BEHAVE Plus Fire Modeling System

The most commonly used software tool for predicting fire behavior in wildland fuels is the BEHAVE Plus Fire Modeling System (freeware), which predicts fire rate of spread in one-dimension. BEHAVE Plus can be used during fires for real-time predictions of either wildfire or prescribed fire behavior. It can also be used in fire behavior training, prescribed fire planning, and dispatch of initial attack fire crews.

The original BEHAVE system was a series of interactive computer programs for estimating wildland fire behavior under various fuel, weather, and topographic situations. Behave was updated in 1998 (BEHAVE Plus) to reflect changes in both user needs and technology. The updated version uses a more user-friendly windows interface, as compared to the original 1984 version written in FORTRAN. Fuel characterization was expanded beyond the fine fuels that carry surface fire spread to include all components: overstory, organic ground fuel, and surface fuel, including the heavy dead and down fuel that burns behind the fire front. BEHAVE Plus utilizes basically the same fire modules as the old Behave: (1) SURFACE - Surface fire spread, intensity, flame length; (2) SIZE - Area and perimeter of a point source fire; (3) SPOT - Spotting distance; (4) SCORCH - Scorch height; (5) MORTALITY - Tree mortality; (6) IGNITE - Probability of ignition; and (7) RH - Relative humidity determination. Other fire models such as crown fire spread, transition to crown fire, large fuel burnout, smoke production, and soil heating are also now included. Worksheets guide the input of values based on the selected modules, input options, and output variables. Values are input directly or by utilizing input "Guide screens" which display a valid range of values and suitable increments for continuous variables and model choices such as grasslands or brush for discrete variables. Units can be entered in either the English or Metric system.

The weather inputs in BEHAVE Plus include a measure of the wind speed (twenty feet above the ground and averaged over ten minutes, midflame or eye-level wind speed, and a wind adjustment factor which accounts for whether or not fuels are sheltered from the wind) and direction (specified as upslope, degrees clockwise from upslope, or degrees clockwise from North). Additional weather inputs are air, wet bulb, and dew point temperatures. Slope steepness (0-45 degrees) and aspect (0-360 degrees clockwise from North) are entered into BEHAVE Plus in the terrain section of the worksheet. Additional parameters entered into the terrain section include site elevation, ridge-to-valley elevation difference, ridge-to-valley horizontal distance, and spotting source location. The Map section of the worksheet uses input values to determine distances and slope steepness using four variables - (1) map representative fraction; (2) contour interval; (3) map distance; and (4) number of contour intervals.

The BEHAVE Plus version 2.0, released in 2003, added modeling capabilities for safety-zone size, containment, lightning ignitions, dynamic palmetto-gallberry fuel models, and diagrammatical output. It is expected that additional features will be added in future releases.

The modeling capabilities of BEHAVE Plus were used in recent research to illustrate the potential fire behavior in pine flatwood forests after treatment with one of three silvicultural techniques at five different ages-of-rough (Brose and Wade 2002). In each stand, understory fuel characteristics were collected as inputs to BEHAVE Plus to build custom fuel models for each treatment/age-of-rough combination. To match the drought conditions of the 1998 wildfires in Florida, fire behavior was simulated for each treatment/rough-age combination under drought as well as normal weather conditions. Fuel models were combined with weather data to calculate specific fire behavior estimates for each combination (Brose and Wade 2002).