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Guidance on Design and Construction of the Built Environment Against Wildland Urban Interface Fire Hazard: A Review

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Wildland-Urban Interface (WUI) fires, a worldwide problem, are gaining more importance over time due to climate change and increased urbanization in WUI areas. Some jurisdictions have provided standards, codes and guidelines, which may greatly help planning, prevention and protection against wildfires. This work presents a wide systematic review of standards, codes and guidelines for the design and construction of the built environment against WUI fire hazard from North American, European, Oceanic countries, alongside with trans-national codes. The main information reviewed includes: the definition of WUI hazards, risk areas and related severity classes, the influence of land and environmental factors, the requirements for building materials, constructions, utilities, fire protection measures and road access. Some common threads among the documents reviewed have been highlighted. They include similar attempts at: (a) defining WUI risk areas and severity classes, (b) considering land factors including the defensible space (also known as ignition zones), (c) prescribing requirements for buildings and access. The main gaps highlighted in the existing standards/guidelines include lacks of detailed and widespread requirements for resources, fire protection measures, and lacks of taking into account environmental factors in detail. The main design and construction principles contained in the reviewed documents are largely based on previous research and/or good practices. Hence, the main contributions of this paper consist in: (a) systematically disseminate these guidance concepts, (b) setting a potential basis for the development of standards/guidelines in other jurisdictions lacking dedicated WUI fire design guidance, (c) highlighting gaps in existing standards/guidelines to be addressed by current and future research.
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Guidance on Design and Construction
of the Built Environment Against Wildland
Urban Interface Fire Hazard: A Review
Paolo Intini, Division of Fire Safety Engineering, Lund University, Lund,
Sweden; Department of Civil, Environmental, Land, Building Engineering
and Chemistry, Polytechnic University of Bari, Bari, Italy
Enrico Ronchi *, Division of Fire Safety Engineering, Lund University, Lund,
Sweden
Steven Gwynne, Movement Strategies, London, UK
Noureddine Be
´nichou, National Research Council, Ottawa, Canada
Received: 28 December 2018/Accepted: 28 August 2019
Abstract. Wildland-Urban Interface (WUI) fires, a worldwide problem, are gaining
more importance over time due to climate change and increased urbanization in WUI
areas. Some jurisdictions have provided standards, codes and guidelines, which may
greatly help planning, prevention and protection against wildfires. This work presents
a wide systematic review of standards, codes and guidelines for the design and con-
struction of the built environment against WUI fire hazard from North American,
European, Oceanic countries, alongside with trans-national codes. The main informa-
tion reviewed includes: the definition of WUI hazards, risk areas and related severity
classes, the influence of land and environmental factors, the requirements for building
materials, constructions, utilities, fire protection measures and road access. Some
common threads among the documents reviewed have been highlighted. They include
similar attempts at: (a) defining WUI risk areas and severity classes, (b) considering
land factors including the defensible space (also known as ignition zones), (c) pre-
scribing requirements for buildings and access. The main gaps highlighted in the
existing standards/guidelines include lacks of detailed and widespread requirements
for resources, fire protection measures, and lacks of taking into account environmen-
tal factors in detail. The main design and construction principles contained in the
reviewed documents are largely based on previous research and/or good practices.
Hence, the main contributions of this paper consist in: (a) systematically disseminate
these guidance concepts, (b) setting a potential basis for the development of stan-
dards/guidelines in other jurisdictions lacking dedicated WUI fire design guidance, (c)
highlighting gaps in existing standards/guidelines to be addressed by current and
future research.
Keywords:Wildland-Urban Interface,WUI,Wildfire,Design guidance,Standard,Fire
* Correspondence should be addressed to: Enrico Ronchi, E-mail: enrico.ronchi@brand.lth.se
Fire Technology
2019 The Author(s)
Manufactured in The United States
https://doi.org/10.1007/s10694-019-00902-z
1
1. Introduction
Fires in the Wildland-Urban Interface (WUI) have become a global issue, with
recent disasters taking place in a number of places, including Europe, North/
South America and Oceania [29]. A wildland fire is defined as an: ‘‘unplanned and
uncontrolled fire spreading through vegetative fuels, at times involving structures’’
[32]. If it develops in a wildfire-prone boundary between structures and vegetation,
than it can be considered as a Wildland Urbane Interface (WUI) fire [30].
The WUI fire issue may get worse in the future, due to climate change [27] and
population growth in the WUI areas [36]. In fact, the current situation may evolve
towards more dangerous scenarios in areas which have already experienced a long
history of fires, such as the USA, Canada, Australia, Southern Europe, etc. [43].
However, other regions which have been not traditionally subject to wildfires may
become more vulnerable in future years, due to climate change and modifications
in the location and wildfire intensity, such as South America, Africa and Northern
Europe [27]. Thus, the phenomenon of fires in WUI areas should be considered
from a broad international perspective.
For example, in Canada, the number of wildfire evacuations per year has
increased by 1.5% from 1980 to 2014, with more than 20 evacuations per year
after 2010. The 2016 Fort McMurray fire alone had the costliest impact in the
Canadian history in terms of insured losses [43]. Due to these urgent needs,
research has started to address the consequences of these incidents [8,30],
provide measures to aid evacuation planning [9], and coupling fire, traffic and
pedestrian models to aid response to such incidents [25,42,43].
The development (and continuous revision) of standards and guidelines can be
crucial in reducing the negative impacts of WUI fires on communities involved
through appropriate dedicated measures and design guidance. Some countries
have already developed standards and codes concerning measures for response
planning, prevention, protection, fighting, etc. of WUI fires. Other jurisdictions
can rely on guidelines and local provisions, or on provisions which cover the issue
of WUI fires, but are included in other general codes (e.g., Building Codes, Envi-
ronmental Codes, Fire Codes, etc.). An International Code for WUI fires is also
currently available [24]. On the other hand, there are other countries which do not
have similar regulatory tools (and which do not adopt international provisions)
and design guidance, even if they are already affected (or they may be affected in
the future) by WUI fires.
The development (or revision) of standard/guidelines for design considering
WUI fire-related issues may be eased by a broad knowledge of the current regio-
nal, national and trans-national design concepts, mainly based on previous
research in this field and/or good practices. For this reason, the main objective of
this work was to review provisions and guidelines available worldwide concerning
WUI fires. This included both documents specifically focused on WUI fires as well
as selected documents which are relevant to WUI fires, but are not explicitly dedi-
cated to them. The document analysis has been done considering mainly countries
with Subarctic, Mediterranean and Oceanic climate.
Fire Technology 2019
The final objectives of this paper involve: (1) highlighting the main commonali-
ties in the documents reviewed, and (2) highlighting the main deficiencies. In fact,
the identification of the common threads through the different provisions and
guidance reviewed may be useful for researchers and practitioners who intend to
develop or revise WUI-based standards and guidelines. In addition, highlighting
deficiencies in standards and guidelines could shed some light on which part of
research should be transferred into regulations or, eventually, if future research is
needed on some specific topics.
2. Methods for the Review
In this section, the main documents reviewed and the methods used for conduct-
ing the review are explained in detail, by focusing on the structure and type of
information which have been retrieved from the considered documents.
The documents reviewed relate to areas in North America, Europe and Ocea-
nia. They were selected given that they had proneness to fires in the WUI simi-
lar to the Canadian environment, considering similarities in industrial
development, environmental and social conditions. Clearly, the European Mediter-
ranean area could have been specifically targeted for the review of documents
given it is prone to WUI fires (i.e., the Iberian peninsula, France, Italy, the Bal-
kan peninsula, see Modugno et al. [31]). Two examples of countries among those
most vulnerable were then considered for the review; namely, Italy and France.
The language knowledge (English, French, Italian) of the authors was also taken
into account in the selection of the reviewed documents. Two trans-national regu-
lations were also considered: International WUI Code and EU Regulations.
The documents reviewed are listed and classified according to the geographic
area to which they belong. Moreover, other reference sources and relevant docu-
ments considered during the review process are also identified. This information is
summarized in Table 1. In this table, groups of documents are defined (e.g., US
Standards, Italian Standards/Guidelines). These definitions are henceforth used
throughout the remainder of the paper.
The following methodology was used to review the standards and guidelines
regarding construction in areas deemed vulnerable to WUI fires. Relevant provi-
sions and/or guidelines for WUI fires were collected from the reviewed documents
according to a common template. The information collected is structured in three
categorical levels:
A macro-category (from A to G);
A second-level sub-category;
A third-level sub-category.
This approach was adopted to ensure a consistent representation of the provi-
sions reviewed. The macro-categories and the second- and third-level sub-cate-
gories considered are reported and explained as follows. Moreover, they are
graphically summarized in Fig. 1.
Guidance on Design and Construction of the Built Environment
Table 1
Summary of the Documents Reviewed Classified According to the Country/Area of Reference, and
Information Concerning Their Type, Main Content and Jurisdiction Level
Country/
Area
General regulatory
conditions Documents reviewed
Type of
document
(Jurisdiction)
1
Definition of
groups of
documents Notes/other referenced documents
Canada No WUI fire-related standards.
Guidelines descending from
community programs
FireSmart Guidebook for Com-
munity Protection (Alberta
Government) [1]
G (S/L) Canadian
guidelines
Includes most of the guidance provided
in (FireSmart, 2003, 2017), and some
guidelines provided in [44]
Example of application of the FireSmart
country-level program to the local level
United
States
WUI fire-relevant Standards,
Federal/State Guidelines, local
programs and guidelines
NFPA 1141 (2017)
NFPA 1142 (2017)
NFPA 1143. (2016)
NFPA 1144 (2013)
S (C) US Stan-
dards
Include provisions regarding WUI fire
prevention, protection, mitigation,
suppression, hazard
definition, and required resources
Reference to other NFPA Standards
California Fire Code, Chapter 49:
Requirements for Wildland-Ur-
ban Interface Fire Areas [46]
S (S) Californian
Standards/
Guidelines
Includes references to other regulations
(e.g. [7], [46]), guidelines (e.g., [45])
Implementation Guidelines for
Executive Order 13,728 WUI
Federal Risk Management [34]
S (C) US Guideli-
nes
Provides minimum acceptable standards
for US Federal buildings in risky WUI
areas, complying with IWUIC [24]
Firewise toolkit [16]G (C) Provides guidelines to the general public
Colorado WUI Hazard Assess-
ment Methodology [12]
G (S) Provides a specific methodology for WUI
hazard and risk assessment
Wildfire Hazard Assessment Guide
for Florida Homeowners [17]
G (S) Provides guidelines to the general public
on different wildfire safety measures,
and a methodology for wildfire hazard
and risk assessment
The Planning for Natural
Hazards: Wildfire Technical
Resource Guide [35]
G (S) Provides guidelines about planning and
protection measures
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Table 1
continued
Country/
Area
General regulatory condi-
tions Documents reviewed
Type of
document
(Jurisdiction)
1
Definition of
groups of
documents Notes/other referenced documents
Australia Standard for buildings in
WUI areas, State guideli-
nes
Construction of buildings in bushfire-
prone areas [3]
S (C) Australian
standards/
guidelines
Includes provisions related to WUI fires
prevention, protection, mitigation,
suppression, hazard definition, and
required resources.
Several other Australian standards
and scientific research articles
referenced in the text
Guidelines of the States of South Aus-
tralia [21] and Tasmania [22]
G (S) Provides guidelines for vegetation, resources,
fire protection measures and access
New
Zeal-
and
No WUI-fire related stan-
dards. Parts of fire codes
relevant for WUI fires
Fire Emergency New Zealand Act
(Fire and Emergency New Zealand
[15]
New Zealand Building Code, Extract:
Clauses C1-C6, A3 [11]
S (C) New Zeal-
and Stan-
dards/
Guidelines
Codes regulating the protection of
buildings and the surrounding areas
from wildfires, relevant for the WUI
fire case too
(Fire and Emergency New Zealand)
[15]
G (C) Provides guidelines concerning fire safety
in rural homes
France No WUI fire-related stan-
dards. Parts of the forest
code relevant for WUI
fires
Code Forestier (Republique
Francaise) [18]
S (C) French
Stan-
dards/
Guidelines
Includes provisions concerning the plans
required for different risky areas [13],
including those related to fire risk
Plans de prevention des risques natur-
els (PPR). Risques d’incendies de
foret. Guide me
´thodologique [37]
G (C/L) Provides guidelines on which features
should be included in the local plans
for preventing
predictable fires (PPRIF). [37]isan
example of application of the PPRIF
to the local level (highly exposed to
wildfires)
Arrete n. 2013071-2002, De
´partement
de la Haute-Corse [10]
G (L) Provides guidelines concerning vegeta-
tion clearing in a WUI-prone region
Guidance on Design and Construction of the Built Environment
Table 1
continued
Country/
Area
General regulatory con-
ditions Documents reviewed
Type of
document
(Jurisdiction)
1
Definition of
groups of
documents Notes/other referenced documents
Italy No WUI fire-related
standards. Parts of the
fire code relevant for
WUI fires
‘‘Legge quadro in materia di incendi
boschivi’’ (Framework law concerning
wildfires), L. 21.11.2000, n. 353 (Repub-
blica Italiana) [41]
S (C) Italian Stan-
dards/
Guidelines
Provides regulations concerning
forecasting, preventing and fighting
of wildfires
Raccomandazioni per un piu` efficace con-
trasto agli incendi boschivi, di interfaccia
e ai rischi conseguenti. Allegato [38]
S (C) Includes explicit reference to
Wildland-Urban Interface fires
Piano Regionale per la Previsione, Preven-
zione e Lotta attiva contro gli incendi
boschivi [40], Prevenzione antincendi
boschivi [5]
G (L) Define regional planning activities with
respect to wildfires, explicitly referenc-
ing interface fires, and including a
framework for
defining danger zones with respect to
structures
World Presence of a WUI fire-
related standard
International Wildland-Urban Interface
Code [24]
S (I) International
Standards
Defines the fire safety provisions to be
adopted in the WUI area, including
references to other International
Codes (e.g., Building and Fire Codes)
Europe No WUI-fire related
standards. Regulations
concerning forest fires
Council Regulation (EEC) No 2158/92 of
23 July 1992 [13]
EC 2152/2003 (Forest Focus) [14]
S (I) European
Standards
Provide directives for the Member
States mainly concerning the
definition of hazard zones and
protection plans concerning
forest fires, do not explicitly mention
WUI fires
1
S = Standard/Code/Regulation (henceforth referred to as ‘‘standards’’), G = Guidelines/Recommendations (henceforth referred to as ‘‘guidelines’’), (I) = applicable at the
international level, (C) = applicable at the country-level, (S) = applicable at the State-level, (L) = applicable at the regional/local level
Fire Technology 2019
Figure 1. Summary of the categories taken into account for the
consistent review of the information contained in the selected
documents. Macrocategories are on the left (named from ‘‘A’’ to
‘‘G’’). Second level sub-categories within each macro-categories are
connected on the right (e.g. Land has sub-categories of Vegetation
and Topography). The third-level sub-categories are reported below
each relevant second-level category (in a lighter colour than the
second-level categories). For instance, Vegetation includes Defensible
Space, amongst other examples.
Guidance on Design and Construction of the Built Environment
The macro-category ‘‘Hazard’’ relates to how hazard and risk zones are identi-
fied and classified. In particular the definition of WUI (Wildland-Urban Interface)
and risk zones, alongside with the procedures used for identifying hazards and cir-
cumscribing zones, are reviewed. The procedures to define the different risk sever-
ity classes, and the thresholds delimiting the different risk categories are reviewed
as well.
The macro-category ‘‘Land’’ relates to the measures adopted for the vegetation
surrounding structures in terms of: (1) creating a defensible space (i.e. fuel modifi-
cation: removal, reduction, substitution) and undertaking specific operations at
given distances from the structures, (2) respecting given clearances between vegeta-
tion and other vegetation types/structures (or other objects); (3) undertaking
maintenance procedures for the defensible space or the vegetation around struc-
tures. Moreover, the procedures that influence the terrain (i.e., slopes) and topog-
raphy on the risk classification are reviewed as well.
The macro-category ‘‘Building construction’’ includes several elements. It
includes the review of the general requirements for buildings and building materi-
als with respect to fire safety: classes of ignition resistance, characteristics required
for ignition resistance of building materials or part of structures, and clearance
between buildings. It also includes the review of requirements for the specific ele-
ments: roofs (and the different parts composing them), walls (and other external
coverings), openings (such as exterior glazing, external doors, vents and other
openings), other structures (decks and other attachments, detachments), interiors
(floors, under-floors and other structures).
The macro-category ‘‘Resources’’ includes several elements. It includes the
review of the requirements for: (1) water supply (concerning the minimum supply
level, the standby power, the location and size of hydrants in case of fire suppres-
sion), and other fire-safety related utilities; (2) firefighters, including procedures
and activities before and during the emergency; (3) plans to be adopted for fire
protection purposes (fire protection plans) and other plans relevant to WUI fire
safety (e.g., emergency or development plans). Moreover, it describes the out-
comes and general public (outreach) to which documents are dedicated.
The macro-category ‘‘Fire protection measures’’ includes the review of the
requirements for water sources to use in fire protections and for buildings. Among
protection measures for buildings, those adopted for sprinklers, manual protection
systems in/near structures (e.g., fire extinguishers), warning systems (e.g., fire
alarms), spark arresters (such as for chimneys), combustible materials and their
distance from structures if allowed (e.g., debris, tanks, gases), private shelters
against wildfires, are reviewed.
The macro-category ‘‘Environment’’ relates to how weather and fire history
influence the measures or procedures to be adopted.
Finally, the macro-category ‘‘Access’’ relates to the fire safety requirements of
the road access to structures. It includes the type and/or number of access roads
required in the risk areas, the requirements concerning road standards (geometry,
materials, parking lots, dedicated lanes) for main access roads and driveways/
dead-end roads, markings (on access roads/streets and dwellings markers), and
vegetation clearing operations to be conducted within the road limits.
Fire Technology 2019
3. General WUI-Relevant Information for the Areas
Considered
Information relevant to WUI fires for the geographical areas considered are
reported below in Fig. 2. This information concerns temperature and rainfall, cli-
mate, population, vegetation (forest types). They are important for considering the
context in which different standards and guidelines are developed and used. Infor-
mation relevant for WUI fires are not reported for standards corresponding to
transnational areas, such as International or EU, since this information is not
location specific. Information concerning temperature, rainfall, climate, population
and vegetation may be useful while developing novel standards/guidelines, since
the latter should be defined according to the local characteristics of the area under
consideration.
The extent of the Wildland-Urban Interface in the areas considered, together
with additional information about fires and other relevant issues, are reported
Figure 2. Summary of the information relevant to WUI fires for the
geographical areas considered. Specific data sources: Climate Change
Knowledge Portal (1901–2015) for temperatures and rainfall, htt
p://www.fao.org/forestry/fra/80298/en for forest types, Ko
¨ppen
scale for climate. Notes *Annual mean daily (1997–2014), **average
monthly rain volume (1961–1990) (US Census/US Geological
Survey).
Guidance on Design and Construction of the Built Environment
as well. Since, in this case, a common world database with data of equivalent
and refinement does not exist, the data used derived from local sources. In fact,
although general definitions of WUI areas may be provided, different buffers
between structures/infrastructures and the vegetation, or different percentages of
built areas may be used for precise definitions of the WUI area. For example,
Modugno et al. (2016) highlight that the definition of WUI area is standardized
in the USA (built areas with <50% vegetation, lying within 2.4 km of an area
with at least 75% wildland vegetation, and at least 5 km
2
wide, as reported by
[39]), based on [20]. In contrast, in some European countries the definition of
WUI areas are not standardized (or they may vary between countries). Thus,
comparisons between countries may be difficult without taking into account the
local legal frameworks. For instance:
Canada WUI area: 32.3 million ha (5.8% of the territory), largest WUI areas in
Quebec (about 6.9 million ha), highest WUI percentages among the total State
in Nova Scotia (45.1%) [26]. 5780 fires/year and >1 million ha burnt by wild-
fires (10-years average, 2017); with most of the fires/year (811) and largest area
burnt/year (>163 k ha) in Alberta.
USA 46 million homes in the WUI area (2012), estimated conversion rate from
wildlands to WUI: about 810,000 ha/year since 1990, 8 million projected new
homes in next 10 years [23]. 89,000 ha designated by State foresters as at WUI
fire high-risk, with about 100,000 wildfires burning 2.8 million ha/year, and
2970 homes/year lost on average since 2000 [23];
California: WUI area estimated in 746,037 ha, estimated number of houses in
the WUI area: >5 million [47]. Average area burned/year by wildfires (period:
2011–2015): 1272 km
2
(US Department of Agriculture, Forest Service).
Australia More than 11,000 houses lost in Australia in the period 1939–2007;
with most of the houses lost in the Victoria State (more than 60% of losses) [4].
New Zealand National average annual total area burned in the period 1991–2007:
5865 ha, average number of wildfires increased from 1200 to 4000 annually in the
same period, with the north islands accounting for two-thirds of all the wildfires,
and grass fires accounting for the majority of area burned (54%) [2].
France WUI area particularly present in some areas (e.g., in Bouches-du-
Rhoˆ ne: >15% of the Department, 47% of fires starting in the WUI). About
4000 fires/year, 5.5 million ha of forests potentially exposed to fire risk, but a
limited State portion severely attacked by fires (e.g., in Provence-Alpes-Cote
dAzur: 7000 burnt ha/year) [19]; MeteoFrance).
Italy In the first seven months of 2017, 74,965 ha burned. The highest amount
of ha. burnt were in the Regions: Sicily, Calabria and Campania [28].
4. Comparative Analysis of the Results from the Review
A comparative analysis of the information collected from the different sources is
conducted here, by highlighting variability in key aspects of standards/guidelines
under consideration. The comparative analysis is conducted separately for each
Fire Technology 2019
macro category, by focusing on the various approaches adopted by different guid-
ance/regulatory provisions. Moreover, for each macro-category (see Fig. 1), a gen-
eral comment is provided at the beginning of the sub-section, and more detailed
comparisons provided for each second-level sub-category, where present (i.e., for
land, building construction, resources, fire protection measures, environment).
4.1. Hazard
A definition of risk and hazard zones and the hazard classification are provided in
all the standards/guidelines reviewed. Specific details concerning the hazard classi-
fication in the documents reviewed are provided in Table 2.
Definitions of wildfire risk and hazard levels are present in all groups of docu-
ments reviewed, except for the New Zealand group. The definition of specific risk
areas is essentially based on some topographic, vegetation and environmental fac-
tors and should be made by the relevant authority. For example, the US stan-
dards base the definition of wildfire risk areas on characteristics such as: fuels, fire
weather, defensible space, terrain, building construction and water supply, while
the Australian standards define the wildfire risk for structures based on surround-
ing vegetation, heat flux exposure, predicted bushfire attack/exposure. The defini-
tion itself of WUI area is slightly different between different standards. In
Australia, those areas are referred to as Bushfire-prone areas, and the wildfire risk
level is defined as Bushfire Attack Level (BAL). Methods for identifying and clas-
sifying severity in the interface areas have been found in all the standards/guideli-
nes reviewed, with different levels of detail. In the more detailed provisions/
guidelines, the severity class is assigned based on a rating obtained as a sum of
partial ratings related to different factors (e.g., in Canadian, US, Australian, and
International documents reviewed). The main factors on which the total severity
rating is obtained are: type of building construction and materials (i.e., roofs,
exterior structures), vegetation (including distance from vegetation), fuels, slopes,
critical fire weather frequency (the latter in the IWUIC, 2015). In the EU Guideli-
nes, it is essentially based on geographic considerations based on fire history.
Specific high-risk zones are identified in this way: Portugal, Spain, Greece, some
regions of France and Italy. Risk assessments should be constantly conducted for
these.
4.2. Land
Provisions/recommendations about the influence of land characteristics on the
measures and procedures to be adopted in wildfire-prone areas are provided in all
the groups of documents reviewed, except for the European Standards.
4.2.1. Vegetation The feature ‘‘vegetation’’ includes the quantitative and qualita-
tive provisions for creating the defensible space, the clearance between different
vegetation types (i.e., between tree crowns and between tree crowns and ground
vegetation) and between vegetation and structures/infrastructures (i.e., buildings,
power lines), and for maintaining vegetation around structures. Even with differ-
ent quantitative provisions, the concept of defensible space is present in all the
Guidance on Design and Construction of the Built Environment
Table 2
Comparative Summary Between the Standards/Guidelines Reviewed, Classified According to the Relative
Jurisdictions
Jurisdiction/
Type of
provision and
public
Type of Hazard
Definition Buffer zone (vegetation) Influence of terrain?
Prescriptions for
structural elements (list) Prescriptions for utilities
Canada (in-
cluding
Canadian
provinces)
Guidelines,
dedicated to
both commu-
nities and
homeowners
Four different ranges of
hazard for structures,
sites, and surround-
ing areas
Three priority zones
with respect to vegeta-
tion management (pri-
ority 1: <10 m,
priority 2: 10–30 m,
priority 3: >30 m).
Mandatory fuel
removal in the priority
zone 1. Recommended
removal, reduction
and species conversion
in the other zones
Factors addressed:
Slopes. Some guideli-
nes for the relative
position building/
slope: building at least
10 m beyond the crest
of the slope, or on the
bottom of the hill.
Severe fuel modifica-
tion on slopes (espe-
cially >10%)
Roof (including covering
and eaves), exterior
walls, glazing, open-
ings, attachments.
Guidelines not much
detailed. Minimum
separation between
structures considered
Water sources (qualitative)
and fire hydrants
United States
Standards
Structures classified
into five classes of
occupancy hazard
and construction
types, with respect to
wildfire risk, based
on a detailed struc-
ture assessment
Mitigation measures for
buildings located £30
feet (9 m) from vege-
tated slopes. Non-
combustible barrier in
case of scarce space
between structures
and vegetation. Fuel
modification provi-
sions to be included in
fire mitigation plans
Factors addressed:
slopes, topographical
factors (flat areas, rid-
ges, saddles, natural
chimneys, canyons).
Topography and ter-
rain included in the
structure wildfire risk
assessment
Roofs (covering, eaves,
gutters), exterior
walls, exterior glazing
and doors, openings,
attachments and
detachments. Specific
provisions for building
separation and igni-
tion resistant materials
Water supply level (specific
guidance on the minimum
water supply). depending on
the occupancy hazard,
construction type,
dimensions and exposures.
Other provisions for water
sources, access, hydrants
Fire Technology 2019
Table 2
continued
Jurisdiction/Type
of provision
and public
Type of Hazard
Definition Buffer zone (vegeta-
tion)
Influence of ter-
rain?
Prescriptions for
structural elements
(list)
Prescriptions for utilities
United States
(Colorado,
Florida, Ore-
gon) Guideli-
nes, dedicated
to communi-
ties, planners
and homeown-
ers
Different methods for
assessing risks and
hazards in the WUI
areas (highly detailed
in the Florida docu-
ment). Common use of
a total hazard score
based on partial scores
for different features
(i.e., vegetation, build-
ings, values, access,
etc.)
Slightly different pre-
scriptions between
states. First area sur-
rounding the building
with heavily reduced
fuel of 30 feet (about
9 m), as a common
requirement
Factors addressed:
slopes, terrain,
generally consid-
ered in the risk
assessment. Speci-
fic requirements
only in Oregon
guidelines
Some building construc-
tion guidelines, espe-
cially for roof covering
and eaves, exterior
walls, glazing, open-
ings, decks
Some guidelines for supply
level, water sources and
their access in the Oregon
guidelines
United States
(California)
Standards/
Guidelines (for
homeowners)
Three risk areas defined
by the State and by
local authorities (addi-
tional fourth risk area)
Up to 100 feet (30.5 m)
for brush, flammable
vegetation and other
combustible growth
(except for some speci-
fic cases)
Factors addressed:
slopes. Different
horizontal and
vertical clearance
between vegeta-
tion depending on
slopes
Roof (including valley
flashings, eaves and
gutters), exterior walls
and coverings (includ-
ing roof eaves, ceilings
and appendages), exte-
rior glazing and doors,
vents, attachments,
underfloor areas. Igni-
tion resistant materials
defined
Not in the specific WUI part
of the Fire Code
Guidance on Design and Construction of the Built Environment
Table 2
continued
Jurisdiction/
Type of
provision
and
public
Type of Hazard
Definition Buffer zone (vegetation) Influence of terrain?
Prescriptions for struc-
tural elements (list) Prescriptions for utilities
Australia
Standards
Structures classified
into seven classes of
Bushfire Hazard
Level (BAL), based
on several factors,
with detailed classifi-
cation guidance
In the extreme bushfire
risk area, at least 10 m
between structures and
vegetation. Otherwise,
structures should com-
ply with specific require-
ments. Specific guidance
on fuel reduction and
protection around struc-
tures in local regulations
and guidelines
Factors addressed: slopes.
Considered in the com-
putation of Bushfire
Hazard Levels. (also by
local guidelines for
defining the protection
area width around struc-
tures)
Roof (including valley
flashings, eaves and gut-
ters), exterior walls and
coverings, exterior glaz-
ing and doors, vents,
attachments and detach-
ments, floors and sub-
floors. Some ignition
resistant materials
defined. Particular
emphasis on external
glazing and doors
Not specifically addressed
in the reviewed standard.
Guidelines about supply
level, water sources,
access and fire hydrants
in local documents
New Zeal-
and Stan-
dards
Five levels of building
types defined (Build-
ing Importance
Levels, BIL), with
respect to fire and
the related risk for
their occupants
Firebreaks should be
cleared from vegetation
(qualitative indications)
Not specifically addressed Exterior walls, floors, other
interior structures (walls
and ceiling materials, fire
cells). Specific provisions
about maximum surface
temperature of com-
bustible materials and
fire spread
Future planning progress
for water supply. Provi-
sions about escape
routes
Fire Technology 2019
Table 2
continued
Jurisdiction/
Type of
provision
and public
Type of Hazard
Definition Buffer zone (vegetation) Influence of terrain?
Prescriptions for
structural elements (list) Prescriptions
for utilities
International
Standards
Three classes of fire haz-
ard severity, depending
on fuel models, critical
fire weather frequency,
slopes
Fuel modification (reducing/
altering non-fire resistive
vegetation) within: -30
feet (9.14 m) for moderate
hazards, -50 feet (15.24
m) for high hazards, -
100 feet (30.48 m) for
extreme hazards. Greater
site-specific distances
Factors addressed: slopes,
topographic factors (eleva-
tion, ridges, drainages,
roads, exposure, etc.), inter-
actions between man-made
infrastructures and geogra-
phy. Slopes considered in
the definition of the severity
classes and in the prescrip-
tions for decks and
detached structures
Roof (including valley flash-
ings, eaves and gutters),
exterior walls, exterior glaz-
ing and doors, openings,
attachments and detach-
ments, underfloor areas.
Three ignition resistant
classes, based on defensible
space, fire hazard severity,
water supply; ignition resis-
tant materials
Water supply
points, includ-
ing prescrip-
tions about
supply level,
water
sources, access
and supply
power
European
Union
Standards
Three risk zones should be
individuated in the terri-
tory of the EU with
respect to forest fires,
based on risk assessment.
WUI fires not explicitly
mentioned
Not specifically addressed Not specifically addressed Not specifically addressed Not specifically
addressed
France (in-
cluding
local
authorities)
Standards
Twomainriskareas(one
where it is not possible to
build new structures).
Some regions defined as
subject to forest fire risk
Vegetation clearing up to
50 m. A buffer distance of
200 m between new con-
structions and the forest.
Specific local prescriptions
(plans) for vegetation
clearing
Factors addressed: slopes,
orientation (e.g. with
respect to wind), sunlight
exposure. Influence of ter-
rain in the definition of
risk areas. Not considered
for vegetation clearing
Roof (including eaves and
gutters), exterior walls and
coverings, vents, detached
structures. All information
in local guidelines
Water supply
points.
Specific local
prescriptions
(plans) for their
characteristics
and distance
from structures
Guidance on Design and Construction of the Built Environment
Table 2
continued
Jurisdiction/Type
of provision and
public
Type of Hazard
Definition Buffer zone (vegetation) Influence of terrain?
Prescriptions for
structural elements (list) Prescriptions for utilities
Italy (including
Regions) Stan-
dards/Guideli-
nes (regional)
dedicated to
planners
Definition of
interfaces and
four danger
zones (regional
guidelines)
based on sev-
eral characteris-
tics
Two areas of defensible space
(within 10 m and 10–20 m
of the structure), with dif-
ferent indications about
fuel removal, reduction
and substitution, clearance
between vegetation and
maintenance (regional
guidelines). Different pre-
scriptions for defensible
space in the two regions
considered
Factors addressed:
slopes. Extension of
the defensible space
for high slopes (re-
gional guidelines)
Building construction,
change of land use des-
tination, planting of
new vegetation not
allowed for defined
periods in recently fire-
prone areas.
Not specifically addressed
Canada (including
Canadian pro-
vinces) Guideli-
nes, dedicated
to both commu-
nities and home-
owners
Guidance on fire-
fighters: cooper-
ation, training
and trust-build-
ing principles
(agencies/practi-
tioners)
Wildfire Preparedness Guide
(for protecting values at
risk, dedicated to emer-
gency response personnel);
Wildfire Mitigation Strat-
egy (activities for reducing
the impact of wildfires on
values). Other plans: Sprin-
kler Deployment,Municipal
Development,Municipal
Emergency Management
plans, Land Use Bylaws
Buildings, in particular
for combustible
materials (debris, fire-
wood, propane tanks,
burning barrels, fire
pits) and spark
arresters
Fire history affects hazard
definition and assess-
ment
Definition of adequate
access, road standards
and fire service access
routes
Fire Technology 2019
Table 2
continued
Jurisdiction/Type of
provision and
public
Prescriptions for
firefighters Type of plans required
Fire protection measures
provided
Influence of
environ-
ment/fire his-
tory?
Prescriptions for
access
United States Stan-
dards
Specific provisions
for planning,
managing and
assessing firefight-
ing activities in
case of wildfire
disasters
Fire protection plan, Mitiga-
tion plan (including fuel
modification provisions),
and other plans concerning:
fire lanes, winter access
maintenance, multi-agency
operation (not specific to
wildfires), minimum water
supply, dry hydrant, fire
response, preparedness, inci-
dent action, containment and
control, construction
Measures for water sources:
connections for sprinkler
systems, fire and dry
hydrants. Measures for
buildings: sprinklers, stand-
pipe systems, fire extinguish-
ers, spark arresters and
provisions for storing com-
bustible materials
Fire history con-
sidered in the
ignition sour-
ces assessment
Provisions about the
number of access
routes, depending on
households. Detailed
standards for main
roads, dead-end roads,
fire lanes, parking, road
signs and markers.
Geometric and
construction
requirements.
Vegetation clearing on
roadsides
United States (Col-
orado, Florida,
Oregon) Guideli-
nes, dedicated to
communities, plan-
ners and home-
owners
Not specifically
addressed
General guidelines on devel-
oping mitigation and
response plans (Florida)
and how to adhere to the
Firewise Communities Pro-
gram
Some generic measures for
water sources (helicopter dip
spots, Florida) and build-
ings (sprinklers, spark
arresters, combustible mate-
rials)
Influence of
some environ-
mental factors
on the hazard
and risk
assessment
Influence of some access
factors on the hazard
and risk assessment.
Specific provisions for
driveways and street
markers (mainly
Florida)
United States (Cali-
fornia) Standards/
Guidelines (for
homeowners)
Not in the specific
WUI part of the
Fire Code
Fire Protection Plan for new
constructions and modifica-
tions
Not in the specific WUI part
of the Fire Code
Influence of
environmental
factors on
defining
hazard zones
Not in the specific WUI
part of the Fire Code
Guidance on Design and Construction of the Built Environment
Table 2
continued
Jurisdiction/
Type of
provision
and public
Prescriptions
for firefighters Type of plans required
Fire protection
measures provided
Influence of environment/
fire history? Prescriptions for access
Australia
Standards
Not specifically
addressed
Local guidelines requiring
protection plans
Some fire protection
measures in local
guidelines (for water
sources and private
shelters)
Influence of some environ-
mental factors on defining
hazard zones
Provisions for main, access
roads and fire trails in local
guidelines (including e.g.
2 m of vegetation clearing
on each side and 4 m high)
New Zealand
Standards
Some qualitative
indications
Provisions about evacuation
plans (and related struc-
tures)
Some indications about
combustible materials
and warning systems
(mainly in the addi-
tional guidelines)
Not specifically addressed Some provisions/guidelines for
markings, general provi-
sions for access from roads
to buildings
International
Standards
Not specifically
addressed
Fire protection plan, Site plan
including specific informa-
tion about wildfire expo-
sure, vegetation
management plan (not
mandatory)
Measures for protecting
water sources, sprin-
klers, spark arresters
and for storing com-
bustible materials
Influence of environmental
factors and fire history on
defining wildfire risk, haz-
ard zones, and fire protec-
tion plans (fire history)
Specific prescriptions for
standards of main roads
and driveways, road signs
and markers
European
Union
Standards
Not specifically
addressed
Fire protection plan and a
scheme for promoting,
improving, and evaluating
forest risk data
Not specifically addres-
sed
Fire history (previous
5 years) considered in
defining fire protection
plans for high-risk areas
Not specifically addressed
France (in-
cluding
local
authorities)
Standards
Storage of mate-
rial for fire-
fighting in
designated pla-
ces in the haz-
ard zones
Local Plan for preventing pre-
dictable natural risk forest
fire (including the definition
of hazard zones and related
prescriptions)
Not specifically addres-
sed
Influence of environmental
factors and fire history on
defining hazard zones
Clearing of roadsides in the
hazard zones (up to 20 m
both sides, 10 m for
driveways). Specific
prescriptions about
geometric features in local
plans
Fire Technology 2019
Table 2
continued
Jurisdiction/Type of
provision and pub-
lic
Prescriptions for
firefighters Type of plans required
Fire protection
measures provided
Influence of
environ-
ment/fire his-
tory?
Prescriptions
for access
Italy (including
Regions) Stan-
dards/Guidelines
(regional) dedicated
to planners
Definition of some pos-
sible firefighting activ-
ities in case of
interface fires (re-
gional plan)
Regional plan for forecasting, prevent-
ing and fighting wildfires, including a
list of requirements, recommenda-
tions,, evacuation plans (regional)
Some qualitative mea-
sures about com-
bustible materials and
private shelters (re-
gional plan)
Not specifically
addressed
Some qualitative
and more
specific
requirements
for main road
standards
(regional
plan and
guidelines)
Guidance on Design and Construction of the Built Environment
standards/guidelines reviewed, except for EU Standards. The same is valid for the
prescriptions/guidelines about clearance between vegetation and structures and/or
between different types of vegetation; and the prescriptions/guidelines about main-
tenance (pruning, removal of dead vegetation, etc.). Specific quantitative details
concerning the defensible space are provided in Table 2. Local French provisions
[37] on clearance are worthy of note due to the high level of details. For example,
clearance between vegetation (trees and bushes) and other plants (e.g., vertical dis-
tance between the lower boundary of a crown tree and the top of a bush should
be high 2 times the height of the bush, but anyway >2 m); structures (e.g.,
trees should be at least 3 m from structures); power lines (e.g., high voltage lines
1000 V should be at least three meters from the vegetation) are mentioned.
4.2.2. Topography/Terrain Topographic and terrain factors are considered in all
the groups of documents reviewed, except for EU and New Zealand standards/
guidelines. Those factors can affect the definition of risk areas and/or the defensi-
ble space for standards/guidelines belonging to USA, California, Australia,
France, Italy, and the IWUIC. In Canadian guidelines, the relative position
between houses and slopes is considered. Specific quantitative details concerning
the influence of topography/terrain are provided in Table 2.
4.3. Building Construction
Provisions/recommendations about the building materials and structures to be
adopted in wildfire-prone areas are provided in all the standards/guidelines
reviewed, except for the EU Standards. The level of detail of the provisions/guide-
lines is extremely variable across the different locations/jurisdictions considered, as
reported in Table 2.
4.3.1. General Requirements General requirements about construction materials to
be used in hazard zones and ignition resistance of building materials have been
found in all standards/guidelines except for the EU, French and Canadian guide-
lines. Some generic requirements have been found in the Californian and Italian
standards. A detailed definition of ignition resistance classes can be found in the
standards reviewed from Australia (Fire Resistance Level -FRL- determined
through three ratings obtained from a standard test representing: structural ade-
quacy, integrity and insulation) and International standards (three classes of igni-
tion resistance -IR- obtained as a combination of three fire hazard severity classes,
and of classes of conformity of water supply and defensible space to standards). A
detailed requirements of ignition resistance for materials can be found in stan-
dards/guidelines reviewed from USA, Australia and the IWUIC code, with refer-
ence to results of standard tests. The prescribed minimum separation distance
between buildings varies between 4.5 m and 15.2 m (US standard, depending on
building height, type, presence of sprinklers), 9 m (Canadian guidelines, for high-
density dwellings), and 10 m [5].
Fire Technology 2019
4.3.2. Roof Requirements concerning roofs have been found in all standards/
guidelines reviewed except for New Zealand, EU and Italy. Provisions about roof
covering, eaves and gutters are given in all those standards/guidelines (except for
gutters in Canadian guidelines). Provisions about valley flashing (i.e., material to
be used, non-combustibility, thickness, etc.) are given only in the Australian, Cali-
fornian and International standards/guidelines. Generally, provisions concerning
roof covering and eaves consist in defining materials to be used and their ignition
resistance.
4.3.3. Walls and Other External Coverings Requirements concerning walls and
other external coverings have been found in all standards/guidelines reviewed
except for EU and Italy. Provisions about exterior walls have been given in all
those standards/guidelines. Provisions about wall coverings have only been found
in the French and Californian standards/guidelines reviewed. Generally, provisions
concerning exterior walls consist in defining materials to be used and their ignition
resistance.
4.3.4. Windows, External Doors and Vents Requirements concerning windows,
external doors and vents have been found in all standards/guidelines reviewed
except for New Zealand, EU and Italy. Provisions about exterior glazing, external
doors and vents have been given in all those standards/guidelines (except for exte-
rior glazing and doors in French documents reviewed, and Canada for doors).
Generally, provisions concerning glazing and doors consist of defining materials
to be used and their ignition resistance. Prescriptions/guidelines concerning vents
and other openings are related to their corrosion-resistance and to the presence of
openings in the metal grid.
4.3.5. Decks and Detachments Requirements concerning decks and detachments
have been found in all standards/guidelines reviewed except for New Zealand, EU
and Italy. Provisions about decks and other attachments have been found in all
those standards/guidelines (except for France). Provisions about detached struc-
tures have been given in the documents reviewed for USA, Australia, Interna-
tional, France. Generally, provisions concerning decks and other attachments
consist in defining materials to be used and their ignition resistance. Provisions/
guidelines concerning detachments include also other information such as the dis-
tance from the main structures (i.e., minimum 9 m in US standards, 6 m in Aus-
tralian standards, except if accessory structures comply with requirements for
main structures or they are separated through appropriate walls, 50 feet/15.24 m
in the IWUIC, otherwise accessory structures should mostly comply with same
requirements for exterior walls).
4.3.6. Floor and Interior Structures Requirements concerning floors and interior
structures have been found in all standards/guidelines reviewed except for EU,
France and Italy. Provisions regarding under-floors have been found in all those
documents, except for New Zealand. Provisions about floors have been found
only in Australian and New Zealand standards, while provisions about other inte-
Guidance on Design and Construction of the Built Environment
rior structures only in New Zealand standards (where fire-cells are defined: inside
spaces, enclosed by a combination of fire separations, external walls, roofs and
floors). Generally, provisions concerning floors consist in defining materials to be
used and their ignition resistance.
4.4. Resources
Provisions/recommendations about resources in wildfire-prone areas have been
provided in all the standards/guidelines reviewed, except for the EU, Californian
and Italian standards. The level of detail of the provisions/guidelines varies
between the different jurisdictions/areas considered, as reported in the summariz-
ing Table 2. For the United States, Australia and in the IWUIC, the provisions
are more quantitative and detailed.
4.4.1. Utilities The category ‘‘utilities’’ includes requirements mainly concerning
water supply, but also other means such as evacuation routes (for New Zealand).
Requirements concerning water supply have been found in all standards/guidelines
reviewed except for California, EU and Italian Standards/Guidelines. Generally,
provisions/guidelines concerning supply level, water sources, access for water sour-
ces and hydrants are given for water supply. A very detailed definition of water
supply was found in the US standards, as a function of the total volume of the
structure, the occupancy hazard and construction classification, and the hazard
exposure. The minimum level of water delivery rate to the fire scene is determined
as well (to be provided at the same level for at least 1–2 h at 138 kPa), based on
the water supply level. According to US standards, water sources should be main-
tained, accessible and they should guarantee the same capacity and delivery on a
1-year basis. Specific standards for fire hydrants are provided concerning mark-
ings, location, spacing, pipe diameters, dead-end pipes. Standards are provided for
dry hydrants for non-pressurized water supply as well. Other detailed definitions
have been found in the IWUIC and the Australian guidelines. In the IWUIC, the
minimum water supply for new buildings, not equipped with sprinkler systems in
the WUI area, is set to 63–95 l/s for 30 min-2 h, depending on floor area and the
number of families. The water source should be £305 m far from the building
and the natural water sources should guarantee a minimum water supply, being
equipped with hydrant/draft site.
4.4.2. Firefighters Requirements concerning firefighters have been found in stan-
dards/guidelines from Canada, USA, New Zealand, France and Italy (in the Ital-
ian case, some information was found in regional guidelines). In this case, the
provisions/guidelines found are heterogenous and scarce. For example, in Cana-
dian guidelines, the cooperation between partner agencies of fire protection, train-
ing and exercises are encouraged. In the US standards, the required number of
firefighters are assessed, and the safety requirements and procedures to be fol-
lowed in case of incident are described.
Fire Technology 2019
4.4.3. Planning Requirements concerning planning have been found in all stan-
dards/guidelines reviewed. In particular, provisions about fire protection plans
have been found in all the other documents reviewed, except for New Zealand.
Some requirements concerning other types of plans different than fire protection
plans, which may be of interest for WUI fire safety (such as emergency or devel-
opment plans), are mentioned in all the other documents, except for California
and France. More detailed provisions about required plans have been found in
the US standards/guidelines and the Canadian guidelines reviewed. Further details
concerning plans provided in all the documents reviewed are reported in Table 2.
The Canadian guidelines include plans for high wildfire hazard and risk zones: the
Wildfire Preparedness Guide, the Wildfire Mitigation Strategy. Other plans sug-
gested are the sprinkler development and the municipal development plans, the
municipal emergency management program guide and the land use bylaws. The
US standards require a mitigation plan including prevention activities, fuel modifi-
cations, hazard mitigation for structures, public information, infrastructures.
Other plans required by the US Standards are: a fire lane, wintertime access main-
tenance, multi-agency operational, minimum water supply, dry hydrant, fire
response, preparedness, incident action, containment and control, construction
plans.
4.4.4. Outreach The outreach in standards/guidelines is variable, depending on
the type of document reviewed. Generally, guidelines for creating defensible space,
clear and maintain vegetation or similar activities are included in documents
intended for use by the general public (e.g., Canadian or Californian guidelines).
Some regulations can be implemented at a local level with modifications allowed
(such as the IWUIC Code which can be adopted by other jurisdictions).
4.5. Fire Protection Measures
Provisions/recommendations about fire protection measures to be adopted in wild-
fire-prone areas are provided in all the standards/guidelines reviewed, concerning
measures for water sources and buildings, except for the EU and French Stan-
dards. The level of detail of the provisions/guidelines varies between the different
areas considered. In fact, the level of detail of Canadian, Californian and Italian
standards is limited. The most significant measures are reported in the sections
below and summarized in Table 2.
4.5.1. Measures for Water Sources Requirements concerning measures for water
sources have been found only in US, Australian and International standards/
guidelines reviewed. Generally, provisions consisted of defining clearing, defensible
space, materials, protection and connections for water sources. The American pro-
visions/guidelines reviewed are the most detailed. The provisions require that: the
fire department connections for sprinkler systems should be <100 feet (30.5 m)
far from fire hydrant; the space around fire hydrants protected by barriers should
be cleared. Protections are required for dry hydrants as well.
Guidance on Design and Construction of the Built Environment
4.5.2. Measures for Buildings Requirements concerning measures for buildings
have been found in all standards/guidelines reviewed except for EU and France.
Only some provisions/guidelines have been found in Californian standard (for
combustible materials), in Australian standard (for private shelters), and in Italian
local standards (for combustible materials and private shelters). Generally, provi-
sions/guidelines concerning sprinklers, protection and warning systems consist in
setting the conditions where they are needed and the tools needed. For example,
the US Standards require that all residential buildings and all the buildings
with >2 stories or >30 feet (9.1 m) tall (with some exceptions) should be pro-
vided with automated sprinkler systems. Standpipe systems with specific fire
department connections (at indicated distances) and fire extinguishers should be
installed in new buildings and other specific buildings in case of available munici-
pal water systems. Automatic fire warning systems, with different prescriptions for
residential and non-residential structures should be installed as well. Combustible
materials, unprotected heat and flame sources, inappropriate storage of liquefied
petroleum gas should be avoided within 30 feet (about 9 m) of the structure.
4.6. Environment
Provisions/indications about the environmental factors related to wildfire-prone
areas are provided only in some of the standards/guidelines reviewed: American
Standards and Guidelines (only for weather in California), Australian standard
(only for weather), IWUIC Code, French provisions and guidelines, EU Regula-
tions (only for fire history), as summarized in Table 2. Environmental factors are
consistently used for risk assessments and definition of hazard zones.
4.6.1. Weather Weather is mentioned in all standards/guidelines reviewed in the
procedures for wildfire risk and hazard definition or for developing fire protection
plans (France), except for Canada, New Zealand, EU and Italy. The weather fac-
tors generally considered are: wind, humidity, temperature, precipitation and fuel-
related features (e.g., fine fuel moisture).
4.6.2. Fire History Requirements concerning fire history have been found in all
standards/guidelines reviewed except for California, Australia, New Zealand and
Italy. Fire history factors in the standards/guidelines reviewed have been consid-
ered mainly for defining risk areas or severity zones; or for developing fire protec-
tion plans (International standard).
4.7. Access
Provisions/recommendations regarding accessibility and road standards to be
adopted in wildfire-prone areas are provided in all the standards/guidelines
reviewed, except for the EU Regulations and in the section of the California Fire
Code concerning WUI fires. The level of detail of the provisions/guidelines varies
between the different areas considered, as summarized in Table 2. Provisions con-
cerning type/number of access roads, road standards, markings (only in US, New
Zealand and International standards) and vegetation clearing between roads and
Fire Technology 2019
vegetation (only in US, Australia and French standard/guidelines). The US stan-
dards reviewed are the most detailed with respect to access requirements. Gener-
ally, the types of access roads/routes are defined in the appropriate section of
standards/guidelines. Access routes for emergency vehicles, fire service, and public
are considered. In the US standard, the number of access routes required is set,
depending on the number of households or parking spaces (e.g., 3 for >600
households or >3000 parking spaces in case of mixed areas). Provisions/guideli-
nes concerning road standards include geometric standards, pavements, turn-
arounds, clearance, loads. In particular, in the US Standards requirements
concerning materials, minimum clear width, minimum vertical clearance, mini-
mum curve radius, intersection control, traffic calming measures, hydraulic calcu-
lations for bridges and culverts, grades, emergency pull-offs, maximum angles of
approach and departure are considered. Generally, provisions/guidelines about
markings concern visibility, location and text on markings.
Standards/guidelines are normally not provided with requirements for vegeta-
tion clearing around roads. An example of these requirements is reported in the
French standard reviewed: both sides of public roads in hazard zones should be
cleared within 20 m, and driveways of structures <200 m from the forest, should
be cleared from vegetation for a distance of 10 m.
5. Discussion
In this section, we identify the common approaches found and the deficiencies in
the reviewed standards/guidelines. A graphical representation of the variables
which can be consistently/partially found or which are neglected in the standards/
guidelines reviewed (see Table 1) is presented in Fig. 3. This figure is simplified
given the need to represent several levels of information in a single summary.
Generally, provisions/guidelines vary between different jurisdictions in the quanti-
tative assessments of the various variables considered, and in the methods used
for defining measures and indicators. However, some common approaches have
been found.
At a general level, the standards reviewed seem to put a great emphasis on the
assessment of both risk and hazard as well as the use of risk mitigation measures
concerning vegetation. It should be noted that fire risk mitigation measures (e.g.
actions on vegetation) are considered in this context within the requirements on
buffer zone and type of plans required. In contrast fire protection measures are
intended as those measures limiting the impact or reducing the fire (e.g. sprinklers,
etc.). The definitions of wildfire risk and hazard levels in the standards/guidelines
reviewed are mainly based on topographic, vegetation and environmental factors
(except for New Zealand, in which buildings are classified based on risk to their
occupants in the event of fires). Methods for identifying and classifying severity in
WUI areas are present in the standards/guidelines reviewed, with different level of
refinement. This may include a sum of partial ratings based on different factors
(e.g., vegetation types, slopes, distance between structures and vegetation) or they
can be based on fire history, such as the case of the EU Guidelines. In this con-
Guidance on Design and Construction of the Built Environment
text, weather is often considered for defining risk areas or severity zones. The con-
sideration of fire history for defining risk areas or severity zones was retrieved in
some groups of standards/guidelines as well. The concept of defensible space is
present in the standards/guidelines reviewed except in the EU regulations. The
same is valid for prescriptions/guidelines for vegetation clearance and distance
between vegetation and other vegetation/structures; and for the influence of topo-
graphic and terrain factors (except for EU and New Zealand). Those factors gen-
erally affect the definition of risk areas (and/or defensible space), or the position
between houses and slopes (Canada). Overall, it seems evident that risk/hazard
assessment and mitigation measures appear as key requirements to be included in
a WUI fire code and they were addressed (although with slightly different approa-
ches) in all standards reviewed.
Requirements concerning building construction seem to be less consistent
among standards and provisions. General requirements for construction materials
and ignition resistance have been found in most of the standards/guidelines
reviewed (except for EU, France, Canada), although in some instances they are
only broadly outlined (e.g., in the Californian and Italian standards) rather than
Figure 3. Simplified graphical representation of the variables and
provisions/recommendations considered in the standards/guidelines
reviewed from different countries. Legend: black if all second-level
sub-categories are considered in detail for the relevant macro-
category listed on the left of the figure, dark grey if all second-level
sub-categories are considered but some of them are less detailed,
light grey if at least one second-level sub-category is missing, white if
only one second-level sub-category is adequately considered, white
with bold contour if the first-level macro-category is neglected.
Fire Technology 2019
treated in detail. Both the type of construction materials and elements taken into
consideration as well as the provisions/requirements provided greatly vary among
standards. This seems to indicate a lower level of maturity in the understanding of
the solutions needed to address this issue and highlight the need for further
research in addressing standardized methods to provide guidance. It should also
be noted that construction materials and processes may vary across countries
(e.g., some countries may have long-standing tradition towards a specific type of
material rather than another), thus any international guidelines should be
reviewed and made applicable to the local building materials. For example, expli-
cit references to fire-retardant treated woods for constructions mentioned in the
IWUIC code were also found only in US and Canadian standards/guidelines.
At a general level, the requirements concerning resources also greatly vary
among standards. Great emphasis is placed on requirements concerning water
supply (supply level, water sources, access, hydrants) as those have been found in
all standards/guidelines reviewed (except for California, EU, Italy). This is also
linked to the actual definitions of water supply provided. Emphasis is placed also
on fire protection plans, although with varying level of details. Commonly dis-
cussed variables in fire protection plans are weather and fire history. Similarly, the
provisions concerning outreach are variable, depending on the type of document
reviewed. Generally, guidelines for creating defensible space, clear and maintain
vegetation are dedicated to the general public (homeowners, communities and/or
planners). Some regulations can be implemented at a local level with modifications
allowed. Most standards also include requirements concerning measures for build-
ings (sprinklers, protection and warning systems), although those are presented
with varying levels of refinement.
Requirements concerning access have been found in most of the standards/
guidelines reviewed (except for California, retrievable in the general Fire Code,
and EU). Those generally discuss the type/number of access roads, and road stan-
dards (geometry, pavements, turnarounds, clearance, loads).
A set of deficiencies can be highlighted in groups of standards/guidelines. In
fact, the requirements concerning resources (firefighters and other types of utili-
ties), fire protection measures (especially for water sources) are often missing or
limited in many of the standards/guidelines reviewed. In particular, requirements
concerning resources (firefighters) have been found only in standards/guidelines
from Canada, USA, New Zealand, France and Italy. Note that other types of
utilities, such as evacuation routes, have only been found in New Zealand stan-
dards. Requirements concerning measures for water sources (clearing, defensible
space, materials, protection, connections for water sources) have only been found
in the USA, Australian and International standards/guidelines reviewed.
For other variables, the level of detail of some groups of standards/guidelines is
limited to high-level provisions (i.e., only for some sub-categories considered in
Fig. 1). This is particularly the case for requirements for building construction
and road access. While all the standards/guidelines reviewed make provisions for
specific building elements, some categories of parameters reviewed are neglected in
some cases. For example, standards from Italy and EU do not consider walls,
windows and other openings, decks/detachments, floors/under-floors. Those from
Guidance on Design and Construction of the Built Environment
New Zealand do not consider windows and other openings and decks/detach-
ments. Moreover, among the third-level sub-variables listed in the methods section
of this paper, wall coverings are considered only in the French and Californian
standards/guidelines reviewed. Provisions about floors (by defining materials to be
used and their ignition resistance) have been found only in Australian and New
Zealand standards (including provisions about other interior structures). More-
over, while most of standards/guidelines include general requirements for roads
(i.e., road standards), some detailed variables have not been considered, such as
road markings. The latter provisions (considering visibility, location, text of mark-
ings) have only been found in the USA, International and New Zealand stan-
dards.
Another limitation was found in relation to how environmental factors (weather
and fire history) are taken into account for defining risk areas or plans. In partic-
ular, weather is only considered in the USA, Australian, French and International
standards/guidelines reviewed. In contrast, fire history is only considered in the
USA, Canadian, French, EU and International standards/guidelines reviewed.
This seems to indicate that there is still not an international consensus on the
variables to be considered during the definition of risk areas. Further research
should explore if these differences in the approaches are mostly driven by the
choice of the regulators or are the result of the local/regional conditions.
6. Conclusions
This paper presents a review a selection of international standards and guidelines
concerning fires in the Wildland-Urban Interface areas. A template was developed
and used to consistently present the information regarding hazard, land, building
construction, utilities, fire protection measures, environment and access. The main
objective was to document the provisions and enable a comparison between the
regulations/guidance examined, in order to identify the underlying common
threads and the main deficiencies. This comparison is summarized in Table 2and
then discussed.
In some locations, provisions for WUI fires are included in general Fire Codes
(e.g., California); elsewhere, requirements are implemented at a local level (e.g.,
France and Italy). Some countries have standards specifically dedicated to the
issue of WUI fires (e.g., USA and Australia).
Based on the review conducted, the following main common themes can be
highlighted: the definition of WUI risk areas and severity classes for these areas,
the influence of land factors including the definition of defensible space, recom-
mendations/requirements for building construction components/materials and
road access. Whereas, the following main deficiencies can be highlighted among
others: the requirements/recommendations about resources, fire protection mea-
sures (for water sources), and the consideration of environmental factors are
scarce or absent in several documents reviewed. Moreover, differences in the
methods for defining severity classes and in the requirements for buildings have
been particularly highlighted.
Fire Technology 2019
The recommendations and requirements identified from the standards and
guidelines considered may be useful for the development or revision of future
standards/guidelines concerning WUI fires prevention, protection, planning and
management. This might become increasingly important as the problem evolves,
especially in those jurisdictions where WUI was previously not a concern, and
therefore, there is no history of adopting regulatory guidance in this domain.
Moreover, the identification of common deficiencies in the existing standards and
guidelines reviewed may help in setting goals for future research and/or to transfer
existing research into practice. In this sense, results from the presented review may
be of use for both researchers and practitioners.
Acknowledgements
Open access funding provided by Lund University. Funding was provided by
National Research Council of Canada (Grant No. Design Guidance on wildland
urban interface (WUI) fires, Contract No. 892587). The authors wish to thank
Chunyun Ma for her comments on the article prior publication.
Open Access
This article is distributed under the terms of the Creative Commons Attribution
4.0 International License (http://creativecommons.org/licenses/by/4.0/), which per-
mits unrestricted use, distribution, and reproduction in any medium, provided you
give appropriate credit to the original author(s) and the source, provide a link to
the Creative Commons license, and indicate if changes were made.
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Most wildland-urban interface (WUI) areas in the world will face severe wildfire risks due to climate warming and rapid urbanization. Mitigating the damage caused by WUI fires has become a worthy topic for fire researchers and managers. In recent years, WUI fires have occurred in China and caused significant property damage, and even threatened some communities. To understand the research status and promote WUI fire management in China, this paper collected all research articles published from 1991 to 2021 on the topic. We performed a bibliometric analysis for the year, author, institution, country, journal, and keywords. The results show that 717 research articles were published in the field of WUI fire management over this period. The annual number of published articles has exceeded 40 since 2013 and is expected to reach 80 in 2022. The United States has the most active research institutions and groups working in the field of WUI fire management, with 507 published articles over the past three decades, accounting for 70.7% of the total articles. Ninety percent of the top ten authors or institutions come from the United States. The International Journal of Wildland Fire, an important journal in the field of wildfire, has published 96 research articles on the topic over the same period, accounting for 13.4% of the total. Research focused on WUI fire occurrence and its influencing factors, fire behavior simulation, fire risk assessment, and fuel treatment. Future research on WUI fire management will explore the impacts of climate change on the WUI fire regime, improve risk assessment methods, and enhance fire mitigation strategies.
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The 2013 Linksview fire destroyed 195 houses in the Blue Mountains of NSW in 2013. In this study, we examined the role of construction codes on the impact of houses exposed to the fire, by extracting details of construction year and standard for 466 houses from the archives of the Blue Mountains City Council. Houses built to standards imposed from 2000 fared better than previous standards, though post-2000 houses assessed at Flame Zone level were vulnerable. Construction year was also a good predictor of impact with pre-1990 houses suffering more than twice the level of impact as post-2000 houses. Older houses tended to have more vegetation within 10 m of the house, and this probably partly explains why they are more vulnerable. Year of modification (i.e. additions to a house) was a worse predictor than year of construction suggesting that imposing strict standards on modifications does not change the vulnerability of the whole house. We briefly discuss four policy implications of the study: Construction standards are clearly useful; Houses in the Flame Zone are vulnerable; Lack of maintenance is a problem; and Construction Standards for building modifications do not improve the resilience of the house.
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Significance When houses are built close to forests or other types of natural vegetation, they pose two problems related to wildfires. First, there will be more wildfires due to human ignitions. Second, wildfires that occur will pose a greater risk to lives and homes, they will be hard to fight, and letting natural fires burn becomes impossible. We examined the number of houses that have been built since 1990 in the United States in or near natural vegetation, in an area known as the wildland-urban interface (WUI), and found that a large number of houses have been built there. Approximately one in three houses and one in ten hectares are now in the WUI. These WUI growth trends will exacerbate wildfire problems in the future.
Technical Report
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The present work describes a novel framework for modelling wildfire urban evacuations. The framework is based on multi-physics simulations that can quantify the evacuation performance. The work argues that an integrated approached requires considering and integrating all three important components of WUI evacuation, namely: fire spread, pedestrian movement, and traffic movement. The report includes a systematic review of each model component, and the key features needed for the integration into a comprehensive toolkit.
Thesis
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Although wildland fires are a beneficial ecosystem process, they can also cause destruction to human-built structures and infrastructure, as evidenced by disasters such as the Fort McMurray fire in 2016 and the Slave Lake fires in 2011. This type of destruction occurs in the “wildland-urban interface” (WUI), which are areas where homes or other burnable community structures meet with or are interspersed within wildland fuels. In order to mitigate destructive WUI fires, basic information such as the location of these areas is required. Unfortunately, Canada does not have a national scale, high-resolution WUI map for use in research or fire management, which hinders our ability to study fires in WUI areas. Therefore, this study focused on defining and mapping the WUI for the national area of Canada, and analysed their spatial distribution and relationships with fuels, structures, and fires. Furthermore, two additional national maps were produced and analysed: a “wildland-industrial interface” (WII) map and an “infrastructure interface” map. These additional maps focus on the interface of wildland fuels with industrial structures (e.g. oil and gas or mining structures) for the WII, or with infrastructure values (e.g. transmission lines, railways, or roads) for the infrastructure interface. This study presents the first maps of these two interface types for anywhere in the world. Industrial structures and infrastructure are not traditionally defined as part of the WUI, but may require protection from fires and are important emerging issues. All three interface types (WUI, WII, and infrastructure interface) were defined as areas of wildland fuels which are within a variable-width buffer (maximum distance: 2400 m) from potentially vulnerable structures or infrastructure. Nationally, it was found that Canada has 32.3 million ha of WUI (3.8% of total national land area), 10.5 million ha of WII (1.2%), and 109.8 million ha of infrastructure interface (13.0%). Interface areas are typically most dense in the southern portion of the country (with the exception of the prairies and southern Ontario). Provinces with the largest amounts of interface include: Quebec, Ontario, Alberta, and British Columbia. However, the eastern provinces of Nova Scotia, New Brunswick, and Prince Edward Island have the highest densities of interface (interface as % of land area). Interface areas were also found to have higher than average hazardous fuel cover types, but lower than average area burned by wildfire. The results of this study, and in particular the interface maps, provide a baseline for future research, including fire risk mapping, change detection, and future predictions of interface areas. The maps produced in this study also have a wide variety of practical applications, including various topics in wildfire mitigation (e.g. FireSmart and industrial fire regulations), long-term planning (e.g. city planning and insurance), and wildfire decision support (e.g. fire prioritization and risk modelling). Citation: Johnston, Lynn M. (2016) Mapping Canadian Wildland Fire Interface Areas. MSc thesis. Department of Renewable Resources. University of Alberta. 161 pgs. doi: 10.7939/R3GT5FR9Z
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An analysis was undertaken of wildfire records in New Zealand from 1991-2007 to determine trends in fire occurrence, area burned and fire causes. Each year an average of 3,033 wildfires burned 5,865 ha. The total area burned was made up of 54% grasslands, 40% scrublands and 6% forests. Unknown and miscellaneous causes accounted for almost half (46%) of the total number of fires and 31% of the area burned. The most significant known cause of wildfires was land clearing (escapes from burnoffs), accounting for 20% of wildfires and 47% of the area burned. Natural causes (lightning) made up only 0.1% of both the number of wildfires and area burned. The South Island accounted for 34% of wildfires and 75% of the total area burned, and Northland and the Eastern North Island accounted for 60% of the remaining area burned in the North Island. There was also a significant increase in the number of wildfires reported annually, from around 1200 in 1991 to more than 4000 in 2007. This is the most detailed and comprehensive analysis of wildfire occurrence undertaken in New Zealand to date, and the findings have relevance for development of wildfire reduction and readiness strategies.
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Over recent decades, Land Use and Cover Change (LUCC) trends in many regions of Europe have reconfigured the landscape structures around many urban areas. In these areas, the proximity to landscape elements with high forest fuels has increased the fire risk to people and property. These Wildland-Urban Interface areas (WUI) can be defined as landscapes where anthropogenic urban land use and forest fuel mass come into contact. Mapping their extent is needed to prioritize fire risk control and inform local forest fire risk management strategies. This study proposes a method to map the extent and spatial patterns of the European WUI areas at continental scale. Using the European map of WUI areas, the hypothesis is tested that the distance from the nearest WUI area is related to the forest fire probability. Statistical relationships between the distance from the nearest WUI area, and large forest fire incidents from satellite remote sensing were subsequently modelled by logistic regression analysis. The first European scale map of the WUI extent and locations is presented. Country-specific positive and negative relationships of large fires and the proximity to the nearest WUI area are found. A regional-scale analysis shows a strong influence of the WUI zones on large fires in parts of the Mediterranean regions. Results indicate that the probability of large burned surfaces increases with diminishing WUI distance in touristic regions like Sardinia, Provence-Alpes-Côte d'Azur, or in regions with a strong peri-urban component as Catalunya, Comunidad de Madrid, Comunidad Valenciana. For the above regions, probability curves of large burned surfaces show statistical relationships (ROC value > 0.5) inside a 5000 m buffer of the nearest WUI. Wise land management can provide a valuable ecosystem service of fire risk reduction that is currently not explicitly included in ecosystem service valuations. The results re-emphasise the importance of including this ecosystem service in landscape valuations to account for the significant landscape function of reducing the risk of catastrophic large fires.
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Climate strongly influences global wildfire activity, and recent wildfire surges may signal fire weather-induced pyrogeographic shifts. Here we use three daily global climate data sets and three fire danger indices to develop a simple annual metric of fire weather season length, and map spatio-temporal trends from 1979 to 2013. We show that fire weather seasons have lengthened across 29.6 million km2 (25.3%) of the Earth’s vegetated surface, resulting in an 18.7% increase in global mean fire weather season length. We also show a doubling (108.1% increase) of global burnable area affected by long fire weather seasons (>1.0 σ above the historical mean) and an increased global frequency of long fire weather seasons across 62.4 million km2 (53.4%) during the second half of the study period. If these fire weather changes are coupled with ignition sources and available fuel, they could markedly impact global ecosystems, societies, economies and climate.
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Fire evacuations at wildland-urban interfaces (WUI) pose a serious challenge to the emergency services, and are a global issue affecting thousands of communities around the world. This paper presents a multi-physics framework for the simulation of evacuation in WUI wildfire incidents, including three main modelling layers: wildfire, pedestrians, and traffic. Currently, these layers have been mostly modelled in isolation and there is no comprehensive model which accounts for their integration. The key features needed for system integration are identified, namely: consistent level of refinement of each layer (i.e. spatial and temporal scales) and their application (e.g. evacuation planning or emergency response), and complete data exchange. Timelines of WUI fire events are analysed using an approach similar to building fire engineering (available vs. required safe egress times for WUI fires, i.e. WASET/WRSET). The proposed framework allows for a paradigm shift from current wildfire risk assessment and mapping tools towards dynamic fire vulnerability mapping. This is the assessment of spatial and temporal vulnerabilities based on the wildfire threat evolution along with variables related to the infrastructure, population and network characteristics. This framework allows for the integration of the three main modelling layers affecting WUI fire evacuation and aims at improving the safety of WUI communities by minimising the consequences of wildfire evacuations.
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Several traffic modeling tools are currently available for evacuation planning and real-time decision support during emergencies. This paper reviews potential traffic-modeling approaches in the context of wildland-urban interface (WUI) fire-evacuation applications. Existing modeling approaches and features are evaluated pertaining to fire-related, spatial, and demographic factors; intended application (planning or decision support); and temporal issues. This systematic review shows the importance of the following modeling approaches: dynamic modeling structures, considering behavioral variability and route choice; activity-based models for short-notice evacuation planning; and macroscopic traffic simulation for real-time evacuation management. Subsequently, the modeling features of 22 traffic models and applications currently available in practice and the literature are reviewed and matched with the benchmark features identified for WUI fire applications. Based on this review analysis, recommendations are made for developing traffic models specifically applicable to WUI fire evacuation, including possible integrations with wildfire and pedestrian models.
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While the wildland-urban interface (WUI) is not a new concept, fires in WUI communities have rapidly expanded in frequency and severity over the past few decades. The number of structures lost per year has increased significantly, due in part to increased development in rural areas, fuel management policies, and climate change, all of which are projected to increase in the future. This two-part review presents an overview of research on the pathways for fire spread in the WUI. Recent involvement of the fire science community in WUI fire research has led to some great advances in knowledge; however, much work is left to be done. While the general pathways for fire spread in the WUI (radiative, flame, and ember exposure) are known, the exposure conditions generated by surrounding wildland fuels, nearby structures or other system-wide factors, and the subsequent response of WUI structures and communities are not well known or well understood. This first part of the review covers the current state of the WUI and existing knowledge on exposure conditions. Recommendations for future research and development are also presented for each part of the review.