Use the Fire Fuel Tool to create a spatial map showing the distribution of fire fuels and burn hazards for a region. Fire fuel mapping can be useful for forest planners, as well as local governments attempting to mitigate fire risks within the rapidly growing forest/urban interface.

High fire fuel distributions contain dry or dying plant material, which contains less water, whereas low fire fuel distributions typically consist of lush, green plants.

If fire fuels are located beneath a closed canopy, they may not be detected by the Fire Fuel Tool. The higher greenness values caused by canopy closure automatically reduce the fire risk calculation. Additionally, dry or senescent VIs are only sensitive to the top layer of the vegetation, causing the dry vegetation beneath it to be obscured by the upper layer of green vegetation. As such, dry materials under a closed canopy may not be properly detected.

Fire fuel analysis uses the following VI categories:

To calculate fire fuel:

  1. From the Toolbox, select Spectral > Vegetation > Fire Fuel Vegetation Analysis. The Vegetation Products Calculation Input File dialog appears.
  2. Select the input file. The file may be a VI output file you created previously using the Vegetation Index Calculator or Spectral Index tool. Or you can select a hyperspectral data file that has been radiometrically calibrated and corrected for atmospheric effects.
  3. Select a spatial subset by clicking Spatial Subset. Using spatial subsetting with the Fire Fuel Tool may further refine the results.
  4. Apply optional masking to the data by clicking Select Mask Band and selecting the desired mask image.
  5. Click OK. The Fire Fuel Parameters dialog appears.
  6. Select a broadband or narrowband greenness VI from the Greenness Index drop-down list.
  7. Enter a Minimum valid greenness value to use in the fire fuel calculation. Any values in the image less than the value you specify are masked out in the classification result. This setting, along with a proper mask selection, is useful for areas that contain different terrain types. The default value is 0.
  8. Select a VI from the Canopy Water drop-down list.
  9. Select a VI from the Dry or Senescent Carbon Index drop-down list.
  10. Output the result to File or Memory.
  11. Click OK. ENVI adds the resulting output to the Layer Manager.

The Fire Fuel Tool divides the input scene into nine classes, from least fuel (lowest apparent fire risk) to most fuel (highest apparent fire risk). Following is the classification map for the Fire Fuel Tool output.

The classifications are relative to the particular input scene only and cannot be generalized to other areas or other scenes. Field examination is essential to link the classes provided by the tool with the real-world conditions they represent. You cannot compare classes between scenes, as the vegetative variability between scenes could be significant, and the actual classification values may not match. For example, a classification color of green in one scene could represent the same field conditions as a classification color of orange in another.

Related Topics

Spectral Indices, Burn Indices Background, Vegetation Indices, Vegetation Analysis Tools, Agricultural Stress Tool, Forest Health Tool, Vegetation and Its Reflectance Properties