Spatial Modeling of Fire in Shrublands using HFire: Model Description and Event Simulation Suggested Running Head: HFire: Model Description and Event Simulation

A raster based, spatially explicit model of surface fire spread called HFire is introduced. HFire uses the Rothermel fire spread equation to determine one dimensional fire spread, which is then fit to two dimensions using the solution to the fire containment problem and the empirical double ellipse formulation of Anderson. HFire borrows the idea of an adaptive time step from previous cell contact raster models and permits fire to spread into a cell from all neighboring cells over multiple time steps as is done in the heat accumulation approach. The model has been developed to support simulations of single fire events and long term fire regimes. The model implements equations for surface fire spread and is appropriate for use in grass or shrubland functional types. Model performance on a synthetic landscape, under controlled conditions was benchmarked using a standard set of tests developed initially to evaluate FARSITE. Additionally, simulations of two Southern California fires spreading through heterogeneous fuels, under realistic conditions showed similar performance between HFire and FARSITE, good agreement to historical reference data, and shorter model run times for HFire. HFire is available for download: http://firecenter.berkeley.edu/hfire. Fifty-Word Summary An efficient raster fire spread model named HFire is introduced. HFire can simulate single fire events or long term fire regimes, using the same fire spread algorithm. This paper describes the HFire algorithm, benchmarks the model using a standard set of tests developed by Finney (1998) for FARSITE, and compares historical and predicted fire spread perimeters for two Southern California fires.