Risk: Net Value Change

When it is not possible to directly link the effect of fire on a highly valued resource or asset (HVRA), response functions can be used instead (Calkin et al. 2010). Response functions translate positive and negative fire effects into net value change (NVC) for HVRAs based on the flame length intensity categories within the FLP file. Response functions are developed by considering the different ways in which HVRAs will respond to fire of different intensities.

Response function examples with percent net value change (+/- %) for six flame length categories.

Example graphs of response functions of net value change by flame length categories for two different HVRAs.

Correlation between the FIL categories output in FlamMap5 FLP files and response function flame length categories. The FIL assigned is based on the mid-point value of the FIL category.

The Net Value Change form in ArcFuels calculates both the expected and conditional NVC. The former represents an expectation of NVC that accounts for the probability of a fire, and the latter represents the change in NVC given that a fire occurs. The process combines burn probability and intensity from the FLP files with the response function to calculate a percentage change in the HVRA. The HVRA can be mapped with either a raster or a shapefile.

FLP and HVRA inputs:

• The FLP Layer is specified using the drop-down list. This is the point shapefile.
• If the calculations are completed for a HVRA that does not cover the entire extent of the FLP it needs to be spatially defined with a raster or a shapefile
  • HVRA Raster (opt) where the raster has a VALUE=1
  • HVRA Shapefile with a HVRA Attribute field defining the area (yes=1, no=0).

Response function values:

• Response function values are entered in the text boxes below Relative net value change by flame length class
• To apply the response function and populate the Relative net vale gain/loss (+/-) boxes click the Apply Response Functions button.
  • ArcFuels will automatically assign the response functions to the correct FIL (Category) based on the input FLP.

Outputs:

• The Output field names to be appended to the FLP shapefile are set for the Expected NVC, and Conditional NVC.
  • These can be typed in the text boxes to create new fields, or selected from existing fields using the drop-down list.
• To Create rastersoption will create rasters for the expected and conditional NVC fields created.
•  Expected NVC raster name and Conditional NVC raster name will need to be typed in the text boxes.
  • Names need to comply with raster naming protocols for ArcMap, less than 13 characters, does not start with a number, and no special characters with the exception of an underscore.
• The Spatial reference is set using the drop-down list.
• The Output format of the rasters can be Individual items, or Geodatabase.
  • Individual itemsare output in the Target Folder . The default is the output folder specified when setting up a project in the Project Settings form.
  • Rasters output into a Geodatabase require the path and name of the Geodatabase and the Work folder. The default location of the Work folder is the same as the Target folder.

Exercise 28—Calculating NVC using a raster extent of lynx habitat

In this exercise, expected loss will be calculated for the supplied hypothetical lynx habitat raster (hvr_lynx) using the el20_FLP.shp (converted in Exercise 24), and response function described below.

For lynx habitat we will assume that fire is increasingly negative for higher flame lengths. And that translates to the following response function:

Click the Risk button on the ArcFuels10 toolbar, then select Net Value Change from the drop-down list.

Fill out the Net Value Change form following the figure below.

• Click the Apply Response Function button.
• Click the Calculate NVC button to complete the calculations.
• A progress meter will open, then close after the calculations are completed.
• A window will open indicating the number of calculations that were completed. Click the OK button to close the window.

• Click the Close button to close the Net Value Change form.

Return to ArcMap.

• The newly created rasters will be within the Conversion Results directory of the Table of Contents in ArcMap.

• Look at the cNVC_lynx raster created. Because the response function applied characterized all fire as having a negative effect on lynx habitat, all of the values of NVC are less than 0. But some areas were not as negatively impacted as others.

Conditional net value change for hypothetical lynx habitat (warmer colors are more negative than cooler colors).

When naming the attribute fields using the Net Value Change form the names can only be 10 characters long. If the names are longer an error window will open. Press Continue to close the window, then close the progress meter using the X in the top right-hand corner, and re-name the fields.

Exercise 29—Calculating NVC using a shapefile extent of elk habitat

In this exercise, expected loss will be calculated for the supplied hypothetical elk habitat using the an attributed shapefile for a sub area of the Mt. Emily landscape where FlamMap5 was run. The FLP we will use was converted in Exercise 25, FLP6_s300_FLP.shp, and response function described below.

For elk habitat we will assume that low severity fire is beneficial but higher severity fire is increasingly negative. And that translates to the following response function:

Click the Risk button on the ArcFuels10 toolbar, then select Net Value Change from the drop-down list.

Fill out the Net Value Change form following the figure below.

• Click the Calculate NVC button to complete the calculations.
• A progress meter will open, then close after the calculations are completed.
• A window will open indicating the number of calculations that were completed. Click OK to close the window.

• Click the Close button to close the Net Value Change form.

Return to ArcMap.

• The newly created rasters will be within the Layers directory of the Table of Contents in ArcMap.

• Look at the cNVC_elk raster, areas where fire is beneficial are shown in the warm (yellow to red) hues and where it is negative are in the cooler (blue to purple) hues.

To continue to the next section go to Expected Impacts.

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