Fuel model

A Fuel Model is a stylized set of fuel bed characteristics used as input for a variety of wildfire modeling applications. Wildfire behavior models, such as those of Rothermel, take into account numerous empirical variables. While these inputs are important for equation outputs, they are often difficult and time-consuming, if not impossible, to measure for each fuel bed. A fuel model defines these input variables for a stylized set of quantitative vegetation characteristics that can be visually identified in the field. Depending on local conditions, one of several fuel models may be appropriate. As Anderson states “Fuel models are simply tools to help the user realistically estimate fire behavior. The user must maintain a flexible frame of mind and an adaptive method of operating to totally utilize these aids". Furthermore, depending on the application, the user must choose a fuel model classification system. The major classification systems for use in the United States include the National Fire Danger Rating System, the 13 ‘original’ fuel models of Anderson and Albini, the subsequent set of 40 fuels produced by Scott and Burgan, and the Fuel Characteristics Classification System.

The concept of a fuel model was first introduced in 1972 with the National Fire Danger Rating System. The first system of its kind, the NFDRS was a standardized set of equations to determine fire danger at specific points on the landscape. Fuel models were at the core of these calculations, with each of its 20 models containing information about the relative loading of different fuel components. Each model is described by the volume of 1-hr, 10-hr, 100-hr, and 1000-hr dead fuels, herbaceous and woody live fuels present as well as the fuel bed depth and moisture of extinction.

The ‘original 13 fuel models’ were presented first by Albini in 1976 and later expanded upon by Anderson in 1982. Unlike the NFDRS, these fuel models were designed for use with Rothermel’s spread models, and are designed to be used at much smaller spatial scales than the 20 NFDRS models. To allow interchangeability between the two systems, Anderson’s report contains a crosswalk chart to allow conversion between similar models. Furthermore, his paper includes photographs to aid the user in selecting a fuel model. These fire behavior fuel models are “for the severe period of the fire season when wildfires pose greater control problems,” and are designed only for use during the dry season, when the fuel bed becomes more uniform. Additionally, Albini’s models have the following assumptions:

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