Thèses sur le sujet « Wildfire behaviour »

Thesis (MSc)--Stellenbosch University, 2014.
ENGLISH ABSTRACT: The Western Cape Province in South Africa is home to one of the most diverse plant communities in the world, and has one of the highest concentrations of plants species in any temperate ecosystem in the world. The dominant vegetation is both fire-prone and fire-dependant (Van Wilgen & Scott 2001, Forsyth et al. 2010). The Western Cape in particular is emerging as a province that is increasingly prone to disaster events, particularly the threat of veld fires. The consequences of large wildfire disaster events are often devastating and far reaching (Van Wilgen & Scott 2001, Forsyth et al. 2010). This study was conducted in an attempt to investigate the drivers of wildfire behaviour, severity and magnitude in the Limietberg Conservation Area in order to gain a greater insight and understanding of the complexity of wildfire risk. Recognising the disaster prone character of the Western Cape and the increasing probabilities of future wildfire events in the province, this study aimed to strengthen the understanding of the drivers of wildland fire behaviour (i.e. wildland fire risk) in the Limietberg Conservation Area by analysing a number of fires to identify a range of drivers and patterns; examining the factors driving both fire danger and fire behaviour, including climate, topography, slope and fuel; examining the factors driving fire frequency and regime; and finally, determining possible ecological damage caused by the last 10 – 20 years of wildfire events in the Limietberg Conservation Area as measured by post-fire seedling ratios. This was achieved through the use of statistical techniques including multiple regression (McDonald 2009), ordination in the form of principal component analysis and non-metric multi-dimensional scaling (Clarke & Warwick 1994), and fieldwork in the form of post-fire regeneration (Proteaceae parent:seedling ratio) monitoring techniques (Bond et al. 1984; Vlok & Yeaton 2000; De Klerk et al. 2007). The results indicated that the interactions between factors driving fire danger and fire behaviour were indeed complex, being influenced mainly by meteorological variables (temperature, relative humidity, wind speed) but also quite strongly influenced by physical environmental factors (slope, topography). The use of ordination techniques in this sort of complex analysis was seen as extremely effective and its use in further fire research was strongly recommended.
AFRIKAANSE OPSOMMING: Die Wes-Kaap provinsie in Suid-Afrika is die tuiste van een van die mees diverse plant gemeenskappe in die wêreld, en het een van die hoogste konsentrasies van plantspesies in enige gematigde ekosisteem in die wêreld. Die dominante plantegroei is beide vuur geneig en vuurafhanklik (Van Wilgen & Scott 2001, Forsyth et al. 2010). Die Wes-Kaap in die besonder is opkomende as 'n provinsie wat toenemend geneig is tot ramp gebeure, veral die bedreiging van veldbrande. Die gevolge van groot veldbrand rampgebeure is dikwels verwoestend en verreikend (Van Wilgen & Scott 2001, Forsyth et al. 2010). Hierdie studie is uitgevoer in 'n poging om die oorsake van veldbrande, die gedrag, erns en omvang daarvan in die Limietberg Bewaringsgebied vir groter insig en begrip van die kompleksiteit van veldbrand risiko te ondersoek. Hierdie studie erken die rampgeneigdheid van die Wes-Kaap en die toenemende waarskynlikheid van toekomstige veldbrande in die provinsie. Dit het ten doel gehad om die oorsake van veldvuur gedrag (bv. brand risiko) in die Limietberg Bewaringsgebied deur die ontleding van 'n aantal brande se oorsake en patrone te identifiseer; die ondersoek van faktore wat beide brandgevaar en vuurgedrag, bepaal insluitend klimaat, topografie, helling en brandstof; die ondersoek van faktore wat vuur frekwensie en regime; en uiteindelik die bepaling van moontlike ekologiese skade veroorsaak deur die laaste 10 - 20 jaar van veldbrand gebeure in die Limietberg Bewaringsgebied, soos gemeet deur navuur saailing verhoudings. Die doel is bereik deur die gebruik van statistiese tegnieke waaronder meervoudige regressie (McDonald 2009), ordening in die vorm van hoofkomponent analise en multi-dimensionele skaling (Clarke & Warwick 1994), en veldwerk in die vorm van navuur herlewing (Proteaceae ouer:saailing verhouding) moniteringstegnieke (Bond et al. 1984; Vlok & Yeaton 2000; De Klerk et al. 2007). Die resultate dui daarop dat die interaksies tussen faktore wat brandgevaar en vuurgedrag inderdaad kompleks aandryf is en hoofsaaklik beïnvloed word deur meteorologiese veranderlikes (temperatuur, relatiewe humiditeit, windspoed), maar ook baie sterk beïnvloed word deur fisiese omgewingsfaktore (helling, topografie). Die gebruik van ordeningstegnieke vir hierdie komplekse tipe analise is bevind as uiters effektief en die gebruik daarvan in verdere vuur navorsing word sterk aanbeveel.

Wildfires affect vegetation dynamics, geomorphological processes, biogeochemical cycles, atmospheric chemistry, and climate, posing a severe threat to human lives and activities interacting with the natural system. As both fire activity and wildland-urban interface exposure are expected to increase under future climate projections, the improvement of our ability to promptly predict wildland fire behaviour, in terms of expected intensity and geographic patterns, has become a tangible need. The general purpose of this research is to investigate on wildland surface fire behaviour simulation models and to support disaster managers in optimising decision making processes in wildfire risk management in a Mediterranean-type climate region, namely Sardinia, Italy. This project is intended to pursue two major objectives: (i) develop and validate a predictive spatially distributed wildland surface fire behaviour simulation model intended for operational use; (ii) design and implement a geospatial decision support system to provide decision makers with appropriate strategies and tools for an integrated wildland fire risk management. Predicting wildland surface fire behaviour requires a deep understanding of the influence of environmental parameters that act as drivers of the fire spread, including geomorphometrical variables, meteorological conditions, and fuel characteristics, on fire descriptors, such as the rate and direction of the maximum fire spread, the eccentricity of the ellipse approximating the fire shape, the intensity of the fire front, and the flame length. The Rothermel’s mathematical model for predicting surface fire spread in wildland fuels is currently the most extensively used method to estimate fire descriptors, especially for operational purposes. The application of the Rothermel’s model for simulating the behaviour of ongoing wildfires calls for the need of a technique for continuous monitoring of the spatiotemporal variability of weather conditions and fuel characteristics, such as fuel height, loading, and moisture content, in the pre-fire environment. Firstly, freely available data sources and remote sensing products and datasets have been investigated to define a pre-processing methodology for the near real-time estimation of the drivers of fire spread. Secondly, the need for flexibility in handling the equations of the Rothermel’s and associated models, together with the necessity of integrating corrections and updates, have led to an original implementation of a computer algorithm that evaluates the fire descriptors as defined by the extended Rothermel’s mathematical model. Then, a proxy model of this implementation has been developed using a machine learning ensemble method in order to analyse the interdependence of the drivers and to understand their relative importance in predicting fire descriptors. Furthermore, the proxy model for predicting fire spread across heterogeneous landscapes has been integrated into an agent-based simulation model developed to predict the surface fire behaviour and growth with the aim of providing fire management authorities with timely information on the expected progress of the fire front. Finally, the developed simulation model has been applied to and validated against historical wildfire events recorded in Sardinia, Italy, to evaluate its performance in terms of predictive capacity. The effects of fire suppression activities have also been simulated according to the availability of accurate information on timing and location of interventions that effectively extinguished the fire’s spread. As a whole, the developed wildland surface fire behaviour simulation model, together with the pre-processing methodology, have resulted in a satisfying accuracy in terms of quantitative agreement between modelled and observed patterns of fire growth. The adoption of the proxy model instead of its original implementation has guaranteed a significative reduction of the computing time in the face of a limited loss in accuracy at the scale of the analysis if compared with the original implementation of the Rothermel’s equations. Results of the validation suggest the model’s suitability for operational uses for predicting wildland surface fire behaviour. The predictive ability of the simulation model could reasonably benefit from the inclusion of some additional mathematical models simulating the potential evolution of the surface fire towards passive or active crown fires or spotting fires. Moreover, major improvements could be granted by implementing in the agent-based simulation model a wider range of fire suppression activities and techniques, ranging from ground to aerial interventions. The proposed predictive model could become a valid tool for the optimization of risk planning, prevention, and management activities. Within the context of this project, three modules of a geospatial decision support system have been designed and implemented with the aim of improving the efficiency of risk management strategies and reducing expected impacts and potential damage. The first module is a dynamic workflow of actions and represents the core of the decision support system. This module aims to guide decision makers in carrying out the procedures of the intervention model compliant with the legislative framework. The workflow is then supported by a second module, a customised version of a geographic information system with dynamic forms designed to support users with limited expertise in geodatabase management. This module will incorporate a structured relational geodatabase storing (i) scenarios of wildfire events, produced by means of the developed predictive wildland surface fire behaviour simulation model, (ii) existing institutional wildfire susceptibility, hazard, and risk maps, (iii) available resources and socioeconomic exposed values, and (iv) real-time data from field surveys. Finally, the decision support system will provide authorities and technicians with a third module composed by web applications for mobile field data collection and sharing. This research strived to investigate principles and accepted theories on the complex dynamics of wildland surface fire behaviour and to shed light on the need for a better understanding of the difference between real and simulated fire behaviour in terms of the importance of the drivers of fire spread in predicting fire spread and growth. The project also tried proposing solutions integrating remote sensing and machine learning techniques with the aim of improving the applicability of near real-time simulation models as well as the effectiveness of decision-making strategies.

For roughly the past 200 years land-managers have used the practice of “muirburning” to manipulate the structure of heather (Calluna vulgaris) to create a patchwork of habitat structures able to provide forage and nesting sites for red grouse (Lagopus lagopus scoticus) as well as grazing for sheep (Ovis aries) and red deer (Cervus elaphus). This thesis investigates both the behaviour and impact of management fires in recognition of the need to develop multi-aim land management practices that ensure both continued productivity and protection of biodiversity in the face of climatic and environmental change. Fuel structure and loading are crucial controlling factors on both fire behaviour and impact governing both rate of spread and heat release to the ground surface. A visual obstruction method is developed that estimates total and fine fuel loading as well as the structure of the heather canopy. In order to adequately understand fire impact a dimensional analysis approach is taken to estimating the mass of burnt heather stems. Experiments at a number of spatial and temporal scales relate variation in heather fuel moisture content to stand structure and variation in weather conditions. Monitoring shows moisture contents to be relatively stable temporally, but spatially variable. Periods of extreme low moisture contents in early spring are associated with frozen ground, winter cuticle damage and physiological drought. Such conditions may have contributed to the large number of wildfires in 2003. A replicated plot design was used to investigate the effect of weather conditions and fuel loading on fire behaviour. An empirical approach is taken to fire behaviour modelling with equations describing rate of spread and fireline intensity being developed on the basis of fuel structure descriptors and windspeed. The theoretical negative correlation between fuel bed density and rate of spread is demonstrated to hold true for heather stands, while the impact of heterogeneity in fuel bed structure is also investigated. Redundancy Analysis is used to investigate the influence of multiple predictors on a number of aspects of fire behaviour including: rate of spread, fireline intensity, flame length and ground surface heating. Data from this and previous studies are used to ground-truth a number of fire behaviour prediction systems including BehavePlus and the Canadian Fire Behaviour Prediction System. Finally linkages between fire behaviour, fire severity and heather regeneration are investigated. A number of proxy measures of ‘Immediate Severity’ are tested and used to examine the influence of fires on plant regeneration. The post-fire development of stands is shown to relate primarily to stand age and structure before burning, and to post-fire substrates rather than variation in fire behaviour and severity.

20 pp.
Arizona Firewise Communities
This publication is an update and adaptation of the widely distributed Living with Fire publication created by the University of Nevada Cooperative Extension and Sierra Front Wildfire Cooperators in 1998. It is an interagency collaboration of the Arizona Firewise subcommittee of the Arizona Interagency Coordinating Group. It involved the combined efforts of the Arizona State Land Department, USDI Bureau of Indian Affairs, USDI Bureau of Land Management, USDI National Park Service, USDA Forest Service, USDI Fish and Wildlife Service, USDA Natural Resources Conservation Service, University of Arizona Cooperative Extension and Arizona Fire Chiefs Association. The need to revise the over seven-year old publication emerged from the subcommittees vision of building in concepts such as Firewise Zone Landscaping and Survivable Space, as well as to update the documents appearance and organization. Its purpose to provide a quality outreach tool to increase public aware concerning Firewise concepts and to encourage and facilitate the implementation of Firewise practices by communities, neighborhoods and property owners. Living with Wildfire is a twelve-page color tabloid that addresses the following topic areas important to homeowners: current situation; fire behavior and the human environment, and in various Arizona vegetation types; detailed recommendations for creating survivable space, including a checklist and landscape management zones; frequently asked questions; and emergency and evacuation guidelines. The tabloid is to be printed in bulk by federal partners and made widely available throughout the state over the next several years.

Wildfires are a natural phenomenon that strongly impacts the environment. Many terrestrial ecosystems depend on fire to maintain their ecological equilibrium and biodiversity, but new destructive fire patterns, often associated with land management practices and rapid climate change, have been degrading soil and water resources, increasing erosion by wind, precipitation and floods, decreasing biodiversity and contributing to desertification. Furthermore, pyrogenic emissions from biomass burning are an important source of atmospheric pollution and they impact the radiative balance of the troposphere, strongly contributing to the greenhouse effect. The objective of this research was to investigate the impact of climate variability on geographic, ecological, seasonal and inter-annual distributions of fires and correspondent pyrogenic emissions, across a variety of ecosystems. With this purpose, 10 years of world, monthly, 1°x1° gridded data, from the Global Fire Emissions Database, were compared with land-cover data, from the Goddard Institute of Space Studies, and with weather data, from the European Centre for Medium Range Weather Forecasting, the Global Precipitation Climatology Centre and the Global Hydrology Resource Centre. Overall, the climate parameters significantly correlated with carbon emissions were air and soil temperature, air and soil humidity, rainfall, wind speed and lightning density during the fire season, and also precipitation and snow cover up to 6 months before the fire season. Good statistical quantitative models of carbon emissions (correlations above 70%, and up to 95%, between estimated and predicted values, with residuals normally distributed) using humidity, temperature or lagged rainfall as predictors, were found almost exclusively in tropical grasslands, shrublands and woodlands, especially in Africa, where fire behaviour was more regular. In boreal and temperate forests and woodlands, where fire patterns were irregular and fire returning periods were larger, there were not enough fires, in 10 years of data, to obtain useful predictive statistical models. The fire models presented here, together with the quantitative statistical relationships found between climate and fire patterns, in different land ecosystems, are apt to be used in predictive climate models, land management, fire risk assessment and mitigation of climate change.

Each year many forest fires have occurred and huge amount of forest areas in each country have been lost. Turkey like many world countries have forest fire problem. 27 % of Turkey&
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s lands are covered by forest and 48 % of these forest areas are productive, however 52 % of them must be protected. There occurred 21000 forest fires due to several reasons between 1993 and 2002. It is estimated that 23477 ha area has been destroyed annually due to wildfires. The fire management strategies can be built on the scenarios derived from the simulation processes. In this study a GIS &
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based fire simulating model is used to simulate a past fire occurred in Marmaris &
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etibeli, Turkey, in August 2002. This model uses Rothermel&
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s surface fire model, Rothermel&
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s and Van Wagner&
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s crown fire model and Albini&
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s torching tree model. The input variables required by the model can be divided into four groups: fuel type, fuel moisture, topography and wind. The suitable fuel type classification of the vegetation of the study area has been performed according to the Northern Forest Fire Laboratory (NFFL) Fuel Model. The fuel moisture data were obtained from the experts working in the General Directorate of Forestry. The fire spread pattern was derived using two IKONOS images representing the pre- and post-fire situations by visual interpretation. Time of arrival, the rate of spread and the spread direction of the fire were obtained as the output and 70 % of the burned area was estimated correctly from the fire simulating model.

The phenomenon of a fire occurring in nature comes with a very high level of complexity. One central obstacle is the range of scales in such fires. In order to understand wildfires, research has to be conducted across these scales in order to study the mechanisms which drive wildfire behavior. The hazard related to such fires is ever more increasing as the living space of communities continues to increase and infringe with the wildland at the wildland-urban interface. In order to do so, a strong understanding on the possible wildfire behavior that may occur is critical. An array of factors impact wildfire behavior, which are generally categorized into three groups: (1) fuel (type, moisture content, loading, structure, continuity); (2) environmental (wind, temperature, relative humidity, precipitation); and (3) topography (slope, aspect). The complexity and coupling of factors impacting various scales of wildfire behavior has been the focus of much experimental and numerical work over the past decades. More recently, the need to quantify wildland fuel flammability and use the knowledge in mitigating risks, for example by categorizing vegetation according to their flammability has been recognized. Fuel flammability is an integral part of understanding wildfire behavior, since it can provide a quantification of the ignition and burning behavior of wildland fuel beds. Determining flammability parameters for vegetative fuels is however not a straight forward task and a rigorous standardized methodology has yet to be established. It is the intent of this work to aid in the path of finding a most suitable methodology to test vegetative fuel flammability. This is achieved by elucidating the fundamental heat and mass transfer mechanisms that drive ignition and burning behavior of porous wildland fuel beds. The work presented herein is a continuation of vegetative fuel flammability research using bench-scale calorimetry (the FM Global Fire Propagation Apparatus). This apparatus allows a high level of control of critical parameters. Experimental studies investigate how varying external heat flux (radiative), ventilation conditions (forced airflow rate, oxygen concentration, and temperature), and moisture content affect the ignition and burning behavior of wildland fuel. Two distinct ignition regimes were observed for radiative heating with forced convection cooling: (1) convection/radiation for low heating rates; and (2) radiation only for high heating rates. The threshold for the given convection conditions was near 45 kW.m-2. For forced convection, ignition behavior is dominated by convection cooling in comparison to dilution; ignition times were constant when the oxygen flow rate was varied (constant flow magnitude). Analysis of a radiative Biot number including heat losses (convection and radiation) indicated that the pine needles tested behaved thermally thin for the given heating rates (up to 60 kW.m-2). A simplified onedimensional, multi-phase heat transfer model for porous media is validated with experimental results (in-depth temperature measurements, critical heat flux and ignition time). The model performance was adequate for two species only, when the convective Froude number is less than 1.0 (only one packing ratio was tested). Increasing air flow rates resulted in higher heat of combustion due to increased pyrolysis rates. In the given experiments (ventilation controlled environment) combustion efficiency decreased with increasing O2 flow rates. Flaming combustion of pine needles in such environments resulted in four times greater CO generation rates compared to post flaming smoldering combustion. A link was made to live fuel flammability that is important for understanding the occurrence of extreme fire conditions such as crowning and to test if live fuel flammability contributes to the occurrence of a typical fire season. Significant seasonal variations were observed for the ignition and burning behavior of conditioned live pine needles. Variation and peak flammability due to ignition time and heat release rate can be associated to the growing season (physical properties and chemical composition of the needles). Seasonal trends were masked when unconditioned needles were tested as the release of water dominated effects. For wet fuel, ignition time increases linearly with fuel moisture content (FMC, R2 = 0.93). The peak heat release rate decreased non-linearly with FMC (R2 = 0.77). It was determined that above a threshold of 60% FMC (d.w.), seasonal variation in the heat release rate can be neglected. A novel live fuel flammability assessment to evaluate the seasonality of ignition and burning behavior is proposed. For the given case (NJ Pine Barrens, USA), the flammability assessment indicated that the live fuel is most flammable in August. Such assessment can provide a framework for a live fuel flammability classification system that is based on rigorous experimentation in well controlled fire environments.

The effectiveness of harvesting slash treatments are questionable when wild fires, fuelled by post harvesting slash, burn out of control. In order to quantify effectiveness of various slash treatments, fire behaviour in Pinus patula and Eucalyptus macarthurii compartments in the Highveld area (Piet Retief) of Mpumalanga, South Africa, were assessed after application of five different post-harvesting slash treatments. Treatments included mulching, chopper rolling, windrowing, removal of slash (inter-windrowing) and broadcasting. Independent fuel and environmental variables were measured prior and during application of fire to the study areas and effects on fire behaviour were compared afterwards. Dependant fire behaviour variables such as the rate of spread, fire temperature and flame height were measured in respective slash treatment plots and compared. Results of the study indicated that fire behaviour assessed in mulched areas in both the P. patula and E. macarthurii compartments were significantly less intense when compared to fire behaviour in chopper roll, broadcast and windrow treatments. Fire behaviour in mulched plots compared favourably with areas where harvesting slash was removed (inter-windrow treatment). Comparisons between fuel loads of different treatments also indicated accelerated mineralization of organic material in mulched areas. Mulching of harvesting slash seems to be an effective method to restrict fire behaviour in post-harvesting compartments and should be considered as part of a fire management strategy.

In an ecological context, ‘flexibility’ refers to an animal’s ability to respond immediately to environmental stimuli through physiological and behavioural adjustments. Specifically, primates exhibit a high degree of ecological flexibility, which allows them to persist through environmental changes that vary in duration and predictability. To cope with the variability of conditions within their habitats, baboons have evolved flexibility in ranging behaviour, social behaviour, and diet. Natural disasters are predicted to increase across the globe, and many parts of the world are experiencing longer wildfire seasons and higher wildfire frequencies than ever before. The aim of this study is to use an existing data set to assess how baboons responded, behaviourally and physiologically, to an extensive wildfire. I compare home range use, activity budgets, faecal glucocorticoid concentrations, and urinary C-peptide concentrations three months after the fire to the same three months in the previous year for the same 16 adult females. In the months following the fire, the baboons had a larger spatial range compared to the same months in the year prior. The additional area incorporated unburnt areas into their home range, which were preferentially used over burnt areas. Behavioural adjustments included notably less time spent engaging in social behaviours than in the year prior. Perhaps most surprisingly, postfire physiological indicators did not suggest high levels of psychological, energetic, or nutritional stress, as glucocorticoid concentrations were significantly lower post-fire compared to the year prior, while C-peptide concentrations were not significantly different between the two periods. The troop appears to have benefited from a surfeit of exotic pine seeds that were released by pine trees as a result of the fire. This unexpected nutritional windfall, in addition to the inclusion of vineyards within their ranging patterns, may explain why there were no physiological indicators of nutritional stress despite the loss of most above ground biomass. Despite suffering the loss of 12 troop members in the fire and injury to a further 12 individuals, adult females in the Tokai troop were able to adjust to a severe and extensive change to their home range. Although primate ecological flexibility has been widely documented, this is the first study to explore the behavioural and physiological responses of baboons to extensive habitat changes resulting from a wildfire, and the potential implications for the management of wildlife on the urban edge.

En dépit de moyens importants consacrés à la lutte, certains feux de forêt, en Europe méditerranéenne, en Australie ou en Amérique du Nord, parcourent de grandes surfaces et développent des comportements violents qui piègent les pompiers. L’étude de rapports internes aux services d’incendie révèle ici les conditions météorologiques et topographiques dans lesquelles se produisent ces feux dangereux. En France, alors que le vent violent est le principal contributeur des feux les plus grands et les plus dangereux, les températures élevées mènent à un autre type d’incendies violents qui se propagent rapidement. En Australie, les pompiers sont souvent piégés par une bascule brutale de la direction du vent mais aussi par des vents forts en terrain accidenté. Au-delà des disparités intercontinentales, la recherche des comportements dynamiques de feu impliqués dans plus de 100 accidents de pompiers à travers le monde amène à distinguer trois types d’incendie. Lors des feux topographiques, en zone de montagne, les accidents sont généralement causés par l’attachement de la flamme sur des pentes supérieures à 20°. Lors des feux guidés par le vent, les zones les plus propices aux accidents sont les pentes déventées où des effets de vortex peuvent se produire. Enfin, lors des feux convectifs, les plus violents, les accidents peuvent se produire loin de toute configuration dangereuse. Pour tenir compte de ces résultats et améliorer leur sécurité, les pompiers doivent adapter leur formation et de développer des compétences d’analyste du feu. Ces experts intègreront les retours d’expérience des incendies passés pour proposer les stratégies de lutte les plus efficaces et sécurisées
Despite the large expenditure that is dedicated to forest fire suppression in Euro-Mediterranean countries, Australia and North-America, firefighters still face large and severe fire events which eventually entrap them. Investigation of Fire Services’ internal reports addresses here the weather and terrain leading to these dangerous fires. In France, strong wind is the main driver of the largest fires and of the fires that entrap firefighters. However, high temperature is also a key contributor as it influences violent fires with high rates of surface spread. In Australia, a lot of firefighters’ entrapments are due to shifts in wind direction, but others are associated to strong winds in rugged terrain. Whatever the regional specificities, more than 100 firefighters’ entrapments across the world were investigated to find the contribution of dynamic fire behaviors in these entrapments. The results return three different types of fires. During topography-influenced fires, in mountainous area, almost all the entrapments happen on slopes steeper than 20°, prone to flame attachment. During wind-driven fires, leeward slopes prone to vorticity-driven lateral fire spread are the most prominent configurations associated with entrapments. Finally, during convective fires, which are the most violent, entrapments can happen far away from any dangerous configuration. Firefighters should adjust their training courses and promote fire behavior analysts (FBAN) capabilities to benefit from the results of this work and improve their safety. FBAN may consider feedbacks from previous fires to suggest the most efficient and secure firefighting strategies and locations

Wildland fuels and fire behavior have been the focus of numerous studies and models which provide operational support to firefighters. However, fuel and fire complexity in live shrubs has resulted in unexpected and sometimes aggressive fire behavior. The combustion of live fuels was studied and modeled, and the results were assimilated into a shrub-scale fire behavior model which assumes fire spread by flame-fuel overlap. Fire spread models have usually assumed that radiation heat transfer is responsible for driving fire spread, but that assumption is a topic of continuing debate, and appears to contradict some experimental observations. A convection-based shrub-scale fire spread model has been developed, building on a heritage of experiments and modeling previously performed at Brigham Young University. This project has (1) characterized fundamental aspects of fire behavior, (2) integrated the resulting submodels of fire behavior into an existing shrub model framework, and (3) produced shrub-scale fire spread experiments and (4) made model comparisons. This research models fire spread as a convection-driven phenomenon and demonstrates strategies for overcoming some of the challenges associated with this novel approach.

Heathlands typically experience regimes consisting of frequent and intense fires. These fire regimes play important roles in the lifecycles and population dynamics of all species in these communities. Prescribed fire is commonly applied to heathlands to minimise the risk of wildfires as well as to promote biodiversity. Ignitions in heathlands tend to either be unsustainable, or quickly develop into rapidly spreading intense fires. This presents a major problem for the application of prescribed fire and is the primary focus of this thesis. Heathland ignition has been investigated in three sections; litter ignition; vertical development of fire into the shrub layer; and horizontal spread through the shrub layer. These were studied in laboratory experiments using miniature versions of field fuels. Ignition success in litter layers was related to the dead fuel moisture content. Litter type, ignition source, and presence of wind were found to affect the range of ignitable fuel moisture contents of a litter bed. The effect of litter type was best explained by density. Dense litter beds required drier conditions for ignition than low density litter beds. The vertical development of fire into shrubs was mostly dependent on live fuel moisture content, but crown base height, presence of wind, ignition source, shrub height and the percentage of dead elevated fuel were also important. Horizontal spread of fires through shrub layers was most affected by the presence of a litter layer, with nearly all ignitions successful when there was an underlying litter fire. Fire spread would only occur in shrubs without a litter layer when the shrub layer was dense and dry, or had a substantial dead fuel component. Spread was more likely to be sustained when there was wind. Models predicting the moisture content of dead fuels were tested in heathlands, and as would be expected those that can be calibrated for different fuel types were found to have the best performance. Fuel moisture content and fuel load models were reviewed for heathlands, and a number of recommendations for future research were made.

A study was undertaken to characterize two dynamic fuel types not included in the Canadian Forest Fire Behaviour Prediction System: forested bogs and blowdown. Fuel load and structure were measured at ten forested bog sites in central Alberta along a 108 year post-fire chronosequence. Canopy bulk density increased following a sigmoidal curve between 0.00 and 0.54 kg•m-3. Crown fire potential was modeled using a general crown fire behaviour model and found to follow a similar sigmoidal pattern increasing with time-since-fire. Blowdown fuel loads were measured at six sites in northwestern Ontario and ranged from 13.4 to 18.9 kg•m-2. Elevated fine blowdown fuels were found to have faster reaction times and dry more rapidly than predicted by the Fine Fuel Moisture Code. Detailed observations were also made of fire behaviour in blowdown fuels

Thesis (M.S.)--University of Wisconsin--Madison, 2004.
Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 101-104).

abstract: Increasingly, wildfires are threatening communities, forcing evacuations, damaging property, and causing loss of life. This is in part due to a century of wildfire policy and an influx of people moving to the wildland urban interface (WUI). National programs have identified and promoted effective wildfire mitigation actions to reduce wildfire risk; yet, many homeowners do not perform these actions. Based on previous literature and using the theory of planned behavior (TPB), this study proposes an integrated wildfire mitigation behavioral model to assess and identify the factors that influence homeowners’ wildfire mitigation behaviors. Specifically, the study tests the validity of the theory of planned behavior as a foundational model in exploring wildfire mitigation behaviors, develops and empirically tests a wildfire mitigation behavioral model, and explores the role of homeowner associations (HOA) on wildfire mitigation behaviors. Structural equation modeling was used on data collected from homeowners with property in the WUI in Prescott, Arizona. Results suggest TPB provides an acceptable model in describing homeowner wildfire mitigation behavior. For HOA residents, attitudes toward wildfire mitigation behaviors play an important role in predicting intentions to perform these behaviors. Additionally, perceived constraints directly influenced actual mitigation actions. For non-HOA residents, subjective norms influenced intentions to mitigate. Implications for research and local wildfire mitigation programs and policy are discussed.
Dissertation/Thesis
Doctoral Dissertation Community Resources and Development 2016

Climate exerts considerable control on wildfire regimes, and climate and wildfire are both major drivers of forest growth and succession in interior Northwest forests. Estimating potential response of these landscapes to anticipated changes in climate helps researchers and land managers understand and mitigate impacts of climate change on important ecological and economic resources. Spatially explicit, mechanistic computer simulation models are powerful tools that permit researchers to incorporate climate and disturbance events along with vegetation physiology and phenology to explore complex potential effects of climate change over wide spatial and temporal scales. In this thesis, I used the simulation model FireBGCv2 to characterize potential response of fire, vegetation, and landscape dynamics to a range of possible future climate and fire management scenarios. The simulation landscape (~43,000 hectares) is part of Deschutes National Forest, which is located at the interface of maritime and continental climates and is known for its beauty and ecological diversity. Simulation scenarios included all combinations of +0��C, +3��C, and +6��C of warming; +10%, ��0%, and -10% historical precipitation; and 10% and 90% fire suppression, and were run for 500 years. To characterize fire dynamics, I investigated how mean fire frequency, intensity, and fuel loadings changed over time in all scenarios, and how fire and tree mortality interacted over time. To explore vegetation and landscape dynamics, I described the distribution and spatial arrangement of vegetation types and forest successional stages on the landscape, and used a nonmetric multidimensional scaling (NMS) ordination to holistically evaluate overall similarity of composition, structure, and landscape pattern among all simulation scenarios over time. Changes in precipitation had little effect on fire characteristics or vegetation and landscape characteristics, indicating that simulated precipitation changes were not sufficient to significantly affect vegetation moisture stress or fire behavior on this landscape. Current heavy fuel loads controlled early fire dynamics, with high mean fire intensities occurring early in all simulations. Increases in fire frequency accompanied all temperature increases, leading to decreasing fuel loads and fire intensities over time in warming scenarios. With no increase in temperature or in fire frequency, high fire intensities and heavier fuel loads were sustained. Over time, more fire associated with warming or less fire suppression increased the percentage of the landscape occupied by non-forest and fire-sensitive early seral forest successional stages, which tended to increase the percentage of fire area burning at high severity (in terms of tree mortality). This fire-vegetation relationship may reflect a return to a more historical range of conditions on this landscape. Higher temperatures and fire frequency led to significant spatial migration of forest types across the landscape, with communities at the highest and lowest elevations particularly affected. Warming led to an upslope shift of warm mixed conifer and ponderosa pine (Pinus ponderosa) forests, severely contracting (under 3�� of warming) or eliminating (under 6�� of warming) area dominated by mountain hemlock (Tsuga mertensiana) and cool, wet conifer forest in the high western portion of the landscape. In lower elevations, warming and fire together contributed to significant expansion of open (<10% tree canopy cover) forest and grass- and shrubland. The compositional changes and spatial shifts simulated in the warming scenarios suggest that climate change is likely to significantly affect forests on this landscape. Warming and associated fire also tended to increase heterogeneity of forest structural stages and landscape pattern, resulting in a more diverse distribution of structural stages, especially in lower elevations, and a more divided landscape of smaller forest stands. The NMS ordination emphasized the dissimilarity between the severe +6�� scenarios and the other two temperature scenarios. The +0�� and +3�� scenarios differed from each other in composition (mainly because cool forest was lost in the +3�� scenarios), but within a given level of fire suppression they remained remarkably similar in terms of overall composition, structure, and landscape pattern, while the +6�� scenarios separated noticeably from them. Such decisive differences suggest that under the simulated ranges of precipitation and fire suppression, the interval between 3 and 6 degrees of warming on this landscape may capture an ecological threshold, or tipping point. Additional simulation research that incorporates (for example) management actions, insects and pathogens, and a wider array of precipitation scenarios could help illuminate more clearly the possible range of future landscape conditions. Still, these results provide a glimpse of potential divergent outcomes on this important landscape under possible future climates, and suggest that these forests will undergo considerable changes from both historical and current conditions in response to higher temperatures expected in this area. Some changes may be inevitable with warming, such as the upslope shift of warm forest types, but careful planning for fire and fuels management might allow land managers to modulate fire behavior and steer vegetation dynamics toward the most desirable outcome possible.
Graduation date: 2013

Dissertação de Mestrado Integrado em Engenharia Mecânica apresentada à Faculdade de Ciências e Tecnologia
The aim of this paper is the study of junction fires as a type of extreme fire behaviour (EFB). This study will be based on the development of numerical simulations and experimental tests. The main purpose of analysing fire behaviour is his prediction in the future and consequently the adoption of preventive and control means . The numerical simulations were elaborated on the Fire Dynamics Simulator (FDS) and were based on real conditions. These were applied on different configurations and parameters. The experimental tests were carried out inside a wind tunnel provided by Fire Research Laboratory of the University of Coimbra (LEIF). The fuel used was pine needles (Pinus Pinaster) with a load like the one existent in a pinewood forest. Different configurations were also tested. Both methodologies intend to verify the influence of some parameters mainly in the rate of spread of the fire, but also in other phenomena like flow speed and temperature. These parameters are the angle between the two fire fronts (15º, 30º and 40º), the wind speed (0m/s, 1m/s, 2m/s and 3m/s), and the wind direction (same as propagation, perpendicular to propagation and opposite to propagation). Those parameters were combined between them. The purpose of studying numerical simulations in parallel with experimental tests is the ability to study some quantities in a more deepen way and to validate the results. Finally, it was concluded that wind plays one of the main roles in the development of junction fires.
Este trabalho tem como objetivo o estudo das frentes convergentes como um tipo de comportamento extremo do fogo, e será assente tanto no desenvolvimento de simulações numéricas como na realização de ensaios experimentais. Ao analisar o comportamento do fogo pretende-se que no futuro sejam possíveis a sua previsão e consequente adoção das medidas necessárias para o seu controlo. As simulações numéricas foram elaboradas no Fire Dynamics Simulator (FDS) e foram baseadas em condições reais. Estas foram aplicadas a diferentes configurações e parâmetros. Os ensaios experimentais foram realizados num túnel de vento no Laboratório de Estudos sobre Incêndios Florestais (LEIF). O combustível utilizado foi agulhas de pinheiro (Pinus Pinaster) com uma carga semelhante à que existiria numa situação real de pinhal e foram igualmente testadas diferentes configurações. Ambas as metodologias pretendem verificar qual a influência de alguns parâmetros na velocidade de propagação do fogo e noutros fenómenos como a velocidade de escoamento e a temperatura. Esses parâmetros são os ângulos entre as duas frentes (15º,30º e 40º), a velocidade do vento (0m/s, 1m/s, 2m/s, 3m/s) e a sua direção (mesma da propagação, perpendicular à propagação e oposta à propagação). Foram realizadas combinações entre estes parâmetros. A finalidade de estudar simulações numéricas em paralelo com ensaios laboratoriais prende-se com a capacidade de poder aprofundar os conhecimentos nas primeiras e validá-las com os segundos.Por fim, concluiu-se que o vento é de facto um dos fatores determinantes no que diz respeito ao desenvolvimento de frentes convergentes.