Exposure Analysis (EA) Considerations

HVRA Sets for Exposure Analysis or Risk Assessment

Deciding what to include in your HVRA set should be based on how you intend to use that set. For HVRA sets intended for Exposure Analyses (EA) or Quantitative Wildfire Risk Assessments (QWRAs), the geographic extent HVRAs selected should reflect the desired extent and components to be quantitatively evaluated and compared. (See the Map values topic for details on how to create an HVRA set).

Tip: For Exposure Analysis and Risk. When identifying which HVRAs to include in your analysis, it is important to limit the list of HVRAs to those of high value. Keeping the scope limited ensures that the interpretation of the results from your analysis remains manageable.

Below we outline some general guidelines for assigning HVRAs for a Quantitative Wildfire Risk Assessment from Scott and others (2013). However, every project is different and there is no one-size-fits-all criteria.

  • Keep the scope limited: When identifying which HVRAs to include in your analysis, it is important to limit the list of HVRAs to those of high value. Keeping the scope limited ensures that the interpretation of the results from your analysis remains manageable. Additionally, the fewer HVRAs that are included in the assessment, the higher their overall contribution to risk.
  • Be deliberate in how you organize Sub-HVRAs: The decision regarding how to categorize and organize your HVRAs should be driven by how you want to compare these values. Exposure Analysis reports provide results at both the Primary and Sub-HVRA level. The Primary HVRA should generally represent a category containing multiple Sub-HVRAs that will be looked at together in a management context for decisions. Primary HVRAs often include wildland urban interface (WUI), structures, and watersheds, they may also include more ecologically significant values such as vegetation structure or type. For instance, Wildlife Habitat can be the Primary HVRA, with Sub-HVRAs identified as individual species or species groups.
  • Needs vary and there are guidance documents available: There are several guiding documents to assist in the assignment of HVRAs, some of these include:
    • Land and Resource Management Plan or Forest Plan
    • Fire Management Plan
    • Wildland Fire Response Guidebook or Forest Response Guidebook
  • Involve Specialists and Analysts: It is critical to involve resource specialists and geospatial analysts in the process of assigning HVRAs. For a detailed 8 step-process on assigning HVRAs, see page 32 of Scott and Others 2013.

Example: Superior National Forest

The Superior National Forest conducted a QWRA as part of their process to develop a Forest-wide fuels treatment strategy. When they assigned HVRAs, the resource or asset’s role or usefulness in driving fire management decision making was the primary criteria:

“For example, human habitation was chosen as an HVRA because the Forest prioritizes fuel reduction treatments adjacent to areas of human habitation to mitigate the potential threat of wildfire moving to or from privately owned lands. Ecological integrity was identified as an HVRA because depicting the potential for wildfire to restore or maintain ecological integrity may help identify prescribed or managed wildfire opportunities” - Don Helmbrecht 2019

HVRAs are Dynamic and Exposure Analysis Data is Static

Important! EA data is static and does not change once the EA is created. If some time has elapsed between the creation of an EA and its use in Quantitative Wildfire Risk Assessment, it may no longer reflect the values currently on the landscape.

Mapped Values and Map Bookmarks that you’ve created may display different data over time. This is because IFTDSS Reference Data are dynamic and are updated over time as more current data becomes available.

Creating an Exposure Analysis (EA) creates a snapshot in time, generating a rasterized version of the Mapped Values that are selected when the analysis is run. The date and EA is created is displayed in My Workspace for easy reference.

This can be helpful when returning to a project that may take a long time to complete. For example, if you are conducting a Quantitative Wildfire Risk Assessment and notice you created your EA a couple years, it may no longer reflect the conditions currently on the landscape or shown in the most current IFTDSS Reference Layers. In such a case, you should consider generating a new EA to capture any updates that have occurred in the Mapped Values so you are working with the most current data.

Interpreting Exposure Analysis Reports

Looking to better understand Exposure Analysis reports? We have a full topic on EA Reports linked here.