How To Generate And Interpret Fire Characteristics Charts For Surface And Crown Fire Behavior

A fire characteristics chart is a graph that presents primary related fire behavior characteristics-rate of spread, flame length, fireline intensity, and heat per unit area. It helps communicate and interpret modeled or observed fire behavior. The Fire Characteristics Chart computer program plots either observed fire behavior or values that have been calculated by another computer program such as the BehavePlus fire modeling system. Program operation is described in this report, and its flexibility in format, color, and labeling is demonstrated for use in a variety of reports. A chart produced by the program is suitable for inclusion in briefings, reports, and presentations. Example applications are given for fire model understanding, observed crown fire behavior, ignition pattern effect on fire behavior, prescribed fire planning, briefings, and case studies. The mathematical foundation for the charts is also described. Separate charts are available for surface fire and crown fire because of differences in the flame length model used for each.

A fire characteristics chart is a graph that presents primary related fire behavior characteristics—rate of spread, flame length, fireline intensity, and heat per unit area. It helps communicate and interpret modeled or observed fire behavior. The Fire Characteristics Chart computer program plots either observed fire behavior or values that have been calculated by another computer program such as the BehavePlus fire modeling system. Program operation is described in this report, and its flexibility in format, color, and labeling is demonstrated for use in a variety of reports. A chart produced by the program is suitable for inclusion in briefings, reports, and presentations. Example applications are given for fire model understanding, observed crown fire behavior, ignition pattern effect on fire behavior, prescribed fire planning, briefings, and case studies. The mathematical foundation for the charts is also described. Separate charts are available for surface fire and crown fire because of differences in the flame length model used for each.

Fire managers are increasingly concerned about the threat of crown fires, yet only now are quantitative methods for assessing crown fire hazard being developed. Links among existing mathematical models of fire behavior are used to develop two indices of crown fire hazard-the Torching Index and Crowning Index. These indices can be used to ordinate different forest stands by their relative susceptibility to crown fire and to compare the effectiveness of crown fire mitigation treatments. The coupled model was used to simulate the wide range of fire behavior possible in a forest stand, from a low-intensity surface fire to a high-intensity active crown fire, for the purpose of comparing potential fire behavior. The hazard indices and behavior simulations incorporate the effects of surface fuel characteristics, dead and live fuel moistures (surface and crown), slope steepness, canopy base height, canopy bulk density, and wind reduction by the canopy. Example simulations are for western Montana Pinus ponderosa and Pinus contorta stands. Although some of the models presented here have had limited testing or restricted geographic applicability, the concepts will apply to models for other regions and new models with greater geographic applicability.