U.S. Forest Service Post-Fire Vegetation Conditions on the National Forests

 

What is RAVG?

The Rapid Assessment of Vegetation Condition after Wildfire (RAVG) process delivers a suite of products to Forests within 30 days following containment of a wildfire that burns 1,000 acres or more of forested National Forest System (NFS) land. RAVG products are generated for NFS lands (including wilderness) to provide information that can assist post-fire vegetation management planning designed to address a number of management objectives. The primary benefit is cost-effective, efficient, and precise identification of potential resource concern areas following wildfire. The RAVG products produced at the Remote Sensing Applications Center (RSAC) include the following for each wildfire processed:

  1. Map and GIS products showing location of basal area loss within fire perimeter.
  2. Summary table of vegetation affected by the fire, separated into four classes of basal area loss.

The RAVG products can assist the Forests' decision-making capabilities and reduce planning and implementation costs associated with post-fire vegetation management. RAVG compliments the Burned Area Emergency Rehabilitation (BAER), which provides information about fire effects to soil, by including information about fire effects to existing vegetation.

How is RAVG created?

The basal area loss summary table and map products are produced by a change detection process using two Landsat Thematic Mapper (TM) images captured before and after a wildfire. The algorithm used is the Relative Differenced Normalized Burn Ratio (RdNBR), which is sensitive to vegetation mortality resulting from the wildfire event. This is a different process from that used for BAER mapping (Burned Area Reflectance Classification – BARC) which uses the Differenced Normalized Burn Ratio (dNBR) and is better correlated with soil burn severity.

The RAVG products are based on a seven-class basal area loss layer modeled from the RdNBR (Miller & Thode 2007). The seven-class layer is recoded into four classes for the GIS overlay analysis and subsequent RAVG table and map generation. The data tables and maps are created using existing vegetation maps overlain with basal area loss results. LANDFIRE Existing Vegetation Types (EVT)(Rollins & Frame 2006) are grouped and used for the GIS overlay analysis.

The seven-class basal area loss layer contains the following classes:

  • Class 0 = outside fire perimeter
  • Class 1 = 0% basal area (BA) loss
  • Class 2 = 0% - < 10% BA loss
  • Class 3 = 10% - < 25% BA loss
  • Class 4 = 25% - < 50% BA loss
  • Class 5 = 50% - < 75% BA loss
  • Class 6 = 75% - < 90% BA loss
  • Class 7 = 90% or greater BA loss

The seven-class basal area loss layer is recoded into the following four classes for the GIS overlay analysis:

  • Class 0 = outside fire perimeter
  • Class 1 = 0% - < 25% BA loss
  • Class 2 = 25% - < 50% BA loss
  • Class 3 = 50% - < 75% BA loss
  • Class 4 = 75% - 100% BA loss

Support for RAVG

The RAVG analysis is performed by both NFS Region 5 (California) and the Forest Service Remote Sensing Applications Center (RSAC). Region 5 initially developed the RAVG analysis process and serves National Forests in Region 5. In 2007, RSAC adapted the Region 5 methodology to be implemented nationally. RSAC provided RAVG analysis for National Forests in the western United States during the 2007 fire season, and has received funding to continue RAVG support for the National Forests across the United States through the 2008 fire season and beyond.

References

U.S. Forest Service
Attn: Forest Management
1400 Independence Ave., SW, Mailstop: 1103
Washington DC 20250-0003

 

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Location: http://www.fs.fed.us/postfirevegcondition/whatis.shtml
Last modified: Thursday, 28-Mar-2013 13:36:11 CDT