A postfire debris-flow deposit in Rubio Canyon, in the Eaton Fire burn area Los Angeles, County, California. Debris flows were triggered by intense rain on the recently burned hillslopes. Mud- to boulder-sized sediment was deposited by the debris flow in this image. The flow also damaged trees near and within the channel where the flow traveled.
What is a debris flow?
Debris flows are fast-moving landslides that are particularly dangerous to life and property because they move quickly, destroy objects in their paths, and often strike without warning. They occur in a wide variety of environments throughout the world, including all 50 states and U.S. Territories. Debris flows generally occur during periods of intense rainfall or rapid snowmelt and usually start on hillsides or mountains. Debris flows can travel at speeds up to and exceeding 35 mph and can carry large items such as boulders, trees, and cars. If a debris flows enters a steep stream channel, they can travel for several miles, impacting areas unaware of the hazard. Areas recently burned by a forest fire are especially susceptible to debris flows, including the areas downslope and outside of the burned area. Debris flows are a type of landslide and are sometimes referred to as mudslides, mudflows, lahars, or debris avalanche.
Learn More:
Related
Can major landslides and debris flows happen in all areas of the U.S.?
Landslides can and do occur in every state and territory of the U.S.; however, the type, severity, and frequency of landslide activity varies from place to place, depending on the terrain, geology, and climate. Major storms have caused major or widespread landslides in Washington state, Oregon, California, Colorado, Idaho, Hawaii, Virginia, Ohio, Pennsylvania, Tennessee, North Carolina, Puerto...
What should I know about wildfires and debris flows?
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...
What is the difference between a landslide advisory, a landslide watch, and a landslide warning?
An advisory is a general statement about the potential of landslide activity in a given region relative to developing rainfall predictions. An advisory may include general statements about rainfall conditions that can lead to debris-flow activity, and list precautions to be taken in the event of heavy rainfall. A watch means that landslide-activity will be possible, but is not imminent. People in...
Why study landslides?
Landslides are a serious geologic hazard common to almost every State in the United States. As people move into new areas of hilly or mountainous terrain, it is important to understand the nature of their potential exposure to landslide hazards, and how cities, towns, and counties can plan for land-use, engineering of new construction and infrastructure which will reduce the costs of living with...
How many deaths result from landslides each year?
An average of 25-50 people are killed by landslides each year in the United States. The worldwide death toll per year due to landslides is in the thousands. Most landslide fatalities are from rock falls, debris flows, or volcanic debris flows (called lahars). Twenty-three people were killed, at least 167 injured, and more than 400 homes were damaged by a series of debris flows that impacted the...
Debris flow in the 2025 Eaton Fire burn area, California
A postfire debris-flow deposit in Rubio Canyon, in the Eaton Fire burn area Los Angeles, County, California. Debris flows were triggered by intense rain on the recently burned hillslopes. Mud- to boulder-sized sediment was deposited by the debris flow in this image. The flow also damaged trees near and within the channel where the flow traveled.
2024 Salt Fire burn area debris-flow deposit
A boulder-rich postfire debris-flow deposit in the 2024 Salt fire burn area. Flooding and debris flows occurred near Ruidoso, New Mexico during rain events shortly following the 2024 wildfires. This photo was taken in Bear Canyon, on the Mescalero Reservation, near the central portion of the burn area.
A boulder-rich postfire debris-flow deposit in the 2024 Salt fire burn area. Flooding and debris flows occurred near Ruidoso, New Mexico during rain events shortly following the 2024 wildfires. This photo was taken in Bear Canyon, on the Mescalero Reservation, near the central portion of the burn area.
Boulders deposited by post-fire debris flow, 2020 Dolan Fire
Boulders deposited by post-fire debris flow at the site of the 2020 Dolan Fire in California.
Boulders deposited by post-fire debris flow at the site of the 2020 Dolan Fire in California.
Debris Flow
A debris flow is a form of rapid mass movement in which a combination of loose soil, rock, organic matter, air, and water mobilizes as a slurry that flows downslope. Debris flows include <50% fines.
A debris flow is a form of rapid mass movement in which a combination of loose soil, rock, organic matter, air, and water mobilizes as a slurry that flows downslope. Debris flows include <50% fines.
House destroyed by postfire debris flow in the Muckamuck Fire, Washington
On July 4, 2022, intense rainfall triggered this debris flow that damaged a home in the 2021 Muckamuck Fire in north-central Washington.
On July 4, 2022, intense rainfall triggered this debris flow that damaged a home in the 2021 Muckamuck Fire in north-central Washington.
PubTalk 10/2018 — Post-fire debris flow early warning
Title: Post-Fire Debris-Flow Early Warning: The case for forecast-based warning systems
Title: Post-Fire Debris-Flow Early Warning: The case for forecast-based warning systems
Montecito after debris flow
The Dec. 4, 2017 Thomas fire, Southern California's largest wildfire on record, burned more than 280,000 acres across Ventura and Santa Barbara counties for nearly a month.
The Dec. 4, 2017 Thomas fire, Southern California's largest wildfire on record, burned more than 280,000 acres across Ventura and Santa Barbara counties for nearly a month.
Post-wildfire debris flow: 2016 Fish Fire, Las Lomas Canyon
The June 2016 Fish Fire burned over 12 km^2 in Los Angeles County, California. After the fire, the USGS installed an automated rain-triggered camera to monitor post-wildfire flooding and debris flow in a small canyon above the Las Lomas debris basin in Duarte. This video shows the peak flow triggered by an intense rainstorm on January 20, 2017.
The June 2016 Fish Fire burned over 12 km^2 in Los Angeles County, California. After the fire, the USGS installed an automated rain-triggered camera to monitor post-wildfire flooding and debris flow in a small canyon above the Las Lomas debris basin in Duarte. This video shows the peak flow triggered by an intense rainstorm on January 20, 2017.
Post-wildfire Flood and Debris Flow: 2014 Silverado Fire
In 2014, the Silverado Fire burned approximately 4 km^2 in Orange County, California. After the fire, the USGS installed an automated rain-triggered camera to monitor post-wildfire flooding and debris flow at the outlet of a small 0.6 km^2 basin within the burn area.
In 2014, the Silverado Fire burned approximately 4 km^2 in Orange County, California. After the fire, the USGS installed an automated rain-triggered camera to monitor post-wildfire flooding and debris flow at the outlet of a small 0.6 km^2 basin within the burn area.
Volcano Web Shorts 2: Debris Flows
Debris flows are hazardous flows of rock, sediment and water that surge down mountain slopes and into adjacent valleys. Hydrologist Richard Iverson describes the nature of debris-flow research and explains how debris flow experiments are conducted at the USGS Debris Flow Flume, west of Eugene, Oregon.
Debris flows are hazardous flows of rock, sediment and water that surge down mountain slopes and into adjacent valleys. Hydrologist Richard Iverson describes the nature of debris-flow research and explains how debris flow experiments are conducted at the USGS Debris Flow Flume, west of Eugene, Oregon.
USGS and California Wildfires: Post Fire Debris Flow (part 1)
Jim Bowers, USGS, California Hydrologic Monitoring Program Chief, talks about an historic streamflow site that was buried by debris flows as a result of the 2003 fires.
Jim Bowers, USGS, California Hydrologic Monitoring Program Chief, talks about an historic streamflow site that was buried by debris flows as a result of the 2003 fires.
USGS and California Wildfires: Post Fire Debris Flow (part 2)
Jim Bowers, USGS, California Hydrologic Monitoring Program Chief talks about the potential for debris flows in central Orange County, Modjeska Canyon, as a result of the 2007 fires.
Jim Bowers, USGS, California Hydrologic Monitoring Program Chief talks about the potential for debris flows in central Orange County, Modjeska Canyon, as a result of the 2007 fires.
Post-fire Debris Flow
Debris Flow in Cable Canyon following the 2003 Old Fire in the San Bernardino Mountains, California.
Debris Flow in Cable Canyon following the 2003 Old Fire in the San Bernardino Mountains, California.
Related
Can major landslides and debris flows happen in all areas of the U.S.?
Landslides can and do occur in every state and territory of the U.S.; however, the type, severity, and frequency of landslide activity varies from place to place, depending on the terrain, geology, and climate. Major storms have caused major or widespread landslides in Washington state, Oregon, California, Colorado, Idaho, Hawaii, Virginia, Ohio, Pennsylvania, Tennessee, North Carolina, Puerto...
What should I know about wildfires and debris flows?
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...
What is the difference between a landslide advisory, a landslide watch, and a landslide warning?
An advisory is a general statement about the potential of landslide activity in a given region relative to developing rainfall predictions. An advisory may include general statements about rainfall conditions that can lead to debris-flow activity, and list precautions to be taken in the event of heavy rainfall. A watch means that landslide-activity will be possible, but is not imminent. People in...
Why study landslides?
Landslides are a serious geologic hazard common to almost every State in the United States. As people move into new areas of hilly or mountainous terrain, it is important to understand the nature of their potential exposure to landslide hazards, and how cities, towns, and counties can plan for land-use, engineering of new construction and infrastructure which will reduce the costs of living with...
How many deaths result from landslides each year?
An average of 25-50 people are killed by landslides each year in the United States. The worldwide death toll per year due to landslides is in the thousands. Most landslide fatalities are from rock falls, debris flows, or volcanic debris flows (called lahars). Twenty-three people were killed, at least 167 injured, and more than 400 homes were damaged by a series of debris flows that impacted the...
Debris flow in the 2025 Eaton Fire burn area, California
A postfire debris-flow deposit in Rubio Canyon, in the Eaton Fire burn area Los Angeles, County, California. Debris flows were triggered by intense rain on the recently burned hillslopes. Mud- to boulder-sized sediment was deposited by the debris flow in this image. The flow also damaged trees near and within the channel where the flow traveled.
A postfire debris-flow deposit in Rubio Canyon, in the Eaton Fire burn area Los Angeles, County, California. Debris flows were triggered by intense rain on the recently burned hillslopes. Mud- to boulder-sized sediment was deposited by the debris flow in this image. The flow also damaged trees near and within the channel where the flow traveled.
2024 Salt Fire burn area debris-flow deposit
A boulder-rich postfire debris-flow deposit in the 2024 Salt fire burn area. Flooding and debris flows occurred near Ruidoso, New Mexico during rain events shortly following the 2024 wildfires. This photo was taken in Bear Canyon, on the Mescalero Reservation, near the central portion of the burn area.
A boulder-rich postfire debris-flow deposit in the 2024 Salt fire burn area. Flooding and debris flows occurred near Ruidoso, New Mexico during rain events shortly following the 2024 wildfires. This photo was taken in Bear Canyon, on the Mescalero Reservation, near the central portion of the burn area.
Boulders deposited by post-fire debris flow, 2020 Dolan Fire
Boulders deposited by post-fire debris flow at the site of the 2020 Dolan Fire in California.
Boulders deposited by post-fire debris flow at the site of the 2020 Dolan Fire in California.
Debris Flow
A debris flow is a form of rapid mass movement in which a combination of loose soil, rock, organic matter, air, and water mobilizes as a slurry that flows downslope. Debris flows include <50% fines.
A debris flow is a form of rapid mass movement in which a combination of loose soil, rock, organic matter, air, and water mobilizes as a slurry that flows downslope. Debris flows include <50% fines.
House destroyed by postfire debris flow in the Muckamuck Fire, Washington
On July 4, 2022, intense rainfall triggered this debris flow that damaged a home in the 2021 Muckamuck Fire in north-central Washington.
On July 4, 2022, intense rainfall triggered this debris flow that damaged a home in the 2021 Muckamuck Fire in north-central Washington.
PubTalk 10/2018 — Post-fire debris flow early warning
Title: Post-Fire Debris-Flow Early Warning: The case for forecast-based warning systems
Title: Post-Fire Debris-Flow Early Warning: The case for forecast-based warning systems
Montecito after debris flow
The Dec. 4, 2017 Thomas fire, Southern California's largest wildfire on record, burned more than 280,000 acres across Ventura and Santa Barbara counties for nearly a month.
The Dec. 4, 2017 Thomas fire, Southern California's largest wildfire on record, burned more than 280,000 acres across Ventura and Santa Barbara counties for nearly a month.
Post-wildfire debris flow: 2016 Fish Fire, Las Lomas Canyon
The June 2016 Fish Fire burned over 12 km^2 in Los Angeles County, California. After the fire, the USGS installed an automated rain-triggered camera to monitor post-wildfire flooding and debris flow in a small canyon above the Las Lomas debris basin in Duarte. This video shows the peak flow triggered by an intense rainstorm on January 20, 2017.
The June 2016 Fish Fire burned over 12 km^2 in Los Angeles County, California. After the fire, the USGS installed an automated rain-triggered camera to monitor post-wildfire flooding and debris flow in a small canyon above the Las Lomas debris basin in Duarte. This video shows the peak flow triggered by an intense rainstorm on January 20, 2017.
Post-wildfire Flood and Debris Flow: 2014 Silverado Fire
In 2014, the Silverado Fire burned approximately 4 km^2 in Orange County, California. After the fire, the USGS installed an automated rain-triggered camera to monitor post-wildfire flooding and debris flow at the outlet of a small 0.6 km^2 basin within the burn area.
In 2014, the Silverado Fire burned approximately 4 km^2 in Orange County, California. After the fire, the USGS installed an automated rain-triggered camera to monitor post-wildfire flooding and debris flow at the outlet of a small 0.6 km^2 basin within the burn area.
Volcano Web Shorts 2: Debris Flows
Debris flows are hazardous flows of rock, sediment and water that surge down mountain slopes and into adjacent valleys. Hydrologist Richard Iverson describes the nature of debris-flow research and explains how debris flow experiments are conducted at the USGS Debris Flow Flume, west of Eugene, Oregon.
Debris flows are hazardous flows of rock, sediment and water that surge down mountain slopes and into adjacent valleys. Hydrologist Richard Iverson describes the nature of debris-flow research and explains how debris flow experiments are conducted at the USGS Debris Flow Flume, west of Eugene, Oregon.
USGS and California Wildfires: Post Fire Debris Flow (part 1)
Jim Bowers, USGS, California Hydrologic Monitoring Program Chief, talks about an historic streamflow site that was buried by debris flows as a result of the 2003 fires.
Jim Bowers, USGS, California Hydrologic Monitoring Program Chief, talks about an historic streamflow site that was buried by debris flows as a result of the 2003 fires.
USGS and California Wildfires: Post Fire Debris Flow (part 2)
Jim Bowers, USGS, California Hydrologic Monitoring Program Chief talks about the potential for debris flows in central Orange County, Modjeska Canyon, as a result of the 2007 fires.
Jim Bowers, USGS, California Hydrologic Monitoring Program Chief talks about the potential for debris flows in central Orange County, Modjeska Canyon, as a result of the 2007 fires.
Post-fire Debris Flow
Debris Flow in Cable Canyon following the 2003 Old Fire in the San Bernardino Mountains, California.
Debris Flow in Cable Canyon following the 2003 Old Fire in the San Bernardino Mountains, California.
Updated Date: February 24, 2025