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On October 27, 2022, Forest Service BAER team specialists completed their field data gathering on federal lands burned by the Bolt Creek, Suiattle, Boulder Lake and Loch Katrine fires. The post-fire maps and data display soil burn severity (SBS) categories of unburned/very low, low, moderate, and high.

The BAER assessment team used preliminary remote sensing data based on satellite imagery of the fire perimeter with field-validated data collected over several days to produce the final SBS maps. The SBS map products are an estimate of fire effects on soils and not a measure of direct effects to vegetation. SBS characterizes the soil surface and below-ground impact, whereas effects on vegetation are estimates of mortality based primarily on changes in vegetation canopy. 

Changes in soil cover, water repellency, and soil physical/biological conditions guide the interpretations to determine the severity burn level of the soil. Water repellency can occur naturally in soil and may change as a result of fire. Fire can increase the strength and thickness (or depth) of water-repellent layers in soil, considerably affecting post-fire water runoff and possibly extending time for recovery of the burned area.

Soil burn severity indicators can be found within the Rocky Mountain Research Station’s General Technical Report 243 – Field Guide for Mapping Post-Fire Soil Burn Severity https://www.fs.usda.gov/rm/pubs/rmrs_gtr243.pdf.

The BAER team will use the SBS data to analyze and model post-fire hydrologic response for each of the watersheds to determine if there are threats or risks to BAER critical values: human life and safety, property, critical natural resources, and critical cultural resources. The team shares its analysis with cooperating agencies such as Washington Department of Natural Resources who have the authority to work with private property owners downstream from the burned area that potentially may have post-fire threats from increased water and debris flows. The BAER team’s analysis and findings will be documented in an assessment report that will be posted to the Post-Fire BAER InciWeb page after the report has been reviewed and approved by Forest Service leadership.

The SBS maps can be downloaded at the “Mt.Baker Snoqualmie Post Fire BAER” InciWeb site (https://inciweb.nwcg.gov/incident-information/wamsf-mt-bakersnoqualmie-postfire-baer) as a JPEG or PDF format image under the “Maps” tab.

For additional information about understanding SBS, see: Post-Fire Effects Understanding Soil Burn Severity - InciWeb the Incident Information System (nwcg.gov).