Post-Wildfire Landslide Hazards
A debris flow generated from hillslopes burned by the South Canyon fire of 1994 traveled across four lanes of Interstate 70, and nearly dammed the Colorado River. Photograph by Jim Scheidt, BLM
Wildland fires are inevitable in the western United States. Expansion of human development into forested areas has created a situation where wildfires can adversely affect lives and property, as can the flooding and landslides that occur in the aftermath of the fires. There is a need to develop tools and methods to identify and quantify the potential hazards posed by landslides produced from burned watersheds. Post-fire landslide hazards include fast-moving, highly destructive debris flows that can occur in the years immediately after wildfires in response to high intensity rainfall events, and those flows that are generated over longer time periods accompanied by root decay and loss of soil strength. Post-fire debris flows are particularly hazardous because they can occur with little warning, can exert great impulsive loads on objects in their paths, can strip vegetation, block drainage ways, damage structures, and endanger human life. Wildfires could potentially result in the destabilization of pre-existing deep-seated landslides over long time periods.
Debris flow generated from basin burned by the 2002 Coal Seam Fire near Glenwood Springs, Colorado. Photograph by Andrea Holland-Sears, USDA Forest Service, White River National Forest.
The focus of this project is to develop tools and methods for the prediction of post-wildfire landslide activity and hazard delineation. Personnel dealing with post-fire rehabilitation and emergency planning need tools to determine the both the probability and magnitude of such potentially destructive events, so we have developed methods to predict which basins might produce post-fire debris flows, and how big these events might be. By utilizing these methods, federal, state, and local land-management agencies can tailor debris-flow specific mitigation efforts to watersheds that are the most prone to the largest debris-flow events.
Recent Publications of Interest
- 2007 Southern California Wildfires & Debris Flow Studies
- Fact Sheet 2005-3104: Flash-Flood and Debris-Flow Early-Warning System
- Fact Sheet 2005-3106: Wildfires and Debris Flows in Southern California
- Debris flow probability
- Debris flow peak discharge
- Debris flow initiation processes
- Effects of wildfire on landslide stability
Sue Cannon, Landslide Hazards Program
P.O. Box 25046; DFC, Mail Stop 966
Denver, CO 80225-0046
cannon [at] usgs [dot] gov