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District
of Mission Community Wildfire Protection Plan Considerations for Wildland Urban
Interface Management in the District of Submitted by: B.A. Blackwell and Associates Ltd. V7J 3B5 Submitted to: Frank Ryan Fire Chief 33330 V2V 2E3 May 2006 |
Executive Summary
The District of Mission (hereinafter referred to as ‘the District’) is embedded within the forest; approximately 40% of the community is forested. This region of the Province is susceptible to both lightning and human caused fires. 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. were retained to develop a Community Wildfire Protection Plan in consultation with District staff from the Fire Rescue Service, Parks Department, Mission Tree Farm and other support staff as required. The project was funded by the District and a supplementary grant from the Union of B.C. Municipalities.
The key priorities for wildfire management planning in the District were identified as:
· Hazard and risk mapping of the District to establish areas of the community that are at greatest risk from 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; and
· Identification of potential locations for strategic fuel breaks and forest stand-level fuel reduction both within and outside the community.
A Wildfire Risk Management System (WRMS) was developed to identify key areas of risk within the community and to support the development of the Plan. A synopsis of key findings and plan recommendations follows. In total, 19 recommendations were developed for consideration by the District. These focus on Communication and Education, Structure Protection, Emergency Response, Training and Post Fire Rehabilitation.
Synopsis of Key Findings
Risk Assessment
The fire risk analysis of probability and consequence indicates that, under high to extreme fire weather conditions, significant areas of the District are vulnerable to wildfire.
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. The highest probability fire scenario is a fire started 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 within and adjacent to the Municipality. The model results indicate that, under extreme fire weather conditions, substantial areas of the community would be vulnerable to spotting at wind speeds averaging 9 kilometres per hour or greater.
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.
Education and Communication
The Mission Fire Rescue Service has been actively working on interface fire related communication and education. Public interest, participation and awareness have been limited within the community. More work is required to engage the community in this issue if successful planning, preparation and risk reduction measures are to be achieved.
Structure Protection
The current building code and District bylaws allow for the development of a community that is vulnerable to a large interface fire event. Both the building standards and the materials used on many structures increase fire risk from an ember shower associated with spotting from a large fire event. Many of the homes and businesses in the District 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.
Emergency Response
While much of the urban interface within the District is accessible, a number of areas are considered isolated because of one-way access in and out. In a number of areas within the District, emergency access for the purposes of fire protection is considered a serious problem.
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
Training
Over the past several years, Mission Fire Rescue Service has undertaken extensive 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.
Fuel Management
The WRMS identified areas of high hazard fuels associated with values at risk within the District. The size and scale of these areas are considered a significant management challenge. The only meaningful way to address the identified fuels problem in the short-term is to utilize existing breaks (roads, railways, and deciduous forest cover) in combination with aggressive emergency response and initial attack. Consideration should be given to protecting the broader landscape with fuel breaks that isolate fuels into compartments, improve suppression capability and slow or limit rates of spread. Specific attention should be given to advanced fuels management planning associated with harvesting on the Mission Tree Farm.
Post Fire Rehabilitation
An extensive fire within the District could have serious and long lasting consequences that include impacts on visual and water quality, recreation and sensitive resource values, and could create 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.
Recommendations
Communication and Education
Recommendation 1: The District
should work with local developers to construct a FireSmart show home to 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 District
should create an interactive website that outlines community fire risks and
proactive steps individual homeowners can take to make their homes safer within
the community. Other information, such as fire danger and FireSmart principles,
could be maintained on the local site so that fire management issues specific
to
Recommendation 3: The Mission Fire
Rescue Service should work with the Mission Regional Chamber of Commerce to
educate the local business community on FireSmart preparation and planning.
Structure Protection
Recommendation 4: Many homes and
businesses are built immediately adjacent to the forest edge. In these
neighbourhoods, trees and vegetation are often in direct contact with homes.
The District should create building set backs with a minimum distance of 10 m
when buildings border the forest interface.
Recommendation 5: The District
should begin a process to review and revise existing bylaws and building codes
to be consistent with the development of a FireSmart Community. For areas that
have been identified as high risk, consideration should be given to the
creation of a Wildfire Bylaw that mandates fire resistant building materials,
provides for good access for emergency response, and specifies fuel management
on both public and private property in areas of identified high wildfire risk.
Recommendation 6: In new
subdivisions within identified high risk areas of the District, roofing
materials that are fire retardant with a Class A and Class B rating should be a
requirement of the development permit. It is recognized that wholesale changes
to existing roofing materials within high risk areas of the District are not
practical, therefore a long-term replacement standard that is phased in over
the roof rotation period would significantly reduce the vulnerability of the
community in areas of historic development.
Recommendation 7: 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.
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.
Emergency Response
Recommendation 8: The District
must work towards improving access in identified areas of the community that
are considered isolated and that have inadequately developed access for
evacuation and fire control.
Recommendation 9: An evacuation
plan should be developed for the community and the outlying road and trail
networks which 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 10: During a large
wildfire it is probable that the valley bottom (location of the fire hall and
Health Care Centre) could be severely impacted by smoke. It is recommended that
contingency plans be developed in the event that smoke causes evacuation of
Mission District. The District should co-operate with Provincial and Regional
governments to develop an alternate incident command location and mobile
facility in the event that the District is evacuated.
Recommendation
11:
Given the values at risk identified in this plan, it is recommended that,
during periods of extreme fire danger, the District work with the Ministry of
Forests and Range to maintain a local helicopter with a bucket on standby
within the District boundaries.
Training
Recommendation 12: 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, the Mission
Fire Rescue Service should adopt an advanced program that fosters continuous
improvement and skill renewal.
Fuel Management
Recommendation 13: 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: 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 14: The District
should work with British Columbia Transmission Corporation (BCTC) to ensure that
transmission infrastructure can be maintained and managed during a wildfire
event. Maintaining the transmission corridor to a fuelbreak 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 15: Within developed
areas of the District there are substantial forested areas that are in close
proximity to homes and businesses. There is currently no available inventory or
orthophotography for these areas. It is recommended that the District undertake
a forest inventory of these areas to determine their hazard and fire behaviour
potential. Such an inventory would provide the District with the necessary
information to develop plans and/or prescriptions to deal with identified
high-risk areas.
Recommendation 16: Prioritize the
development of a fuelbreak network that builds on existing breaks such as the
highway, railway corridor, and BC Transmission Corridor running through the
District.
Recommendation 17: Within the
Mission Tree Farm, integrate the development of future fuelbreaks with harvest
planning using existing cutblocks, logging roads, and topographic features to
address identified problem fuel types and spotting potential.
Recommendation 18: A qualified
professional, with a sound understanding of fire behaviour and fire
suppression, should develop fuelbreak plans and prescriptions.
Post Fire Rehabilitation
Recommendation 19: The District
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 lays out the necessary steps to stabilize and
rehabilitate the burn area.
Table of Contents
4.0 Wildland Urban Interface Defined
4.1 Vulnerability
of the Wildland Urban Interface to Fire
5.0 Wildland Urban Interface Continuum
5.1 Communication
and Education
5.6 Post
Fire Response – Rehabilitation
6.0 Communication and Education
6.1 Communication
and Education Goals
6.6 Media
Contacts, Use and Coordination
6.7.2 Government
Ministries, District and Municipal Officials, Disaster Planning Services,
Utilities
7.1.2 Building
Exterior - Siding Material
7.5 Joint
District Cooperation
7.6 Structured
FireSmart Assessments of High Risk Areas
10.0 Vegetation (Fuel) Management
10.1 Principles
of Fuel Management
10.2.1 The
Principles of Landscape Fuelbreak Design
10.2.2 Existing
Landscape Fuelbreaks Within the District
10.2.3 Proposed
Landscape Fuelbreaks within the District
11.0 Post Wildfire Rehabilitation Planning
List of Figures
Figure 7. Moist rich site dominated by red alder –
classified as a D1 fuel type.
Figure 10. Wildland urban interface defined by red border
where the forest meets the community.
Figure 11. Graphical example showing variation in the
definition of interface.
Figure 14. Wildland urban interface continuum.
Figure 16. Example of home with wood siding and open
decks and balconies.
Figure 18. High surface fuel loading under a forest canopy
Figure 19. Comparisons showing stand level differences in
the height to live crown.
Figure 20. Comparisons showing stand level differences in
crown closure.
Figure 21. Comparisons showing stand level differences in
density and mortality.
Figure 23. High Vulnerability Interface Areas
Figure 24. Schematic showing the principles of thinning
to reduce stand level hazard.
Figure 25. Final overlay of probability and consequence
from the Wildfire Risk Management System.
Figure 26. Conceptual diagram of a shaded fuelbreak pre
treatment and post treatment.
Figure 27. 1994 Tyee Fire shaded fuelbreak example.
1.0 Introduction
1.1 Background
In 2005 B.A. Blackwell and Associates Ltd. was retained to assist the District of Mission in developing a Community Wildfire Protection Plan, hereinafter referred to as “the Plan”. ‘FireSmart – Protecting Your Community from Wildfire’ (Partners in Protection 2004) was used to guide the protection planning process. Within the municipality, the assessment considered important elements of community wildfire protection that included communication and education, structure protection, training, emergency response, and vegetation management.
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 within that community.
While the probability of fire in coastal communities is substantially lower
when compared to the interior of
The results of this study will provide the District with a framework that can be used to review and assess areas of identified high fire risk. Additionally, the information contained in this report should help to guide the development of emergency plans, emergency response, communication and education programs, bylaw development in areas of fire risk, and the management of forest lands adjacent to the municipality.
1.2 Purpose and Scope
The Plan was initiated
by Mission Fire Rescue Service and was jointly funded by the District of
Mission 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
The scope of this
project included three distinct phases of work:
·
Phase I
–Assessment of fire risk and
development of a Wildfire Risk Management System to spatially quantify the
probability and consequence of fire.
·
Phase
II – Identification of
hazardous fuel types and estimation of spotting risk.
·
Phase
III – Development of the Plan,
which outlines measures to mitigate the identified risk through structure
protection, emergency response, training, communication, and education.
2.0 District of Mission
2.1 Study Area
The District of Mission is situated on the
north side of the
Figure 1. Map showing the study area covered by this plan, the District boundary and land ownership categories.
2.2 Population
The District had an estimated population of
32,931 people in 2000 and the 6th fastest population growth rate in
BC[1]. In subsequent years, land availability, affordable housing and
land prices, improved public transportation and urban expansion of the Lower
Mainland into the
2.3 Economy
The economy of
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MAJOR EMPLOYERS IN MISSION[3] |
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Employer |
Activity |
Employees |
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School District No. 75 |
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800-900 |
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Corrections |
|
300 |
|
Meeker Cedar |
|
125 |
|
DOM |
Door frame systems and wood mouldings |
200 |
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International Bag |
|
140 |
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V.I.P. Soap |
|
20 |
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Source: |
||
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MAJOR MANUFACTURING EMPLOYERS[4] |
||
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Employer |
Product |
Employees |
|
Meeker Cedar |
Shakes and
shingles |
125 |
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Source: |
||
2.4 Infrastructure
The local Fire Rescue
Service and
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
series of surrounding forested watersheds. These watersheds provide water to a
complex network of gravity fed reservoirs. Any disturbances (human and/or
natural) within these watersheds have the potential to impact the supply of drinking
water to the community.
Electrical service to
the community comes from a complex network of transmission infrastructure that
runs in numerous directions through the community. A large fire has the
potential to impact this service by causing a disruption in network
distribution through direct or indirect means. For example, heat from the
flames or fallen trees associated with a fire event may cause power outages.
Consideration must be given to protecting this critical service 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 System.
The results of this analysis indicate that consideration must be given to
protection of the critical infrastructure identified above.
3.0 Fire Environment
3.1 Fire Weather
The Canadian Forest Fire Danger Rating System (CFFDRS), developed by the Canadian Forestry Service, is used to assess fire danger and potential fire behaviour. The Ministry of Forests and Range (MOFR) maintains a network of fire weather stations during the fire season that is used to determine fire danger on forestlands within the District. Similarly, other lower mainland communities monitor fire weather information provided by the MOFR Protection Branch to determine hazard ratings and associated fire bans and closures within their respective municipalities.
It is important to understand the
likelihood of exposure to periods of high fire danger, defined as Danger Class
IV (high) and V (extreme), in order to determine appropriate prevention
programs, levels of response, and management strategies. Fire danger within the
District can vary from season to season. The District is defined by the
regional climate of the Coastal Western Hemlock dry maritime (CWHdm), very dry
maritime (CWHxm1, CWHxm2), submontane very wet maritime (CWHvm1), montane very
wet maritime (CWHvm2) and Mountain Hemlock windward moist maritime (MHmm1)
biogeoclimatic units.
Figure 2. is a
compilation of available weather station data within the CWHdm1 biogeoclimatic
unit (representative of the District) that dates back to 1970 and provides a
summary of the total number of Danger Class IV and V da
Figure 2. Fire season summary (April to October) of key indicators of potential high to extreme fire weather.
3.2 Fuels
Fuel classification was based on the CFFDRS and a summary of fuel type attributes collected in the field. Typically, the CFFDRS fuel types only adequately describe the variation in fuels present in the District. In a number of areas, the classification was not correct. This was primarily a function of plantation forests being classified as D1 when, in fact, they were better represented by another CFFDRS fuel type (Figure 3). For each type identified, we have attempted a best approximation of the CFFDRS classification and have supported this classification with a summary of detailed attributes. The updated Ministry of Forests and Range fuel typing was improved upon and adjusted to incorporate local variation.
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Figure 3. Comparison of original MOF fuel typing (left) and updated fuel typing (right) for the District.
The following is a general description
of the dominant fuel types within the District of Mission
C3 fuel type
Fuels within this type are classified as CFFDRS fuel type C3. Stands are typically pole sapling to young forest and at lower elevations are dominated by the following species: Douglas-fir, western hemlock, western red cedar, and amabilis fir. Average stand inventory age is approximately 50 years old. Stand density in this fuel type ranges from approximately 1000 to 1200 stems/ha. Average inventory tree height is approximately 20 m with crown closure averaging 60%. The height to live crown averages approximately10 m. Surface fuel loading is less than 5 kg/m2. Burning difficulty and crown fire hazard are considered moderate. Figure 4 shows an example of C3 fuels.
· Stand density: 1000 to 1200 stems/ha
· Woody fuels: <5kg/ m2
· Average height to live crown: 10 m
· Average stand age: 50 years
· Average crown closure: 60%
· Vegetation: understory vegetation is typically low given low light levels (< 35% cover)
· Burn difficulty is moderate; however, if fire is wind driven then there is a high potential for extreme fire behaviour and active crown fire.
Figure 4. Example of evenly stocked, moderate density second growth stand – classified as a C3 fuel type.
C4 fuel type
Fuels within this type are classified as CFFDRS fuel type C4. Stands are typically classified as pole sapling and at lower elevations are dominated by the following species: Douglas-fir, western hemlock, western red cedar and amabilis fir. Average stand age is approximately 25 years old. Stand density in this fuel type ranges from approximately 1000 to 1500 stems/ha. Average tree height is 10 m with crown closure averaging 50%. The height to live crown averages 7 m. Surface fuel loading is less than 5 kg/m2. Burning difficulty is considered moderate but the crown fire hazard is considered high. Figure 5 shows an example of C4 fuels.
· Stand density: 1000 to 1500 stems/ha
· Woody fuels: <5kg/ m2
· Average height to live crown: 7 m
· Average stand age: 25 years
· Average crown closure: 50%
· Vegetation: understory vegetation is typically low given low light levels (< 25% cover)
· Burn difficulty is moderate; however, if fire is wind driven then there is a high potential for extreme fire behaviour and active crown fire.
Figure 5. Example of a moderate to high-density second growth stand of hemlock and Douglas-fir classified as a C4 fuel type.
C5 fuel type
Fuels within this type are classified as CFFDRS fuel type C5. Stands are structurally classified as mature and old forest and, at lower elevations, are dominated by the following species: Douglas-fir, western hemlock, and amabilis fir. Stand density in this fuel type ranges from approximately 700 to 900 stems/ha. Average inventory tree height is 30 m with crown closure averaging 60%. The height to live crown averages 15 m. Surface fuel loading is less than 5 kg/m2. Burning difficulty is considered low to moderate but the crown fire hazard is considered moderate. Figure 6 shows an example of C5 fuels.
· Stand density: 700 to 900 stems/ha
· Woody fuels: <5kg/ m2
· Average height to live crown: 15 m
· Average crown closure: 60%
· Vegetation: understory vegetation is typically shrub and herb dominated (> 40% cover)
· Burn difficulty is low; low fire behaviour and moderate crown fire potential.
Figure
6. Example of young
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 1,627 ha. Stands are typically classified as pole sapling to young forest and at lower elevations are dominated by Alnus rubra (red alder). Inventory stand density in this fuel type ranges from approximately 700 to 1000 stems/ha. Inventory average tree height is greater than 10 m with crown closure averaging 30%. The height to live crown averages less than 10 m. Surface fuel loading is less than 3 kg/m2. Burning difficulty is considered low and the crown fire hazard is considered low. Figure 7 shows an example of D1 fuels.
· Stand density: 700 to 1000 stems/ha
· Woody fuels: <3kg/ m2
· Average height to live crown: 10 m
· Average stand age: 30 years
· Average crown closure: 30%
· Vegetation: understory vegetation is typically shrub and herb dominated (> 90% cover)
· Burn difficulty is low; low fire behaviour and low crown fire potential.
Figure 7. Moist rich site dominated by red alder – classified as a D1 fuel type.
In addition to the previously mentioned fuel types, M2 (mixed coniferous deciduous stands and very young plantations) and C7 fuel types occurred in the study area but represented such minor areas that they have not been described in this report
3.3 Topography
The Stave River System bisects the District
to the northwest of the urban centre. The
The following excerpt from the Natural
Resources Canada Website[5] describes how the
The
Approximate
location of
Figure 8. View of topographic relief of the District looking north (sourced from Google EarthTM, 2006).
3.4 Historic Ignitions
The MOFR fire reporting s
Table 1 summarizes the fires that have occurred between 1950 and 1999 in the study area by size class and cause (lightning and human caused). The total number of fires during this period was 186, of which 83% were the result of human causes. The remaining 17% of fire ignitions were lightning caused. Eighty-nine percent of all fires that burned between 1950 and 1999 were smaller than four hectares, while only 17 fires were greater than 10 hectares. The largest fire within the District since 1950 occurred in 1974 and burned an area of 348 hectares.
Table 2 summarizes fire cause by decade and provides some interesting insight into the nature of fire within the study area. Through the time of record, human caused fires have far out-numbered those caused by lightning. On average, there are 37 fires each decade (minimum 25 in the ‘70s and maximum 57 in the ‘60s). The majority of fires have been inconsequential in size.
Table 1. Fire history summary within the study area from 1950 - 1999.
|
Size Class
(ha) |
Total
Number of Fires |
% of Total |
Lightning
Caused |
Human
Caused |
|
<4.0 |
166 |
89 |
31 |
135 |
|
4.0-10.0 |
3 |
2 |
0 |
3 |
|
>10.0 |
17 |
9 |
0 |
17 |
|
|
186 |
100% |
31 |
155 |
Table 2. Summary of fire cause within the study area.
|
Decade |
Lightning |
Direct
Human1 |
Industrial2 |
Miscellaneous |
Total |
|
1950-1959 |
4 (11) |
16 (43) |
0 (0) |
17 (46) |
37 |
|
1960-1969 |
8 (14) |
23 (40) |
14 (25) |
12 (21) |
57 |
|
1970-1979 |
6 (24) |
15 (60) |
3 (12) |
1 (4) |
25 |
|
1980-1989 |
8 (23) |
24 (68) |
2 (6) |
1 (3) |
35 |
|
1990-1999 |
5 (15) |
23 (70) |
3 (9) |
2 (6) |
33 |
|
Total Years |
31 |
101 |
22 |
33 |
187 |
1 Campfire, smoker, incendiary, juvenile set, fire use
2 Equipment, railway
Note: Numbers in parentheses ( ) indicate percentage of total fires for a given decade.
Figure
9.
A
spatial summary of human and lightning caused fire ignitions within the
District (1950 to present).
4.0 Wildland Urban Interface Defined
The classical definition of wildland urban interface (WUI) is the place where the “forest meets the community” and is graphically depicted in Figure 10. Other configurations of the WUI can be described as intermixed. Intermixed areas include smaller, more isolated developments that are embedded within the forest. An example of an intermixed interface is shown in Figure 10.
In each of these cases, fire has the ability to spread from the forest into the community or from the community out into the forest. Although these two scenarios are quite different, they are of equal importance when considering interface fire risk. Within the District, the probability of a fire moving out of the community and into the forest is equal or greater to the probability of fire moving from the forest into the community. Regardless of which scenario occurs, there will be consequences for the District and this will have an impact on the way in which the community plans and prepares for interface fires.
Figure 10. Wildland urban interface defined by red border where the forest meets the community.
Figure 11. Graphical example showing variation in the definition of interface.
4.1 Vulnerability of the Wildland Urban Interface to Fire
Fires spreading into the WUI from the
forest can impact homes in two distinct wa
Figure 12. Firebrand caused ignitions: burning embers are carried ahead of the fire front and alight on vulnerable building surfaces.
Figure 13. Radiant heat and flame contact allows fire to spread from vegetation to structure or from structure to structure.
5.0 Wildland Urban Interface Continuum
The wildland urban interface continuum (Figure 14) summarizes the main options available for addressing WUI fire risk. In addition to standard fire management actions, the issue of post fire rehabilitation is identified as a management concern that should be addressed in areas (such as the District) where slope stability and protection of water quality are of primary concern following wildfire.
Figure 14. Wildland urban interface continuum.
The appropriate management response to a given wildfire risk profile is based on the combination and level of emphasis of several key elements: communication and education, training, emergency response, structure protection, and vegetation management. For example, in an interface area with a high-risk profile, equal weight may be given to all elements. Alternatively, in this same high-risk example, active intervention through vegetation management may be given a higher emphasis. This change in emphasis is based on the values at risk (consequence) and level of desired protection required. In a low risk situation the emphasis may be on communication and education combined with emergency response and training. In other words, a variety of management responses within the District of Mission are appropriate and can be defined by the wildfire risk profile.
5.1 Communication and Education
One of the key elements to developing FireSmart communities and neighbourhoods is cultivating an understanding of fire risk in the wildland urban interface. An effective communication strategy should target elected officials (regional and local governments), structural and wildland fire personnel, appropriate municipal departments (planning, bylaw, and environment), and the public and private sector. The principles of effective communication include:
· Developing clear and explicit objectives, or working toward clear understanding;
· Involving all parties that have an interest in a transparent process;
· Identifying and addressing specific interests of different groups;
· Coordinating with a broad range of organizations and groups;
· Not minimizing or exaggerating the level of risk;
· Only making commitments that you can keep;
· Planning carefully and evaluating your effort; and
· Listening to the concerns of your target audience.
5.2 Structure Protection
Another important consideration in protecting the wildland urban interface zone from fire is ensuring that homes can withstand an interface fire event. Often, it is a burning ember traveling some distance (spotting) and landing on vulnerable housing materials, rather than direct fire/flame (vegetation to house) contact, that ignites a structure. Alternatively, the convective or radiant heating produced by one structure may ignite an adjacent structure if it is within close proximity. Structure protection is focused on ensuring that building materials and construction standards are appropriate to protect individual homes from interface fire. Materials and construction standards used in roofing, exterior siding, window and door glazing, eaves, vents, openings, balconies, decks and porches are primary considerations in developing FireSmart neighbourhoods. Housing built using appropriate construction techniques and materials is less likely to be impacted by interface fires.
While many neighbourhoods established to date were built without significant consideration with regard to interface fire, there are still ways to reduce home vulnerability. Changes to roofing materials, siding, and decking can ultimately be achieved through long-term changes in bylaws and building codes.
5.3 Emergency Response
The availability and timing of emergency response personnel often dictates whether interface fire protection is successful. Well-planned strategies to deal with different and difficult interface fire scenarios are part of a comprehensive approach to addressing interface fire risk. In communities where the risk is considered low, emergency response alone may be considered an adequate management response to protect the community. As risk increases so too should the level of emergency response. Emergency response alone may not be an adequate management strategy to develop depending on the level of risk.
Unlike static emergencies (e.g. landslides), fires are dynamic and situations can change dramatically over short periods of time, potentially overwhelming resources. Therefore, it is important to consider a wide range of issues including, but not limited to, evacuation strategies, access for emergency vehicles and equipment, management of utility hazards associated with hydroelectric and gas infrastructure, and the reliability and availability of key fire fighting infrastructure during a fire event.
5.4 Training
The events of the 2003 fire season increased Fire Rescue Service awareness with regard to necessary training and equipment improvements. The division between local Fire Rescue Services and the MOFR Protection Branch has narrowed through improved training and communication. Training is fundamental to managing interface fire risk. Crossover abilities between provincial wildland fire and municipal structural fire personnel will enhance and improve the collective agency response to wildland urban interface fire. Therefore, all management strategies designed to protect the wildland urban interface should be supported by an adequate level of training to ensure emergency response addresses both wildland and structural fire.
5.5 Vegetation Management
Vegetation management is considered a key element of the FireSmart approach. Given public concerns, vegetation management is often difficult to implement and must be carefully rationalized in an open and transparent process. Vegetation management should be strategically focused on minimizing impact while maximizing value to the community. For example, understory thinning or surface fuel removal may suffice to lower fire risk. In situations where the risk is high, a more aggressive vegetation management strategy may be necessary. Vegetation management must be evaluated against the other elements outlined above to determine its necessity. Its effectiveness depends on the longevity of treatment (vegetation grows back), cost, and the resultant effect on fire behaviour.
5.6 Post Fire Response – Rehabilitation
Wildfires have immediate short and long-term impacts on the social, economic and environmental values of an interface community. In steep environments, post fire impacts (i.e. removal of ground cover) can result in an elevated risk of landslides and debris flows. Within watersheds, post fire impacts can include increased nutrient and sediment flow into reservoirs. These impacts can be reduced or avoided through the development of post fire mitigation plans and effective response following fire. In municipalities such as the District, which have identified risk of landslide and debris flow, it is appropriate to consider the development of a post fire rehabilitation plan that will guide actions following a fire event.
6.0 Communication and Education
To effectively minimize fire risk in the interface zone requires the coordination and cooperation of many levels of government including the B.C. Ministry of Forests and Range, the Fraser Valley Regional District, local Municipal government departments, and other government agencies. However, if prevention programs are to be effective, fire risk reduction within interface areas of the District must engage the local residents. This requires a commitment to well-planned education and communication programs that are dedicated to interface fire risk reduction. There is generally a lack of understanding about interface fire and the simple steps that can be taken to minimize risk in communities. Typically, there is either apathy and/or an aversion to dealing with many of the issues highlighted in this report. Public conception of fire risk is often underdeveloped due to public confidence and reliance on local and provincial fire rescue services.
6.1 Communication and Education Goals
Clearly outlining the desired results of an education program is vital to specific program success. During development of educational material and communication strategies, goals provide a reference point to ensure that strategies and material are consistent with the desired results. Within the District, a number of issues have been identified that could be addressed by a well-designed and implemented communication and education program. These include:
· Educating residents and businesses on actions they can take to reduce fire risk on private property;
· Establishing a sense of homeowner responsibility for reducing fire hazards;
· Raising the awareness of elected officials as to the resources required and the risk that wildfire poses to community;
· Making residents and businesses aware that their community is an interface community and educating them about the associated risks;
· Increasing awareness of the limitation of municipal and provincial firefighting resources to encourage proactive and self-reliant attitudes; and
· Working diligently to reduce ignitions during periods of high fire danger.
6.2 Target Audiences
Historically, there has been limited
understanding of wildland urban interface fire risks within many communities of
· Homeowners within areas that could be impacted by interface fire;
· Local businesses;
· Municipal councils and staff;
· Fraser Valley Regional District directors;
· Local utilities; and
· Media.
6.3 Pilot Projects
A number of pilot projects that demonstrate and communicate the principles of FireSmart and its application to Community Wildfire Protection should be considered. The District should work together with local residents and the business community to establish demonstration FireSmart homes and businesses. The focus of these pilot projects should be to demonstrate appropriate building materials and construction techniques in combination with the FireSmart principles of vegetation management. Several homes and businesses could be identified by the District to serve a communication and education function that would allow residents to see the proper implementation of FireSmart principles.
These pilot projects are considered a high priority for the urban interface to provide information on different fire hazard reduction techniques and demonstrate appropriate fire risk reduction methods to the community including municipal staff, community leaders and the public. These demonstration areas will also provide sites for improved public understanding of the methods to mitigate fire risk that can be applied on individual properties.
Recommendation 1: The District should work with local developers to construct a FireSmart show home to 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.
6.4 Communication Plan
A communication plan for the District and outlying areas of the community is required to outline the purpose, methods and desired results of communication and education from this plan. The communication and education plan should cover the principles of fire risk to the community, fire behaviour, spotting, structure protection and vegetation management.
6.5 Website
The District website is considered one of the best and most cost effective methods of communication available to the District. Currently some good information is available on the Fire Rescue page of the District website. A FireSmart link and other fire related information about District Fire Rescue, fire danger and fire restrictions should be included on this site. Additionally, the fire risk assessment that was developed as part of this planning exercise should be added to the website. Pictures and text that outline demonstration/pilot projects discussed above could also be included. During fire season it is suggested that wildfire safety related information be posted on the home page so that it is more easily accessible to the general public.
Recommendation
2: The District should create an interactive website
that outlines community fire risks and proactive steps individual homeowners
can take to make their homes safer within the community. Other information,
such as fire danger and FireSmart principles, could be maintained on the local
site so that fire management issues specific to
6.6 Media Contacts, Use and Coordination
Media contact plays an essential role in
improving public awareness about fire risk in the community. The
Key issues in dealing with the media include:
· Assignment of a media spokesperson for the District;
· Providing regular information updates during the fire season regarding conditions and hazards; and
· Providing news releases regarding the interface issues and risks facing the community.
6.7 Other Methods
Educational information and communication tools need to be stakeholder specific. To establish effective communication within target groups, spokespersons who can best establish communication ties and provide the educational information required should be selected. The following subsections outline potential communication methods for specific stakeholder groups.
6.7.1 Homeowners
· Conduct surveys and consult the public to ascertain current attitudes.
· Designate spokespersons to communicate to this group and establish a rapport.
· Establish community information meetings conducted by spokespersons.
· Mail out informational material.
· Provide FireSmart hazard assessment forms and information.
· Provide signage at trailheads and other prominent locations.
6.7.2 Government Ministries, District and Municipal Officials, Disaster Planning Services, Utilities
· Develop material specific to the educational needs of the officials.
· Present councils with information and encourage cooperative projects between municipalities.
· Establish memoranda of understanding between agencies.
· Appoint a spokesperson to communicate to the groups and help foster inter-agency communication.
· Raise awareness of officials as to the views of the public regarding interface risks in their community.
6.8 General Messages
Education and communication messages should be simple yet comprehensive. The level of complexity and detail of the message should be specific to the target audience. A complex, wordy message with overly technical jargon will be less effective than a simple, straightforward message. A basic level of background information is required to enable a solid understanding of fire risk issues. Generally, messages should have at least the following three components:
1. Background Information
· Outline general issues facing interface communities.
· Communicate specific conditions in the community that cause concern.
· Provide examples of potential wildfire behaviour in the community.
·
Provide examples of how wildfire has affected
other communities.
·
Explain
the effects that a wildfire could have upon the community.
·
Convey
FireSmart Principles.
2. Current Implementation and Future Interface Planning
· Provide information on the current planning situation.
·
Explain
who is involved in interface planning.
· Explain the objectives of interface wildfire planning.
· Explain the limitation of firefighting crews and equipment in case of a wildfire.
· Outline the emergency procedure during a wildfire.
3. Responsibilities and Actions
· Outline the responsibilities of each group in reducing wildfire hazards.
· Explain the actions that each group may take to meet these responsibilities.
Recommendation 3: The Mission Fire Rescue Service should work with the Mission Regional Chamber of Commerce to educate the local business community on FireSmart preparation and planning.
7.0 Structure Protection
7.1 FireSmart
The FireSmart approach has been adopted by a wide range of governments and is a recognized template for reducing and managing fire risk in the wildland urban interface. The most important components of the FireSmart approach are the adoption of the hazard assessment systems for wildfire, site and structure hazard assessment, and the proposed solutions and mitigation outlined for vegetation management, structure protection, and infrastructure. At a minimum, this standard should be applied to all new subdivision developments within the District. Wherever possible, the standard should be integrated into changes to, and new construction within, existing subdivisions and built up areas of the community.
Within the District, the majority of homes would not meet the FireSmart structure hazard standards for interface fire safety. This is a result of a number of factors, which are briefly summarized in the sections below.
7.1.1 Roofing Material
Roofing material is one of the most important characteristics influencing a home’s vulnerability to fire. Roofing materials that can be ignited by burning embers increase the probability of fire related damage to a home during an interface fire event.
Currently, there is no fire vulnerability standard for roofing material used in the District. Many homes are constructed with unrated materials that are considered a major hazard during a large fire event. In addition to the vulnerability of roofing materials within the community, adjacent vegetation is often in contact with roofs, or roof surfaces are covered with litter fall and leaves from adjacent trees.
Figure 15. Photograph showing unrated roofing material present on many homes within the District wildland urban interface.
7.1.2 Building Exterior - Siding Material
The building exterior of many homes is constructed of wood, which is considered the second highest contributor to structural hazard after roofing material. Wood siding within the interface zone is vulnerable to direct flame or may ignite when sufficiently heated by nearby burning fuels. Winds caused by convection will transport burning embers, which may lodge against siding materials. Siding materials, such as wood shingles, boards, or vinyl are susceptible to fire. Brick, stucco, or heavy timber materials offer much better resistance to fire.
Figure 16. Example of home with wood siding and open decks and balconies.
7.1.3 Balconies and Decking
Open balconies and decks increase fire vulnerability through their ability to trap rising heat, by permitting the entry of sparks and embers, and enabling fire access to these areas. Closing these structures off limits ember access to these areas and reduces fire vulnerability.
7.1.4 Combustible Materials
Combustible materials stored within 10 m of residences are also considered a significant issue. Woodpiles or other flammable materials adjacent to the home provide fuel and ignitable surfaces for embers. Locating these fuels away from structures helps to reduce structural fire hazards.
7.2 Planning
Local governments have an important role in managing community fire hazard and risk. Through the Local Government Act, Development Permit Areas authorize local governments to regulate development in sensitive or hazardous areas where special conditions exist.
For example, Development Permit Areas can be designated for such purposes as:
· Protection of the natural environment;
· Protection from hazardous conditions;
· Protection of provincial or municipal heritage sites;
· Revitalization of designated commercial areas; or
· Regulation of form and character of commercial, industrial and multi-family residential development.
As a land use planning tool, the establishment of Development Permit Areas for interface fire hazards could protect new developments from wildfire in the urban interface. For the purpose of fire hazard and risk reduction a development permit may:
· Include specific requirements related to building character, landscaping, setbacks, form and finish; and
· Establish restrictions on type and placement of trees and other vegetation in proximity to the development.
Recommendation 4: Many homes and businesses are built immediately adjacent to the forest edge. In these neighbourhoods, trees and vegetation are often in direct contact with homes. The District should create building set backs with a minimum distance of 10 m when buildings border the forest interface.
7.3 Bylaws
This planning process has identified two specific issues that may be corrected through the bylaw process. Throughout the District, roofing materials contribute significantly to fire risk. In the short term, a resolution to this issue is difficult given the significant cost to homeowners. However, over the long-term, the District may wish to consider altering the building code or bylaws to encourage a change in roofing materials when roof replacement of individual residences is required.
The second issue identified by this process relates to the creation of large setbacks between buildings and the forest. There are many areas within the District where forest trees encroach onto balconies and building faces. This is an unnecessary hazard that will reduce the ability of the Fire Rescue Service to extinguish both wildland and structural fires throughout the community. These two suggestions represent only a fraction of the changes that could be considered relating to building and landscaping materials. A complete review of current bylaws as they relate to fire risk should be considered by the District.
Recommendation 5: The District should begin a process to review and revise existing bylaws and building codes to be consistent with the development of a FireSmart Community. For areas that have been identified as high risk, consideration should be given to the creation of a Wildfire Bylaw that mandates fire resistant building materials, provides for good access for emergency response, and specifies fuel management on both public and private property in areas of identified high wildfire risk.
Recommendation 6: In new subdivisions within identified high risk areas of the District, roofing materials that are fire retardant with a Class A and Class B rating should be a requirement of the development permit. It is recognized that wholesale changes to existing roofing materials within high risk areas of the District are not practical, therefore a long-term replacement standard that is phased in over the roof rotation period would significantly reduce the vulnerability of the community in areas of historic development.
7.4 Sprinklers
As part of the Firestorm 2003 Provincial
Review, the provincial government responded to the interface fire issue by
purchasing mobile sprinkler kits that can be deployed during interface fires.
Given the size and value of the interface in the District, it is recommended
that consideration be given to the purchase of a sprinkler system dedicated to
the community or to the communities in the Sea to Sky corridor at large
(Squamish,
Recommendation 7: 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. 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.
7.5 Joint District Cooperation
The District has taken a proactive role in facilitating cooperation, training and response to the wildland urban interface issue. This process should be further enhanced by MOFR, Fraser Valley Regional District and municipal cooperation through joint training exercises and regular meetings. The primary focus to date has been increasing agency awareness on issues related to resource capacity, training, mutual aid, and equipment sharing. An expanded role for this relationship could include developing community based communication and education tools for use throughout the region. Currently, municipalities are developing in house standards and materials to improve public awareness. A more unified approach could improve efficiency, create consistent messages, and more broadly inform the public of interface fire issues and risk. It is recommended that the District take a lead role in working with other lower mainland municipalities and the MOFR to enhance education and communication related to this issue.
7.6 Structured FireSmart Assessments of High Risk Areas
The WRMS has identified subdivisions and specific areas of high risk within the District. It is recommended that District conduct detailed FireSmart assessments in these identified areas of the community to further communicate and promote fire risk reduction on private property. The development of a more focused strategy is warranted given the level of risk within the community. The WRMS developed for the District provides a sound scientific framework on which to complete more detailed local neighbourhood risk assessments.
8.0 Emergency Response
8.1 Access and Evacuation
The recent
In any emergency, evacuation is a critical function of emergency services. Given that a forest fire is a dynamic event, evacuation planning is considered of critical importance. The Fire Rescue Service must be prepared for evacuation of the sick, disabled, and the elderly when dealing with a wildland fire emergency. This issue adds complexity to any emergency situation.
Evacuation of residents and access for emergency personnel is an important consideration given the isolation of a number of neighbourhoods in the District and the amount of forest fuels in close proximity to many homes. Within the neighbourhoods identified in Figure 17 there is only one access and evacuation route available to motor vehicles and emergency responders. Given the number of homes and the potential for heavy traffic in some of these locations, prompt evacuation could be difficult. The situation could be further complicated by smoke and poor visibility, creating the necessity for traffic control in specific neighbourhoods. The District should consider establishing secondary or alternate evacuation routes for these neighbourhoods.
In addition to the evacuation of residents, safety of firefighting personnel is a major consideration. Figure 17 emphasizes that under extreme fire conditions it may be difficult for the Mission Fire Rescue Service to access specific areas within the District due to the potential for resources to be isolated or cut off. Defence of these neighbourhoods would be secondary to safety considerations.
Figure 17. Overview of access routes in the District – Note: yellow highlights indicate neighbourhoods or portions of the District with poor access and evacuation routes.
Recommendation 8: The District must work towards improving access in identified areas of the community that are considered isolated and that have inadequately developed access for evacuation and fire control.
Recommendation
9: An evacuation plan should be developed for the
community and the outlying road and trail networks, which could be cut off or
impacted by fire. A large fire may require the evacuation of heavily used
trails where vehicle access is restricted.
8.2 Fire Response
Fire suppression efforts in the District are constrained by the ability of firefighters to successfully defend residences with:
· Contiguous fuels between the forest and adjacent homes;
· Steep slopes of greater than 35%; and
· Human caused fuel accumulations and fuel tanks adjacent to homes.
The close proximity of fuels to homes and vulnerable roofing material are the two most significant factors that reduce the ability of firefighters to defend residences. During ember showers, multiple fires could ignite on vulnerable roofs within the wildland urban interface. The fuel continuity that currently exists provides a pathway for fire between the forest and many homes in the neighbourhood. The lack of fuel breaks between houses and forest is likely to increase suppression resource requirements. While there will always be a limited ability to protect homes from extreme fire behaviour, or to modify fuels and topography in the District, the community does have control over issues such as defensible space and home construction materials, and can make changes to reduce community vulnerability to fire.
Residences and businesses on steep slopes located throughout the District are vulnerable to increased fire behaviour potential and should be the immediate focus of initial attack if there is a fire start within these areas. Flame length and rate of spread will increase on these slopes, resulting in suppression difficulty and increased safety issues for both wildland and structural fire fighters.
Another significant issue that could affect
emergency response is the impact of smoke on the District Fire Rescue Service,
the Health Care Centre and the
Recommendation 10: During a large wildfire it is probable that the valley bottom (location of the fire hall and Health Care Centre) could be severely impacted by smoke. It is recommended that contingency plans be developed in the event that smoke causes evacuation of the District of Mission. The District should co-operate with Provincial and Regional governments to develop an alternate incident command location and mobile facility in the event that the District is evacuated.
In the event of a forest fire, the District relies heavily on the MOFR to action fires in the forests within the District. Historically, the District has worked cooperatively with the MOFR to extinguish wildland fires and this has been a successful relationship. However, during periods of high fire load throughout the Province, resources of the MOFR can be stretched thin. Often high fire activity is concentrated in the interior of the Province and availability of aircraft and equipment can be limited on the coast. In steep heavily forested terrain such as Mission Tree Farm, the most effective method of fire control is generally air tanker action or bucketing with water from a helicopter. Therefore, under extreme fire conditions within the District, consideration should be given to retaining a contract helicopter on standby. This may be the District’s best chance of containing a fire during the most severe part of the fire season, and may provide the MOFR with the time necessary to mobilize equipment and resources from other parts of the Province.
Recommendation 11: Given the values at risk identified in this plan, it is recommended that, during periods of extreme fire danger, the District work with the Ministry of Forests and Range to maintain a local helicopter with a bucket on standby within the District boundaries.
9.0 Training Needs
It is recommended that all Mission Fire
Rescue Service staff and Mission Tree Farm staff be trained in the S-100 Basic
Wildland Fire Fighting course on a yearly basis. This is carried out by instructors
endorsed by the
It is recommended that:
·
The S-100 course instruction be
continued on an annual basis;
·
District Parks outside staff be
given the S-100 course on an annual basis;
·
A review of the S-215 course
instruction be given on a yearly basis;
·
The S-215 course instruction be
given to new career staff and Paid On-Call officers on an ongoing basis; and
·
Incident Command System
training be given to all career and Paid On-Call officers.
Although not a true course, it is also
recommended that Mission Fire Rescue Service and the
Recommendation 12: 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, the Mission Fire Rescue Service should adopt an advanced program that fosters continuous improvement and skill renewal.
10.0 Vegetation (Fuel) Management
10.1 Principles of Fuel Management
10.1.1 Definition
Fuel management is the planned manipulation and/or reduction of living and dead forest fuels for land management objectives (e.g. hazard reduction). It can be achieved by a number of methods including:
· Prescribed fire;
· Mechanical means; and
· Biological means.
10.1.2 Purpose
The goal
is to proactively lessen the potential fire behaviour, thereby increasing the
probability of successful containment and minimizing adverse impacts. More
specifically, the goal is to decrease the rate of fire spread, and in turn fire
size and intensity, as well as crowning and spotting potential (Alexander
2003).
Fire triangle
Fire is a chemical
reaction that requires three main ingredients:
· Fuel (carbon);
· Oxygen; and
· Heat.
These three ingredients make up the fire triangle. If any one is not present, a fire will not burn.
Fuel is generally available in ample quantities in the forest. Fuel must contain carbon. It comes from living or dead plant materials (organic matter). Trees and branches lying on the ground are a major source of fuel in a forest. Such fuel can accumulate gradually as trees in the stand die. Fuel can also build up in large amounts after catastrophic events, such as insect infestations or disease.
Oxygen is present in the air. As oxygen is used up by fire, it is replenished quickly by wind.
Heat is needed to start and maintain a fire. Heat can be supplied by nature through lightning. People also supply a heat source through misuse of matches, campfires, trash fires, and cigarettes. Once a fire has started, it provides its own heat source as it spreads.
10.1.3
Forest
Fuels
The amount of fuel available to burn on any
site is a function of biomass production and decomposition. Many of the forest
ecosystems within
A hazardous fuel type can be defined by high surface fuel loadings; high proportions of fine fuels (<1 cm) relative to larger size classes, high fuel continuity between the ground surface and overstory tree canopies, and high stand densities. A fuel complex is defined by any combination of these attributes at the stand level and may include groupings of stands.
10.1.4 Surface Fuels
Surface fuels consist of forest floor,
understory vegetation (grasses, herbs and shrubs, and small trees), and coarse
woody debris that are in contact with the forest floor (Figure 18).
Surface fuels typically include all combustible material lying on or immediately above the ground. Often roots and organic soils have the potential to be consumed by fire and are included in the surface fuel category.
Surface fuels that are less than 12 cm in diameter contribute to surface fire spread; these fuels often dry quickly and are ignited more easily than larger diameter fuels. Therefore, this category of fuel is the most important when considering a fuel reduction treatment. Larger surface fuels greater than 12 cm are important in the contribution to sustained burning conditions, but are often not as contiguous and are less flammable because of delayed drying and high moisture content, when compared with smaller size classes. In some cases where these lager size classes form a contiguous surface layer, such as following a windthrow event or wildfire, they can contribute an enormous amount of fuel, which will increase fire severity and potential for fire damage.
Figure 18. High surface fuel loading under a forest canopy
10.1.5 Aerial Fuels
Aerial fuels include all dead and living material that is not in direct contact with the forest floor surface. The fire potential of these fuels is dependent on type, size, moisture content, and overall vertical continuity. Dead branches and bark on trees and snags (dead standing trees) are important aerial fuel. Concentrations of dead branches and foliage increase the aerial fuel bulk density and enable fire to move from tree to tree. The exception is for deciduous trees where the live leaves will not normally carry fire. Numerous species of moss, lichens, and plants hanging on trees are light and flashy aerial fuels. All of the fuels above the ground surface and below the upper forest canopy are described as ladder fuels.
Two measures that describe crown fire potential of aerial fuels are the height to live crown and crown closure (Figure 19 and Figure 20). The height to live crown describes fuel continuity between the ground surface and lower limit of the upper tree canopy. Crown closure describes the inter-tree crown continuity and reflects how easily fire can be propagated from tree to tree. In addition to crown closure, tree density is an important measure of the distribution of aerial fuels and has significant influence on the overall crown and surface fire conditions (Figure 20). Higher stand density is associated with lower inter tree spacing, which increases overall crown continuity. While high density stands may increase the potential for fire spread in the upper canopy, a combination of high crown closure and high stand density usually results in a reduction in light levels associated with these stand types. Reduced light levels accelerate self-tree pruning, inhibit the growth of lower branches, and decrease the cover and biomass of understory vegetation.
Figure 19. Comparisons showing stand level differences in the height to live crown.
Figure 20. Comparisons showing stand level differences in crown closure.
Figure 21. Comparisons showing stand level differences in density and mortality.
10.2 Fuel Treatment Needs
The WRMS has identified areas
of high hazard fuels (C3 and C4 fuel types) associated with values at risk
within the District. The size and scale of these areas are considered a
significant management challenge (Figure
22). The only meaningful way to address the identified
fuels problem in the short-term is to utilize existing breaks (roads, railwa
There a number of hazardous stands of C3 and C4
fuel types in the study area (Figure 22). These areas of hazardous fuels should be the focus
of a long-term fuel reduction program. The total area of priority 1 and 2
stands within the study area are 1,126 ha and 3,892 ha respectively. The total
area of priority 1 fuel type outside the District boundary but within the study
area is 3,264 ha. While it is probably not feasible to treat all of these areas
in the short-term, it is possible to develop an annual program that targets
progressive fuel reduction in these areas over the next decade.
Figure
22. Overview of high priority
fuel types within the District that pose a spotting and interface fire risk.
Figure 23. High
Vulnerability Interface Areas
Thinning is a preferred approach to fuels treatment (Figure 24) and offers several advantages compared to other methods:
· Thinning provides the most control over stand level attributes such as species composition, vertical structure, tree density, and spatial pattern, as well as the retention of snags and coarse woody debris for maintenance of wildlife habitat and biodiversity.
· Unlike prescribed fire treatments, thinning is comparatively low risk, is not constrained to short weather windows, and can be implemented at any time.
· Thinning may provide marketable materials that can be utilized by the local economy.
· Thinning does not produce smoke (unless thinned materials are later burned), which is considered a public health hazard.
· Thinning can be carried out using sensitive methods that limit soil disturbance, minimize damage to leave trees, and provide benefits to other values such as wildlife.
The following summarizes the guiding principles
that should be applied in developing thinning prescriptions:
· Protect public safety and property both within and adjacent to the urban interface.
· Reduce the risk of human caused fires in the immediate vicinity of the urban interface.
· Improve fire suppression capability in the immediate vicinity of the urban interface.
· Reduce the continuity of overstory fuel loads and related high crown fire risk.
· Maintain the diversity of wildlife habitat through the removal of dense understory western hemlock, western red cedar, amabilis fir, Douglas fir and other minor tree species.
· Minimize negative impacts on aesthetic values, soil, non-targeted vegetation, water and air quality, and wildlife.
The main wildfire objective of thinning is to shift stands from having a high crown fire potential to having a low surface fire potential. In general, the goals of thinning are to:
· Reduce stem density below a critical threshold to minimize the potential for crown fire spread. Target crown closure is less than 35%;
· Prune to increase the height to live crown to a minimum of 2.5 meters or 30% of the live crown (the lesser of the two) to reduce the potential of surface fire spreading into tree crowns; and
· Remove slash created by spacing and pruning to maintain surface fuel loadings below 5 kg/m2.
Recommendation 13: 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: 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.
Figure 24. Schematic
showing the principles of thinning to reduce stand level hazard.
10.2.1 The Principles of Landscape Fuelbreak Design
The WRMS developed in support of this plan identified that the core area of the District is at significant risk from wildfire (Figure 25). Public safety, and many of the important values, facilities and structures, may be severely impacted by a major fire in the District. This section of the fire management plan attempts to identify areas that, following treatment, could be used as landscape-level shaded fuelbreaks. Fuelbreaks can be defined as strategically placed strips of low volume fuel where firefighters can make a stand against fire and provide safe access for fire crews in the vicinity of wildfires, often for the purpose of lighting backfires. Fuelbreaks in the District would act as staging areas where fire suppression crews could anchor their fire suppression efforts, thus increasing the likelihood that fires could be stopped, or fire behaviour minimized, so that the potential for a fire to move fluidly through the District and into the interface is substantially reduced.
Figure 25. Final overlay of probability and consequence from the Wildfire Risk Management System.
The District must be sensitive to visual concerns and public perception. Therefore, shaded fuelbreaks, in combination with specific area treatments or other manual/mechanical methods, are most desirable. A shaded fuelbreak is created by reducing surface fuels, increasing height to live crown and lowering stand density through tree removal (Figure 26). Fuelbreaks can be developed using a variety of prescriptive methods that may include understory and overstory fuel removal, timing of treatment, synergistic effects with other treatments, and placement on the landscape.
Figure 26. Conceptual diagram of a shaded fuelbreak pre treatment and post treatment.
The information contained within this section has been inserted from “The Use of Fuelbreaks in Landscape Fire Management” by James K. Agee, Benii Bahro, Mark A. Finney, Philip N. Omi, David B. Sapsis, Carl N. Skinner, Jan W. van Wagtendonk, and C. Philli Weatherspoon. This article succinctly describes the principles and use of fuelbreaks in landscape fire management.
The principal objective behind the use of fuelbreaks, as well as any other fuel treatment, is to alter fire behaviour over the area of treatment. As discussed above, fuelbreaks provide points of anchor for suppression activities.
Surface fuel management can limit fireline intensity (Byram 1959) and lower potential fire severity (Ryan and Noste 1985). The management of surface fuels so that potential fireline intensity remains below some critical level can be accomplished through several strategies and techniques. Among the common strategies are fuel removal by prescribed fire, adjusting fuel arrangement to produce a less flammable fuelbed (e.g., crushing), or "introducing" live understory vegetation to raise average moisture content of surface fuels (Agee 1996). Wildland fire behaviour has been observed to decrease with fuel treatment (Buckley 1992), and simulations conducted by van Wagtendonk (1996) found both pile burning and prescribed fire, which reduced fuel loads, to decrease subsequent fire behaviour. These treatments usually result in efficient fire line construction rates, so that control potential (reducing "resistance to control") can increase dramatically after fuel treatment.
The various surface fuel categories interact with one another to influence fireline intensity. Although more litter and fine branch fuel on the forest floor usually results in higher intensities, that is not always the case. If additional fuels are packed tightly (low fuelbed porosity), they may result in lower intensities. Although larger fuels (>3 inches) - are not included in fire spread models, as they do not usually affect the spread of the fire (unless decomposed [Rothennel 1991]), they may result in higher energy releases over longer periods of time when a fire occurs, having significant effects on fire severity, and they reduce rates of fireline construction.
The effect of herb and shrub fuels on fireline intensity is not simply predicted. First of all, more herb and shrub fuels usually imply more open conditions. These should be associated with lower relative humidity and higher surface windspeeds. Dead fuels may be drier - and the rate of spread may be higher - because of the altered microclimate compared to more closed canopy forest with less understory. Live fuels, with higher foliar moisture while green, will have a dampening effect on fire behaviour. However, if the grasses and forbs cure, the fine dead fuel can increase fireline intensity and localized spotting.
· Conditions That Initiate Crown Fire
A fire moving through a stand of trees may move as a surface fire, an independent crown fire, or as a combination of intermediate types of fire (Van Wagner 1977). The initiation of crown fire behaviour is a function of surface fireline intensity and of the forest canopy: its height above ground and moisture content (Van Wagner 1977). The critical surface fire intensity needed to initiate crown fire behaviour can be calculated for a range of crown base heights and foliar moisture contents, and represents the minimum level of fireline intensity necessary to initiate crown fire (Table 3); Alexander 1988, Agee 1996). Fireline intensity or flame length below this critical level may result in fires that do not crown but may still be of stand replacement severity. For the limited range of crown base heights and foliar moistures shown in Table 3, the critical levels of flame length appear more sensitive to height to crown base than to foliar moisture (Alexander 1988).
Table 3. Flame lengths associated with critical levels of fireline
intensity that are associated with initiating crown fire, using Byram's (1959)
equation.
|
Foliar Moisture |
Height of Crown Base |
|||
|
|
2 meters |
6 meters |
12 meters |
20 meters |
|
6 feet |
20 feet |
40 feet |
66 feet |
|
|
M ft |
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