[MCN] Key Points by Jack Cohen on how to protect homes--and it's not by logging the forest--please pass on to friends

[Matthew Koehler]

---------- Forwarded message ----------
From: George Wuerthner <gwuerthner at gmail.com>
Date: Mon, Jul 20, 2015 at 10:28 AM
Subject: Key Points by Jack Cohen on how to protect homes--and it's not by
logging the forest--please pass on to friends
To: Ann Harvey <aharvey at wyom.net>


*The vast majority of logging projects are justified based on the notion
that logging can protect homes--when it is clearly not the important
factor. Yet nearly all collaboratives operate under the assumption that
logging/fuel reductions will protect homes, and also preclude large
wildfires--neither of which is true. Nor is it the responsibility of the FS
or BLM to protect homes since nearly all responsibility lies with private
homeowners. It is worth repeating over and over--if  your goal is to reduce
wildfire threat to homes--protect the homes and don't build more homes in
the fire plain. *
*Key Points of Cohen's Paper*

Introduction and Bulleted Points by Timothy Ingalsbee, Ph.D.

*Director, Western Fire Ecology CenterEugene, Oregon*

*Introduction*

Jack Cohen, research scientist at the Fire Sciences Laboratory in the
Forest Service's Rocky Mountain Research Station, presented the paper below
at the Fire Economics Symposium in San Diego, California on April 12, 1999.
His research findings could potentially eliminate arguments for increased
public lands logging, road-building, and grazing as alleged means of
protecting private homes from wildfires.

*Key Points of Jack Cohen's Research Paper*

   - Home ignitability, rather than wildland fuels, is the principal cause
   of home losses during wildland/urban interface fires. Key items are
   flammable roofing materials (e.g. cedar shingles) and the presence of
   burnable vegetation (e.g. ornamental trees, shrubs, wood piles) immediately
   adjacent to homes.

   - Cohen's Structure Ignition Assessment Model (SIAM) indicates that
   intense flame fronts (e.g. crown fires) will not ignite wooden walls at
   distances greater than 40 meters (approx. 130 feet) away. Field tests of
   experimental crown fires revealed that wooden walls can successfully
   survive intense flame fronts from as close as 10 meters (approx. 30 feet)
   away!

   -

   Current strategies for wildland fuel reduction may be inefficient and
   ineffective for reducing home losses, for extensive wildland fuel reduction
   on public lands does not effectively reduce home ignitability on private
   lands.

   -

   The so-called "wildland/urban interface zone" overgeneralizes and
   misrepresents the zone of prime fire risk and fuel hazards: the home and
   its adjacent vegetation.

   -

   Opportunities to use prescribed fire for the sake of ecosystem
   restoration may be greatly enhanced in wildland/urban interface areas if
   home ignitability is reduced.

   -

   The primary and ultimate responsibility for home wildfire protection
   lies with private homeowners, not public land management agencies (or
   taxpayers).

   -

   Given nonflammable roofs, Stanford Research Institute found that 95
   percent of homes survived where vegetation clearance of 10 to 18 meters was
   maintained around the homes.

------------------------------


*Reducing the Wildland Fire Threat to Homes: Where and How Much?*

By Jack D. Cohen, Ph.D.
*Research Physical Scientist *
*Rocky Mountain Research Station*

_______________________________________________________
*Abstract* Understanding how ignitions occur is critical for effectively
mitigating home fire losses during wildland fires. The threat of life and
property losses during wildland fires is a significant issue for Federal,
state, and local agencies that have responsibilities involving homes within
and adjacent to wildlands. Agencies have shifted attention to communities
adjacent to wildlands through pre-suppression and suppression activities.
Research for the Structure Ignition Assessment Model (SIAM) that includes
modeling, experiments, and case studies, indicates that effective
residential fire loss mitigation must focus on the home and its immediate
surroundings. This has significant implications for agency policy and
specific activities such as hazard mapping and fuel management.
------------------------------

The threat of life and property losses during wildland fires is a
significant issue for Federal, state, and local fire and planning agencies
who must consider residential development within and adjacent to wildlands.
The 1995 USDA Forest Service Strategic Assessment of Fire Management (USDA
Forest Service 1995) lists five principal fire management issues. One of
those issues is the "loss of lives, property, and resources associated with
fire in the wildland/urban interface." The report further identifies "the
management of fire and fuels in the wildland/urban interface" as topic for
further assessment. More than a Forest Service issue, the National
Wildland/Urban Interface Fire Protection Program, a multi-agency endeavor,
has been established for over a decade and is sponsored by the Department
of Interior land management agencies, the USDA Forest Service, the National
Association of State Foresters, and the National Fire Protection
Association. This program also has an advisory committee associated with
the multi-agency National Wildfire Coordinating Group. These examples
indicate that the wildland fire threat to homes significantly influences
fire management policies and suggests that this issue has significant
economic impacts through management activities, direct property losses and
associated tort claims.

The wildland fire threat to homes is commonly termed the wildland/urban
interface (WUI) fire problem. This and similar terms (e.g., wildland/urban
intermix) refer to an area or location where a wildland fire can
potentially ignite homes. A senior physicist at the Stanford Research
Institute, C.P. Butler (1974), coined the term "urban-wildland interface"
and described this fire problem as follows:
"In its simplest terms, the fire interface is any point where the fuel
feeding a wildfire changes from natural (wildland) fuel to man-made (urban)
fuel. ...For this to happen, wildland fire must be close enough for its
flying brands or flames to contact the flammable parts of the structure."
In his definition, Butler provides important references to the
characteristics of this problem. He identifies homes ("urban") as potential
fuel and indicates that the distance between the wildland fire and the home
("close enough") is an important factor for structure ignition. How close
the fire is to a home relates to how much heat the structure will receive.

These two factors, the homes and fire proximity, represent the fuel and
heat "sides" of the fire triangle, respectively. The fire triangle--fuel,
heat, and oxygen--represents the critical factors for combustion. Fires
burn and ignitions occur only if a sufficient supply of each factor is
present. By characterizing the home as fuel and the heat from flames and
firebrands, we can describe a home's ignitability. An understanding of home
ignitability provides a basis for reducing potential WUI fire losses in a
more effective and efficient manner than current approaches.

*Ignition and Fire Spread are a Local Process*

Fire spreads as a continually propagating process, not as a moving mass.
Unlike a flash flood or an avalanche where a mass engulfs objects in its
path, fire spreads because the locations along the path meet the
requirements for combustion. For example, C.P. Butler (1974) provides the
following 1848 account by Henry Lewis about pioneers being caught on the
Great Plains during a fire.
"...When the emigrants are surprised by a prairie fire, they mow down the
grass on a patch of land large enough for the wagon, horse, etc., to stand
on. They then pile up the grass and light it. The same wind which is
sweeping the original fire toward them now drives the second fire away from
them. Thus, although they are surrounded by a sea of flames, they are
relatively safe. Where the grass is cut, the fire has no fuel and goes no
further. In this way, experienced people may escape a terrible fate." It is
important to note that the complete success of this technique also relies
on their wagons and other goods not igniting and burning from firebrands.
This account describes a situation that has similarities with the WUI fire
problem.

A wildland fire does not spread to homes unless the homes meet the fuel and
heat requirements sufficient for ignition and continued combustion. In the
prairie fire situation, sufficient fuel was removed (by their escape fire)
adjacent to the wagons to prevent burning (and injury) and the wagons were
ignition resistant enough to not ignite and burn from firebrands.
Similarly, the flammables adjacent to a home can be managed with the home's
materials and design chosen to minimize potential firebrand ignitions. This
can occur regardless of how intensely or fast spreading other fires are
burning. Reducing WUI fire losses must involve a reduction in the
flammability of the home (fuel) in relation to its potential severe-case
exposure from flames and firebrands (heat). The essential question remains
as to how much reduction in flammables (e.g., how much vegetative fuel
clearance) must be done relative to the home fuel characteristics to
significantly reduce the potential home losses associated with wildland
fires.

*Insights for Reducing Ignitions from Flames*

Recent research provides insights for determining the vegetation clearance
required for reducing home ignitions. Structure ignition modeling, fire
experiments, and WUI fire case studies provide a consistent indication of
the fuel and heat required for home ignitions.The Structure Ignition
Assessment Model (SIAM) (Cohen 1995) assesses the potential ignitability of
a structure related to the WUI fire context. SIAM calculates the amount of
heat transferred to a structure from a flame source based on the flame
characteristics and the flame distance from a structure. Then, given this
thermal exposure, SIAM calculates the amount of time required for the
occurrence of wood ignition and flaming (Tran and others 1992). Based on
severe-case assumptions of flame radiation and exposure time, SIAM
calculations indicate that large wildland flame fronts (e.g., forest crown
fires) will not ignite wood surfaces (e.g., the typical variety of exterior
wood walls) at distances greater than 40 meters (Cohen and Butler [In
press]). Figure 1 illustrates this by displaying the amount of heat a wall
would receive from flames depending on its distance from the fire (the
incident radiant heat flux decreases as the distance increases). This
figure also displays the calculated time required for a wood wall to ignite
depending on its distance from a flame front of the given height and width.
But the flame's burning time compared to the required ignition time is
important. If at some distance the fire front produces a heat flux
sufficient to ignite a wood wall, but the flaming duration is less than
that required for ignition, then ignition will not occur. For example,
Figure 1 shows that at a distance of 40 meters, the radiant heat flux is
less than 20 kilowatts per square meter, which corresponds to a minimum
ignition time of greater than 10 minutes. Crown fire experiments in forests
and shrublands indicate that the burning duration of these large flames is
on the order of one minute at a specific location . This is because these
wildland fires depend on the rapid consumption of the fine dead and live
vegetation (e.g., forest crown fires).

Figure 1-- SIAM calculates the incident radiant heat flux
(energy/unit-area/time reaching a surface) and the minimum time for piloted
ignition (ignition with a small ignition flame or spark) as a function of
distance for the given flame size. The flame is assumed to be a uniform,
parallel plane, black body emitter.

Experimental fire studies associated with the International Crown Fire
Modeling Experiment (Alexander and others 1998) generally concur with the
SIAM calculations. Data were obtained from instrumented wall sections that
were placed 10 meters from the forest edge of the crown fire burn plots.
Comparisons between SIAM calculations and the observed heat flux data
indicate that SIAM overestimates the amount of heat received . For example,
the SIAM calculated potential radiant heat flux for an experimental crown
fire was 69 kW/sq meter as compared to the measured maximum of 46 kW/sq
meter. This is expected since SIAM assumes a uniform and constant heat
source and flames are not uniform and constant. Thus, the SIAM calculations
in Figure 1 for an arbitrary flame front represent a severe-case estimate
of the heat received and the potential for ignition. The distances in
Figure 1 represent an upper estimate of the separation required to prevent
flame ignitions.

Past fire case studies also generally concur with SIAM estimates and the
crown fire observations. Analyses of southern California home losses done
by the Stanford Research Institute for the 1961 Belair-Brentwood Fire
(Howard and others 1973) and by the University of California, Berkeley, for
the 1990 Painted Cave Fire (Foote and Gilless 1996) are consistent with
SIAM estimates and the experimental crown fire data. Given nonflammable
roofs, Stanford Research Institute (Howard and others 1973) found a 95
percent survival with a clearance of 10 to 18 meters and Foote and Gilless
(1996) at Berkeley, found 86 percent home survival with a clearance of 10
meters or more.
The results of the diverse analytical methods are congruent and
consistently indicate that ignitions from flames occur over relatively
short distances--tens of meters not hundreds of meters. The severe-case
estimate of SIAM indicates distances of 40 meters or less. Experimental
wood walls did not ignite at 10 meters when exposed to experimental crown
fires. And, case studies found that vegetation clearance of at least 10
meters was associated with a high occurrence of home survival.

As previously mentioned, firebrands are also a principal WUI ignition
factor. Highly ignitable homes can ignite during wildland fires without
fire spreading near the structure. This occurs when firebrands are lofted
downwind from fires. The firebrands subsequently collect on and ignite
flammable home materials and adjacent flammables. Firebrands that result in
ignitions can originate from wildland fires that are at a distance of 1
kilometer or more. For example, during the 1980 Panorama Fire (San
Bernardino, CA), the initial firebrand ignitions to homes occurred when the
wildland fire was burning in low shrubs approximately one kilometer from
the neighborhood. During severe WUI fires, firebrand ignitions are
particularly evident for homes with flammable roofs. Often these houses
ignite and burn without the surrounding vegetation also burning. This
suggests that homes can be more flammable than the surrounding vegetation.
For example, during the 1991 Spokane, WA fires , houses with flammable
roofs ignited without the adjacent vegetation already burning. Although
firebrands may be lofted over considerable distances to ignite homes, a
home's materials and design and its adjacent flammables largely determine
the firebrand ignition potential.

*Research Conclusions*

SIAM modeling, crown fire experiments, and WUI fire case studies show that
effective fuel modification for reducing potential WUI fire losses need
only occur within a few tens of meters from a home, not hundreds of meters
or more from a home. This research indicates that home losses can be
effectively reduced by focusing mitigation efforts on the structure and its
immediate surroundings. Those characteristics of a structure's materials
and design and the surrounding flammables that determine the potential for
a home to ignite during wildland fires (or any fires outside the home)
will, hereafter, be referred to as home ignitability.

The evidence suggests that wildland fuel reduction for reducing home losses
may be inefficient and ineffective. Inefficient because wildland fuel
reduction for several hundred meters or more around homes is greater than
necessary for reducing ignitions from flames. Ineffective because it does
not sufficiently reduce firebrand ignitions. To be effective, given no
modification of home ignition characteristics, wildland vegetation
management would have to significantly reduce firebrand production and
potentially extend for several kilometers away from homes.

*Management Implications*

These research conclusions redefine the WUI fire problem as a home
ignitability issue largely independent of wildland fuel management issues.
Consequently, this description has significant implications for the
necessary actions and accompanying economic considerations for fire
agencies.
One aspect of the USDA Forest Service approach to reducing their WUI fire
problem is to determine where the problem is and focus fuel management
activities in those areas. The Strategic Assessment of Fire Management
(1995) states:

"...The Forest Service should manage National Forest lands to mitigate
hazards and enhance the ability to control fires in the wildland/urban
interface. The risk of wildland fire to communities can be lessened by
reducing hazards on Forest Service lands adjacent to built-up areas.
...Broad-scale assessment processes for the next generation of forest plans
should identify high risk areas related to the wildland/urban interface.
...The highest risk areas within the United States should be identified and
mitigation efforts directed to these locations."

The Strategic Assessment describes a costly, intensive and extensive WUI
hazard mapping and mitigation effort specifically for reducing home fire
losses. As described, this approach is not necessary.
The congruence of research findings from different analytical methods
suggests that home ignitability is the principal cause of home losses
during wildland fires. Any WUI home fire loss assessment method that does
not account for home ignitability will be critically under specified and
likely unreliable. Thus, land classification and mapping related to
potential home loss must assess home ignitability. Home ignitability also
dictates that effective mitigating actions focus on the home and its
immediate surroundings rather than on extensive wildland fuel
management. Because
homeowners typically assert their authority for the home and its immediate
surroundings, the responsibility for effectively reducing home ignitability
can only reside with the property owner rather than wildland agencies. The
next sections further address the management implications related to WUI
hazard mapping, fuel reduction, and responsibilities.

*Mapping Home Loss Potential*

As stated, the evidence indicates that home ignitions depend on the home
materials and design and only those flammables within a few tens of meters
of the home (home ignitability). The wildland fuel characteristics beyond
the home site have little if any significance to WUI home fire losses.
Thus, the wildland fire threat to homes is better defined by home
ignitability, an ignition and combustion consideration, than by the
location and behavior of potential wildland fires.

This has implications for identifying WUI fire problem areas and suggests
that the geographical implication of the term "wildland/urban interface" as
a general area or zone misrepresents the physical nature of the wildland
fire threat to homes. The wildland fire threat to homes is not where it
happens related to wildlands (a location), but how it happens related to
home ignitability (the combustion process). Therefore, to reliably map WUI
home fire loss potential, home ignitability must be the principal mapping
characteristic.

*Wildland Fuel Hazard Reduction*

Extensive wildland vegetation management does not effectively change home
ignitability. This should not imply that wildland vegetation management is
without a purpose and should not occur for other reasons. However, it does
imply the imperative to separate the problem of the wildland fire threat to
homes from the problem of ecosystem sustainability due to changes in
wildland fuels. For example, a WUI area could be a high priority for
extensive vegetation management due to high aesthetic, watershed, erosion,
or other values, but not for reducing potential home fire losses.
Vegetation management strategies would likely be different without
including the WUI home fire loss issue. It also suggests that given a low
level of home ignitability (reduced wildland fire threat to homes), fire
use opportunities for sustaining ecosystems may increase in and around WUI
locations.

*WUI Home Loss Responsibility*

Home ignitability implies that homeowners have the ultimate responsibility
for WUI home fire loss potential. As shown, the ignition and flammability
characteristics of a structure and its immediate surroundings determine the
home fire loss potential. Thus, the home should not be considered a victim
of wildland fire, but rather a potential participant in the continuation of
the wildland fire. Home ignitability, i.e., the potential for WUI home fire
loss, is the homeowner's choice and responsibility.
However, public and management perceptions may impede homeowners from
taking principal responsibility. For example, the Federal Wildland Fire
Management, Policy and Program Review (1995) observes, "There is a
widespread misconception by elected officials, agency managers, and the
public that wildland/urban interface protection is solely a fire service
concern." In a Journal of Forestry article, Beebe and Omi (1993) concur,
stating that, "Public reaction to wildfire suggests that many Americans
want competent professionals to manage fire flawlessly, reducing the risks
to life, property, and public lands to nil." These statements agree with
Bradshaw's (1988) description of the societal roles in the WUI problem. He
observes that homeowners expect that fire protection will be provided by
others. Contrary to these expectations for fire protection, the fire
services have neither the resources for effectively protecting highly
ignitable homes during severe WUI fires, nor the authority to reduce home
ignitability.

*An Alternative*

Home ignitability ultimately implies the necessity for a change in the
relationship between homeowners and the fire services. Instead of
pre-suppression and fire protection responsibilities residing with fire
agencies, homeowners take the principal responsibility for assuring
adequately low home ignitability. The fire services become a community
partner providing homeowners with technical assistance as well as fire
response in a strategy of assisted and managed community self-sufficiency
(Cohen and Saveland 1997). For success, this perspective must be shared and
implemented equally by homeowners and the fire services.

*Literature Cited*

Alexander, M.E.; Stocks, B.J.; Wotton, B.M.; Flannigan, M.D.; Todd, J.B.;
Butler, B.W.; Lanoville, R.A. 1998. The international crown fire modelling
experiment: an overview and progress report. In: Proceedings of the second
symposium on fire and forest meteorology; 1998 January 12-14; Phoenix, AZ.
Boston, MA: American Meteorological Society; 20-23.

Beebe, Grant S.; Omi, Philip N. 1993. Wildland burning: the perception of
risk. Journal of Forestry 91(9): 19-24.

Bradshaw, William G. 1988. Fire protection in the urban/wildland interface:
who plays what role? Fire Technology 24(3): 195-203.

Butler, C.P. 1974. The urban/wildland fire interface. In: Proceedings of
Western states section/Combustion Institute papers, vol. 74, no. 15; 1974
May 6-7; Spokane, WA. Pullman, WA: Washington State Univ.; 1-17.

Cohen, Jack D. 1995. Structure ignition assessment model (SIAM). In: Weise,
David R.; Martin, Robert E., technical coordinators. Proceedings of the
Biswell symposium: fire issues and solutions in urban interface and
wildland ecosystems. 1994 February 15-17; Walnut Creek, CA. Gen. Tech. Rep.
PSW-GTR-158. Albany, CA: Pacific Southwest Research Station, Forest
Service, U.S. Department of Agriculture; 85-92.

Cohen, Jack D.; Butler, Bret W. [In press]. Modeling potential ignitions
from flame radiation exposure with implications for wildland/urban
interface fire management. In: Proceedings of the 13th conference on fire
and forest meteorology. 1996 October 27-31; Lorne, Victoria, Australia.
Fairfield, WA: International Association of Wildland Fire.

Cohen, Jack; Saveland, Jim. 1997. Structure Ignition Assessment Can Help
Reduce Fire Damages in the W-UI. Fire Management Notes 57(4): 19-23.

Foote, Ethan I.D.; Gilless, J. Keith. 1996. Structural survival. In:
Slaughter, Rodney, ed. California's I-zone. Sacramento, CA: CFESTES;
112-121.

Howard, Ronald A.; North, D. Warner; Offensend, Fred L.; Smart, Charles N.
1973. Decision analysis of fire protection strategy for the Santa Monica
mountains: an initial assessment. Menlo Park, CA: Stanford Research
Institute. 159 p.

Tran, Hao C.; Cohen, Jack D.; Chase, Richard A. 1992. Modeling ignition of
structures in wildland/urban interface fires. In: Proceedings of the 1st
international fire and materials conference; 1992 September 24-25;
Arlington, VA. London, UK: Inter Science Communications Limited; 253-262.

USDA. 1995. Strategic assessment of fire management in the USDA Forest
Service. 1995 January 13. Washington, DC: U.S. Forest Service, Department
of Agriculture; 31 p.

USDI/USDA. 1995. Federal wildland fire management: policy & review. 1995
December 18. Washington, DC: Department of the Interior and Department of
Agriculture; 45 p.
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