U.S. Forest Service Post-Fire Vegetation Conditions on the National Forests
Burn Severity Estimates from RSAC’s BAER Imagery Support, RAVG, and MTBS Programs
It is important to understand that the burn severity estimates derived from the Remote Sensing Applications Center’s (RSAC) BAER Imagery Support, RAVG, and MTBS programs are different. Each program’s burn severity products are developed with different methods and mapping protocols, and have different intended audiences. The following provides a brief description of each program’s burn severity estimates.
BAER Imagery Support
The BAER (Burned Area Emergency Response) Imagery Support program is a cooperative effort between the USDA Forest Service RSAC and the U.S. Geological Survey Center for Earth Resources Observation and Science (EROS). The two Centers provide rapid delivery of satellite imagery, Burned Area Reflectance Classifications (BARC), and other geospatial data to Forest Service and Department of the Interior (DOI) BAER teams. BAER Teams perform emergency assessments and soil stabilization treatments immediately following containment of wildfires. The BARC is a satellite-derived map that serves as the main input into the development of the final burn severity map produced by BAER Teams. The BARC has four classes: high, moderate, low, and unburned, and it is derived from the Differenced Normalized Burn Ratio (dNBR). BAER Imagery Support is considered an emergency assessment, and the program’s products and data are delivered to BAER Teams within hours of receiving useable post-fire imagery.
The Rapid Assessment of Vegetation Condition after Wildfire (RAVG) program produces data describing post-fire vegetation conditions on National Forest System (NFS) lands for all fires that burn 1,000 acres or more of forested NFS land. Forest Service Regional Silviculturists, Reforestation, and Restoration Specialists primarily use RAVG data to assess and prioritize post-fire vegetation management. A similar change detection process used for the BAER Imagery Support program produces RAVG burn severity products. RAVG uses the Relative Differenced Normalized Burn Ratio (RdNBR), which is derived directly from the dNBR, but is considered more sensitive to vegetation mortality than the dNBR. RAVG is considered an initial assessment, which describes initial vegetation mortality (typically 30 days post-fire containment), but does not capture delayed vegetation mortality.
Monitoring Trends in Burn Severity (MTBS) is a multi-year project designed to map consistently the burn severity and perimeters of fires across all lands of the United States between 1984 and present. The data generated by MTBS will be used to identify national trends in burn severity, providing information necessary to monitor the effectiveness and effects of the National Fire Plan and Healthy Forests Restoration Act. The Wildland Fire Leadership Council (WFLC), a multi-agency oversight group responsible for implementing and coordinating the National Fire Plan and Federal Wildland Fire Management Policy and Program Review, sponsors MTBS. The project is conducted through a partnership between EROS and RSAC. MTBS maps burn severity using the dNBR; however, the RdNBR is used to adjust burn severity thresholds to better describe post-fire effects to vegetation. MTBS is considered an extended assessment because most fires are mapped using images acquired one-year post-fire (at peak of greenness). This provides the ability to capture delayed vegetation mortality during the mapping process.
Administrative Ownership Data Used for RAVG
The administrative ownership layer used for the Geographic Information Sytem (GIS) overlay portion of RAVG analysis is the same one used in the MTBS program. It is important to recognize that any geospatial data layer has various degrees of spatial accuracy depending on the mapping scale used to produce those data. The administrative ownership layer used for MTBS was chosen for RAVG because it offers complete coverage over the entire United States (a RAVG mapping requirement), and its quality and accuracy have been tested and validated for use in the MTBS program. RAVG generalizes the relevant ownership information into the following four classes for the GIS overlay operation during RAVG analysis: USFS, Non-USFS, USFS Wilderness, and Non-USFS Wilderness. This simplifies the creation of RAVG Tables and protects the privacy of landowners.
Late Season Satellite Image Acquisitions and Their Effects on RAVG Burn Severity Estimates
The post-fire vegetation severity assessments for fires on this website are initial draft estimates developed typically 30 days post-fire containment. Imagery used to make initial assessments may be acquired late in the year when sun angles are low due to fire containment dates. Fire effects on north facing slopes may be hidden due to topographic shadows caused by low sun angles. Therefore high severity fire effects in these data may be under-represented in these areas. Low to moderate severity in dense stands on east, west, or south aspects may also be under-represented due to the low sun illumination angles. These fires will be re-mapped one-year post-fire by the Monitoring Trends in Burn Severity (MTBS) program.
U.S. Forest Service
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Last modified: Monday, 28-Feb-2011 13:23:50 EST