Wilderness Ridge Fire.pdf

Document Sample
Wilderness Ridge Fire.pdf Powered By Docstoc
					Wilderness Ridge Fire
             Bastrop County
  The most destructive wildfire in Central Texas
                  A Case Study
Wilderness Ridge Fire
                     Bastrop County

The most destructive wildfire in Central Texas




                             A case study




                              March 25, 2009
        Wilderness Ridge Fire Case Study © 2009 Texas Forest Service
 This document was prepared by Texas Forest Service. Any
reproduction of the document should be copyrighted to Texas Forest
Service. For more information or to order additional copies of this
report, contact Texas Forest Service, 301 Tarrow, Suite 304, College
Station, TX 77840-7896.

 Texas Forest Service was created in 1915 by the 34th Legislature as an
integral part of The Texas A&M University System. It is mandated by
law to “assume direction of all forest interests and all matters pertaining
to forestry within the jurisdiction of the state.”
                  Acknowledgements
 This report could not have been prepared without the diligent field collection work done by the East
Texas WUI Team. Special thanks to those team members.

                      Justice Jones – Mitigation and Prevention Coordinator
                 Karen Stafford – Regional Wildland Urban Interface Coordinator
                Jan Amen – Wildland Urban Interface Specialist and Photographer
              Tammy Russell – Office Associate II/Wilderness Ridge Project Assistant
Table of Contents
   Abstract......................................................... 1

   Dedication..................................................... 2

   Definitions..................................................... 3

   Introduction ................................................. 4

   Wilderness Ridge Fire Event...................... 5

   Case Study Methodology............................ 12

   Results............................................................ 21

   Conclusions................................................... 28

   References......................................................29




            Prepared by
Rich Gray - Wildland Urban Interface State Coordinator
         Karen Ridenour – GIS Specialist II
     Misty Wilburn – Communications Specialist
                                    Abstract
 The purpose of this publication is to examine the destruction that occurred on Feb. 28, 2009, in
Bastrop County, Texas, during the Wilderness Ridge Fire. Drought conditions, extremely dry and
windy weather, and a small spark all came together to form the devastating wildfire. Sparks from
downed power lines ignited the Wilderness Ridge Fire, the most destructive wildfire in Central
Texas. Fuels were critically dry due to the entrenched drought that was present across Central Texas.
The fast-moving timber wildfire immediately threatened homes and thousands of acres in the Lost
Pines of Central Texas. The Wilderness Ridge Fire ultimately destroyed 26 homes, 20 businesses and
1,491 acres of endangered species habitat.




                                                  1
                                Dedication
 This report is dedicated to the families who lost their homes and the business whose contribution to
the community will be missed. We extend our thanks to all the firefighters and agencies who worked
diligently to protect hundreds of homes and prevent the loss lives.




                                                  2
                                 Definitions
Air attack – Small, fixed-wing aircraft that has an air tactical group supervisor along with the pilot.
These “eyes in the sky” assist ground resources with information about the wildfire.

Aerial supervision module – A combination of lead plane and air attack.

Air tanker – A fixed-wing aircraft that has been certified by FAA to carry and deliver fire retardant.

Crown fire – A fire that is burning in the treetops.

Engine – A ground vehicle that can provide a specific level of pumping, water and hose capacity.

FEMA Declared Wildfire (FMAG – FEMA Management Assistance Grant) – Provides partial
reimbursement to the state for the cost of the wildfire.

Fuel – Any combustible material; includes trees, grass, needles, wood, etc.

Ladder fuels – Provide a vertical link between fuels. They allow the fire to move from the ground to
shrubs and trees easily. They also help start crown fires.

Litter – Composed of twigs, branches, dead sticks and fallen leaves or needles.

Needle drape – Dead pine needles that have fallen down and are now hung on other vegetation.

Single engine air tanker (SEAT) – More commonly known as crop dusters. These aircraft drop water
or retardant at lower levels than large air tankers.

Spotting – Embers from the main wildfire land in receptive fuel beds ahead of the main fire and start
new ignitions.

TFS – Texas Forest Service

TPWD – Texas Parks and Wildlife Department

TXANG – Texas Army National Guard

Type (1-6) – generally refers to dozers, engines and water tender capabilities. A Type 1 resource is
larger in size, power, capacity, etc., than a Type 6. Typing allows managers to pick the best resource
for the job at hand.

VFD – Volunteer Fire Department

Water tenders – Any ground vehicle that can transport a large amount of water – generally 2,000 to
5,000 gallons.

WUI – The line, area or zone where structures and other human development meet or intermingle
with wildland.
                                                 3
                            Introduction
Historical WUI fires across the country

 In October 1991, the Oakland/Berkeley Hill Fire destroyed 2,449 single-family dwellings and burned
more than 1,600 acres in Oakland, California. A five-year drought, wooden decks extending out from
homes, and pine trees overhanging homes were noted as factors underlying home loss. Some of the
recent significant WUI wildfires that destroyed homes were Hayman Fire in Denver, Mack Lake Fire
near Mio, Michigan, Cedar Fire in San Diego County, California, Rodeo-Chediski Fire in East Central
Arizona, and the list will continue to grow. Knowledge about why homes are destroyed is gained
from examining those lost homes. However, more knowledge can be found by examining homes that
were only damaged or unaffected where no mitigation efforts occurred during the wildfire.


Historical WUI fires in Texas

 On Dec. 27, 2005, 110 homes, numerous outbuildings and a local church were lost in Cross Plains,
Texas, to a wildfire. This wildfire occurred in a prairie ecosystem. According to a case study
conducted by Texas Forest Service, the X-factors that were possible causes for the loss of homes in the
Cross Plains Fire were analogous to the Wilderness Ridge Fire. The X-factors in the Cross Plains Fire
were:
      - Open wooden decks
      - Wooden fences connected to structures
      - No skirting on open foundations
      - Combustible materials near structure
      - Open soffits and eaves




                                                   4
     Wilderness Ridge Fire Event
Fire Statistics                                  Resources

Acreage: 1,491                                   State agencies: TFS, TPWD and TXANG
                                                 4 Type 3 dozers
Threatened Area: 14.7 square miles               3 Type 6 engines
                                                 1 10-person hand-crew
Ignition Cause: Power Lines
                                                 VFD: 22 departments
Homes Saved: 408                                 3 Type 1 engines
                                                 27 Type 6 engines
Homes Lost: 26                                   6 Type 2 water tenders

Outbuildings Saved: 118                          Aviation: Non-suppression
                                                 1 Type 3 helicopter – state agency
Outbuildings Lost: 44                            1 aerial supervision module – federal agency
                                                 1 air attack – contract
Businesses Saved: 6
                                                 Aviation: Suppression
Businesses Lost: 20                              1 Type 1 air tanker – contract
                                                 1 Type 2 air tanker – contract
Under County Burn Ban                            2 SEATs – contract
                                                 1 Type 1 helicopter – contract
Fire Occurred on Private Property                2 Type 1 helicopters – TXANG

Class F Size Fire (1000-4999 acres)

Start 2/28/2009 @ 1205

Contained 3/09/2009 @ 1800

WUI: Interface fire

FEMA declared wildfire

Responding VFDs from local and surrounding counties

Bastrop County: 3-N-1, 5 Points, Bastrop, Bluebonnet, Elgin, Heart-of-Pines, McDade, Paige,
Smithville

Fayette County: Carmine, Fayetteville, Flatonia, La Grange, Muldoom, Winchester

Williamson County: Cedar Park, Coupland, Florence, Georgetown, Leander, Taylor, Wier

TPWD, TXANG, FCI-Bastrop


                                                 5
                                         WEATHER

 Despite tropical storm Edouard and hurricanes Dolly, Gustav and Ike soaking parts of Texas in 2008,
every part of the state — 100 percent — is experiencing some drought according to the most recent
                                                                     U.S. Drought Monitor map,
                                                                     released March 10, 2009.

                                                                      Parts of Central Texas and the
                                                                     Hill Country, more than eight
                                                                     percent of the state, are not
                                                                     only in exceptional drought
                                                                     — the most severe stage of
                                                                     dryness — but they are now
                                                                     the driest region in the country
                                                                     and the driest they have
                                                                     been since 1918. It is the only
                                                                     place in the U.S. experiencing
                                                                     exceptional drought.




 Weather conditions that lead to
high wildfire danger also affect the
moisture content and temperature
of a house. On Feb. 28, a large
portion of the state was under a
red flag warning due to forecast
winds of 20 to 30 mph with gust of
40 mph and low relative humidity
values predicted in the mid to
lower teens. Of the 1,491 acres
burned during the Wilderness
Ridge Fire, 245 acres were in
grazed pastureland and the
remaining 1,246 acres were in pine
and oak fuels.
                                                 6
 The lack of rainfall during February 2009 continued the long spell of rainfall deficits that began in
September 2007. Due to the continued lack of rainfall, most locations were at least one to three inches
below the long-term normal for the first two months of 2009. Wildfire danger was high to very high
across the region. Most fuels were cured and the continued lack of significant rains had increased the
wildfire threat.




Precipitation from January 1, 2009, to February 28, 2009, and departure from normal:

                           2009 RAINFALL        NORMAL TO DATE             DEPARTURE
AUSTIN MABRY                     2.21                4.02                     -1.81
AUSTIN BERGSTROM                 1.34                4.38                     -3.04


 The long-range outlook for April through June is calling for increased chances of above normal
temperatures and equal chances for below normal or normal rainfall (Drought Information Statement
Issued by NWS Austin/San Antonio, Texas).




                                                   7
                              The end of a drought is defined by a PHDI value of -0.5.
                    Drought amelioration (health) is achieved when a PHDI value of -2.0 is reached.



 The wide variety of disciplines affected by drought; its diverse geographical and temporal
distribution, and the many scales drought operates on, make it difficult to develop both a definition
to describe drought and an index to measure it. Common to all types of drought is the fact that they
originate from a deficiency of precipitation resulting from an unusual weather pattern. If the weather
pattern lasts a short time (e.g., a few weeks or a couple months), the drought is considered short-
term. If the weather or atmospheric circulation pattern becomes entrenched and the precipitation
deficits last for several months to several years, the drought is considered to be long-term. The
hydrological impacts of drought (e.g., reservoir levels, groundwater levels, etc.) take longer to
develop and it takes longer to recover from them. The Palmer Hydrological Drought Index (PHDI),
another long-term drought index, was developed to quantify these hydrological effects.




                                                          8
                                   Location of Fire


Why was this one different?

 Texas has begun seeing shorter, wetter winters and warmer, drier summers. Due to prolonged
drought and effects of climate change, ecosystems will be altered significantly in structure,
composition and distribution of species within the next 30 years. This change will result in wildfires
occurring in geographic areas throughout the state that have not traditionally experienced such
events.

 Build up of mid-story fuel loads, such as young trees, in forests and woodlands, plus flammable
invasive species in rangelands and grasslands, will alter traditional wildfire behavior. This behavior
alteration will result in unprecedented wildfire activity, which will make control of these wildfires
difficult.


Historically

 The Wilderness Ridge Fire occurred in the Lost Pines of Bastrop County. This area is a disjunct
population of Pinus taeda located in Central Texas near Bastrop at the westernmost edge of the
species’ natural range. Historically (Pre-Euro-American Settlement), this area’s forest composition
was dominated by loblolly pine (50 to 70 feet tall) and widely scattered oak species, such as post oak
and black oak on xeric, or extremely dry habitat, sites. In areas with frequent natural wildfires, the
understory would have been dominated by native perennial grasses and forbs such as little bluestem,
big bluestem (Andropogon gerardii), pinewoods dropseed (Sporobolus junceus), asters (Symphiotrichum
sp.) and bracken fern (Pteridium aquilinum).


Currently

 Due to urban development and protection of endangered species’ habitat, fire has been absent in
this area, which has allowed the understory to change. The current state of the Lost Pines is primarily
closed canopy, with a dense understory of yaupon. This closed condition and understory component,
have lead to excessive needle drape, increased fuel loading and ladder fuels. These elements have
created conditions favorable for extreme wildfire behavior.




                                                   9
                        Endangered species habitat
 The entire perimeter of the Wilderness Ridge Fire occurred within the Houston toad (Bufo
houstonensis) habitat. The largest living population of Houston toads is found Bastrop County. The
Houston toad depends on healthy and mature forest ecosystems with mixed species composition,
moderate canopy cover, an open understory layer with a herbaceous component, and shaded
breeding pools. Unmanaged forests and forests that sustain other types of land uses such as
residential, recreational, or agricultural activities can become less suitable as Houston toad habitat
over time. Without active management, forests can become too dense and shaded, accumulate
dangerous levels of burnable duff and debris, and be negatively impacted by cattle, pollutants and
vehicles. Historically, periodic wildfire played an important role in maintaining native bunchgrass
communities in loblolly pine and post oak savannah. Due to poor grazing management practices and
wildfire suppression since the arrival of European man, much of the former savannah grasslands of
the post oak region have grown into brush thickets devoid of herbaceous vegetation. Houston toads
need the herbaceous layer of bunchgrasses for cover and foraging habitat.




                                                  10
                                  Wildfire behavior
 On-site wildfire observation noted
very active wildfire behavior with
torching and spotting up to 20 yards
on the flanks and at least 200 yards
at the head. This type of wildfire
behavior was due in part to local live
fuel moistures, which are measured
monthly to determine the status
of vegetation. For February, live
fuel values were near or at critical
thresholds with pine species at 112,
yaupon at 97 and juniper at 84. The
wildfire exhibited rates of spread
in pine stands at approximately 415
ft/hr and in grass fuels at 4006 ft/
hr with sustained wind speeds of
10 mph. At 14:07, after traveling        Two hours after the initial fire started, the wildfire jumped State Highway 71.
two miles in two hours, the wildfire
jumped a major state highway and
continued spreading quickly in grass
fuels towards the Colorado River.

                      Bastrop Remote Automated Weather Stations (RAWS)
                            BTRT2 Feb. 28, 2009, Weather Conditions
    Central Standard     Temp °F Relative humidity       Winds      Gusts                              Fuel Temp
         Time                           (percent)         (mph)     (mph)                                  °F
               12:08:00     58              32               8        25                                   75
               13:08:00     60              26              10        27                                   77
               14:08:00     61              24              10        25                                   79
               15:08:00     62              23               9        23                                   77
               16:08:00     62              21              13        22                                   74
               17:08:00     60              20              13        27                                   67
               18:08:00     57              22               8        24                                   57
               19:08:00     52              25               6        21                                   47
               20:08:00     49              30               4        16                                   43
               21:08:00     46              33               4        15                                   40
               22:08:00     44              35               5        12                                   39
               23:08:00     42              35               6        17                                   38
                0:08:00     41              33               5        16                                   36
   Average                  58              25               9        23                                   66
   Maximum                  62              35              13        27                                   79
   Minimum                  41              20               4        12                                   36

                                                      11
          Case Study Methodology
The science behind the problem

 Homeowners need to understand that any wooden structures on their homes are just trees in a
different shape. Embers most commonly ignite solid wood during wildfires.

 In the absence of an open
flame, wood typically ignites
at temperatures above 550
degrees Fahrenheit (F)
depending on the species,
moisture content and
how long it is exposed to
elevated temperatures. In the
presence of a flame, ignition
temperatures are lower
(American Forest & Paper
Association, Inc., 2006).

 Texas Forest Service is
conducting research in
grassland ecosystems
to develop an accurate
understanding of wildfire
behavior in grass fuels. During
the research, multiple heat-
gathering instruments were
buried in the ground to record
the heat output from a fire
as the fire burned over them.
The data was collected and
averaged. Averages for three
burns ranged from 695 F to 910
F, with maximum heat outputs
ranging from 1196 F to 1228 F.

 These heat ranges are short
in duration – a minute or less
– but even in grass, produce
temperatures that are high enough to ignite wood. It is hoped that research in timber type fuels in the
future will reveal additional information in regards to potential heat outputs.




                                                  12
Soffits

 The underside of an eave is known as a soffit. The venting that often occurs on the underside of
eaves, or soffits, can allow embers, as well as flames, to enter the attic of a home. As a wildfire
approaches a structure, the flames burn up to a side of the structure and the flames become blocked.
Blocked flames will climb higher than flames that are not in contact with a wall. Flames that run into
a corner will climb even higher. The flame plume will spread onto the surface of the eave (soffit) if an
overhang exists.

 Research at the University of California Forest Products Laboratory Fire Research Laboratory
showed that flames enter soffit vents located in an open eave and strip vents installed in boxed
eaves almost immediately after a flame source was ignited at the base of the wall. New vent designs,
developed by private companies will soon to be on the market. These vents have done a much better
job of stopping embers in laboratory experiments; however, they also reduced airflow. According to
Quarles (2002), the airflow problem could be countered by installing more vents. The lowly house
vent could be the key to saving homes (Quarles 2002).




             This house received protection from volunteer fire departments during the Wilderness Ridge Fire.




                                                            13
Foundation vents

 Open foundations, as seen in pier and beam construction, allow for airflow under a home. This
feature also allows debris to build up under non-enclosed foundations and in close proximity to
landscape vegetation. Debris under the house and close to landscape vegetation increases the chance
of flame entry into the crawlspace. Firewise construction should allow moisture to flow out , while
creating a barrier that prevents embers from entering the foundation of the home.

 The home below was lost during the Wilderness Ridge Fire. Open foundation vents with minimal
screening allowed embers to enter the structure. X-factors such as a wooden deck, wooden window
shutters and landscape timbers also contributed to the loss of this home.




 The home below utilized available rocks on the property to create a small wall, which kept debris
from accumulating under the foundation. Low growing vegetation aided in reducing fire contact
with exterior walls.




                                                 14
Wooden decks

 Spaced-board decks allow for air circulation and water drainage, which improves the drying
potential of the deck boards and the underlying support framing. These same gaps allow flames to
extend upward through the gaps between boards, thereby increasing the rate at which the deck is
degraded. Research has shown that when deck boards are butted, flames cannot easily penetrate
between the board spaces and rate of burning is minimized (Quarles 2002).

 In Australia, research on timber decks found that hardwood timber decking tends to burn slowly.
Each board burns separately, which results in a heat load on exterior walls similar to a medium-sized
ignition source such as one pound of tree litter. Researchers suggest that separating the combustible
aspects of decks from the wall and using a non-combustible subfloor could make durable hardwood
timber decks significantly safer in terms of the potential heat loading on exterior walls (Macindoe et
al., 2007).

 The research also concluded that the radiation on a component, such as a wall, is approximately
the sum of the radiation from the contributing sources. Hence a 15 kW/m² radiation load from the
radiation wall plus the radiation from the ignition source can result in a combined radiation load of
20 kW/m², i.e. enough to ignite cedar weatherboards within two to three minutes.

Examples of thermal radiation levels:
    - 0.7 kW/m² = hot summer sunshine
    - 5 kW/m² = limit for a person to escape
    - 12.5 kW/m² = wood, paper and paint ignite




                                                                    This deck, suspended over the sloping
                                                                    topography, permitted embers and the
                                                                    wildfire to burn underneath the deck igniting
                                                                    leaf litter, grass and support beams. Burning
                                                                    most likely ceased once heat was removed
                                                                    as ground fuels were consumed and only
                                                                    smoldering continued.




                                                  15
Fencing

 There are a number of reasons why fences are a concern during wildfires. First, a combustible fence
attached to a structure is a threat because fire can move along the wooden fuel to the home. Fence
ignition can occur where debris has collected along the bottom, which creates a bed of fuel for embers
and surface fire.

 Second, many wooden fence boards are in contact with soil at the bottom, which will eventually lead
to decay. This decay makes the fence easier to ignite.

 Third, fence boards are usually spaced and not in direct contact with one another. This vertical
opening allows embers to lodge between boards and can cause the boards to ignite. Research shows
that the thinner the fence boards, the greater the risk of ignition (Quarles 2002).




                                                 16
Windows

 In the wildland urban interface, windows represent one of the most vulnerable features of a home.
Research has shown that double pane windows help protect a structure. The first pane will break and
direct heating of the second pane begins. The second pane may provide the extra time needed for the
window to survive the short-duration burst of the passing fire front, if the first pane is compromised.

 In a realistic wildfire context, an airborne ember may
ignite a bush or tree some distance from the window.
For typical vegetation, this heat source will have a short
duration before extinction. If the second pane extends
the life of the window beyond vegetation burnout, the
window integrity will not be compromised (Cuzzillo and
Pagni, 1998).

 The window frame is also susceptible to burn-through
under direct flame exposure. Radiant or convective
heating might not break the glass but could ignite or
deform the window frame. This deformity can allow the
glass to fall out of the frame and expose the building to
flame entry.

 Homeowners should maintain a vegetation-free area
from the home to reduce radiant heat sources that could
compromise frames and windows.




Exterior ignition sources
                                     There are many possible exterior ignition sources in a wildland
                                    urban interface fire. Often, plants, stacks of firewood and other
                                    combustible materials are adjacent to the structure. Flying
                                    embers can easily ignite these materials.

                                     Plastic or wood furniture on patios and decks can also ignite
                                    from flying embers. If ignited, all of these items can expose the
                                    building or the deck to a flame source for some period.




                                                  17
Flame duration

 Burn time of common fine fuels, which is often responsible for behavior of the main wildfire front,
is between 15 to 33 seconds. Heavier fuel (such as logs and branches) on a forest floor may burn for
many hours. More localized flame attack from elements immediately around the structure may burn
for many hours. Rough estimation of burn times are provided in the table:

                      Fuel sources        Approx. duration        Approx. maximum
                                             (minutes)            flame length (feet)
                    Stored material            5-120                   various
                   Forest fuels - fine        .25-.55                     165
                  Forest fuels - heavy        30-125                      6.5
                     Garden sheds               30-60                     6.5
                   Detached garage             30-120                      13
                  Combustible fences            10-30                     6.5
                   Adjacent houses             60-180                      13
                    Motor vehicles              30-60                       9


 The accumulation of unburned debris during and after the wildfire front passes can cause long-term
localized attack on those areas vulnerable to fine fuel accumulation. Observations of embers and
debris-based flame attack on structures many hours after the main wildfire front has passed have
been observed in past wildfires. During this time, the nature of the flame attack is through a build up
and ignition of debris rather than a continuous flame attack (Leonard et al., 2004).




      Photos by Jarred Lemmon




                                                  18
Embers

 Embers can be as small as a pinhead or as large as a flying sheet of plywood. They can be tossed
by winds a mile or more ahead of a wildfire. After the main flame front moves on, burning debris
continues to spit them out.

 “The main body of the fire will stay at a house a few minutes, no more than 10,” Quarles said. “The
ember shower can last for 30 minutes or more before the fire and two hours or more after the fire has
passed.”

 The glowing fragments blow through house vents and pile up in attics like tiny smoldering
snowdrifts. They nestle under the eaves, on decks and in roof corners. Some homes within the
wildfire perimeter were separated from the main wildfire by roads, but wind driven embers easily
crossed the streets and ignited fuels around the homes. Cavities such as gutters are also vulnerable
features. A common misunderstanding is that cleaning gutters immediately before a wildfire event
mitigates the risk of flame attack. It has been found that the extensive airborne debris from a wildfire
quickly accumulates in gutters to provide the necessary fuel load (Leonard et al., 2004).




 Note the absence of burning away from the structure in these photos. Blowing embers were
stopped by the structure, then smoldered along the base of the home and melted the skirting. The
slowly spreading wildfire would have had time to move along needle litter and skirting. With no
suppression efforts, the wildfire would have eventually ignited the wooden steps.

                                                   19
Slope

 The slope of terrain plays an important role in the rate of spread of a wildfire. Generally, a wildfire
will move faster up a slope and produce longer flame lengths than a wildfire on level ground. This
is because hot gases rise in front of the wildfire and the path is pre-heated by flames that are bent
towards ground fuels. This pre-heating results in faster ignition of fuels. In July 1989, the Black Tiger
Fire destroyed 44 homes near Boulder, Colorado. Of the 44 destroyed homes, 21 were located in what
was classified as good slopes of 15 percent or less. How far homes lost were set back from the slope
was not mentioned in the report. The Wilderness Ridge Fire assessment determined that slope ranged
from 12 to 18 percent where homes were lost. Homes lost were set back less than 50 feet from the
crest of the slope. These findings reveal that wildfires can involve homes even when slopes are mild
and set-back from slope is minimal. This metal storage building foundation footprint was less than
35 feet from the crest of the slope. The building was compromised due to heat from crowning, slope
location and single pane windows. The unburned home found in a different location on the 40-acre
property, was set back more than 100 feet from the slope crest.




                                                   20
                                      Results
                      A Closer Look – Homes that survived


Example 1: Concrete slab, rock siding, metal roof

 Enclosed soffits and double-pane tempered windows saved this home. Double-pane tempered
windows are shown to resist breakage better than regular double-pane windows. Also, the wooden
handrails do not extend to the house, so flames had no way to travel and make contact with the
house. This home was over 90 feet from the nearest slope. A metal storage building only 35 feet from
the slope was lost to the wildfire, along with all content.




Example 2 – Pier-and-beam, vinyl siding, metal roof
Despite the open wooden porch, this home survived because of simple measures. The open
foundation was skirted with Hardiboard and had no gaps. The metal roof helped prevent ignition
from embers and soffits were enclosed. Pea gravel separated the wooden fencing from the house
and a metal gate connected the fence to the house. Trees near the house had been removed to create
defensible space.




                                                 21
Example 3 – Concrete slab, rock siding, composite roof

 Even though this home was saved, X-factors, that could have contributed to loss if suppression
efforts had not been available, would have been the back wooden porch, wooden foundation
entrance door and railroad ties used for landscape elevation. Stone exterior, concrete foundation and
absence of vegetation near the home assisted in reducing threats. A concrete porch and stone work
for support walls would give this home a higher chance of survival during future wildfire events.




Example 4 – Pier-and-beam, vinyl siding, metal roof

 Firefighters removed this home’s back porch prior to the wildfire front arrival, which contributed to
the save. The fire burned though the over-story vegetation, leaf litter and around the structure. There
was no burning in the grassy front yard. The aluminum skirting helped reduce embers from blowing
under the foundation of the home.




                                                  22
                               Data on homes lost
                                 Exterior              Set back       Value of        Additional X-factors for
House Foundation     Roof                     Deck
                                  walls               from slope        loss                 ignition
                                                                                      Open deck, combustible
        Cinder                                             no slope
  1                  Metal     Vinyl siding   Yes                     13,260.00        materials near home,
        Block                                             influence
                                                                                        vegetation contact
        Cinder                                             no slope                 Two open decks, incomplete
  2                Composite   Vinyl siding   Yes                     103,191.00
        Block                                             influence                          skirting
        Cinder                                            back - 50
  3                Composite   Vinyl siding   Yes                     58,107.00    Open deck, proximate to slope
        Block                                               feet
        Cinder                                            back - 50
  4                Composite   Vinyl siding   Yes                     52,702.00    Open deck, proximate to slope
        Block                                               feet
                                                                                   Open deck, pine needle drape,
        Pier and                                          back - 24
  5                  Metal     Hardiboard     Yes                     51,836.00     combustible materials near
         Beam                                               feet
                                                                                              home
                                                                                   Open deck, pine needle drape,
       Concrete                                            no slope
  6                  Metal        Wood        Yes                     129,645.00    combustible materials near
         Slab                                             influence
                                                                                              home
        Cinder                                            back - 20                 Open deck, wooden planter,
  7                Composite   Vinyl siding   Yes                     54,364.00
        Block                                               feet                        Pine needle drape
        Pier and                                           no slope                Eyewitness ignition on wooden
  8                  Metal        Wood        Yes                     42,378.00
         Beam                                             influence                  deck, single pane windows
        Cinder                                             no slope                 Open deck, open addition on
  9                  Metal     Vinyl siding   Yes                     16,108.00
        Block                                             influence                            back
        Cinder                                             no slope                 Open deck, open addition on
 10                  Metal     Vinyl siding   Yes                     10,080.00
        Block                                             influence                            back
                                                                                       Open deck, no skirting,
        Cinder                                             no slope
 11                  Metal     Vinyl siding   Yes                      7,670.00      combustible materials near
        Block                                             influence
                                                                                              home
        Cinder                                             no slope
 12                  Metal        Wood        Yes                      1,945.00              open deck
        Block                                             influence




                                                     23
                                                                                       No skirting, railroad
     Cinder                                            no slope                      tie foundation support,
13              Composite   Vinyl siding   Yes                     3,184.00
     Block                                            influence                    combustible materials near
                                                                                              home
                                                                                    No skirting, single pane
     Cinder                                            no slope
14              Composite   Vinyl siding   No                      1,361.00         windows, combustible
     Block                                            influence
                                                                                     materials near home
     Pier and                                          no slope                    Open deck wrapped entire
15              Composite      Wood        Yes                    158,210.00
      Beam                                            influence                    house, vegetation contact
     Pier and                                          no slope                  Open foundation, single pane
16                Metal        Wood        Yes                     22,555.00
      Beam                                            influence                           windows
     Cinder                                            no slope                    Open deck front and back,
17                Metal     Vinyl siding   Yes                     30,023.00
     Block                                            influence                       vegetation contact
     Cinder                                           back - 35
18              Composite   Hardiboard     Yes                     66,272.00      Open deck, attached garage
     Block                                              feet
     Pier and                                      midway
19                Metal        Wood        Yes                     37,175.00       Open deck, wooden fence
      Beam                                        down slope
                                                                                  Open deck, attached garage,
     Pier and                                          no slope
20                Metal        Wood        Yes                     61,207.00      combustible materials near
      Beam                                            influence
                                                                                            home
     Cinder                 Aluminum                   no slope                    Wooden steps, vegetation
21                Metal                    Yes                     2,791.00
     Block                    siding                  influence                  contact, single pane windows
     Pier and                                          no slope
22                Metal        Wood        Yes                       N/A           Open deck, wooden fence
      Beam                                            influence
                                                   back - 27
     Pier and                                                                    Elevated open deck, vegetation
23                Metal     Wood-cedar     Yes    feet, sides -    71,969.00
      Beam                                                                        contact, single pane windows
                                                    43 feet
     Pier and                                          no slope                   Open deck, wooden shutters,
24                Metal        Brick       Yes                    105,064.00
      Beam                                            influence                   telephone pole next to home,
     Cinder                                            no slope                   Open deck, single pane win-
25                Metal     Vinyl siding   Yes                     33,790.00
     Block                                            influence                             dows
     Cinder                                            no slope                  Open deck, telephone pole next
26                Metal     Vinyl siding   Yes                     9,208.00
     Block                                            influence                   to home, vegetation contact
                                                       Total:     1,144,095.00




                                                 24
                                   Economic Impacts
 Texas has building codes, but it is left up to local jurisdictions (counties, cities) to either opt-in or
opt-out of adopting the state code. In some cases, should a local jurisdiction choose to enforce a
building code, it could be the adopted state code or something similar. The level of state support
varies widely. Without constant coding regulations for homes built in wildfire prone areas,
substandard homes will continue to be built in areas of high wildfire risk. Construction materials and
elements are assigned fire ratings, usually in terms of hours until structural failure would occur in a
fire. The fire ratings are for ignitions that occur within the home as a single structural fire that will be
controlled by multiple fire departments. Ideally, construction codes should address materials that can
sustain burning conditions for several hours in the event that no mitigation efforts are available for
extended periods of time. As development continues to take place in rural areas throughout the state,
the wildland urban interface risk will continue to increase. Efforts need to be made to examine past
wildfire events to start developing building code standards in Texas that regulate the manufacturing
and use of building materials designed to withstand wildfire attacks.

Owners often start the blame game when their home was lost. Why did I lose my home? Why did my
neighbors’ homes survive? Did the fire department try to save my home? Reports continue to show
from past case studies involving wildfires in all types of ecosystems and weather extremes that little
things can determine the survivability of a home.

 The number of homes and businesses destroyed by a wildfire is always tragic to the community
and homeowners. It is almost impossible to know for certain why a particular home is destroyed by
a wildfire. Using reverse risk assessment allows specialists to hypothesize the reasons one home was
lost and another was spared. Using a questionnaire, specialists examine construction, ingress/egress,
defensible space, topography, fuels, weather components and analysis of fire behavior to develop a
fire chronology of events that contribute to home loss.




                                                    25
 After the Wilderness Ridge Fire, the East Zone Wildland Urban Interface program of the Texas
Forest Service went into the area to assess the damage. The following data was collected by the team’s
extensive forensic examination. This data focuses on construction of the homes lost.




• Based on the examination of the home sites, tax appraisal cards and homeowner interviews, the
findings indicate that of the 26 single-family homes, 25 of the homes were constructed on pier-and-
beam or cinder block open foundation. It is theorized that years of debris and leaf litter accumulation
permitted the wildfire to burn under the homes, smolder and cause ignitions.

• Of the 25 open foundation homes, 10 were constructed with wood siding. Similar to 100-hour fuels,
the wood siding dries out making the building material similar to dried vegetation, which is easily
ignitable after decades of drought and drying conditions.
• Vinyl siding, a petroleum product which is more flammable than other types of siding, was used in
14 of the 26 homes. Vinyl siding melts when subjected to even moderate heat.

• Attached wooden porches or decks, another potential ignition source, were seen in 21 of the 26
homes.

• There were three homes lost that were constructed of brick or Hardiboard construction, which are
Firewise construction materials; however, all three homes had wooden decks.

• The six homes lost on Felix Drive were all located less than 50 feet of each other. This proximity
possibly contributed to structure-to-structure ignition.

• In areas where homes were lost, torching/crowning in loblolly pines was observed.

• Total value of single family dwellings lost: $ 1,144,095.00 based on available tax records.



                                                       26
 As continued efforts are made to study home location, construction and other parameters that
lead to the loss of homes, there is continued evidence that it is the “little things” or X-factors that
determine the survivability of a home. Whether you have a brick home or mobile home, live in the
forest or on rangeland, the features on structures that can compromise the survivability of homes
have been documented in other case studies. In the Wilderness Ridge Fire, potential X-factors that
may have aided in ignition were:

       1. Open wooden decks

       2. Wooden fences connected to structures

       3. No skirting on open foundations

       4. Vegetation in contact with structure – needle drape

       5. Combustible materials near structures




                                                   27
                               Conclusions
 The Wilderness Ridge Fire was a result of “perfect storm” conditions. In Feb. 2009, the Central Texas
region was entrenched in a severe drought. The day of the wildfire, relative humidity values fell to 20
percent and wind speeds average was nine mph with average gusts of 23 mph. The spark from power
lines was the final piece needed to complete this destructive puzzle.

 The Wilderness Ridge Fire is the largest wildfire to affect Central Texas to date. It is hoped that this
study will inform both the private and public sectors on the importance of wildfire mitigation and
preparedness. This study is just part of a learning process that began in 1915 for Texas Forest Service.
TFS will continue to do its part to conserve, protect and lead the citizens of Texas.

 Protection of human life is the first priority in wildland fire management. Property and resources are
the second priority.

 Agencies and the public cannot expect that all wildfires can be controlled or suppressed. No
organization, technology or equipment can provide absolute protection when unusual fuel build-
ups, extreme weather conditions, multiple ignitions and extreme wildfire behavior come together to
form catastrophic events. The Wilderness Ridge Fire effortlessly jumped major highways and roads.
In many cases, spotting occurred hundreds of feet ahead of the main fire. At times, wildfire behavior
was beyond the limit of control because of crowning and torching in the pine trees. In some instances,
structure protection was the only option because of the intensity of the fire.

 During a major wildfire, rarely are there enough resources to defend every structure threatened by
the advancing blaze. The only feasible strategy for preventing losses in the wildland urban interface
is utilizing fire resistant building materials and modifying fuels in the home ignition zone.

 The responsibility rests with all of us when dealing with wildland fire issues within our community.
Homeowners need to maintain regular maintenance and prepare their home prior to a wildfire event.
Contractors need to request the development of building codes for Firewise construction materials.
Developers need to design and implement plans for communities that are Firewise. Local officials
need to support prescribed burning programs and the development and implementation of building
code regulations. State government support is needed to fund mitigation projects and research within
Texas.

 Fuel load concentrations will continue to build because of changing land uses. This is not only true
for communities in brush and timber areas but for grasslands as well. As Texas continues through the
current drought cycle, we will most likely experience more of these wildland urban interface fires.
To prevent devastating loss to a community, homeowners must become informed on how to protect
their homes. Community leaders should develop and implement Community Wildfire Protection
Plans (CWPP). Local response agencies should train for, plan and execute a rapid, coordinated
response to all wildland incidents.

 Continued wildfire occurrence is assured; it will take cooperation and action from homeowners,
community leaders and response agencies prior to a wildland event to most effectively protect homes
and lives in the wildland urban interface.

                                                   28
                                 References
American Forest & Paper Association, Inc. (2006). Fire Performance of Wood Products Awareness
 Guide. Washington, DC: American Forest & Paper Association, Inc.

Hyde, A., Lasko, R., Murphy, T., McManus, B., Smith, D., Artley, D., & Hilbruner, M. (2009).
 Quadrennial Fire Review 2009.

Leonard, J. E., Blanchi R., Bowditch, P.A. (2004). Bushfire impact from a house’s perspective. Earth
 Wind and Fire –Bushfire 2004 Conference, Adelaide.

Macindoe, L., Sargeant, A., Bowditch P. A., & Lenoard J. (2007). Fire Tests at the Interface between
Timber Decks and Exterior Walls.

Quarles, S.L. (2002 March). Conflicting design issues in wood frame construction. Paper
 presented at 9th Durability Building Materials Conference, Brisbane, Australia.




                                                  29

				
DOCUMENT INFO
Shared By:
Categories:
Tags:
Stats:
views:0
posted:7/12/2012
language:
pages:35
yan198555 yan198555
About