FSim and the expanding uses of fire risk simulation

FSim is a wildfire simulation system that produces national-scale maps of wildfire probability and intensity—critical components of risk. By modeling hundreds of millions of possible large fire events, it overcomes the limitations of sparse historical records and supports applications from community wildfire planning to the insurance sector. Its hazard maps, updated regularly, now underpin key programs such as Wildfire Risk to Communities, the Fireshed Registry, and national fuel treatment planning.

FSim was developed at the USDA Forest Service Missoula Fire Sciences Laboratory in 2007 to estimate wildfire hazard, a key component of wildfire risk. Risk is formally defined as the product of probability and consequence; in this framework, hazard refers to the probabilistic components.  

Estimating both probability and consequence is uniquely difficult for wildfire. Large fires account for most burned areas and risks, yet they often ignite far from where they ultimately spread, limiting the usefulness of historical records alone. Because the number and spatial coverage of reported large fires are insufficient for precise estimates of probabilities, spatial simulation is required and is very computationally intensive. FSim was designed to address this challenge by simulating the growth and behavior of hundreds of millions of large fires and their annual probabilities. FSim combines historical fire occurrence and weather records with synthetic weather sequences, fuel moisture, and current data on fuels, vegetation, and terrain. It contains methods for statistically approximating the complex effects of suppression on fire growth and subsequent behavior.

Using FSim, wildfire probability and intensity can be mapped for any location in the United States. At national scales, simulations have been conducted at 270 m resolution, while smaller areas can be resolved at 90 m. Hazard maps must be updated every one to two years to account for landscape changes (for example, recent wildfires and management activities), new ignition and weather records, and advances in fire science. These maps now underpin a wide range of applications, including Wildfire Risk to Communities; the Fireshed Registry; Wildfire Risk to Carbon Stocks; and assessments of fuel treatment effectiveness and wildfire impacts on communities, water resources, and critical infrastructure. 

Photo Credit

USDA Forest Service

Burn probability map generated by FSim for the conterminous United States.