Flagstaff Area Wildfire Risk Assessment
A Collaborative Effort in Cooperation with the Ponderosa Fire Advisory Council

"In addition to changes in forest conditions, the increasing number of people moving from urban areas to rural areas near public lands has resulted in more homes and structures being built in wildland environments near national forests. We commonly call these lands wildland urban interface areas. Because of their location, these structures are extremely vulnerable to fire should wildland fire occur. This trend, coupled with the increased hazard from fuels accumulation, is resulting in a volatile situation that must be addressed." (Janice McDougle, Deputy Chief of the Forest Service to Congressional Subcommittee on Forests and Forest Health, June 1999)

INTRODUCTION

The Coconino National Forest surrounds the entire Flagstaff area. Though forest types include the pinyon-juniper woodlands and the mixed conifer type, the vast majority of the forest vegetation within the area is ponderosa pine. The city of Flagstaff has a population of about 60,000 and the corporate area is about 65 square miles (41,600 acres). Highly urbanized county subdivisions outside the city include Doney Park, Timberline, Fernwood, Fort Valley, Kachina Village, Mountainaire, and Forest Highlands. Urban areas that intermingle with the forest are the urban interface. The Flagstaff Urban Interface consists of about 180,000 acres of national forest, state of Arizona, military, national park, Flagstaff City, and privately owned lands.

The ponderosa pine forest ecosystem historically had relatively benign, low intensity surface fires, which kept the stands in open, park-like structures (Covington and others 1997; Johnson and others 1998). Many decades of fire exclusion, in combination with grazing and timber management practices, have allowed these fire-adapted ecosystems to grow from open, park-like structures to overly crowded stands. With high levels of biomass and high levels of ground fuels, wildfires increasingly result in catastrophic, stand-replacing fires. These conditions threaten both urban dwellings and infrastructure and the forested values people treasure for recreation and spiritual well being.

"It is clear from many years of study and published works that the thinning action of pre-settlement surface fires maintained open stand conditions and thereby prevented the historically anomalous occurrence of catastrophic crown fires that we are experiencing in today's Southwestern forests." (Covington and others 1997)

"Fire suppression has caused both the build-up of woody and fine fuels and the increase in woody vegetation, such as the formation of densely overstocked understory thickets. These factors have also contributed to the decline of native grasses, due to the increased shading and accumulation of thick mats of pine needle litter. The current policy of fire suppression will result in further fuel buildups in both forest types, threatening modern forests with high-intensity conflagrations such as the La Mesa Fire of 1977 (Foxx and Potter 1978)." (Touchan and others 1994)

FIRE HISTORY

There is no shortage of wildfire starts. Each has the potential to become large and destructive. Approximately 600 wildland fires occur annually in the greater Flagstaff area, 60% being caused by lightning. Records for large fires are sketchy prior to 1970, especially so prior to 1948. In the 35 years prior to 1948, there were 10 years which recorded burned forest lands in excess of 1,000 acres.

Coconino National Forest
10 Largest Recorded Wildfires

An average 1,180 acres burned each year from 1913-1969. From 1970 to the present, the average increased to 2,900 acres per year, and a majority of these acres burned catastrophically (crown fires which killed large areas of trees). There is no scientific evidence of stand replacement fires over 500 acres in size over the entire southern Colorado Plateau in the 400-500 years prior to European arrival (Covington 1997). Such fires are common today, especially in the last 30 years. Most of the crown fire sites occurring in the last 50 years still exhibit mostly grass and small brush, with trees generally being absent. The Coconino National Forest currently averages three large fires per year. There have also been three large fires within the Flagstaff City limits (not counted above), but no dwellings have yet been lost to forest wildfire.

Of the 92 major wildfires, 43% were caused by lightning. Humans caused the remaining fires --smoking and campfires being the major reasons. Logging operations caused less than 2% of the acres burned (936 acres).

Large fires have been recorded in every month of the year. However, large fires predominantly occur in the early summer and fall when winds blow from the southwest to the northeast, the prevailing wind pattern around Flagstaff.

"The prevailing conditions of today's ecosystems are not the conditions which existed in the days before total suppression - we are operating under a set of changed parameters. We do not have open, park-like stands of large, mature trees with grass understories. Many forested areas are now characterized by excessively thick growth of small and medium-sized trees underlain with heavy leaf, needle and branch debris." (Cartledge 1994)

RISK FOR CATASTROPHIC (CROWN OR STAND REPLACEMENT) WILDFIRES

An assessment of the catastrophic fire risk within and immediately adjacent to Flagstaff has been done (an approximate 94,000 acre area--see map). The boundary of this assessment area is generally within 1/2-1 mile of major developments (like Doney Park or Kachina Village) or city lands. This boundary was selected for several reasons.

• Firebrands from an approaching catastrophic fire can be carried 1/2 mile or more in the smoke plume before falling to the ground and igniting other fires (spot fires).
• This zone is an area where many human caused fires begin in the interface (transients, homeowners, kids playing with matches).
• This zone would give fire fighting forces a good chance to hold firelines from an approaching catastrophic fire.
• Jack Cohen, a researcher on home flammability in wildfire situations, suggests an effective wildland vegetation management distance of about 1 mile (USDA 1999).

Approximately 23,000 acres of national forest, state and private lands have been identified as a high potential for catastrophic wildfire. Generally, these stands are dense and/or have significant ground fuels and/or ladder fuels. Another 16,100 acres have been identified as a moderate risk. Many of these high and moderate risk stands are adjacent or within residential and urban neighborhoods, parks or other structures like observatories. In addition, there are about 16,000 acres (not reflected in the table) of highly urbanized residential/business acres, which have an unknown amount of high and moderate fire potential within them. The following table summarizes the potential for catastrophic fire within the 94,100-acre urban fire zone.

"Catastrophic" in this assessment refers to large-scale tree mortality. Catastrophic fire within or approaching urbanized areas presents tremendous potential for loss of lives and property. In fact, any fire has the potential to destroy lives and property, a "catastrophic" event when tragedy strikes.

Fires with High Catastrophic Potential are characterized by active crown fire, one that spreads through the green needles and tops of trees independently or at the same time as a ground level fire. Most of the trees burned are killed.

Fires with Moderate Catastrophic Potential are characterized by running ground fires with individual trees or groups of trees burning. These fires may produce large areas of killed trees or merely scattered clumps of tree mortality.

Fires with Low Catastrophic Potential are characterized by ground level surface fires with flame lengths generally less than four feet. These are usually not catastrophic fires, with mortality generally among the very young trees.

CATASTROPHIC FIRE RISK REDUCTION

Catastrophic (crown) fire potential is decreased by reducing the amount of ground fuels, ladder fuels, and tree canopy fuels (Ottmar 1997; Agee and others 1999; Buckley 1992; Van Wagtendonk 1996).

• Reducing ground fuels limits the fuel load and fire intensity that could initiate a crown fire.
• Removing ladder fuels will reduce the potential for ground fire reaching the tree crowns.
• Increasing the amount of discontinuous canopy layer will reduce the ability of a crown fire to maintain its integrity (that is, being able to "jump" from tree to tree or group to group).

Fuels reduction may be accomplished through natural means (wildfire) or managed means (prescribed fire and thinning). Allowing wildfires to selectively thin pine forests of the southwest may be most detrimental in retaining what old growth remains (Weatherspoon 1996). Thinning fuels reduction by wildfire offers little, if any, control over the time, place, and quantity of ground fuels and trees that are consumed. Allowing wildfire in locations with high fuel loadings and tree densities often results in many unwanted consequences. In the urban interface, private property values and public safety greatly complicates the use of wildfire as a thinning tool.

Prescribed Fire and Thinning

There are management actions for reducing forest fuels. Ground, ladder, and aerial fuels can be managed by thinning and burning. Beginning in the 1930s, research was conducted to evaluate the effectiveness of a range of treatment strategies to reduce stand densities and fuel loads. Many researchers initially believed that simply reintroducing fire would be sufficient to substantially reduce both stand densities and fuel loads. Prescribed fire has been a successful means of fuel reduction in some forest types (Biswell and others 1973, Knorr 1963, Weaver 1952).

However, these attempts to use fire alone to thin dense stands frequently resulted in high levels of mortality in the residual stands (Swezy and Agee 1991, Sackett and others 1996, Ryan and Losensky 1988, Covington and Sackett 1984). Over thirty years of study (since 1976) at the Fort Valley Experimental Forest has demonstrated that fire alone cannot effectively reduce stand levels enough to protect remaining mature and old growth trees. Post-fire mortality among old growth trees was 23% higher in burned plots than in the unburned controls over a 20-year period (Sackett and others 1996).

Prescribed fire is not a very selective thinning tool, because a number of fires are required to reduce fuels, change the understory, and overcome the effects caused by fire exclusion (Harrington and Sackett 1990). Gaines and others (1958), Woolridge and Weaver (1965), and Lindemuth (1960) all reported that fire was a rather imperfect tool for thinning. Harrington (1987) reported significant reductions in tree density within sites occupied by "dog-hair" thickets, while the same prescribed fire did little to reduce tree density where sites were dominated by larger trees. Sackett (1980), Davis and others (1968), and Campbell and others (1977) reported similar results in both prescribed and natural fires.

In an extensive 1995 report to Congress, the Sierra Nevada Ecosystem Project (SNEP) authors concluded that an extensive modification of forest structure by thinning and burning is needed to minimize severe fires in the future (McKelvey and others 1995). Ponderosa pine is a major forest type in the Sierra Nevada.

In an extensive scientific evaluation (involving over 100 scientists) of the effects of Forest Service management practices on the sustainability of eastern Oregon and Washington ecosystems, Everett and others (1994) found a need to utilize thinning as one of several actions to restore wildfire to more natural behavior.

In a report of the National Commission on Wildfire Disasters, Sampson (1994) states many forest situations will require mechanical removal of excess trees via thinning before fire can safely be re-introduced.

Substantial research has demonstrated the effectiveness of thinning as one component in a forest restoration program (Swezy and Agee 1991, Fiedler 1996, Fenny and others 1996, Weatherspoon 1996, Edminster and Olsen 1996, Covington and others 1997, Scott 1998, Harrington and Sackett 1990).

From his study on prescribed burns, Knorr (1963) estimated a 60% reduction in the actual size of wildfires that burned in areas previously treated with a prescribed burn. A spatial simulation of fire suppression scenarios using the fire growth model FARSITE (Finney and other in press) showed for the central California Sierra Nevada that area-wide fuel treatments (prescribed fire and thinning) had an effect on decreasing fire size and cost. Harrington and Sackett (1990) recommend a repeat prescribed burn about every 3 years to maintain a low forest fuel level in Southwest ponderosa pine forests.

Therefore, some combination of thinning, manual fuel removal, and prescribed burning will be necessary to restore ponderosa pine ecosystems to more natural conditions (Arno 1996; Fiedler 1996; Swezy and Agee 1991; Oliver and others 1994).

Logging and Fire Risk

Logging (thinning or tree harvesting with mechanical equipment) can decrease fire risk if:

• Resulting debris (slash) is treated (removed or burned),
• The large or old growth trees are retained, but smaller, more flammable young trees are removed,
• The stand is effectively thinned removing fuel ladders and dense tree conditions (Weatherspoon and Skinner 1995; Huff and others 1995; Weatherspoon 1996).

"Forest restoration treatment appears to represent a middle ground treatment that balances aesthetics, income production, and forest health--truly an ecosystem management--treatment with broad application. Any treatment that couples a low thinning with a broadcast burn should reduce wildfire hazards; the data show that this treatment was the most effective in reducing fire hazard. Even with the high cost of the broadcast burn, this treatment showed a modest return per acre." (Scott 1998)

Restoration seeks to restore forest functions (ecological processes) and conditions. Ecological functions needing restoration around the Flagstaff Urban Interface include the return of low intensity wildfire and a host of other forest functions (water flow, old growth dynamics, wildlife movement and reproduction, etc.). Primary actions that lead to restoration of many of the forest functions are reducing the excess number of trees (thinning) and reintroduction of fire (prescribed burning). A restored forest does not support catastrophic wildfire conditions; thus, restoration treatments that emulate the natural tree densities of historical ponderosa pine forests will substantially reduce the risk of catastrophic wildfire.

Central to ecological restoration is the idea that ecosystems function best under conditions in which they have adapted over evolutionary time (Swanson and others 1994). Therefore, ecological restoration prescriptions attempt to emulate, as closely as possible, the conditions characteristic of their evolutionary state. For example, Covington and others (1997) found the combination of thinning and burning resulting in tree conditions more like the tree patterns of historical ponderosa pine forests changed fire behavior from fuel model 9 (in which crown fires are common) to fuel model 2, in which surface fires occur, but crown fires are highly improbable.

Fuels reduction seeks primarily to alter forest fuel conditions such that resulting wildfires are low in intensity. Primary actions that reduce catastrophic fire behavior include the removal of ground, ladder, and aerial fuels. Thinning and burning are common techniques to achieve the desired forest fuel conditions. The reduction of excess trees and the reintroduction of fire leads toward healthier ecological processes, but does not necessarily restore them to their natural conditions.

Therefore, ecological restoration treatments inherently meet the fire hazard reduction objectives; however, fuel reduction treatments do not necessarily meet the ecological objectives of ecological restoration.

"Ironically, exclusion of low-intensity fires virtually assures eventual occurrence of large high-intensity fires that kill most trees. Roughly half of the more than 3 million acres that burned in wildfires in 1994 in the Western United States was in these ponderosa pine forests. In an active wildfire year, the expense of attempting to exclude fire from these forests can reach one billion dollars. Paradoxically, these costly attempts at suppression are often unsuccessful. In comparison, costs of restoration treatments are modest." (Arno 1996)

LOCAL WILDFIRE RISK REDUCTION EFFORTS

Forest management has been occurring within and surrounding the Flagstaff area for nearly 130 years. However, thinning and burning treatments have not kept pace with tree growth and fuels deposition. Annual growth in the Coconino National Forest (excluding wilderness areas) is about 27 million cubic feet. In the 1990's, thinning has removed about 930 thousand cubic feet annually, or about 1/3 of the annual growth. Annual fuel accumulations are from 0.6-3.5 tons per acre, depending on stand age and density. Twenty years of fire exclusion even in highly managed stands will result in fuel loads that can cause fire suppression problems. As fuels treatments are not keeping up with the amount of fuel deposition and tree growth, the modest gains from ongoing thinning and burning are continually being compromised.

The expense of treatments in the urban interface, the resistance efforts by those against thinning and burning, and the continual tree growth and fuels deposition have resulted in substantial portions of the Flagstaff area needing thinning and prescribed fire. Further complicating the thinning effort is the current poor to nonexistent market for small diameter trees. It costs approximately $300 per acre for planning and implementation of thinning and prescribed fire. For instance, under current market conditions, it would cost $12,000,000 to treat the approximate 40,000 acres of high and moderate catastrophic fire risk identified in this assessment.

A number of current efforts are underway to reduce the risk of catastrophic wildfire within the Flagstaff Urban Interface. The Grand Canyon Forests Partnership was formed about three years ago as a community approach to forest restoration and catastrophic fire risk reduction. The Partnership's first project area is just northwest of town on National Forest lands in the area of the Snowbowl road, and is called the Fort Valley Forest Restoration Project. This area represents the Partnership's first block of land to be analyzed and treated for the reduction of catastrophic wildfire as well as the restoration of forest health within the Flagstaff Urban Interface. Fuels reduction is being accomplished through thinning and prescribed fire.

The Coconino National Forest has numerous thinning and burning projects completed, currently planned, or ongoing within Flagstaff and on National Forest lands surrounding the greater Flagstaff area. These areas include Fort Valley, A-1 Mountain, Skunk Canyon (along Lake Mary Road), Lake Mary, Pumphouse (around Kachina and Forest Highlands), and Mars Hill (Thorpe Park).

The Arizona State Land Department has also been managing forest fuels conditions for decades. A small department that has budgetary limitations, the State Department is currently thinning dense, young tree stands in the Equestrian Estates/University Heights area.

The Flagstaff Fire Department is devoting substantial resources toward reducing catastrophic fire conditions in and around the city. The department has added a seasonal thinning crew, a Fuel Management Officer, and upgraded wildland fire equipment. The Flagstaff Fire Department is currently engaged in thinning and prescribed fire activities throughout the city.

The Ponderosa Fire Advisory Council (PFAC) has recently begun a fuel management program within developed areas of member fire departments.

A summary of current fuels reduction/forest restoration projects follows. This table does not list the numerous past projects, which have contributed to the current areas of low risk to catastrophic fire. The table includes projects that spill over the 94,100-acre risk assessment area. Combined, these projects currently address about 10% of the approximate 40,000 acres of identified high and moderate risk for catastrophic fire.

Flagstaff Urban Interface
1999 Fuels Reduction/Forest Restoration Projects

	Project Name	Description	Lead Agency	Emphasis
1	A-1 Mountain*	Thinning-burning on	Forest Service	Fuels Reduction
2	Equestrian	Thinning-burning on	State Land Dept	Fuels Reduction
3	Pumphouse*	Thinning-burning on	Forest Service	Fuels Reduction
4	Arboretum*	Thinning-burning on	Forest Service	Fuels Reduction
5	Lake Mary*	Thinning-burning on	Forest Service	Fuels Reduction
6	Skunk	Thinning-burning on	Forest Service	Fuels Reduction
7	Mars Hill	Thinning-burning on	City of Flagstaff	Fuels Reduction
8	Sinagua High School	Thinning-burning on	City of Flagstaff	Fuels Reduction
9	Mary's Cafe	Thinning-burning on	Forest Service	Fuels Reduction
10	Airport	Thinning-burning on	City of Flagstaff	Fuels Reduction
11	Fort Valley*	Thinning-burning on 5,000 acres; meadow	Forest Service	Restoration
12	Various City	Thinning-burning on 1,000 acres of	City of Flagstaff	Fuels Reduction
13	Munds Park	Thinning-burning on 15 acre demonstration	Ponderosa Fire Advisory Council	Fuels Reduction

* not all acres are within the urban fire zone

"The evidence suggests that wildland fuel reduction for reducing home losses may be inefficient and ineffective: inefficient because wildland fuel reduction for several 100 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." (Cohen 1999)

Both the City of Flagstaff and Coconino County have encouraged homeowners to become responsible for preventing damage and loss from wildfires. Over the years, substantial efforts by all area fire agencies have been made toward fire safety education and homeowner responsibilities for fire prevention. The Flagstaff Fire Department has recently launched the "Be Prepared" program, which provides private landowners with actions for reducing damage and loss from potential wildfires in and around their homes and property.

Building codes and zoning regulations address private property requirements. The city of Flagstaff's land development code dictates the amount of tree removal allowed in city areas. New subdivisions require Forest Stewardship Plans, which have a review process by the Flagstaff Fire Department for compatibility with wildland fire protection. In addition, the city has a class B roof ordinance (non-flammable material) and water requirements sufficient for fire protection.

Cohen (1999) looked at the likelihood of a structure being ignited by radiation from an approaching fire or from an ember igniting burnable surfaces such as shake shingles. He found a distance of about 200 feet was needed free of flammable materials and vegetation to prevent combustion to a piece of home siding. While a solution to protecting private property from wildfire damage may be to create 200-foot "clearcuts" around people's homes, such a practice does nothing for the ecological, spiritual and social values of the forestland surrounding the community. Quite simply, catastrophic wildfire is not consistent with sustaining ponderosa pine ecosystems, of which people are members.

Furthermore, in absence of a 200-foot clearing, Cohen suggests that wildland vegetation management would have to occur potentially up to several kilometers (1.3 miles) away from homes (USDA 1999). Therefore, a combination of wildland and private property fire reduction treatment is the most effective means of protecting all of the values in the Flagstaff Urban Interface.

FOR MORE INFORMATION

For information on thinning/burning on city/private land and general fire information:

Paul Summerfelt
Fuel Management Officer
Chair for Ponderosa Fire Advisory Council
Flagstaff Fire Department
211 West Aspen Avenue
Flagstaff AZ 86001
Telephone: (928) 779-7688
Fax: (928) 779-7668
E-Mail: psummerfelt@ci.flagstaff.az.us

For information on State and Private Forestry thinning/burning programs:

Kevin Boness
Forestry Section Chief
Arizona State Land Department
3650 Lake Mary Road
Flagstaff AZ 86001
Telephone: (928) 774-1425
Fax: (928) 779-2143
E-mail: kbonessaz@cybertrails.com

For National Forest thinning/burning and general fire information:

Hunter Wistrand
Air/Fire/Safety Staff
Coconino National Forest
2323 E Greenlaw Lane
Flagstaff AZ 86004
Telephone: (928) 527-3550
Fax: (928) 527-3620
E-mail: hwistrand/ r3_coconino@fs.fed.us

For information about the Grand Canyon Forests Partnership or its programs:

Taylor McKinnon
Grand Canyon Forests Partnership
2601 N Fort Valley Road
Flagstaff AZ 86001
Telephone: (928) 774-7488
Fax: (928) 774-7570
E-Mail: mckinnon@grandcanyontrust.org

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