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The Fuel Characteristic Classification System (FCCS) includes equations that calculate energy release and one-dimensional spread rate in quasi-steady state fires in heterogeneous but spatially-uniform wildland fuelbeds, using a reformulation of the widely used Rothermel fire spread model. This reformulation provides an automated means to predict fire behavior under any environmental conditions in any natural, modified, or simulated wildland fuelbed. The formulation may be used to compare potential fire behavior between fuelbeds that differ in time, space, or as a result of management, and provides a means to classify and map fuelbeds based on their expected surface fire behavior under any set of defined environmental conditions (i.e., effective wind speed and fuel moisture content). Model reformulation preserves the basic mathematical framework of the Rothermel fire spread model, reinterprets data from two of the original basic equations in his model, and offers a new conceptual formulation that allows the direct use of inventoried fuel properties instead of stylized fuel models. Alternative methods for calculating the effect of wind speed and fuel moisture, based on more recent literature, are also provided. This reformulation provides a framework for the incremental improvement in quantifying fire behaviour parameters in complex fuelbeds and for modeling fire spread.

The Fuel Characteristic Classification System (FCCS) is a systematic catalog of inherent physical properties of wildland fuelbeds that allows land managers, policy makers, and scientists to build and calculate fuel characteristics with complete or incomplete information. The FCCS is equipped with a set of equations to calculate the potential of any real-world or simulated fuelbed to spread fire across the surface and in the crowns, and consume fuels. FCCS fire potentials are a set of relative values that rate the intrinsic physical capacity of a wildland fuelbed to release energy and to spread, crown, consume, and smolder under known or benchmark weather and fuel moisture conditions. The FCCS reports eight component fire potentials for every fuelbed, arranged in three categories: surface fire behaviour (reaction intensity, spread rate, and flame length), crown fire potential (torching and active crown fire), and available fuel potential (flaming, smouldering, and residual smouldering). FCCS fire potentials may be used to classify or compare fuelbeds that differ because of location, structure, passage of time, or management action, based on expected fire behavior or effect outcomes. As a classification tool, they are offered as an objective alternative to categorizing bulk properties of fuelbeds or stylized model inputs.

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.Résumé : Cet article présente un cadre conceptuel pour classer le potentiel de feu de cimes des couches de combustibles en milieu naturel où il y a des canopées forestières. Cette approche pousse plus loin les travaux de Van Wagner et de Rothermel et introduit plusieurs concepts physiques nouveaux dans la modélisation du comportement des feux de cimes dérivés des concepts reformulés de Rothermel pour la modélisation des feux de surface proposés par Sandburg et al. (ce numéro). Ce cadre forme la base pour calculer les potentiels de feu de cimes des couches de combustibles du système de classification des caractéristiques des combustibles (SCCC) (Ottmar et al., ce numéro). Deux nouvelles possibilités de feux de cimes sont proposées : (i) la possibilité de flambée en chandelle et (ii) la possibilité de feu de cime dépendant. Une comparaison systématique de ces deux types de feux de cimes avec des observations sur le terrain et les prévisions du modèle de l'É cole canadienne d'enquêtes sur les incendies a donné des résultats encourageants. Ces résultats indiquent que le cadre du SCCC pourrait s'avérer un outil utile que les responsables de la gestion des incendies devraient considérer pour classer le potentiel de feu de cimes ou pour évaluer le comportement relatif des feux de cimes dans les canopées forestières.[Traduit par la Rédaction]

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