildfire Protection in the Wildland-Urban Interface
Contents
What Is the Wildland-Urban Interface? ........................................................................................... 1
Fire Suppression .............................................................................................................................. 2
In the Aftermath............................................................................................................................... 3
Minimizing Wildfire Damages ........................................................................................................ 4
Protecting Structures.................................................................................................................. 4
Protecting Wildlands ................................................................................................................. 5
Protecting the WUI.................................................................................................................... 5
Issues for Congress .......................................................................................................................... 6
Figures
Figure 1. 2000 WUI Map................................................................................................................. 2
Contacts
Author Contact Information............................................................................................................. 8
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Wildfire Protection in the Wildland-Urban Interface
ildfires have made national headlines in recent years, with major fires in the West and
South killing firefighters, burning homes, and threatening communities. With the
W population and size of the wildland-urban interface (WUI) expanding, more money is
being spent on fire management in these locales. Federal funding for fire protection has more than
doubled in the past decade, and administration and congressional leaders have urged additional
wildfire protection. In FY2010, nearly $3.4 billion was spent to protect federal lands and
approximately $133 million to assist in protecting nonfederal lands.1 The U.S. Forest Service
(USFS) in the Department of Agriculture, along with the Department of the Interior (DOI), are
responsible for protecting the majority of federal lands from wildfire, including any federal areas
that comprise a WUI. Wildfire funding accounted for nearly half of the USFS budget and roughly
7% of the DOI budget in 2010. While attention has focused on protecting life, property, and
communities in the WUI, opinions vary over how to provide protection. This report describes the
growth of the wildland-urban interface, wildfire suppression efforts, post-fire responses, and
especially the programs and options for protecting the interface before the next wildfire strikes.
What Is the Wildland-Urban Interface?
The term wildland-urban interface (WUI) has been used for more than two decades to suggest an
area where structures (usually homes) are in or near wildlands (forests or rangelands). There is no
standard WUI definition. However, the definition listed in a 2001 Federal Register notice is
commonly referenced—the urban-wildland interface community exists where humans and their
development meet or intermix with wildland fuel.2 In this same notice, the USFS and DOI
identified three types of WUI communities: interface, intermix, and occluded.3 Based on state
data, they listed nearly 4,500 interface communities (with 11 states not providing data). The
agencies defined an interface community as one where wildlands abut structures with a clear line
of demarcation between residential, business, and public structures and wildland fuels, while an
intermix community is where structures are scattered and intermingled with wildlands and fuels.
An occluded community, generally existing within a city, is where structures abut an island of
wildland fuels (e.g., park or open space).
One source indicates that all states within the contiguous United States contain land classified as
WUI.4 See Figure 1. Furthermore, approximately 9% of all land within the lower 48 states is
classified as WUI, with a significant concentration along the East Coast, although western states
have the highest proportions of their homes in the WUI.5 Recent research has found that the area
of intermix communities is large and is growing faster than the area of interface communities.6 In
2000, intermix communities in the three Pacific Coast states totaled 9.8 million acres, almost
1 For more information, see Tables 2 and 4 in CRS Report RL33990, Federal Funding for Wildfire Control and
Management, by Ross W. Gorte.
2 U.S. Dept. of Agriculture and Dept. of the Interior, “Urban Wildland Interface Communities Within the Vicinity of
Federal Lands That Are at High Risk From Wildfire,” 66 Federal Register 753 (January 4, 2001).
3 Ibid.
4 U.S. Forest Service, The Public and Wildland Fire Management: Social Science Findings for Managers, November
2006, http://www.fs.fed.us/nrs/pubs/gtr/gtr_nrs1.pdf.
5 Personal communication with Susan Stewart, USFS, January 11, 2012.
6 R. B. Hammer, V. C. Radeloff, J. S. Fried, and S. L. Stewart, “Wildland-Urban Interface Housing Growth During the
1990s in California, Oregon, and Washington,” International Journal of Wildland Fire, v. 16 (2007): pp. 255-265.
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three times the 3.3 million acres in interface communities in those states.7 The 10-year growth in
area of intermix communities was 14.1%, compared to only 2.5% for interface communities.
However, the study acknowledged that determining the area of WUI communities was imprecise:
“Mapping [the Federal Register] definition of the WUI using data and operational definitions we
developed, we arrived at one possible representation of the WUI.”8 The intermingled nature of
intermix communities poses significant challenges for fire protection efforts.
Figure 1. 2000 WUI Map
Source: U.S. Forest Service, United States Wildland Urban Interface Maps, 2011, http://silvis.forest.wisc.edu/maps/
wui/state.
Fire Suppression
In most of the United States, wildfires are inevitable. Biomass plus dry conditions equals fuel to
burn. Add an ignition source (e.g., lightning or a match) and a wildfire may ignite. Fire is a self-
sustaining chemical reaction that perpetuates itself as long as all three elements of the fire
triangle—fuel, heat, and oxygen—remain available. Fire control focuses on removing one of
those elements.
7 The data for 2000 is the most recent available.
8 Hammer et al., “Wildland-Urban Interface Housing Growth,” p. 256.
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There are two principal kinds of wildfire, although an individual wildfire may contain areas of
both kinds.9 A surface fire burns the needles or leaves, grass, and other small biomass within a
foot or so of the ground and quickly moves on. Such fires are relatively easy to control by
removing fuel with a fireline, essentially a dirt path wide enough to eliminate the continuous fuels
needed to sustain the fire, or by cooling or smothering the flames with water or dirt.10
A crown fire burns biomass at all levels, from the surface through the tops of the trees. Crown
fires do not consume all the biomass; rather, a crown fire quickly burns the needles or leaves and
small twigs and limbs on the surface and throughout the crown of the trees. Because the needles
and leaves in the crown are green, they require more energy to burn than dry fuels on the surface.
Furthermore, because of the green fuels and the often discontinuous biomass of the canopy, wind
is usually needed to sustain a crown fire. Once burning vigorously, a crown fire can create its own
wind—the strong upward convection of the heated air can draw in cooler air from surrounding
areas, thus creating a wind that feeds the fire. The strong upward convection can also lift burning
biomass (firebrands) and send it soaring ahead of the fire, creating spot fires and accelerating the
spread of the wildfire. Thus, crown fires are difficult, if not impossible, to control. Firelines are
often ineffective, especially if winds are causing spot fires. Water or fire retardant (slurry)
dropped from helicopters or airplanes can sometimes knock a crown fire down (back to a surface
fire) if the area burning and the winds are not too great. Often, however, crown fires burn until
they run out of fuel or the weather changes (the wind dies or it rains or snows).
Fires burn structures in one of three ways: through direct contact with fire (the fire burning right
up to the structure); through radiation (heating from exposure to flames); and through firebrands
landing on a flammable roof.11 Surface fires generally only burn houses through direct contact,
and protection is a relatively simple matter of a break in the continuous burnable material. In
observing houses that burned in Los Alamos in 2000, one researcher stated “in several cases, a
scratch line that removed [pine] needles from the base of a wood wall kept the house from
igniting.”12 Crown fires, however, can burn houses in any of the three ways. The opportunity and
ability to prevent structures from burning during a crown fire is small. Occasionally, water or
some other wetting agent sprayed on walls or roofs can prevent ignition or extinguish firebrands
from an advancing wildfire, but the firefighters could die of heat exposure or smoke inhalation
from the approaching fire.
In the Aftermath
Recovery and efforts to support recovery after a severe wildfire vary, depending on the nature of
the damages. For burned structures, insurance payment is the standard means for homeowners to
pay for recovery—repair, if that is possible, or replacement, depending on the insurance policy. In
9 See S. F. Arno and S. Allison-Bunnell, Flames in Our Forest: Disaster or Renewal? (Washington, DC: Island Press,
2002), pp. 45-46.
10 A fireline may be as narrow as 1 foot for suppressing a fire in shortgrasses and light fuels, or can be more than 100
feet wide for heavier-fueled fires. U.S. Forest Service, About Handcrews, http://www.fs.fed.us/fire/people/handcrews/
about_handcrews.html.
11 National Wildland/Urban Interface, Fire Protection Program, Wildland/Urban Interface Fire Hazard Assessment
Methodology, p. 5, at http://www.firewise.org/resources/files/wham.pdf.
12 Jack Cohen, “The Cerro Grande Fire: Why Houses Burned,” Forest Trust Quarterly Report, no. 13 (December
2000): p. 11.
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a severe event, a presidential declaration of an emergency (in response to a request from a
governor) initiates a process for federal assistance to state and local governments and to families
and individuals to help with recovery. The nature and extent of the assistance depends on several
factors, such as the nature and severity of damages and the insurance coverage of the affected
parties.13
For burned areas, site rehabilitation is sometimes warranted. In many temperate ecosystems,
wildfires (including crown fires) are natural events, and the ecosystems are adapted to recover
from the fire. Often, in severely burned areas, grass seed is spread to try to accelerate growth of
ground cover and slow erosion, but grass often inhibits tree seed germination and growth, and
thus may slow forest recovery. Rehabilitation efforts commonly focus on the firelines created to
try to control the fire, since firelines consist of exposed bare earth and often run uphill, and thus
can readily erode into gullies if left untreated. Some severely burned areas, particularly in coastal
southern California, are susceptible to landslides during the subsequent rainy season. Monitoring
can provide a warning to homeowners to evacuate an area prior to a landslide, but little can be
done to prevent landslides in such situations.
Minimizing Wildfire Damages
Various efforts can protect structures and wildlands from some of the damages of wildfires. (See
CRS Report RL34517, Wildfire Damages to Homes and Resources: Understanding Causes and
Reducing Losses, by Ross W. Gorte.)
Protecting Structures
A structure’s characteristics and landscaping significantly affect its chance of surviving a wildfire.
Evidence from models, experiments, and case studies demonstrates that structural characteristics,
especially the roofing materials, largely determine whether a home burns in a wildfire. Homes of
brick or adobe with non-flammable roofs (e.g., tile, slate, metal) are far less likely to burn than
homes with wood siding and flammable roofs (e.g., wood shingles).14 Burnable materials (such as
trees, shrubs, grass, pine needles, woodpiles, wood decks, and wooden deck furniture) within 40
meters (131 feet) of the structure also strongly influence whether the structure burns in a
wildfire.15
Furthermore, the structure and landscape characteristics are more important than the intensity of
the fire in determining whether a house burns. The Hayman Fire, in Colorado in June 2002,
burned 132 houses—70 houses (53%) were surrounded by crown fire, while 62 houses (47%)
were surrounded by surface fire.16 In addition, 662 homes (83% of all homes within the fire
perimeter) survived the fire, even though 35% of the area was severely burned and 16% was
13 For more information, see CRS Report RL34146, FEMA’s Disaster Declaration Process: A Primer, by Francis X.
McCarthy; and CRS Report RL33053, Federal Stafford Act Disaster Assistance: Presidential Declarations, Eligible
Activities, and Funding, by Francis X. McCarthy.
14 Jack D. Cohen, “Preventing Disaster: Home Ignitability in the Wildland-Urban Interface,” Journal of Forestry, v. 98,
no. 3 (March 2000): 15-21.
15 Cohen, “Preventing Disaster.”
16 Jack Cohen and Rick Stratton, “Home Destruction Within the Hayman Fire Perimeter,” Hayman Fire Case Study,
Gen. Tech. Rept. RMRS-GTR-114 (Ft. Collins, CO: USDA Forest Service, September 2003), p. 264.
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moderately burned.17 This suggests that at least some of the structures survived despite a crown
fire around them.
Protecting Wildlands
The impact of wildfires on wildlands depends largely on the nature of the ecosystem. Some
ecosystems are adapted to and recover from periodic crown fires—perennial grasslands,
chaparral, lodgepole and jack pines, and more. In these ecosystems, the plants have evolved to
resprout or reseed the burned areas, and thus recover from crown fires by outcompeting other
plant species. Eliminating crown fires could eventually eliminate these ecosystems. However,
eliminating crown fires in these ecosystems is probably impossible, since the plants contribute to
the development and spread of crown fires—grasses burn quickly; chaparral has a high volatile-
oils content; and lodgepole and jack pines grow in dense, even-aged stands.
Other ecosystems are adapted to relatively frequent (5- to 35-year intervals) surface fires. Fire
suppression has been moderately successful in controlling surface fires, and thus the needles,
twigs, and other fine and small fuels have been accumulating for three or more fire cycles. This
abnormal fuel accumulation, combined with fuel ladders of brush, small trees, and low limbs
(many of which would have burned in a surface fire), have led to crown fires where such fires
were historically rare. Fuel reduction treatments can restore conditions in frequent-surface-fire
ecosystems to again make crown fires rare occurrences, reducing damages to resources.
Protecting the WUI
Reducing fuels in the WUI has been a controversial aspect of congressional debates over fire
protection legislation. The evidence discussed above indicates that fuel reduction provides little
protection for structures. However, some observers have noted that the WUI is more than just a
collection of houses:18
A town is not just the place where people have homes. Communities are in the forest because
they are emotionally, economically, and socially linked and dependent on the forest. When we
consider the areas that need immediate treatment we should consider the human community
“impact area”—the entire area that, if impacted by a catastrophic fire, will undermine the health
and livelihood of a community.
At a minimum, most would agree on the need for an area of defensible space around homes that
needs to be cleared of burnable materials—at least 10 meters (33 feet) and possibly as much as 40
meters (131 feet). One observer recommended that protecting communities should include
intensive treatment to reduce fuels and burnable materials in the home ignition zone, up to 200
meters (655 feet) around structures, with less intensive fuel treatment in the community protection
zone, generally up to 500 meters (1,640 feet, or about a third of a mile) from structures.19
17 Peter Robichaud, Lee MacDonald, Jeff Freeouf, Dan Neary, Deborah Martin, and Louise Ashman, “Postfire
Rehabilitation of the Hayman Fire,” Hayman Fire Case Study, Gen. Tech. Rept. RMRS-GTR-114 (Ft. Collins, CO:
USDA Forest Service, September 2003), p. 294.
18 W. Wallace Covington, Director, The Ecological Restoration Institute, Northern Arizona University, “Prepared
Statement,” National Fire Plan, hearing before the Senate Committee on Energy and Natural Resources, July 16, 2002,
S.Hrg. 107-834 (Washington, DC: GPO, 2003), p. 61.
19 Brian Nowicki, Effectively Treating the Wildland-Urban Interface to Protect Houses and Communities from the
(continued...)
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The National Fire Protection Association’s (NFPA’s) Firewise Communities program assists
communities with specific wildfire safety needs. The term “Firewise” describes the goal of
teaching residents about wildfire and about smart practices around their homes that can reduce the
risk of destruction. The program started in 1986 as a national project and gradually evolved to
become a national program in 2002. The program, co-sponsored by the USFS, DOI, and the
National Association of State Foresters, encourages local solutions for wildfire safety by
involving homeowners, community leaders, planners, developers, firefighters, and others in the
effort to protect people and property from wildfire risks.
The Healthy Forests Restoration Act of 2003 (HFRA; P.L. 108-148; 16 U.S.C. § 6511)
established a somewhat broader standard for fuel reduction activities under its authorities. Section
101(16) of HFRA defined the WUI to include an area out to ½ mile from the boundary of an at-
risk community or 1½ miles from the boundary if a sustained steep slope could cause dangerous
fire behavior or to an effective fire break, such as a road or ridge top. HFRA included no guidance
on how to apply these standards in intermix communities, with no definitive boundary.
Issues for Congress
While slightly fewer total fires and total acres have burned in recent years as compared to a peak
experienced in 2006 and 2007,20 people are still at risk from wildfires when they occur in the
WUI. The National Interagency Fire Center (NIFC) reports that more than 5,240 structures
burned in 2011.21 Congress faces increasing pressures for wildfire protection. Congress decides
what programs to authorize and fund to protect the WUI from wildfires. Many programs exist,
and other options are possible.
Firefighting uses the majority of wildfire management funding, accounting for $1.1 to $1.9 billion
annually (including emergency supplemental funds) since FY2003. Appropriations for wildfire
suppression have risen in nearly every year for a decade, going from $277 million for FY1999 to
$809.3 million for FY2012. The public and policymakers expect the agencies to clearly
demonstrate that they are doing what they can to stop threatening and damaging fires, and this
often involves large sums of money. However, given the difficulty of suppressing crown fires, and
the difficulty and cost associated with measuring what has burned and what was suppressed,
some may question the effectiveness of continued increases in suppression funding.
To date, Congress has mostly addressed wildfire prevention and suppression by increasing
funding. It is difficult to gauge if the funding amounts provided by Congress each year are
adequate. National data on what transpired during the year is hard to locate and is disjointed when
available. More comprehensive and accurate national performance measures (e.g., number of
fires that started on federal lands, number of structures burned due to wildfires) could give better
insight into the effectiveness of wildfire prevention and suppression efforts.22 National wildland
(...continued)
Threat of Forest Fire (Tucson, AZ: Center for Biological Diversity, August 2002).
20 National Interagency Fire Center, Historical Year End Fire Stats By State (2002-2010), http://www.nifc.gov/fireInfo/
fireInfo_statistics.html.
21 Structures include primary residences, commercial buildings, outbuildings and seasonal dwellings. Information
provided in an email from NIFC on January 9, 2012.
22 This is not a new issue. The Government Accountability Office (GAO) has produced numerous reports addressing
(continued...)
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fire data collection and analysis could start with Congress explicitly requesting the numerous fire
reporting agencies to work together to provide annual statistics and performance measures.23 Such
a directive could require more resources than are available at the moment. Given the current
economic climate, better national data could provide insight as to whether or not other options to
address wildfire management (e.g., a reduction in funding or a do-nothing approach) should
receive more careful consideration.
Federal programs to protect homes are currently limited to information for homeowners on how
to protect their homes, primarily provided through the NFPA Firewise Communities program,.
Programs could be expanded to educate homeowners, state and local governments, and the
insurance industry about the ways to protect homes through actions, planning, and zoning and
building regulations. Congress could create and fund new programs to assist homeowners in
renovations to make their homes fire-safe and to create defensible space around their structures,
through direct federal assistance or through the states.
Congress could also consider expanding protection for defensible space beyond the home ignition
zone to a community protection zone. HFRA authorizes an expedited review process for activities
on federal lands in the WUI. Perhaps other changes could further accelerate action. Funding for
fuel reduction in the WUI could also be expanded. Appropriations for fuel reduction have
averaged $500 million annually since FY2006, but only a portion is used in the WUI, and funding
is far below the estimated amount needed to treat the lands at risk. (See the discussion in CRS
Report RL33990, Federal Funding for Wildfire Control and Management, by Ross W. Gorte).
State fire assistance funding through the Forest Service could be used for fuel reduction in the
WUI, at the discretion of the states, but funding has averaged $88 million annually and the states
have many wildfire priorities. Additional funding through the states for fuel reduction on private
lands in the WUI is a possibility that Congress could contemplate.
In addition, Congress might debate choices for compensating homeowners for property losses due
to wildfires. One option might be to restrict compensation to those who had acted to protect their
homes, but got burned anyway. Another option might be to require that compensation for
rebuilding be used only for fire-safe building designs and materials. Alternatively, Congress could
establish a national wildfire insurance program, with premiums based on fire threats, the fire-
safety of the structures, and the defensible space being maintained.
Finally, Congress could consider compensation for landowners that suffer resource losses from
wildfires. An emergency reforestation assistance program has existed for many years, although it
has not been funded since FY1993. (See CRS Report RL31065, Forestry Assistance Programs,
by Ross W. Gorte.) In the 2008 farm bill, Congress included forest restoration assistance in an
existing emergency conservation program. (See CRS Report RL33917, Forestry in the 2008
Farm Bill, by Ross W. Gorte and Megan Stubbs.) These programs can provide assistance in
recovery from a wildfire disaster, but do not compensate landowners for losses in the way that
(...continued)
various aspects of fire strategies by both the FS and DOI. The most recent GAO report discusses measures federal
agencies can take to ensure that federal dollars, on a national basis, are spent wisely on wildland fire prevention. U.S.
Government Accountability Office, Federal Agencies Have Taken Important Steps Forward, but Additional, Strategic
Action Is Needed to Capitalize on Those Steps, GAO-09-877, September 9, 2009, http://www.gao.gov/products/GAO-
09-877.
23 Most wildland fire data comes from NIFC, USFS, and NFPA.
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homeowners are compensated for the loss of their homes. Congress might consider such
additional compensation.
The 112th Congress has proposed legislation that would address some of the issues stated above.
For example, H.R. 1485 would, in part, authorize an expedited review process by the FS and DOI
for fuel reduction and forest restoration projects in the WUI. Some measures were introduced that
would reduce wildfire program funding, such as H.Amdt. 764 to H.R. 2584, which sought to
reduce funding for the Wildfire Suppression Program by $50 million and to increase funding for
the Forest Legacy Program by a similar amount.
Author Contact Information
Ross W. Gorte
Kelsi Bracmort
Specialist in Natural Resources Policy
Specialist in Agricultural Conservation and Natural
rgorte@crs.loc.gov, 7-7266
Resources Policy
kbracmort@crs.loc.gov, 7-7283
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