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Abstract
Wildfire risk assessments rely on flame-length probabilities - the conditional probabilities that fire intensity will be within various flame-length classes. The factors affecting flame-length probability include the elements of the fire-behavior triangle - fuel, weather, and topography - plus the orientation of the flaming front relative to the heading direction. Current methods for determining flame-length probabilities include: (1) a single deterministic simulation of flame length at the head of the fire for one weather type (wind speed, wind direction, fuel moisture content); (2) multiple deterministic simulations of flame length at the head of the fire (for several weather types), which are then integrated; and (3) stochastic simulation of fire growth and flame length across a few to several dozen weather types. In this paper, we describe a deterministic process, called FLEP-Gen, that addresses shortcomings of the current methods. It improves upon the multiple-simulation approach by (1) incorporating fire intensity in non-heading spread directions and (2) weighting the weather types by their relative area burned rather than just their temporal relative frequencies. We present the mathematical basis for the process - based on the geometry of an ellipse - as well as spatial and nonspatial examples of its application to various fire management problems.
Parent Publication
Citation
Scott, Joe H. 2020. A deterministic method for generating flame-length probabilities. In: Hood, Sharon M.; Drury, Stacy; Steelman, Toddi; Steffens, Ron, [eds.]. Proceedings of the Fire Continuum-Preparing for the future of wildland fire; 2018 May 21-24; Missoula, MT. Proceedings RMRS-P-78. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station. p. 195-205.
