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City of
Community Wildfire Protection Plan
Considerations for
Wildland Urban Interface Management in the City of Submitted
by B.A. Blackwell
and Associates Ltd. V7J 3B5 Submitted to Don Stewart and
Brian Schmitz City of December 2005 |
Table of Contents
2.2 Communication
and Education
3.1 Communication
and Education
6.3 Mountain
Pine Beetle and the Impact on Forest Fuels
7.0 Wildland Urban Interface Defined
7.1 Vulnerability
of the Wildland Urban Interface to Fire
8.0 Wildland Urban Interface
Continuum
8.1 Communication
and Education
8.6 Post
Fire Response – Rehabilitation
9.0 Communication and Education
9.1 Communication
and Education Goals
9.6 Media
Contacts, Use and Coordination
9.7.2 Government Ministries, City and Municipal
Officials, Disaster Planning Services, Utilities
10.1.2 Building Exterior – Siding Material
10.5 Joint City EKRD Cooperation
10.6 Structured FireSmart Assessments of
High Risk Areas
13.0 Vegetation (Fuel) Management
13.1 Principles of Fuel Management
13.2.1 Mountain Pine Beetle Fuel Management
13.2.2 Stand Level Fuel Treatment Needs
13.2.3 The Principles of Landscape Fuelbreak Design
13.2.4 Existing Landscape Fuelbreaks Within the City
13.2.5 Proposed Landscape Fuelbreaks within the City
14.0 Post Wildfire Rehabilitation
Planning
List of Figures
Figure 2. Fire season summary (April to October) of key indicators
that affect fire behaviour.
Figure 3. Updated fuel types for the study area.
Figure 7. Moist rich site dominated by aspen – classified
as a D1 fuel type.
Figure 9. Graphical summary of fire hazard changes
associated with an MPB outbreak.
Figure 10. Blowdown and breakage contributing to fuel
loading.
Figure 11. Accumulation of surface fuels (left). Snow
damage (right).
Figure 12. Fire hazard succession following attack.
Figure 13. Projected MPB infestation levels (percentage)
for 2005 and 2020 within the study area.
Figure 17. Graphical example showing variation in the
definition of interface and intermix.
Figure 18. Wildland urban interface and intermix
communities in the City.
Figure 21. Wildland urban interface continuum.
Figure 22. Example of typical home with wood siding and
open decks and balconies.
Figure 24. Showing high surface fuel loadings under a
forest canopy
Figure 25. Comparisons showing stand level differences in
the height to live crown.
Figure 26. Comparisons showing stand level differences in
crown closure.
Figure 27. Comparisons showing stand level differences in
density and mortality.
Figure 29. High vulnerability interface areas
Figure 30. Schematic showing the principles of thinning to reduce stand level
hazard.
Figure 31. Final overlay of probability and consequence
from the Wildfire Risk Management System.
Figure 32. Conceptual diagram of a shaded fuelbreak pre
treatment and post treatment.
Figure 33. 1994 Tyee Fire shaded fuelbreak example.
Figure 35. Overview of proposed and potential fuelbreaks..
List of Tables
Table
1. Fire history summary within the study area from 1950 - 1999.
Table
2. Summary of fire cause within the study area.
The City of
Fernie
is located on Highway #3 (The Crow’s Nest Pass Highway) in an area renowned for
its world class recreation and outstanding mountain environment. Fernie has
deep roots in the coal mining industry and was incorporated as a municipality
more than 100 years ago. It is a community shaped by tragedy and triumph, being
devastated by fire on two occasions and suffering several major mining
disasters where many lives were lost. Despite these challenges, the community
has persevered and is now poised for another renewal as a mountain resort
economy emerges.
Traditionally mining, railway and forest
sector based, the area is rapidly evolving into a more mature and diversified
socio-economic region. While mining and forestry remain very important to the
City, other growth sectors include food, beverage, accommodation,
entertainment, recreation, retail, personal services, construction, government
services and industries that do not need a specific location (such as software
development) but want to locate here for lifestyle reasons.
The
natural resources and people of Fernie and area are its greatest assets. A long
history, significant heritage assets, resiliency in the face of adversity,
continued employment in traditional resource economies and a bright future make
Fernie an authentic Mountain Resort Community[1].
This region of the province is susceptible to both lightning and human caused fires. Additionally, an ongoing Mountain Pine Beetle outbreak has the potential to significantly impact the forest fire hazard adjacent to the community over the next twenty years. Overall the community could be classified with a fire risk profile described by a moderate fire probability and high to extreme consequence based on the values at risk.
B.A. Blackwell and Associates Ltd. was retained to develop a Community Wildfire Protection Plan in consultation with City staff Don Stewart – Leisure Services Department, Brian Schmitz – Fire Rescue, and other support staff as required. The City and a supplementary grant from the Union of B.C. Municipalities funded the project.
The key priorities for wildfire management planning in the City were identified as:
· Hazard and risk mapping of the City to establish areas of the community that are at greatest risk to fire
· Facilitation of communication and education to local residents, all levels of government, and the general public
· Facilitation of a review and amendment of existing and proposed Development permits based on the hazard mapping assessment
· Facilitation of revisions to building standards and bylaws
· Identification of potential locations for strategic fuel breaks and forest stand level fuel reduction both within and outside the community
A Wildfire Risk Management
S
The fire risk anal
While much of the study area has a low to moderate fire probability, the consequence of fire defined by the values at risk is considered high within City limits and immediately adjacent to the municipal boundary. The highest probability fire scenario is a fire start from human ignition within the community that spreads out into the surrounding forest.
Under high to extreme fire weather conditions, spotting of burning embers was modeled. The model results indicate that, under high extreme fire weather conditions, a number of forested areas surrounding and within the community would be vulnerable to spotting at wind speeds averaging 9 kilometres per hour or greater. When wind speeds are in excess of 16 kilometres per hour, significant portions of the built up areas of the community would be vulnerable to fire propagation by spotting.
Significant portions of the community are immediately adjacent to the forest interface and many of the bordering fuel types are considered high hazard given their spotting and fire behaviour potential.
2.2 Communication and Education
The Fernie Fire Service needs to begin actively working on interface fire related communication and education. Public interest and participation in this process is likely to be complicated by the number of absentee owners and part time residents within the community. A significant amount of work is required to engage the community in this issue if successful planning, preparation and risk reduction measures are to be achieved.
Older businesses and homes in the core of the City are either constructed from materials that have low fire vulnerability or are a safe distance away from forest fuels. The most significant problems related to structure protection are associated with recent and new construction where aesthetic character has influenced the design and construction of homes and businesses without consideration of fire vulnerability and proximity to the forest interface. The building standards and the materials used on these recently constructed structures increase fire risk from an ember shower associated with spotting from a large fire event. In a number of subdivisions, homes and businesses would fail a FireSmart Assessment (the new provincial planning standard for interface communities). Given the extensive nature of the problem and the significant costs involved, this is an issue that cannot easily be rectified in the short term.
In general, the City has
good access for emergency response and fire suppression. However, there are
portions of the City considered isolated because of constrained access in and
out. For example, new subdivision construction in the northeast corner of city,
above the highway, has one-way access. Emergency access for the purposes of
fire protection, in isolated areas within the City of
Over the past several years Fernie Fire Rescue has undertaken S-100 and S-215 training to deal with interface fires. The current level of training and available equipment related to interface fire response is considered adequate but, given the risk of fire to the community, an advanced program that fosters continuous improvement and skill renewal would be beneficial.
The fire risk assessment indicates that the areas most vulnerable to smoke are the lower elevation areas within the main valley. Heavy smoke pooling in the valley bottom will require evacuation of the community and may cripple emergency response given that both the fire hall and local hospital are located in the valley bottom.
All Fernie Fire Rescue staff are currently trained in the S-100 Basic Wildland Fire Fighting course on a yearly basis. The current level of training and available equipment related to interface fire response is considered adequate but, given the risk of fire to the community, an advanced program that fosters continuous improvement and skill renewal would be beneficial.
An extensive fire within the City or within the watershed could have serious and long lasting consequences that include impacts on visual and water quality, recreation and sensitive resource values, and creation of environmental hazards. Additionally, there could be significant economic losses associated with loss of tourism and overall business revenue. Prompt rehabilitation efforts to restore and green-up burn areas are considered important and should be addressed through a comprehensive post rehabilitation planning exercise.
3.1 Communication and Education
Recommendation 1: The City should
work with local developers to construct a FireSmart show home that can be used
as a tool to educate and communicate the principles of FireSmart to the public.
The demonstration home would be built to FireSmart standards using recommended
materials for interface communities. Additionally, vegetation adjacent to the
home would be managed to guidelines outlined in the FireSmart program.
Recommendation 2: The City should
add
Recommendation 3: Similar to the
ski condition reporting available to guests in resorts and businesses, the City
should work toward communicating the fire danger during periods of high and
extreme danger to businesses and resorts within the City. This
Recommendation 4: The Fernie Fire
Rescue Department should work with the local Chamber of Commerce to educate the
local business community on FireSmart preparation and planning.
Recommendation 5: At a minimum the planning department should
integrate the FireSmart standard into the design of all new subdivision
developments within the City. Wherever possible this standard should be
integrated into changes to existing and new construction within subdivisions
and built-up areas of the community.
Recommendation 6: Many homes and
businesses are built immediately adjacent to the forest edge. In these
interface neighbourhoods, or where developments occur adjacent to park space,
trees and vegetation are often in direct contact with homes. The planning
department should create building set backs with a minimum distance of 10m when
buildings border the forest interface.
Recommendation 7: The City’s
Planning Department and Fernie Fire Rescue should begin a process to review and
revise existing bylaws and building codes to be consistent with the development
of a FireSmart Community.
Recommendation 8: In new
subdivisions the City should require roofing materials that are fire retardant
with a Class A and Class B rating. While it is recognized that wholesale
changes to existing roofing materials within the City of
Recommendation 9: Given the
wildfire risk profile of the community, an emergency sprinkler kit capable of
protecting 30 to 50 homes should be purchased and maintained in the community
or shared with the regional district. Fernie Fire Rescue personnel, or a
designate of the department, should be trained to mobilize and set up the
equipment efficiently and effectively during a fire event.
Recommendation 10: The City must
work towards improving access in identified areas of the community that are
considered isolated and that have inadequate access for evacuation and fire control.
Recommendation 11: An evacuation
plan should be developed for the community and the outlying road and trail
networks that could be cut off or impacted by fire. A large fire may require
the evacuation of heavily used trails where vehicle access is restricted.
Recommendation 12: During a large
wildfire it is probable that the valley bottom (location of the fire hall and
hospital) could be severely impacted by smoke. The City should cooperate with provincial
and regional governments to develop contingency plans, including an alternate
incident command centre and mobile facility, in the event that smoke causes the
evacuation of Fernie.
Recommendation 13: The current
level of training and available equipment related to interface fire response is
considered adequate, but given the risk of fire to the community, Fernie Fire
Rescue should adopt an advanced program that fosters continuous improvement and
skill renewal.
Recommendation 14: The modelling
of projected beetle attack in the Fernie valley indicates that significant
changes in fuels and fire risk are expected in 2020 and beyond. Fuel treatment
strategies should target removal of beetle susceptible lodgepole pine. The City
should work with the province and TEMBEC to monitor and quantify changes in
fire risk associated with the Mountain Pine Beetle outbreak.
Recommendation 15: Both the
provincial and federal governments have recently announced programs specifically
to address the wildfire hazard associated with Mountain Pine Beetle. The City
should work with the province to secure funding through these programs to
address the problem of a projected outbreak within the City of
Recommendation 16: A number of
high hazard areas immediately adjacent to, or embedded in, the community have
been identified as part of the wildfire risk assessment. These high hazard
areas should be the focus of a progressive thinning program that is implemented
over the next five to ten years. Thinning should be focused on the highest
priority areas: C2, C3 and C4 fuel types. The goals of thinning are to remove
hazardous fuels and to reduce the overall fire behaviour potential adjacent to
the community.
Recommendation 17: On lands
adjacent to the City limits, ownership complicates the fuel treatment issue.
There are areas of crown and private land that have been identified as
hazardous. The City should work with the RDEK and the province to secure
funding for treatment of crown land adjacent to the City. The City should also
work with private land owners (in particular TEMBEC) to address hazardous fuels
on private land.
Recommendation 18: The City should
work with British Columbia Transmission Corporation (BCTC) and BC Hydro to
ensure that transmission infrastructure can be maintained and managed during a
wildfire event. Maintaining the transmission corridor to a fuel break standard
will provide the community with a more reliable power supply that is less likely
to fail during a fire event and will reduce the probability of fire spreading
into the community.
Recommendation 19: The City should
prioritize the development of a fuel break network that builds on existing
breaks such as the highway, deciduous fuel types, and BC Transmission and BC
Hydro corridors running through the City.
Recommendation 20: The City should
develop further fuel breaks using existing topographic and water features.
Given the visual and resource sensitivity of the City, shaded fuel breaks
(retaining overstory trees) should be constructed to a size and standard that
will minimize fire behaviour potential and aid suppression resources in
containing and controlling wildfire.
Recommendation 21: Important trail
networks should be thinned and understory fuels removed within a 5-metre area
on each side of the trail networks. Given the level of pedestrian and bicycle
traffic in these areas, thinning will limit the ability of fire to spread and
improve fire suppression capability throughout the valley.
Recommendation 22: A qualified
professional, with a sound understanding of fire behaviour and fire
suppression, should develop fuel break plans and prescriptions.
Recommendation 23: A significant
area of high hazard fuel types identified in this anal
Recommendation 24: The City should
develop a plan for post fire rehabilitation that considers the procurement of
seed, seedlings and materials required to regenerate an extensive burn area (1,000-5,000
ha). The opportunity to conduct meaningful rehabilitation post fire will be
limited to a short fall season (September to November). The focus of initial
rehabilitation efforts should be on slope stabilization and infrastructure
protection. These issues should form the foundation of an action plan that la
In 2005 B.A. Blackwell and
Associates Ltd. was retained to assist the City of
The social, economic and
environmental losses associated with the 2003 fire season emphasized the need
for greater consideration and due diligence in regard to fire risk in the
wildland urban interface (WUI). In considering wildfire risk in the WUI, it is
important to understand the specific risk profile of a given community, which
can be defined by the probability and the associated consequence of fire
occurring within that community. While the probability of fire in the Fernie
area is somewhat lower than in the southern interior of
The results of this study
will provide the City with a framework that can be used to review and assess
areas of identified high fire risk. Additionally, the
The
plan was initiated by the City’s Fire Rescue Department and Leisure Services
Department, and was jointly funded by the City and the Union of B.C.
Municipalities. The purpose of the plan is to quantify and identify fire risk
within the community, develop plans and management actions that can be undertaken
to minimize the risk, and provide a tool to communicate and educate the
residents and visitors in Fernie about fire risk and management issues.
The
scope of this project included three distinct phases of work:
Phase
I –Assessment
of fire risk and development of a Wildfire Risk Management S
Phase
II – Identification
of hazardous fuel types and estimation of spotting risk
Phase
5.0
The City
of
Figure 1 outlines the area that is encompassed by this plan
and the municipal boundary of the City. The total study area that makes up this
plan includes map sheet numbers 082G.054, 082G.055, 082G.056, 082G.044,
082G.045 and 082.046. The gross area of the City is 16,050 ha and the total
study area is 57,640 ha. All area within the City boundary is designated as
private ownership according to provincial resource inventory data. Of the total
study area, federally owned land accounts for 968 ha (0.02%), provincially
owned land for 27,067 ha (46.96%), and privately owned land for 29,603 ha
(51.34%). The remaining 1.68% is out of ownership (e.g. waterwa
Figure
1. Map
showing the study area covered by this plan, the City boundary and land
ownership categories.
The City is a premier destination in winter and summer with a population of 4,611[2] permanent residents as determined by the 2001 Canada Census. However, more recent, unofficial estimates put the permanent population at approximately 5,200[3]. Seasonal visitors are likely to substantially increase the population, particularly in the winter.
A
small hospital and Fernie Fire Rescue are critical to emergency response
service in the community. Both are considered essential in a community where
outdoor activities contribute to injuries and accidents on a daily basis. These
facilities also provide the foundation for an incident command center during a
large fire event and therefore must be prepared to deal with large and complex
emergency situations.
Emergency
response is dependent on electrical and water service within the community in
the event of a large-scale emergency. The community is dependent on surface
water from a single watershed. This watershed provides water to the City
through a gravity fed s
Fernie’s
electrical service comes from the transmission network, running west to east,
that bisects the community. A large fire has the potential to impact this
service through disruption in network distribution. Fallen trees associated
with a fire event may cause power outages. Consideration must be given to
protecting this critical function and providing power back up at key facilities
to ensure that the emergency response functions are reliable.
The
key infrastructure discussed above was considered as part of the Wildfire Risk
Management S
The economy
of Fernie is primarily based on resource extraction industries, with 50% of the
population working in areas directly or indirectly related to these industries.
However, due to industrial tax sharing agreements, the community’s economy is
actually more dependent on these industries than is apparent through
employment. Recreation-based tourism, community services, retail services and
construction trades form the remainder of the business base[4]. Recreation-based tourism is perceived as the
major driver of growth in the City.
External
trends such as changing demographics, climate change, globalization, emerging
resorts, and growing competition could all have a significant impact on the
economy of the City. A large fire within and/or adjacent to the community could
have short and long term implications for the stability of the Fernie economy.
The Canadian Forest Fire
Danger Rating S
Fire danger within the City
can vary significantly from season to season. The City is defined by the
regional climate of the Interior Cedar Hemlock (
Figure
2. Fire
season summary (April to October) of key indicators that affect fire behaviour.
Fuel classification was
based on the Canadian Forest Fire Danger Rating S
Figure 3. Updated fuel types for the study area.
The following is a general description of the dominant fuel types within the City.
C2 fuel type
Fuels within this type are classified as CFFDRS fuel type C2. The total area classified as C2 within the study area was 7,395 ha. Stands are structurally classified as pole sapling to young forest, and at lower elevations are dominated by one of the following: Thuja plicata (western red cedar), Pseudotsuga menziesii (Douglas-fir), Pinus contorta (lodgepole pine), Larix occidentalis (western larch) and Picea spp (Spruce). Stand density in this fuel type is as high as 15,520 stems/ha (average is 3833 stems/ha). Average tree height is 12.3 m with average crown closure from forest cover at 31%. The average height of live crown is typically less than 2 meters. Surface fuel loading is less than 5 kg/m2 and the duff depth ranges from 5 to 10 cm. Burning difficulty is considered moderate but the crown fire hazard is considered extreme. Figure 4 shows an example of C2 fuels.
· Stand density: 3833 stems/ha
· Woody surface fuels: <5 kg/ m2
· Height to live crown: <2 m
· Average stand age: 102 years
· Average crown closure: 31%
· Vegetation: understory vegetation is sparse to none given extremely low light levels (< 5% cover)
· Burn difficulty: moderate; if fire is wind driven then there is a high potential for extreme fire behaviour and active crown fire within this fuel type.
Figure 4. Example of a high-density pole sapling Pinus
contorta (lodgepole pine) stand – classified
as a C2 fuel type
C3 fuel type
Fuels within this type are classified as CFFDRS fuel type C3. The total area classified as C3 within the plan area was 2,590 ha. Stands are typically classified as young forest and at lower elevations are dominated by one of the following Pseudotsuga menziesii (Douglas-fir), Thuja plicata (western red cedar), Pinus contorta (lodgepole pine) or Larix occidentalis (western larch). Average stand age is approximately 94 years old. Stand density in this fuel type averages 4665 stems/ha. Average tree height is 23 m with crown closure averaging 51%. The crown base height is typically greater than 6m. Surface fuel loading is less than 5 kg/m2 and the duff depth ranges from 5 to 7 cm. Burn difficulty is considered low to moderate but the crown fire hazard is considered moderate. Figure 5 shows an example of C3 fuels.
· Stand density: 4665 stems/ha
· Woody surface fuels: <5kg/ m2
· Crown base height: >6 m
· Average stand age: 94 years
· Average crown closure: average 51%
· Vegetation: understory vegetation is typically low given low light levels (< 30% cover)
· Burn difficulty: low to moderate; if fire is wind driven then there is a high potential for extreme fire behaviour and active crown fire.
Figure
5. Example
of evenly stocked moderate density second growth stand of Pinus contorta (lodgepole pine) –
classified as C3 fuel type.
C4 fuel type
Fuels within this type are classified as CFFDRS fuel type C4. The total area classified as C4 within the plan area was 3,570 ha. Typically, stands in this fuel type are structurally classified as young forest[AJN1] and at lower elevations are dominated by one of the following Pseudotsuga menziesii (Douglas-fir), Thuja plicata (western red cedar), Pinus contorta (lodgepole pine) or Larix occidentalis (western larch). Average stand age is approximately 75 years old. Average stand density in this fuel type is 3100 stems/ha. Average tree height is 14.8 m with crown closure averaging 51%. The crown base height ranges between 2 and 6 m. Surface fuel loading is less than 5 kg/m2 and the duff depth ranges from 5 to 10 cm. Burning difficulty is considered moderate but the crown fire hazard is considered high. Figure 6 shows an example of C4 fuels.
· Stand density: 3100 stems/ha
· Woody surface fuels: <5kg/ m2
· Crown base height: 2-6m
· Average stand age: 75 years
· Average crown closure: average 51%
· Vegetation: understory vegetation is typically low given low light levels (< 25% cover)
· Burn difficulty: moderate; if fire is wind driven then there is a high potential for extreme fire behaviour and active crown fire.
Figure
6. Example
of a moderate to high-density second growth stand of Thuja plicata (western red cedar) Pseudotsuga menziesii (Douglas fir) and Larix occidentalis
(western larch) –
classified as C4 fuel type.
D1 fuel type
Fuels within this type are
classified as CFFDRS fuel type D1. The total area classified as D1 within the
plan area was 4,732 ha. Stands are structurally classified as young forest[AJN2] and at lower elevations are dominated by Populus tremuloides
(trembling aspen), Populus balsamifera (balsa
· Stand density: 4213 stems/ha
· Woody surface fuels: <5kg/ m2
· Crown base height: > 6m
· Average stand age: 83 years
· Average crown closure: 22%
· Vegetation: understory vegetation is typically shrub and herb dominated (> 90% cover)
· Burn difficulty: low; low overall fire behaviour potential and low crown fire potential.
Figure
7. Moist
rich site dominated by aspen – classified as a D1 fuel type.
M2 fuel type
Fuels within this type are
classified as CFFDRS fuel type M2. The total area classified as M2 within the plan
area was 10,253 ha. Stands are structurally classified as pole sapling to young
forest and at lower elevations are dominated by Populus tremuloides
(trembling aspen), Populus balsamifera (balsa
· Stand density: 4302 stems/ha
· Woody surface fuels: <5kg/ m2
· Crown base height: > 6m
· Average stand age: 102 years
· Average crown closure: 42%
· Vegetation: understory vegetation is typically shrub and herb dominated (> 70% cover)
· Burn difficulty: low to moderate; if fire is wind driven then there is a high potential for passive to active crown fire.
6.3 Mountain Pine Beetle and the Impact on Forest Fuels
Similar
to many communities in B.C., Fernie is experiencing an outbreak of Mountain
Pine Beetle. Lodgepole pine is particularly susceptible to attack by Mountain
Pine Beetle, and is one of the major wood species harvested in the region.
From
a fire perspective, the current outbreak is a concern because it contributes
surface fuels that will accelerate fire spread and fire intensity, allowing
fires to move more easily into the tree crowns. The intimate relationship and
critical role that bark beetles and fire play in the natural succession of
lodgepole pine forests has been well documented. These forests, which occupy
millions of hectares in the Pacific Northwest, are generally even aged stands
younger than 100 years old. This even-aged forest structure is a result of
periodic wildfires which follow high mortality from bark beetle attacks (Fellin
1979; Mitchell and Martin 1980; Koch 1996; Price 1991; Schowalter et al. 1981).
The stands have adapted to these natural rotations, which tend to repeat every
100 years. Examples illustrating this cycle include the 1988 wildfires in
Yellowstone
Mountain pine beetle outbreaks occur mainly in mature forests, which are 80 to 150 years old. The outbreaks subside when most of the large diameter trees are killed. The dead trees then fuel subsequent fires, which regenerate the stand (Amman 1990; Fellin 1979; Geiszler et al. 1980; Price 1991). It has been hypothesized that these two agents of disturbance interact to maintain the structure and function of pine forests. Fire regulates forest regeneration in space and time, which is necessary for the pine beetle, and the pine beetle regulates the turnover of patches of dead trees conducive to burning (Schowalter et al. 1981).
Figure 8. Outline of complex lodgepole pine successional relationships and potential fire severity (From White and Feller et al. 2005)
In the past, agents of
disturbance were viewed as a threat to the health of the valuable forest
resource. Therefore, standard policy has been to suppress all wildfire and
eliminate forest pests. In pine forests, this has resulted in unstable forests
that are increasingly susceptible to ph
Healthy stands typically have a low fire hazard with crown closure ranging from 35 to 45%. This may vary in stands where pine is not the dominant species. Beetle mortality results in a short-term immediate increase in stand level fire hazard during the red attack stage. Fire behaviour observations suggest that rates of spread and head fire intensity are greater when fires burn through red-attacked stands.
The red attack stage of the beetle infestation is followed by foliar inputs to the forest floor, and the creation of standing dead snags (attacked stand). Depending on the site conditions, the loss of overstory tree foliage increases light levels to the forest floor surface and can result in a flush of understory vegetation including new seedlings that regenerate naturally (understory release). This flush depends on a number of factors but is primarily a function of available light, nutrients, moisture and the existing seed bank and plant community. Over time, the seedlings begin to dominate the understory forming a contiguous sapling layer (seedling dominance). At this same time, the dead trees originally killed by beetle attack have become decaying snags, and begin to fall creating high inputs of surface fuel (pine dominated understory). At this point, the stand has reached its highest fire hazard with the combination of a contiguous fuel load from the surface of the forest floor into the overstory canopy. These characteristics yield a stand that is now highly susceptible to stand replacing crown fire.
Figure 9. Graphical summary of fire hazard changes associated with an MPB outbreak.
Figure 10, Figure 11 and Figure 12 illustrate the initial stages of fuel loading and an increasing fire hazard.
Figure 10. Blowdown and breakage contributing to
fuel loading.
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Figure 11. Accumulation
of surface fuels (left). Snow damage (right).
Modelling
projections of the Mountain Pine Beetle outbreak (Eng 2004) suggest that, over the
next 15 years, the forests adjacent to the City will experience significant
mortality of lodgepole pine in the absence of any intervention (falling and
burning or control through harvest) (Figure
13). Based on the discussion above it is expected that
surface fuel loads will increase over the next 20 years and landscape level
fire hazard in pine dominated forests around the community will peak between 30
and 40 years. Any harvest within close proximity of the City, or tree removal
within city limits, should target mature lodgepole pine to reduce the overall
landscape level susceptibility. Any prescribed fuel treatments and/or creation
of firebreaks should focus on the removal of lodgepole pine. Taking this approach
will help to reduce the overall landscape level hazard and potentially limit
the size and distribution of the forecasted outbreak.
Recent beetle
attack has been limited to the outskirts of the City (to the south and north).
The current Mountain Pine Beetle outbreak within the study area is not
significantly contributing to fuel loadings and associated fire risk. However,
properties along the eastern boundary of the city will be the most heavily
impacted by the outbreak based on the projections. The stands surrounding these
areas have a low to moderate component of susceptible pine. Left unmanaged,
these stands have a high probability of supporting moderate to high fuel loads
and will follow the fire hazard succession outlined in Figure 12. Figure14 shows an example of the interface zones dominated by
pine.
Figure 12