Wildland-urban Interface Research Articles

Fusing Social Media, Remote Sensing, and Fire Dynamics to Track Wildland-Urban Interface Fire

Wildfire is one of the main hazards affecting large areas and causes great damage all over the world, and the rapid development of the wildland-urban interface (WUI) increases the threat of wildfires that have ecological, social, and economic consequences. As one of the most widely used methods for tracking fire, remote sensing can provide valuable information about fires, but it is not always available, and needs to be supplemented by data from other sources. Social media is an emerging but underutilized data source for emergency management, contains a wealth of disaster information, and reflects the public’s real-time witness and feedback to fires. In this paper, we propose a fusion framework of multi-source data analysis, including social media data and remote sensing data, cellphone signaling data, terrain data, and meteorological data to track WUI fires. Using semantic web technology, the framework has been implemented as a Knowledge Base Service and runs on top of WUIFire ontology. WUIFire ontology represents WUI fire–related knowledge and consists of three modules: system, monitoring, and spread, and tracks wildfires happening in WUIs. It provides a basis for tracking and analyzing a WUI fire by fusing multi-source data. To showcase the utility of our approach in a real-world scenario, we take the fire in the Yaji Mountain Scenic Area, Beijing, China, in 2019 as a case study. With object information identified from remote sensing, fire situation information extracted from Weibo, and fire perimeters constructed through fire spread simulation, a knowledge graph is constructed and an analysis using a semantic query is carried out to realize situational awareness and determine countermeasures. The experimental results demonstrate the benefits of using a semantically improved multi-source data fusion framework for tracking WUI fire.

Machine learning framework for Hazard Extraction and Analysis of Trends (HEAT) in wildfire response

This research proposes a natural language processing enabled risk analysis framework, named Hazard Extraction and Analysis of Trends (HEAT), and applies the framework to the ICS-209-PLUS data set of wildfire incident response forms. The HEAT framework produces safety- and risk-relevant analyses, consisting of: (1) a set of hazards extracted from text data, (2) a primary analysis using hazard-relevant metrics, such as rate and severity, to form an FMEA-style table and risk matrix, (3) a time series analysis of metric trends, and (4) a secondary analysis examining potential predictors for hazards. Results from HEAT provide quantitative risk-relevant information for high-level hazards documented in existing-state operations. Because of the generalizability of the steps and limited data requirements, HEAT can be applied to any dataset containing narrative text, thus providing a framework for data-driven machine learning-enabled quantitative risk analysis across a variety of domains. To demonstrate HEAT in a case study, we apply the framework to the ICS-209-PLUS dataset of wildland fire incident response forms. Hazards identified in wildfire response arise from environmental conditions, the mission, and the wildland urban interface. The resulting risk matrix identifies evacuations as high-risk hazards, while all other identified hazards are medium or serious risk.

On the Growth of Wildland Fires from a Small Ignition Source

ABSTRACT Wildland and Wildland-Urban-Interface (WUI) fires are an important problem that may have major consequences in terms of safety, air quality, and damage to buildings, infrastructure, and the ecosystem. It is expected that with climate change, the wildland fire and WUI fire problem will only intensify. Wildland fires are often initiated by small ignition sources caused either by human intervention (hot metal fragments or burning biomass) or by natural events (lighting or sun heating). Once the wildfire or structural fire has been ignited and grows, it can spread rapidly through ember spotting, where pieces of burning materials are lifted by the plume of the fire and then transported forward by the wind, landing where they can start spot fires downwind. The ignition mechanisms for all of these fires have the common characteristic of a small and localized area of origin, with the subsequent spread of the fire to wider and larger areas. Because of the three-dimensional characteristics of this type of propagating fire, its rate of spread has an initial acceleration phase leading to an equilibrium rate of spread when the fire reaches a certain size, which is referred to as a “line-fire” type of spread. Most of the studies on wildland fire propagation have been conducted with line fires and have been concerned with characterizing the equilibrium rate of spread rather than the initial spread from a small ignition source. In this paper, some of the studies conducted to date on the subject of wildland fire growth from a small ignition source, and the physics supporting the mathematical expressions that are used to describe the growth of the fire are discussed. An attempt is also made to provide support for these works through a more fundamental approach to model the problem.

Firebrand deposition on cubic structures in tandem and parallel arrangements

Spot fires created by wind–carrying firebrands are common in wildland–urban interface (WUI) fires. Firebrand deposition over cubic blocks in tandem and parallel arrangements representing simplified nearby small structures in WUI was studied. The flow turbulence was modeled by large eddy simulation, and the firebrands were simulated in the Lagrangian framework. Both translational and rotational motions, and the thermal degradation of firebrands were accounted for. Various separation distances between blocks and wind speeds were considered. Simulations revealed that the blocks shielded their immediate leeward areas on the ground from firebrand deposition. These areas were distinguished by having no deposited firebrands, and were hence called safe zones, which were nearly in the shape of an isosceles trapezoid. The longer base of the trapezoid coincided with the bottom edge of the block’s leeward face, and the shorter base and the legs of the trapezoid constituted the borderlines of the safe zone. The safe zone length (i.e. the trapezoid height) in the wind direction increased with the wind speeds without a significant sensitivity to the block position in either arrangement. For the blocks in the tandem arrangement with a smaller separation distance and/or higher wind speeds, the safe zone encroaches on the windward face of the downwind block. Therefore, an upwind block also shielded the lower part of the windward face of the downwind block from firebrand deposition in these cases. In none of the simulations, firebrands were deposited on the leeward faces. In all simulations, the firebrands deposited on the lateral faces that were parallel to the wind direction were much less than those on the windward faces.

The global wildland-urban interface.

The wildland-urban interface (WUI) is where buildings and wildland vegetation meet or intermingle1,2. It is where human-environmental conflicts and risks can be concentrated, including the loss of houses and lives to wildfire, habitat loss and fragmentation and the spread of zoonotic diseases3. However, a global analysis of the WUI has been lacking. Here, we present a global map of the 2020 WUI at 10 m resolution using a globally consistent and validated approach based on remote sensing-derived datasets of building area4 and wildland vegetation5. We show that the WUI is a global phenomenon, identify many previously undocumented WUI hotspots and highlight the wide range of population density, land cover types and biomass levels in different parts of the global WUI. The WUI covers only 4.7% of the land surface but is home to nearly half its population (3.5 billion). The WUI is especially widespread in Europe (15% of the land area) and the temperate broadleaf and mixed forests biome (18%). Of all people living near 2003-2020 wildfires (0.4 billion), twothirds have their home in the WUI, most of them in Africa (150 million). Given that wildfire activity is predicted to increase because of climate change in many regions6, there is a need to understand housing growth and vegetation patterns as drivers of WUI change.

Exploring and Testing Wildfire Risk Decision-Making in the Face of Deep Uncertainty

We integrated a mechanistic wildfire simulation system with an agent-based landscape change model to investigate the feedbacks among climate change, population growth, development, landowner decision-making, vegetative succession, and wildfire. Our goal was to develop an adaptable simulation platform for anticipating risk-mitigation tradeoffs in a fire-prone wildland–urban interface (WUI) facing conditions outside the bounds of experience. We describe how five social and ecological system (SES) submodels interact over time and space to generate highly variable alternative futures even within the same scenario as stochastic elements in simulated wildfire, succession, and landowner decisions create large sets of unique, path-dependent futures for analysis. We applied the modeling system to an 815 km2 study area in western Oregon at a sub-taxlot parcel grain and annual timestep, generating hundreds of alternative futures for 2007–2056 (50 years) to explore how WUI communities facing compound risks from increasing wildfire and expanding periurban development can situate and assess alternative risk management approaches in their localized SES context. The ability to link trends and uncertainties across many futures to processes and events that unfold in individual futures is central to the modeling system. By contrasting selected alternative futures, we illustrate how assessing simulated feedbacks between wildfire and other SES processes can identify tradeoffs and leverage points in fire-prone WUI landscapes. Assessments include a detailed “post-mortem” of a rare, extreme wildfire event, and uncovered, unexpected stabilizing feedbacks from treatment costs that reduced the effectiveness of agent responses to signs of increasing risk.

Assessment of vegetation regrowth and spatial patterns and severity factors of wildfires in wildland-urban interface - the case of the large wildfire in Baião (2019)

Portugal is one of the countries most affected by forest fires in southern Europe, with recurrent events and frequent impacts. The demographic and social changes that have occurred in rural areas have driven land neglect in recent years, which, in turn, influences forest management and wildland-urban interface (WUI) areas that are related to fires. Therefore, it is the aim of this study to develop a case study in the municipality of Baião, based on the large wildfire (LWF) of 2019, defining and mapping the WUI areas, as well as evaluate, the recurrence, the GIF severity and in a period of 2 years, the regeneration of vegetation, in areas with different land uses and affected by different severities. The study was organized into 4 stages, being that in the first proceeded to the mapping of fire occurrences, the second of the wildland-urban interfaces, the third the characterization of the recurrence of large fires, the fourth corresponded to the evaluation of the severity of the large wildfire of 2019 and the evaluation of the vegetation regeneration, as a function of land use. The WUI represent 26.7% of the territory of the municipality of Baião, during the years 2001 to 2021 the municipality registered 3 770 fire occurrences. The LWF of Baião burned an area corresponding to 853 ha, the burned area in 2019 presented a maximum number of 12 fires between the years of 1975 to 2019, resulting in a maximum degree of 11 recurrences for the same area. We can verify that 2 years after the LWF, the area occupied by forest and scrub classes, which were hit by high severity, already showed significant levels of vegetation regeneration. With this, the main conclusions consider studies in this line contribute to the understanding of the patterns created by the wildfire in different landscapes, being information valuable for forest managers to understand the consequences (beneficial or not) and plan actions of prevention, restoration, and environmental education.

Is critical infrastructure safe from wildfires? A case study of wildland-industrial and -urban interface areas in South Korea

Global climate change, global warming, and unplanned urbanization have resulted in industrial facilities and livelihoods encroaching on wildlands. Wildfire risks concerns about natural hazards triggering technological accidents (Natech) caused by wildfires in wildland-industrial and -urban interface areas are globally increasing. As wildfires that could trigger Natech accidents occur infrequently but often with unpredicted and uncontrollable consequences, critical infrastructure and industrial facilities should prepare for the potential catastrophic impact of wildfires beforehand. This paper describes a case study of wildfire-threatened critical energy infrastructure located in wildland-industrial interface (WII) and wildland-urban interface (WUI) areas in South Korea. The energy infrastructure avoided a serious Natech accident through intensive risk and emergency management. Although there was no Natech disaster or dreadful damage to the energy facility, this threat to the energy infrastructure is a reminder to prepare for future Natech disasters in WII and WUI areas that could result in unmanageable consequences. This study highlights the need for intensive and integrated wildfire-specific Natech risk management, considering critical infrastructure and industrial facilities in WII and WUI areas, that should include all stakeholders with local residents and enhance Natech resilience.

Measuring firebrand heat flux with a thin-skin calorimeter

While the impact of wildland-urban interface fires is growing, firebrand exposure is a significant but not well understood contributor to fire spread. The ignition threat of firebrand exposures can be characterized by measuring the heat transfer of glowing firebrands to a surface. The current study presents a novel method for conducting time-resolved heat transfer measurements from individual firebrands across a range of flow conditions. Experiments are conducted with individual glowing firebrands generated from birch discs and placed on a copper thin skin calorimeter of the same diameter, which is embedded in the substrate. The net heat flux from the firebrand to the thin skin calorimeter is obtained from the thermal energy storage in the thin skin calorimeter, plus heat conduction losses to the substrate. Values of peak net heat flux, total heating, duration of heating are reported under different flow conditions from 0.05 m/s to 1.6 m/s. The average peak net heat flux for the disc-shaped birch firebrands is 45 kW/m2, and does not change significantly with flow condition. However, there is an increase in the total heating, duration of heating, and total mass consumed as the flow velocity increases.

Building wildland–urban interface zone resilience through performance-based wildfire engineering. A holistic theoretical framework

In recent years, a worldwide expansion in the frequency of large, uncontrolled, and catastrophic wildfire events has occurred, creating drastic social, economic, and environmental damage, especially in wildland–urban interface (WUI) zones. This damage includes losses of life, infrastructure, and ecosystem services. The impacts of wildfires at the WUI derive from the complicated and multidimensional interconnected relationships present in the Anthropocene. To enforce resilience of the environment and human communities against wildfires, it is critical to comprehend the local social-ecological systems holistically. In this paper, we present a theoretical framework approach, built on performance-based wildfire engineering, that is envisioned to be a stepping stone towards WUI resilience. To attain this objective, performance benchmarking and design is disaggregated into explicit components of a rigorous mathematical framework. They are linked to a causal inference chain, providing an integrated picture and enabling decision analysis to identify the optimal management strategies based on quantitative parameters. The proposed framework is developed from the total probability theorem and divides the risk assessment into single parts, in particular (1) hazard (wildfire) analysis, (2) social-ecological impact characterization, (3) social-ecological interaction analysis, (4) social-ecological impact analysis, (5) damage analysis, and (6) loss analysis. Therefore, the proposed framework can be applied by emergency agencies directly to assess the performance of society and ecosystem recovery after a wildfire, making emergency management and resilience policy-making more effective.

The wildland-urban interface in Poland reflects legacies of historical national borders

ContextThe wildland-urban interface (WUI) is an area where houses are located near wildland vegetation. As such, the WUI is a focal area of wildfire risk, human-wildlife conflicts, and other human-nature interactions. Although there is a wide consensus on the impact WUI existence might have, little is known about the WUI spatial determinants over long periods, especially in countries with long settlement history.ObjectivesOur goal here was to map the WUI across Poland, and to quantify the extent to which historical legacies shape current WUI pattern, since Poland is one of the countries, which experienced substantial political changes over time, which had an impact on historical settlement development.MethodsWe analysed a database of nearly 15 million building locations and a 10-m Sentinel-2-based land cover map to produce a country-wide WUI map of Poland. Then we compared the WUI pattern among parts of Poland which belonged to different political entities in 1900s and 1930s and also among different ecoregions. Lastly, we verified the effects of the historical borders or landscape units borders on WUI patterns with a discontinuity analysis.ResultsWe found that a substantial part of Poland is WUI, and over 60% of all buildings are in WUI. However, WUI patterns differ considerably across the country, and WUI hotspots are located around the largest metropolitan areas in central and southern part of Poland and in the Carpathians. Furthermore, WUI patterns reflect pre-1945 national borders indicating long-term legacies of past settlement patterns and urban planning approaches. Diversity among ecoregions was much less pronounced than among past political entities.ConclusionsOur work shows that current WUI pattern is to large extent shaped by former political conditions, which is likely true not only in Poland, but also in many parts of Europe and elsewhere where settlement history goes back centuries.

Mapping fireline intensity and flame height of prescribed gorse wildland fires

Wildfires currently represent an imminent danger to communities around the world due to their increasing severity and frequency. It is critical to expand current knowledge on wildfire behaviour to improve risk management practices, firefighting operation and engineering design in the Wildland Urban Interface (WUI). This paper reports 2D high resolution measurements of Byram's fireline intensity generated during a 150 × 200 m2 gorse shrub burn generated from visual and infrared video footage of the prescribed fire, and Light-Detection-and-Ranging (LiDAR) data of the vegetation canopy, both acquired using Unmanned Aerial Vehicles (UAV) technology. The results show that the fireline intensity was highly variable across the plot, reaching localized peak values over 40,000 kW/m and an averaged intensity of 14,300 kW/m approximately. An empirical correlation for estimating the average flame height was derived from the fireline intensity maps and from experimental measurements carried out during the prescribed burn. The correlation was used to produce a 2D detailed map of the average flame height of the prescribed fire, achieving a 11% of error compared to in-fire measurements. The findings from this research suggests that non-linear variabilities of fireline intensity should be carefully considered to adequately describe wildifire behavior of shrubland fires.

Estimating proximity effects to wildfire fuels treatments on house prices in Cibola National Forest, New Mexico, USA

Forested landscapes in the Western United States are subject to growing size and severity of wildfires, in part due to historical management strategies focusing on wildfire suppression. Forest restoration treatments and fuels reductions, including thinning and prescribed burning, can reduce the frequency and intensity of wildfires. Extensive restoration and fuels treatment efforts are underway across many areas in the Southwestern United States, including New Mexico. The tradeoff between amenity values provided by forested landscapes and the wildfire risk associated with forested landscapes is becoming increasingly important to understand as development in the wildland-urban interface increases. Understanding how house proximity, relative to forest restoration or fuels treatments, is capitalized into home sale prices can provide useful information about how individuals value forested landscapes that have been altered to reduce wildfire risk or severity. We use a Hedonic Property Model to estimate the average treatment effect of proximity to forest restoration or fuel treatments in New Mexico, United States. We use matching methods to estimate the average treatment effect of proximity to forest restoration. We find that proximity to the forest has a positive amenity value; however, proximity to recent forest restoration or fuel treatments results in a decrease in house sale prices. We combine the results of our two models and calculate that homes not within one kilometer of a treated forest and within one kilometer of Cibola National Forest sell for an average $73,626 premium. The average premium drops to $22,996 for homes within one kilometer of a forest that has been recently treated and within one kilometer of Cibola National Forest.

The Flora and Wildland–Urban Interface of Doe Mountain Recreation Area: Adjuncts to Conservation

The Flora and Wildland–Urban Interface of Doe Mountain Recreation Area: Adjuncts to Conservation

Perceptions of wildfire management practices in a California wildland-urban interface

Perceptions of wildfire management practices in a California wildland-urban interface

Wildland-urban interface typologies prone to high severity fires in Spain

Due to complex interactions between climate and land use changes, large forest fires have increased in frequency and severity over the last decades, impacting dramatically on biodiversity and society. In southern European countries affected by demographic challenges, fire risk and danger play special relevance at the wildland-urban interfaces (WUIs), where decision-making and land management have strong socio-ecological implications. WUIs have been historically typified according to both fire occurrence probability and settlement vulnerability, but those classifications lack generality regarding fire regime components. We aim to develop an integrated and comprehensive scheme for identifying the WUI typologies most at risk to fire severity across large territories. We selected fourteen large wildfires (over than 500 ha) occurred in Spain (2016–2021) containing different WUI scenarios. First, based on a building cartography and a multi-temporal series of Sentinel-2 imagery, each WUI was delimited and spatially characterized according to building density and pre-fire fuel characteristics (type, amount, and structure). Afterwards, a decision tree regression model was applied to identify the most relevant pre-fire vegetation parameters driving burn severity. The combined effect of the selected pre-fire vegetation drivers and the building density patterns on fire severity was evaluated using linear mixed models. Finally, the WUI typologies most prone to high burn severity were recognized using Tukey post-hoc tests. Results indicated that building density, land cover class and vegetation cover fraction determined fire severity in areas close to human settlements. Specifically, isolated, scattered and sparsely clustered buildings enclosed in a high-cover shrub matrix were the WUI typologies most susceptible to high-severity fires. These findings contribute to the development of appropriate strategies to minimize the risk of severe fires in WUIs and avoid potential losses of multiple ecosystem services valuable for society.

IX International Conference on Forest Fire Research and 17th International Wildland Fire Safety Summit: introduction to special issue (Part 3)

The ninth International Conference on Forest Fire Research, organised by the Forest Fire Research Center of the Association for Developmental of Industrial Aerodynamics every 4 years since 1990, was held in November 2022 in Coimbra, Portugal. The conference was held in conjunction with the 17th International Wildland Fire Safety Summit, sponsored by the International Association of Wildland Fire. The number and quality of the submissions for this joint event was very high, and the authors were encouraged to submit a full paper to a special issue of the International Journal of Wildland Fire (IJWF). Given the large number of submissions, the Journal decided to publish the special issue in several parts. Part 1 was published in January 2023, with eight papers, and Part 2 in March 2023, with 10 papers. This third part presents 15 original papers in five topical areas: decision support systems and tools (3), risk reduction (2), risk assessment (3), wildland urban interface (3) and wildfire management and safety (4). All the papers in this special issue are published Open Access.

The effect of broadleaf forests in wildfire mitigation in the WUI – A simulation study

The increasing occurrence of large wildfires in Southern European countries calls for the adoption of more effective measures of fire prevention, to protect people and infrastructures, namely in the Wildland-Urban Interface (WUI). Previous research suggests that broadleaf forests could mitigate the effects of these wildfires due to their lower flammability. However, few attempts have been made to investigate the possibility of using broadleaf-based green firebreaks to protect infrastructures, as an alternative to current less ecologically and economically sustainable fuel reduction techniques. Here, we assess the relevance of a broadleaves fuel model in reducing fire hazard in the WUI, by analyzing a set of six Industrial Zones (IZs) in Central Portugal, severely affected by wildfires during the catastrophic fire season of 2017. We developed alternative scenarios for the spatial simulation of fire behavior, using a factorial combination of weather conditions (standard and extreme), buffer around each IZ (distances of 100 m and 500 m) and land cover (current and broadleaves fuel model). The simulations were grounded on real-world data obtained from reconstructed fire front isochrones and fieldwork. Our results suggest that replacing the flammable vegetation present in the WUI with broadleaf forests could reduce fireline intensity by up to five times, even under extreme weather conditions. This reduction occurs subtly as the broadleaf cover interface is expanded from 100 m to 500 m. Our results show that fires that exceed the suppression capacity in pine and eucalypt forests (>4 m flame length) can be effectively suppressed in broadleaf forests under extreme fire weather (1.4 m flame length) and easily suppressed in broadleaf forests in standard weather (0.8 m flame length). Due to significant changes in land use and extreme weather events, future large wildfires could occur again in Portugal. In this regard, our results corroborate the urgent need to discuss forest management in the country, which has already proven to be insufficient to prevent fire disasters in the WUI.

Hazardous air pollutant emissions estimates from wildfires in the wildland urban interface.

Fires that occur in the wildland urban interface (WUI) often burn structures, vehicles, and their contents in addition to biomass in the natural landscape. Because these fires burn near population centers, their emissions may have a sizeable impact on public health, necessitating a better understanding of criteria and hazardous air pollutants emitted from these fires and how they differ from wildland fires. Previous studies on the toxicity of emissions from the combustion of building materials and vehicles have shown that urban fires may emit numerous toxic species such as hydrogen cyanide, hydrogen fluoride, hydrogen chloride, isocyanates, polycyclic aromatic hydrocarbons (PAHs), dioxins and furans, and a range of toxic organic compounds (e.g. benzene toluene, xylenes, styrene, and formaldehyde) and metals (e.g. lead, chromium, cadmium, and arsenic). We surveyed the literature to create a compendium of emission factors for species emitted from the combustion of building and vehicle materials and compared them with those from wildland fires. Emission factors for some toxic species like PAH and some organic compounds were several orders of magnitude greater than those from wildfires. We used this emission factor compendium to calculate a bounding estimate of the emissions from several notable WUI fires in the western United States to show that urban fuels may contribute a sizeable portion of the toxic emissions into the atmosphere. However, large gaps remain in our understanding of the fuel composition, fuel consumption, and combustion conditions in WUI fires that constrain our ability to estimate the impact of WUI fires.

Flammability study of decking sections found at the Wildland–Urban interface at different scales

This work presents a study of the fire reaction of two types of decking sections (wood and thermoplastic) exposed to a radiant heat source. The flammability was studied at two scales: a cone calorimeter was used at product scale (36 cm2) and at assembly scale (around 1300 cm2), experiments were performed under a Large Scale Heat Release calorimeter with a radiant burner. Since the wood decking sections have gaps, the influence of the orientation of the sections facing the burner was further investigated. At product scale, the wood sections ignite sooner than the thermoplastic sections whereas the thermoplastic sections have a higher peak of heat release rate. At assembly scale, the thermoplastic decking sections ignite sooner and have a higher peak of heat release rate than wood decking sections, regardless of the orientation adopted. Wood sections with boards oriented perpendicular to the burner ignite sooner and have a higher peak of heat release rate than those oriented parallel. The fire tests at both scales highlighted the influence of the shape of the products on their ability to ignite. Flame retardant should be included in decking assemblies to decrease the fire risk at WUI.