United States Department of Agriculture

Farsite: Fire Area Simulator?model Development and Evaluation United States Department of Agriculture

Publisher Marketing: This paper reports on the structure of a fire growth simulation model, FARSITE, and its performance under simplified test conditions. FARSITE incorporates existing models of surface fire, crown fire, point-source fire acceleration, spotting, and fuel moisture. This documentation of how the simulation was constructed, and how the individual fire behavior models perform, will be useful to researchers and managers who use FARSITE or are interested in fire growth simulation. The models were integrated using a vector propagation technique for fire perimeter expansion that controls for both space and time resolution of fire growth over the landscape. The model produces vector fire perimeters (polygons) at specified time intervals. The vertices of these polygons contain information on the fire's spread rate and intensity, which are interpolated to produce raster maps of fire behavior. Because fire behavior at each vertex is assumed independent of the others, the simulation outputs illustrate the strict spatial consequences to fire behavior of incorporating the models into a two-dimensional simulation. Simplified test conditions show that surface fire growth and intensity conform to idealized patterns. Similarities also exist between simulated crown fires and observed patterns of extreme wind-driven fires. Complex patterns of fire growth and behavior result from the spatial and temporal dependencies in the model. The limitations and assumptions of this approach are discussed.