Skip to main content
U.S. flag

An official website of the United States government

Postfire Landslide Monitoring Station: “Maria Ygnacio” (2019 Cave Fire) near Santa Barbara, California Active

By Landslide Hazards Program October 23, 2023

Wildfire can increase landslide susceptibility in mountainous terrain. The USGS maintains postfire landslide monitoring stations to track hillslope hydrologic conditions in the years following fire.

Recent Conditions

Instrumentation was installed within the footprint of the 2019 Cave Fire in the Santa Ynez Mountains of southern California. The surface and subsurface data are used to monitor and detect changes in local hillslope hydrologic conditions. Soil-water content, soil suction, and groundwater pressure are measured in a single nest on the same hillslope. Telemetered data for the site include:

Data are recorded every minute and updated on the graphs every 60 minutes.

Person kneeling next to equipment surrounded by rocks and shrubs on a hillslope
Sources/Usage: Public Domain. View Media Details
The USGS Postfire Landslide Monitoring Station “Maria Ygnacio” is located within the Los Padres National Forest in the Santa Ynez Mountains of southern California. The site consists of surface and subsurface instrumentation that is monitoring the hillslope shown in this image.

Project Background

Following a 9 January 2023 atmospheric river storm in southern California, the U.S. Geological Survey (USGS; Landslide Hazards Program), California Geological Survey (Burned Watershed Geohazards Program), and U.S. Forest Service observed abundant landslide activity in the Santa Ynez Mountains within Santa Barbara County. A greater proportion of these infiltration-generated landslides, which mobilized into debris flows, occurred in the 2017 Thomas Fire and 2019 Cave Fire, compared to similarly steep terrain in the 2008 Tea Fire, 2009 Jesusita Fire, and areas that have not burned in more than 30 years. The varying degrees of postfire landscape recovery may have played a role in the apparent contrast in landslide activity. To resolve process-based controls on postfire landsliding and to contribute to the development of antecedent soil moisture and rainfall thresholds for the region, a monitoring station was installed in Maria Ygnacio Canyon within the Los Padres National Forest. The surface and near-surface hydrologic monitoring will provide valuable constraints on the conditions leading up to, and during, rainstorms that produce landslides.

Dirt, rocks, and shrubs surround a landslide on the side of a hillslope
Sources/Usage: Public Domain. View Media Details
Example of a landslide that initiated within the footprint of the 2019 Cave Fire during the 9 January 2023 rainstorm. The landslide source area is shown in the upper left of this image. The debris-flow runout path is shown in the center and lower right of this image.

Wildfire can increase landslide susceptibility in mountainous terrain. The USGS maintains postfire landslide monitoring stations to track hillslope hydrologic conditions in the years following fire.

Recent Conditions

Instrumentation was installed within the footprint of the 2019 Cave Fire in the Santa Ynez Mountains of southern California. The surface and subsurface data are used to monitor and detect changes in local hillslope hydrologic conditions. Soil-water content, soil suction, and groundwater pressure are measured in a single nest on the same hillslope. Telemetered data for the site include:

Data are recorded every minute and updated on the graphs every 60 minutes.

Person kneeling next to equipment surrounded by rocks and shrubs on a hillslope
Sources/Usage: Public Domain. View Media Details
The USGS Postfire Landslide Monitoring Station “Maria Ygnacio” is located within the Los Padres National Forest in the Santa Ynez Mountains of southern California. The site consists of surface and subsurface instrumentation that is monitoring the hillslope shown in this image.

Project Background

Following a 9 January 2023 atmospheric river storm in southern California, the U.S. Geological Survey (USGS; Landslide Hazards Program), California Geological Survey (Burned Watershed Geohazards Program), and U.S. Forest Service observed abundant landslide activity in the Santa Ynez Mountains within Santa Barbara County. A greater proportion of these infiltration-generated landslides, which mobilized into debris flows, occurred in the 2017 Thomas Fire and 2019 Cave Fire, compared to similarly steep terrain in the 2008 Tea Fire, 2009 Jesusita Fire, and areas that have not burned in more than 30 years. The varying degrees of postfire landscape recovery may have played a role in the apparent contrast in landslide activity. To resolve process-based controls on postfire landsliding and to contribute to the development of antecedent soil moisture and rainfall thresholds for the region, a monitoring station was installed in Maria Ygnacio Canyon within the Los Padres National Forest. The surface and near-surface hydrologic monitoring will provide valuable constraints on the conditions leading up to, and during, rainstorms that produce landslides.

Dirt, rocks, and shrubs surround a landslide on the side of a hillslope
Sources/Usage: Public Domain. View Media Details
Example of a landslide that initiated within the footprint of the 2019 Cave Fire during the 9 January 2023 rainstorm. The landslide source area is shown in the upper left of this image. The debris-flow runout path is shown in the center and lower right of this image.