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 within 45 days following containment of a wildfire that burns 1,000 acres of forested National Forest System (NFS) lands (500 acres for Regions 8 and 9 as of 2016). 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 Geospatial Technology and Applications Center (GTAC) (formerly 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 complements the Burned Area Emergency Rehabilitation (BAER) program whose first priority is to address emergency stabilization needs to prevent further damage to life, property, natural, and cultural resources 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 or other multi-spectral imagery captured before and after a wildfire. The algorithm uses 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 and 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 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 basal area loss data tables and maps:

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

Note that these classes differ from those of the four-class BA loss raster dataset included in the data bundle. In addition, each of the thematic rasters identifies areas outside the fire perimeter with pixel value 0 and unmappable areas with pixel value 9. Please refer to the metadata for a full description of the RAVG raster datasets.

Support for RAVG

RAVG analysis is performed by NFS Region 5 (California) and GTAC. Region 5 developed the RAVG analysis process to serve the National Forests in the Region. GTAC adapted the methods for national implementation and provided RAVG analysis for National Forests in the western United States during the 2007 fire season. As of 2008, GTAC provides RAVG support for wildfires that meet the qualifying criteria across the conterminous United States.


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


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Location: https://www.fs.fed.us/postfirevegcondition/whatis.shtml
Last modified: Tuesday, 16-Jan-2018 17:30:06 CST