Black Hills Region South Dakota 2017 Legion Lake Fire Burned and Unburned Plot Measurements

Publication Date

2022-04-13

Start Date

2018-09-05

End Date

2020-07-01

Irwin, J.R., Peterson, B.E., Picotte, J.J., and Nelson, K.J., 2022, Black Hills Region South Dakota 2017 Legion Lake Fire Burned and Unburned Plot Measurements: U.S. Geological Survey data release, https://doi.org/10.5066/P9UJB4LW.

On December 11th, 2017, the Legion Lake Fire ignited when a tree fell onto a powerline in the Black Hills of South Dakota. During the seven days in which the fire burned, nearly 22,000 hectares (over 54,000 acres) were engulfed, making it the third largest fire on record in the Black Hills region. The fire mainly occurred on Custer State Park lands, however, private lands and Wind Cave National Park were also impacted. The Monitoring Trends in Burn Severity (MTBS) Program (https://mtbs.gov/) uses 30 m Landsat data to map burn severity (vegetation change) for large fires on federal lands, as the project did for the Legion Lake Fire. Burn severity is estimated by calculating the Normalized Burn Ratio (NBR) from pre- and post-fire Landsat images and taking the difference of the two to create a differenced NBR (dNBR) image. An analyst then applies thresholding to the dNBR image to map unburned, low, moderate, and high burn severity classes within the fire perimeter. Satellite imagery derived estimates for burn severity, such as the methodology used by MTBS, are not able to directly measure changes in vegetation structure and are actually measuring changes in vegetation greenness. These field data, collected from unburned and burned plots from the Legion Lake Fire, were gathered to initiate an investigation into the vegetation structural changes that occur during wildland fires. While no known ground-based or airborne pre-fire lidar data exist for this region, researchers can use data from the unburned area surrounding the Legion Lake Fire to estimate pre-fire conditions by substituting space for time. These data may also offer a path forward for large scale post-fire disturbance structural change mapping through development of relationships between lidar based structural change measurements at the plot level that can then be related to similar metrics from airborne and spaceborne lidar instruments. These outputs, in combination with metrics derived from multi-spectral satellite imagery, can help integrate structure and spectral assessments of burn severity. This work was funded by the Monitoring Trends in Burn Severity Program and the USGS Land Change Science Program.

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