While the community of Gatlinburg, Tennessee grieves their losses and starts planning how to recover and rebuild, a new threat confronts the area. An inch and a half of winter rain helped put out the horrific fire over the weekend, but as we’ve covered in the past, wildfire-scorched areas often have an increased risk of landslides and mudslides. Local fire crews have thus far reported several small landslides that are slowing their ability to access damaged areas.
How a Fire Can Increase Landslide Risk?
Depending on soil type and topography, vegetation and land cover have a significant impact on the stability of the soil. Under normal conditions, leaf litter and other surface vegetation slow the rainfall water moving down a given slope. This allows much of that moisture to permeate through the soil and drain into the water table or aquifer below, leaving the surface soil relatively stable. Even during heavy rainfall when surface soil becomes saturated, root systems from brush and trees help to keep the soil from moving downhill.
However, when vegetation is lost due to wildfire (or other reasons such as construction), the factors that keep soil in place are minimized, and there is greater risk that the soil’s surface tension in a given area is overcome by gravity and washes down the slope.
Gatlinburg is in the Great Smoky Mountains, a very old mountain range within the Appalachian Mountain region. Due to the age of the mountains and the region’s climate, the mountains themselves are very weathered, and have much deeper soils than the mountains in the Western United States. The region is also heavily wooded, so the roots of the dense vegetation help to stabilize the nearby soil. When the wildfires recently moved through the area, the vegetation and leaf litter was burned out, and the stabilizing root systems were compromised. Storms then came and assisted in firefighting efforts, but the lack of vegetation due to the recent burns caused a few small slides. Before winter brings snow to the normally wet area, an increased likelihood for flooding, mudslides, and landslides remains a worrying possibility. As of December 7th, there is little rain forecasted in the region for several days.
Visit ready.gov to learn about how to better protect yourself, your family, and your property from landslides and other hazards.