Idaho Panhandle National Forest
U.S. Forest Service
3232 West Nursery Road
Coeur d'Alene, ID 83815
The Burned Area Emergency Response (BAER) team finalized its soil burn severity map for the Tumbledown fire. The BAER team consists of specialists across affected resource areas, including soil scientists, hydrologists, engineers, and recreation specialists. The map identifies 5 percent of the fire area as having high soil burn severity, and 34 percent with moderate burn severity. The remaining 61 percent has either burned at low severity or is unburned.
High burn severity is evidenced by the consumption of all ground cover and surface organic matter (tree litter, duff, fine roots), sometimes leaving a layer of ash behind. Moderate burn severity areas will have up to 80 percent ground cover consumed, however roots and soil structure are generally unchanged, and the native seedbank is likely still viable. In areas with low burn severity, the ground often appears lightly charred.
A soil burn severity map is generated using satellite imagery and validated and adjusted by field surveys, which the BAER team wrapped up last week. In areas that experience high intensity fire, the team observed roots below the soil surface were generally intact and providing soil stability, water is able to infiltrate into the soil at deeper depths, and soil structure was not degraded.
There still is the risk of erosion on steep, burned hillslopes that lack ground cover. These risks will remain for several years until vegetation recovers. The higher the burn severity, the less likely soil is capable to absorb rainfall, increasing surface runoff and risk of erosion, debris flows, and flooding. The BAER team focuses on evaluating critical values downstream or downslope of highly burned areas that may be at risk. Critical values include public safety, roads, recreation sites, Bull Trout and their habitat, trails, the St. Joe Wild and Scenic River, and more.