Modelling the rate of fire spread and uncertainty associated with the onset and propagation of crown fires in conifer forest stands

2017 ◽  
Vol 26 (5) ◽  
pp. 413 ◽  
Author(s):  
Miguel G. Cruz ◽  
Martin E. Alexander
Keyword(s):  
Monte Carlo ◽  
Average Rate ◽  
Fire Spread ◽  
Prediction Errors ◽  
Crown Fire ◽  
Conifer Forest ◽  
Fire Behaviour ◽  
Crown Fires ◽  
Deterministic Modelling ◽  
Eastern Australia

Crown fires are complex, unstable phenomena dependent on feedback mechanisms between the combustion products of distinct fuel layers. We describe non-linear fire behaviour associated with crowning and the uncertainty they cause in fire behaviour predictions by running a semiphysical modelling system within a simple Monte Carlo simulation framework. The method was able to capture the dynamics of passive and active crown fire spread regimes, providing estimates of average rate of spread and the extent of crown fire activity. System outputs were evaluated against data collected from a wildfire that occurred in a radiata pine plantation in south-eastern Australia. The Monte Carlo method reduced prediction errors relative to the more commonly used deterministic modelling approach, and allowed a more complete description of the level of crown fire behaviour to expect. The method also provides uncertainty measures and probabilistic outputs, extending the range of questions that can be answered by fire behaviour models.

Variation in wind and crown fire behaviour in a northern jack pine – black spruce forest

2004 ◽  
Vol 34 (8) ◽  
pp. 1561-1576 ◽  
Author(s):  
S W Taylor ◽  
B M Wotton ◽  
M E Alexander ◽  
G N Dalrymple
Keyword(s):  
Black Spruce ◽  
Flame Temperature ◽  
Fire Spread ◽  
Crown Fire ◽  
Fire Behaviour ◽  
Canopy Layer ◽  
Crown Fires ◽  
Video Observations ◽  
Before And After ◽  
Fire Front

Fire spread and flame temperature were examined in a series of nine experimental crown fires conducted in the Northwest Territories, Canada. Average rates of spread were 17.8–66.8 m·min–1 (0.3–1.1 m·s–1) over burning periods from about 1.5–10 min across 75 m × 75 m to 150 m × 150 m plots. Detailed maps of fire front progression revealed areas with higher rates of spread in the order of tens of metres in horizontal dimension and tens of seconds in duration in several of the fires, which is consistent with the influence of coherent wind gusts. Comparison of open and in-stand wind speed before and after burning suggests that defoliation in the canopy layer during burning would result in the flaming zone having greater exposure to the ambient wind. Estimates of flame front residence from video observations at the surface averaged 34 s; estimates from temperature measurements decreased significantly with height from 74 s at the surface to 31 s below the canopy.

The role of weather, past fire and topography in crown fire occurrence in eastern Australia

2016 ◽  
Vol 25 (10) ◽  
pp. 1048 ◽  
Author(s):  
Michael Storey ◽  
Owen Price ◽  
Elizabeth Tasker
Keyword(s):  
Prescribed Burning ◽  
Nonlinear Effects ◽  
Fire Spread ◽  
Fire Weather ◽  
Crown Fire ◽  
Fire Behaviour ◽  
Eastern Australia ◽  
Fuel Accumulation ◽  
Behaviour Models

We analysed the influence of weather, time since fire (TSF) and topography on the occurrence of crown fire, as mapped from satellite imagery, in 23 of the largest wildfires in dry sclerophyll forests in eastern Australia from 2002 to 2013. Fires were analysed both individually and as groups. Fire weather was the most important predictor of crown consumption. TSF (a surrogate for fuel accumulation) had complex nonlinear effects that varied among fires. Crown fire likelihood was low up to 4 years post-fire, peaked at ~10 years post-fire and then declined. There was no clear indication that recent burning became more or less effective as fire weather became more severe. Steeper slope reduced crown fire likelihood, contrary to the assumptions of common fire behaviour equations. More exposed areas (ridges and plains) had higher crown fire likelihood. Our results suggest prescribed burning to maintain an average of 10 years’ TSF may actually increase crown fire likelihood, but burning much more frequently can be effective for risk reduction. Our results also suggest the effects of weather, TSF and slope are not adequately represented in the underlying equations of most fire behaviour models, potentially leading to poor prediction of fire spread and risk.

Got to burn to learn: the effect of fuel load on grassland fire behaviour and its management implications

2018 ◽  
Vol 27 (11) ◽  
pp. 727 ◽  
Author(s):  
Miguel G. Cruz ◽  
Andrew L. Sullivan ◽  
James S. Gould ◽  
Richard J. Hurley ◽  
Matt P. Plucinski
Keyword(s):  
Fire Spread ◽  
Flame Height ◽  
Fuel Load ◽  
Limiting Factor ◽  
Fire Behaviour ◽  
Load Effect ◽  
Fire Propagation ◽  
Rate Of Spread ◽  
Eastern Australia ◽  
Modelling Assumptions

The effect of grass fuel load on fire behaviour and fire danger has been a contentious issue for some time in Australia. Existing operational models have placed different emphases on the effect of fuel load on model outputs, which has created uncertainty in the operational assessment of fire potential and has led to end-user and public distrust of model outcomes. A field-based experimental burning program was conducted to quantify the effect of fuel load on headfire rate of spread and other fire behaviour characteristics in grasslands. A total of 58 experimental fires conducted at six sites across eastern Australia were analysed. We found an inverse relationship between fuel load and the rate of spread in grasslands, which is contrary to current, untested, modelling assumptions. This result is valid for grasslands where fuel load is not a limiting factor for fire propagation. We discuss the reasons for this effect and model it to produce a fuel load effect function that can be applied to operational grassfire spread models used in Australia. We also analyse the effect of fuel load on flame characteristics and develop a model for flame height as a function of rate of fire spread and fuel load.

scholarly journals Assessment of crown fire initiation and spread models in Mediterranean conifer forests by using data from field and laboratory experiments

2017 ◽  
Vol 26 (2) ◽  
pp. e02S ◽  
Author(s):  
Francisco Rodríguez y Silva ◽  
Mercedes Guijarro ◽  
Javier Madrigal ◽  
Enrique Jiménez ◽  
Juan R. Molina ◽  
...  
Keyword(s):  
Fire Spread ◽  
Full Scale ◽  
Research Centre ◽  
Crown Fire ◽  
Fire Behaviour ◽  
Bench Scale ◽  
Fire Experiment ◽  
Fire Initiation ◽  
Scale Experiment

Aims of study: To conduct the first full-scale crown fire experiment carried out in a Mediterranean conifer stand in Spain; to use different data sources to assess crown fire initiation and spread models, and to evaluate the role of convection in crown fire initiation.Area of study: The Sierra Morena mountains (Coordinates ETRS89 30N: X: 284793-285038; Y: 4218650-4218766), southern Spain, and the outdoor facilities of the Lourizán Forest Research Centre, northwestern Spain.Material and methods: The full-scale crown fire experiment was conducted in a young Pinus pinea stand. Field data were compared with data predicted using the most used crown fire spread models. A small-scale experiment was developed with Pinus pinaster trees to evaluate the role of convection in crown fire initiation. Mass loss calorimeter tests were conducted with P. pinea needles to estimate residence time of the flame, which was used to validate the crown fire spread model.Main results: The commonly used crown fire models underestimated the crown fire spread rate observed in the full-scale experiment, but the proposed new integrated approach yielded better fits. Without wind-forced convection, tree crowns did not ignite until flames from an intense surface fire contacted tree foliage. Bench-scale tests based on radiation heat flux therefore offer a limited insight to full-scale phenomena.Research highlights: Existing crown fire behaviour models may underestimate the rate of spread of crown fires in many Mediterranean ecosystems. New bench-scale methods based on flame buoyancy and more crown field experiments allowing detailed measurements of fire behaviour are needed.

scholarly journals Quantifying Stand Targets for Silvicultural Prevention of Crown Fires

2002 ◽  
Vol 17 (2) ◽  
pp. 101-109 ◽  
Author(s):  
Christopher R. Keyes ◽  
Kevin L. O'Hara
Keyword(s):  
Stand Structure ◽  
Fire Spread ◽  
Crown Fire ◽  
Fuel Management ◽  
Data Types ◽  
Crown Fires ◽  
Quantitative Basis ◽  
The Relationship ◽  
Stand Conditions ◽  
Forest Managers

Abstract Forest managers are expressing a growing interest in proactively reducing susceptibility to crown fires, but the quantitative basis for defining specific stand targets and prescribing silvicultural regimes for this objective is lacking. A procedure is presented for creating resistant stand structures that exploits the relationship between crown fire development and characteristics of stand structure. The BEHAVE surface fire model was integrated with modified versions of the Van Wagner crown ignition and crown fire spread equations in order to quantify structural targets for mitigative silvicultural practices. The procedure tolerates an array of input data types for weather, site, and surface fuel variables so that hazard-reducing guidelines are tailored to specific site and stand conditions. Suggested strategies for achieving crown fire-resistant stand targets include pruning, low thinning, and surface fuel management. West. J. Appl. For. 17(2):101–109.

Crown fire behaviour in a northern jack pine – black spruce forest

2004 ◽  
Vol 34 (8) ◽  
pp. 1548-1560 ◽  
Author(s):  
B J Stocks ◽  
M E Alexander ◽  
B M Wotton ◽  
C N Stefner ◽  
M D Flannigan ◽  
...  
Keyword(s):  
Black Spruce ◽  
Significant Proportion ◽  
Weather Conditions ◽  
Crown Fire ◽  
Fire Behaviour ◽  
Fire Modelling ◽  
Crown Fires ◽  
Floor Layer ◽  
Prediction Systems ◽  
High Degree

This paper reports on the behaviour of 10 experimental crown fires conducted between 1997 and 2000 during the International Crown Fire Modelling Experiment (ICFME) in Canada's Northwest Territories. The primary goal of ICFME was a replicated series of high-intensity crown fires designed to validate and improve existing theoretical and empirical models of crown fire behaviour. Fire behaviour characteristics were typical for fully developed boreal forest crown fires, with fires advancing at 15–70 m/min, consuming significant quantities of fuel (2.8–5.5 kg/m2) and releasing vast amounts of thermal heat energy. The resulting flame fronts commonly extended 25–40 m above the ground with head fire intensities up to 90 000 kW/m. Depth of burn ranged from 1.4–3.6 cm, representing a 25%–65% reduction in the thickness of the forest floor layer. Most of the smaller diameter (<3.0 cm) woody surface fuels were consumed, along with a significant proportion of the larger downed woody material. A high degree of fuel consumption occurred in the understory and overstory canopy with very little material less than 1.0 cm in diameter remaining. The documentation of fire behaviour, fire danger, and fire weather conditions carried out during ICFME permitted the evaluation of several empirically based North American fire behaviour prediction systems and models.

Conditions for the start and spread of crown fire

1977 ◽  
Vol 7 (1) ◽  
pp. 23-34 ◽  
Author(s):  
C. E. Van Wagner
Keyword(s):  
Heat Transfer ◽  
Bulk Density ◽  
Combustion Zone ◽  
Ground Surface ◽  
Conifer Forests ◽  
Crown Fire ◽  
Surface Phase ◽  
Conifer Forest ◽  
Crown Fires

Some theory and observations are presented on the factors governing the start and spread of crown fire in conifer forests. Crown fires are classified in three ways according to the degree of dependence of the crown phase of the fire on the ground surface phase. The crown fuel is pictured as a layer of uniform bulk density and height above ground. Simple criteria are presented for the initiation of crown combustion and for the minimum rates of spread and heat transfer into the crown combustion zone at which the crown fire will spread. The theory is partially supported by some observations in four kinds of conifer forest.

Relating flame radiation to home ignition using modeling and experimental crown fires

2004 ◽  
Vol 34 (8) ◽  
pp. 1616-1626 ◽  
Author(s):  
Jack D Cohen
Keyword(s):  
Forest Canopy ◽  
Severe Case ◽  
Fire Spread ◽  
Forest Plot ◽  
Crown Fire ◽  
Flame Radiation ◽  
Flame Heating ◽  
Crown Fires ◽  
Piloted Ignition ◽  
Fire Experiments

Wildland–urban fire destruction depends on homes igniting and thus requires an examination of the ignition requirements. A physical–theoretical model, based on severe case conditions and ideal heat transfer characteristics, estimated wood wall ignition occurrence from flame radiation heating and piloted ignition requirements. Crown fire experiments provided an opportunity for assessing model reliability. The crown fire experiments were specifically instrumented with wood wall sections and heat flux sensors to investigate direct flame heating leading to home ignition during wildland fires. The experimental results indicated that the flame radiation model overestimated the structure-to-flame distance that would result in wood wall ignition. Wall sections that ignited during the experimental crown fires did not sustain flaming after crown fire burnout. The experiments also revealed that the forest canopy attenuated the flame radiation as the crown fire spread within the forest plot. Ignition modeling and the associated crown fire experiments described the flame-to-structure distance scale associated with flame heating related to wall ignition.

A radiation-driven model for crown fire spread

2004 ◽  
Vol 34 (8) ◽  
pp. 1588-1599 ◽  
Author(s):  
B W Butler ◽  
M A Finney ◽  
P L Andrews ◽  
F A Albini
Keyword(s):  
Closed Form ◽  
A Priori ◽  
Radiant Energy ◽  
Fire Spread ◽  
Crown Fire ◽  
Spread Rate ◽  
Fire Modelling ◽  
Crown Fires ◽  
Environment Variables ◽  
Fire Front

A numerical model for the prediction of the spread rate and intensity of forest crown fires has been developed. The model is the culmination of over 20 years of previously reported fire modeling research and experiments; however, it is only recently that it has been formulated in a closed form that permits a priori prediction of crown fire spread rates. This study presents a brief review of the development and structure of the model followed by a discussion of recent modifications made to formulate a fully predictive model. The model is based on the assumption that radiant energy transfer dominates energy exchange between the fire and unignited fuel with provisions for convective cooling of the fuels ahead of the fire front. Model predictions are compared against measured spread rates of selected experimental fires conducted during the International Crown Fire Modelling Experiment. Results of the comparison indicate that the closed form of the model accurately predicts the relative response of fire spread rate to fuel and environment variables but overpredicts the magnitude of fire spread rates.

A conceptual framework for ranking crown fire potential in wildland fuelbedsThis article is one of a selection of papers published in the Special Forum on the Fuel Characteristic Classification System.

2007 ◽  
Vol 37 (12) ◽  
pp. 2464-2478 ◽  
Author(s):  
Mark D. Schaaf ◽  
David V. Sandberg ◽  
Maarten D. Schreuder ◽  
Cynthia L. Riccardi
Keyword(s):  
Conceptual Framework ◽  
Classification System ◽  
Field Observations ◽  
Crown Fire ◽  
Fire Behaviour ◽  
Forest Canopies ◽  
Crown Fires ◽  
Fire Initiation ◽  
Fuel Characteristic ◽  
Selection Of

This paper presents a conceptual framework for ranking the crown fire potential of wildland fuelbeds with forest canopies. This approach extends the work by Van Wagner and Rothermel, and introduces several new physical concepts to the modeling of crown fire behaviour derived from the reformulated Rothermel surface fire modeling concepts proposed by Sandberg et al. (this issue). This framework forms the basis for calculating the crown fire potentials of Fuel Characteristic Classification System (FCCS) fuelbeds (Ottmar et al., this issue). Two new crown fire potentials are proposed (i) the torching potential (TP) and (ii) the active crown potential (AP). A systematic comparison of TP and AP against field observations and Crown Fire Initiation and Spread (CFIS) model outputs produced encouraging results, suggesting that the FCCS framework might be a useful tool for fire managers to consider when ranking the potential for crown fires or evaluating the relative behaviour of crown fires in forest canopies.

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