Last Updated: September 19, 2021
Key Points about Post-Fire Debris Flows
Normally, vegetation absorbs rainfall, reducing runoff. However, wildfires leave the ground charred, barren, and unable to absorb water, creating conditions ripe for flash flooding and mudflow.
Flood risk remains significantly higher until vegetation is restored—up to 5 years after a wildfire.
While some floods develop over time, flash floods—particularly common after wildfires—can occur within minutes after the onset of a rainstorm. Even areas that are not traditionally flood-prone are at risk, due to changes to the landscape caused by fire.
Source: National Weather Service Post Wild Fire Flash Flood and Debris Flow Guide
Latest Additions
Added US Forest Service BAER Maps/Reports for the Dixie, Lava, Salt, and Tennant Fires.
General Resources About Debris Flows After Fires
National Weather Service Post Wildfire Flash Flood and Debris Flow Guide
USGS Emergency Assessment of Post-Fire Debris-Flow Hazards – Links to each of the California fires are including in the county information below. Links for fires in other states can be found here. FAQs about USGS assessment
California Department of Conservation – Post-Fire Debris Flow Facts
California Department of Conservation – Wildfire and Debris Flow: A Geologic Hazard
Drought Influences on Post- Wildfire Flooding and Debris Flow Hazard
Forest Service Post Fire Restoration – After the Fire Dos and Don’ts
Flood After Fire Video – California Department of Water Resources
USDA – After the Fire Sandbag Barrier
US Forest Service – Field Guide for Mapping Post-Fire Soil Burn Severity (technical document)
Debris Flow Hazards Webinar Recording
On December 7, 2020 the California Resilience Alliance hosted a Winter Weather Outlook & Debris Flow Hazards Webinar. Don Lindsay from the California Geological Society presented on post-fire effects including erosion-induced debris flows, post-fire models currently being applied to predict hazard, and monitoring program to test models and improve ability to predict post-fire hazards. The video picks up at the Debris Flow Hazards portion of the combined webinar.
Debris Flow Hazard Assessment Maps & County Specific Resources
Wildfires that crossed county lines are included under each of the counties where a burn scar was left. The impacts of a debris flow may cross into adjacent counties. If your locations of interest are near county lines, it is recommended that you also look at the neighboring county to see if there is potential risk from nearby burn scars.
USGS Hazard Assessments: depict the likelihood of debris-flow generation and estimates of flow magnitude in locations where debris flows initiate. The models do not predict downstream impacts, potential debris-flow runout paths, and the areal extent of debris-flow or flood inundation. Downloadable Goedatabase, Shapefile, and PDFs of the hazard assessment maps are available. Hazard assessments are not updated in subsequent years.
Layers Menu in the top right corner of the USGS Hazard Assessment Maps offers the following options (all are in response to the design rainstorm with a peak 15-minute rainfall intensity of 24mm/hr / 0.94 inches/hr):
- Basin / Segment Probability (probability of a debris flow as a percent range)
- Basin / Segment Volume (predicted volume in cubic meters)
- Basin / Segment Hazard (combined relative debris flow hazard)
Alameda County
SCU Lightning Complex (2020): Basin hazard per USGS assessment is low to moderate. Cal OES and the California Department of Conservation have released a Watershed Emergency Response Team Evaluation for the SCU Lightning Complex.
Alpine County
Tamarack Fire (2021): Basin hazard per USGS assessment is mostly moderate with a few areas of high.
Slink Fire (2020): Basin hazard per USGS assessment is low to moderate.
Donnell and McCormick Fire (2018): Basin hazard per USGS assessment is mostly mostly moderate with some areas of high.
McCormick Fire (2017): Basin hazard per USGS assessment is moderate to high.
Butte County
Dixie Fire (2021): Basin hazard per USGS assessment is mostly moderate with areas of high. (preliminary assessment). US Forest Service Burned Area Emergency Response (BAER) Soil Burn Severity Maps are also available.
North Complex (2020): Basin hazard per USGS assessment is moderate to high.
Camp Fire (2018): Basin hazard per USGS assessment is low to moderate with some areas of high.
Cherokee Fire (2017): Basin hazard per USGS assessment is mostly low with an area of moderate.
Wind Complex – Cascade Fire (2017): Basin hazard per USGS assessment is mostly low with a few areas of moderate.
Colusa County
LNU Lightning Complex – Hennessey Fire (2020): Basin hazard per USGS assessment is mostly low to moderate with a larger area of high south of Lake Berryessa. Cal OES and the California Department of Conservation have released a Watershed Emergency Response Team Evaluation for the Hennessey Fire.
Del Norte County
Slater Fire (2020): Basin hazard per USGS assessment is high. US Forest Service Burned Area Emergency Response (BAER) full report and Soil Burn Severity Maps are also available.
Eclipse Complex – Oak Fire (2017): Basin hazard per USGS assessment is moderate to high.
Orleans Complex – Haypress Fire (2017): Basin hazard per USGS assessment is low to moderate with an area of high.
Orleans Complex – Ukonom Fire (2017): Basin hazard per USGS assessment is low to moderate.
Fresno County
Creek Fire (2020): Basin hazard per USGS assessment is moderate to high. US Forest Service Burned Area Emergency Response (BAER) Soil Burn Severity Maps are also available.
Glenn County
August Complex (2020): Basin hazard per USGS assessment is mostly moderate with some areas of high. US Forest Service Burned Area Emergency Response (BAER) Soil Burn Severity Maps are also available. A full BAER report is also available for the South Zone.
Humboldt County
Red Salmon Complex (2020): Basin hazard per USGS assessment is mostly moderate with some areas of high. US Forest Service Burned Area Emergency Response (BAER) Soil Burn Severity Maps are also available, including a text description.
Lake County
August Complex (2020): Basin hazard per USGS assessment is mostly moderate with some areas of high. US Forest Service Burned Area Emergency Response (BAER) Soil Burn Severity Maps are also available. A full BAER report is also available for the South Zone.
LNU Lightning Complex – Hennessey Fire (2020): Basin hazard per USGS assessment is mostly low to moderate with a larger area of high south of Lake Berryessa. Cal OES and the California Department of Conservation have released a Watershed Emergency Response Team Evaluation for the Hennessey Fire.
Mendocino Lake Complex – Sulfur Fire (2017): Basin hazard per USGS assessment is low to moderate.
Lassen County
Beckwourth Complex (2021): Basin hazard per USGS assessment is moderate with one area of high.
Loyalton Fire (2020): Basin hazard per USGS assessment is low to moderate.
Sheep Fire (2020): Basin hazard per USGS assessment is moderate with some areas low.
Los Angeles County
Department of Public Works – Debris and Mudflow Potential Forecast
Bobcat Fire (2020): Basin hazard per USGS assessment is moderate to high, with the high being mostly in the southern portion. US Forest Service Burned Area Emergency Response (BAER) Soil Burn Severity Maps are also available.
Lake Fire (2020): Basin hazard per USGS assessment is moderate to high. US Forest Service Burned Area Emergency Response (BAER) full report and Soil Burn Severity Maps are also available.
Ranch 2 Fire (2020): Basin hazard per USGS assessment is high. US Forest Service Burned Area Emergency Response (BAER) full report and Soil Burn Severity Maps are also available.
Getty Fire (2019): Basin hazard per USGS assessment is low to moderate.
Saddle Ridge Fire (2019): Basin hazard per USGS assessment is low to moderate.
Tick Fire (2019): Basin hazard per USGS assessment is low.
Woolsey Fire (2018): Basin hazard per USGS assessment is mostly moderate with some larger areas of high.
Creek Fire (2017): Basin hazard per USGS assessment is moderate to high.
La Tuna Fire (2017): Basin hazard per USGS assessment is moderate to high.
Rye Fire (2017): Basin hazard per USGS assessment is low.
Skirball Fire (2017): Basin hazard per USGS assessment is low to moderate.
Madera County
Creek Fire (2020): Basin hazard per USGS assessment is moderate to high. US Forest Service Burned Area Emergency Response (BAER) Soil Burn Severity Maps are also available.
Railroad Fire (2017): Basin hazard per USGS assessment is low to moderate with two small areas of high.
South Fork Fire (2017): Basin hazard per USGS assessment is low to moderate.
Marin County
Woodward Fire (2020): Basin hazard per USGS assessment is mostly low to moderate with one area of high.
Mariposa County
Briceburg Fire (2019): Basin hazard per USGS assessment is moderate.
Detwiler Fire (2017): Basin hazard per USGS assessment is moderate with a few areas of high.
Railroad Fire (2017): Basin hazard per USGS assessment is low to moderate with two small areas of high.
South Fork Fire (2017): Basin hazard per USGS assessment is low to moderate.
Mendocino County
August Complex (2020): Basin hazard per USGS assessment is mostly moderate with some areas of high. US Forest Service Burned Area Emergency Response (BAER) Soil Burn Severity Maps are also available. A full BAER report is also available for the South Zone.
Mendocino Lake Complex – Redwood Valley Fire (2017): Basin hazard per USGS assessment is mostly moderate with one area of high.
Merced County
SCU Lightning Complex (2020): Basin hazard per USGS assessment is low to moderate. Cal OES and the California Department of Conservation have released a Watershed Emergency Response Team Evaluation for the SCU Lightning Complex.
Modoc County
Cove Fire (2017): Basin hazard per USGS assessment is low to moderate.
Parker 2 Fire (2017): Basin hazard per USGS assessment is mostly moderate.
Steele Fire (2017): Basin hazard per USGS assessment is low.
Mono County
Slink Fire (2020): Basin hazard per USGS assessment is low to moderate.
Boot Fire (2018): Basin hazard per USGS assessment is moderate.
Slinkard Fire (2017): Basin hazard per USGS assessment is moderate.
Monterey County
Monterey County Post-Fire Watershed Values at Risk Map
Willow Fire (2021): Basin hazard per USGS assessment is high.
Carmel Fire (2020): Basin hazard per USGS assessment is low to moderate. Cal OES and the California Department of Conservation have released a Watershed Emergency Response Team Evaluation for the River and Carmel Fires.
Dolan Fire (2020): Basin hazard per USGS assessment is moderate to high. US Forest Service Burned Area Emergency Response (BAER) Soil Burn Severity Maps are also available. The Forest Service has also released its Dolan Fire Burn Area Report.
River Fire (2020): Basin hazard per USGS assessment is mostly low to moderate with two area of high hazard. Cal OES and the California Department of Conservation have released a Watershed Emergency Response Team Evaluation for the River and Carmel Fires.
Napa County
Napa County Watershed Emergency Response Team Report
Glass Fire (2020): Basin hazard per USGS assessment is mostly low to moderate with some areas of high. Cal OES and the California Department of Conservation have released a Watershed Emergency Response Team Evaluation for the Glass Fire. Napa County has also created a WERT Map for the Glass Fire.
LNU Lightning Complex – Hennessey Fire (2020): Basin hazard per USGS assessment is mostly low to moderate with a larger area of high south of Lake Berryessa. Cal OES and the California Department of Conservation have released a Watershed Emergency Response Team Evaluation for the Hennessey Fire. Napa County has also created a WERT Map for the LNU Lightning Complex – Hennessey Fire.
Kincade Fire (2019): Basin hazard per USGS assessment is mostly moderate with a larger portion of high in the northern section.
Atlas Fire (2017): Basin hazard per USGS assessment is low to moderate with one small area of high.
Nuns Fire (2017): Basin hazard per USGS assessment is low to moderate with a few areas of high in the northern portion.
Tubbs Fire (2017): Basin hazard per USGS assessment is low to moderate.
Nevada County
Farad Fire (2017): Basin hazard per USGS assessment is low to moderate.
Wind Complex – Lobo Fire (2017): Basin hazard per USGS assessment is low with a few areas of moderate.
Wind Complex – McCourtney Fire (2017): Basin hazard per USGS assessment is low.
Orange County
Orange County Public Work’s Homeowners’ Guide for Flood, Debris, and Erosion Control after Fires
Blue Ridge Fire (2020): Basin hazard per USGS assessment is low to moderate.
Bond Fire (2020): Basin hazard per USGS assessment is low to moderate.
Silverado Fire (2020): Basin hazard per USGS assessment is low to moderate.
Holy Fire (2018): Basin hazard per USGS assessment is mostly high.
Canyon Fire (2017): Basin hazard per USGS assessment is low to moderate.
Canyon 2 Fire (2017): Basin hazard per USGS assessment is low to moderate.
Plumas County
Beckwourth Complex (2021): Basin hazard per USGS assessment is moderate with one area of high.
Dixie Fire (2021): Basin hazard per USGS assessment is mostly moderate with areas of high. (preliminary assessment). US Forest Service Burned Area Emergency Response (BAER) Soil Burn Severity Maps are also available.
Loyalton Fire (2020): Basin hazard per USGS assessment is low to moderate.
North Complex (2020): Basin hazard per USGS assessment is moderate to high.
North Complex – Claremont Fire (2020): Basin hazard per USGS assessment is mostly moderate to high with some perimeter areas being low.
Sheep Fire (2020): Basin hazard per USGS assessment is moderate with some areas low.
Walker Fire (2019): Basin hazard per USGS assessment is mostly low to moderate with some areas of high.
Minerva 5 Fire (2017): Basin hazard per USGS assessment is moderate.
Riverside County
Blue Ridge Fire (2020): Basin hazard per USGS assessment is low to moderate.
Snow Fire (2020): Basin hazard per USGS assessment is low to moderate. US Forest Service Burned Area Emergency Response (BAER) Burned Area Reflectance Classification Maps are also available. The Forest Service has also released its Snow Fire Burn Area Report.
Apple and El Dorado Fires (2020): Basin hazard per USGS assessment is moderate to high. US Forest Service Burned Area Emergency Response (BAER) Soil Burn Severity and Slope Maps are also available for the Apple Fire and Soil Burn Severity Maps for the El Dorado Fire. The Forest Service has also released its El Dorado Fire Burn Area Report and Apple Fire Burn Area Report. On September 30 Riverside County hosted a Flood After Fires Community Meeting for the Apple Fire.
Tenaja Fire (2019): Basin hazard per USGS assessment is low to moderate.
Holy Fire (2018): Basin hazard per USGS assessment is mostly high. The County has released the California Geological Survey’s Holy Fire Debris Flow Inundation Hazard Assessment within Riverside County Report
Canyon Fire (2017): Basin hazard per USGS assessment is low to moderate.
Canyon 2 Fire (2017): Basin hazard per USGS assessment is low to moderate.
Wildomar Fire (2017): Basin hazard per USGS assessment is low.
San Bernardino County
Apple and El Dorado Fires (2020): Basin hazard per USGS assessment is moderate to high. US Forest Service Burned Area Emergency Response (BAER) Soil Burn Severity and Slope Maps are also available for the Apple Fire and Soil Burn Severity Maps for the El Dorado Fire. The Forest Service has also released its El Dorado Fire Burn Area Report and Apple Fire Burn Area Report.
Blue Ridge Fire (2020): Basin hazard per USGS assessment is low to moderate.
Hillside Fire (2019): Basin hazard per USGS assessment is low.
San Diego County
Valley Fire (2020): Basin hazard per USGS assessment is low to moderate. US Forest Service Burned Area Emergency Response (BAER) Soil Burn Severity, Debris Flow, and Erosion Maps are also available. The Forest Service has also released several additional reports related to post fire hazards from the Valley Fire: Burn Area Report, BAER Assessment Specialist Report – Geological Hazards, Soils Report, and a Post-Fire Watershed Response: Hydrology Report.
Gate Fire (2017): Basin hazard per USGS assessment is low to moderate.
Lilac Fire (2017): Basin hazard per USGS assessment is low.
Jennings 2 Fire (2017): Basin hazard per USGS assessment is low to moderate.
San Joaquin County
SCU Lightning Complex (2020): Basin hazard per USGS assessment is low to moderate. Cal OES and the California Department of Conservation have released a Watershed Emergency Response Team Evaluation for the SCU Lightning Complex.
San Mateo County
CZU Lightning Complex (2020): Basin hazard per USGS assessment is moderate to high with some areas of low. Cal OES and the California Department of Conservation have released a Watershed Emergency Response Team Evaluation for the CZU Lightning Complex. Map showing evacuation zones and debris flow risk throughout the CZU Lightning Complex fire zone.
Santa Barbara County
Scorpion Fire (2020): Basin Hazard per USGS assessment is low. This fire is in Channel Island National Park on one of the islands off the coast of California.
Cave Fire (2019): Basin hazard per USGS assessment is moderate with some of the southern portions low.
Thomas Fire (2017): Basin hazard per USGS assessment is moderate too high.
Whittier Fire (2017): Basin hazard per USGS assessment is moderate to high.
Santa Clara County
SCU Lightning Complex (2020): Basin hazard per USGS assessment is low to moderate. Cal OES and the California Department of Conservation have released a Watershed Emergency Response Team Evaluation for the SCU Lightning Complex.
Santa Cruz County
County Resource Conservation District – Post Fire Recovery
CZU Lightning Complex (2020): Basin hazard per USGS assessment is moderate to high with some areas of low. A Memorandum “Landslide and Debris Flow Hazard Conditions Now Threatening the San Lorenzo Valley, Caused by the CZU Wildfire” to the District Board of Directors and public also provides addition information about the post-fire risks in the area. Cal OES and the California Department of Conservation have released a Watershed Emergency Response Team Evaluation for the CZU Lightning Complex. The California Department of Conservation also conducted a Boulder Creek Post-WERT Study for this fire. Map showing evacuation zones and debris flow risk throughout the CZU Lightning Complex fire zone. Santa Cruz County Potential Debris Flow Hazard Area Map. Recordings of County Debris Flow Town Hall Meetings – District Five (11/12/20) and District Three (11/13/20). Recording of the County Board of Supervisors presentation Post-CZU lightning Complex Fire Debris Flow Hazards (9/29/20). Santa Cruz County has also released a 2020 CZU Lightning Complex Fire Post-Fire Watershed Recovery Guide – Learn how to stay safe, protect your property, and preserve our natural resources.
Shasta County
Salt Fire (2021): Basin hazard per USGS assessment is mostly moderate with some areas of high. US Forest Service Burned Area Emergency Response (BAER) full report and Soil Burn Severity Maps are also available.
Carr Fire (2018): Basin hazard per USGS assessment is moderate to high.
Hirz and Delta Fires (2018): Basin hazard per USGS assessment is moderate to high.
Sierra County
Loyalton Fire (2020): Basin hazard per USGS assessment is low to moderate.
Farad Fire (2017): Basin hazard per USGS assessment is low to moderate.
Siskiyou County
Lava Fire (2021): Basin hazard per USGS assessment is moderate. US Forest Service Burned Area Emergency Response (BAER) full report and Soil Burn Severity Maps are also available.
Tennant Fire (2021): Basin hazard per USGS assessment is low to moderate. US Forest Service Burned Area Emergency Response (BAER) full report and Soil Burn Severity Maps are also available.
Devil Fire (2020): Basin hazard per USGS assessment is moderate. US Forest Service Burned Area Emergency Response (BAER) Soil Burn Severity Maps are also available.
Red Salmon Complex (2020): Basin hazard per USGS assessment is mostly moderate with some areas of high. US Forest Service Burned Area Emergency Response (BAER) Soil Burn Severity Maps are also available, including a text description.
Slater Fire (2020): Basin hazard per USGS assessment is high. US Forest Service Burned Area Emergency Response (BAER) full report and Soil Burn Severity Maps are also available.
Lime Fire (2019): Basin hazard per USGS assessment is moderate.
Eclipse Complex – Abney Fire (2017): Basin hazard per USGS assessment is moderate to high.
Eclipse Complex – Cedar Fire (2017): Basin hazard per USGS assessment is mostly moderate.
Eclipse Complex – Oak Fire (2017): Basin hazard per USGS assessment is moderate to high.
Salmon Complex Fire (2017): Basin hazard per USGS assessment is moderate to high.
Solano County
LNU Lightning Complex – Hennessey Fire (2020): Basin hazard per USGS assessment is mostly low to moderate with a larger area of high south of Lake Berryessa. Cal OES and the California Department of Conservation have released a Watershed Emergency Response Team Evaluation for the Hennessey Fire.
Atlas Fire (2017): Basin hazard per USGS assessment is low to moderate with one small area of high.
Sonoma County
County of Sonoma Post-Fire Hazard Assessment Map
Sonoma County – Preparing for Rain After Wildfires
How to Prepare Burned Properties for Rain after the Glass Fire
City of Santa Rosa – Preparing for Rain After Wildfires
Glass Fire (2020): Basin hazard per USGS assessment is mostly low to moderate with some areas of high. Cal OES and the California Department of Conservation have released a Watershed Emergency Response Team Evaluation for the Glass Fire.
LNU Lightning Complex – Meyers Fire (2020): Basin hazard per USGS assessment is mostly low to moderate with one area high.
LNU Lightning Complex – Walbridge Fire (2020): Basin hazard per USGS assessment is mostly low to moderate with two larger areas of high.
Kincade Fire (2019): Basin hazard per USGS assessment is mostly moderate with a larger portion of high in the northern section. Sonoma County also has a post-fire hazard assessment map that includes debris flow.
Nuns Fire (2017): Basin hazard per USGS assessment is low to moderate with a few areas of high in the northern portion.
Pocket Fire (2017): Basin hazard per USGS assessment is low to moderate with one area of high.
Tubbs Fire (2017): Basin hazard per USGS assessment is low to moderate.
Sonoma County also has a Post Fire Debris Flow Likelihood for Nuns, Tubbs and Atlas Fires GIS Maps
Stanislaus County
SCU Lightning Complex (2020): Basin hazard per USGS assessment is low to moderate. Cal OES and the California Department of Conservation have released a Watershed Emergency Response Team Evaluation for the SCU Lightning Complex.
Tehama County
August Complex (2020): Basin hazard per USGS assessment is mostly moderate with some areas of high. US Forest Service Burned Area Emergency Response (BAER) Soil Burn Severity Maps are also available. A full BAER report is also available for the South Zone.
Trinity County
August Complex (2020): Basin hazard per USGS assessment is mostly moderate with some areas of high. US Forest Service Burned Area Emergency Response (BAER) Soil Burn Severity Maps are also available. A full BAER report is also available for the South Zone.
Red Salmon Complex (2020): Basin hazard per USGS assessment is mostly moderate with some areas of high. US Forest Service Burned Area Emergency Response (BAER) Soil Burn Severity Maps are also available, including a text description.
Helena and Fork Fire (2017): Basin hazard per USGS assessment is moderate with two areas of high.
Tulare County
SQF Complex – Castle Fire (2020): Basin hazard per USGS assessment is mostly moderate with some areas of high. US Forest Service Burned Area Emergency Response (BAER) full report and Soil Burn Severity and Debris Flow Maps are also available along with a text description of the soil burn severity map.
SQF Complex – Rattlesnake Fire (2020): Basin hazard per USGS assessment is los to moderate.
Pier Fire (2017): Basin hazard per USGS assessment is moderate to high.
Tuolumne County
Donnell and McCormick Fire (2018): Basin hazard per USGS assessment is mostly moderate with some areas of high.
McCormick Fire (2017): Basin hazard per USGS assessment is moderate to high.
Ventura County
Maria Fire (2019): Basin hazard per USGS assessment is mostly moderate with one area of high.
Hill Fire (2018): Basin hazard per USGS assessment is low.
Woolsey Fire (2018): Basin hazard per USGS assessment is mostly moderate with some larger areas of high.
Thomas Fire (2017): Basin hazard per USGS assessment is moderate too high.
Yolo County
LNU Lightning Complex – Hennessey Fire (2020): Basin hazard per USGS assessment is mostly low to moderate with a larger area of high south of Lake Berryessa. Cal OES and the California Department of Conservation have released a Watershed Emergency Response Team Evaluation for the Hennessey Fire.
Yuba County
Wind Complex – Cascade Fire (2017): Basin hazard per USGS assessment is mostly low with a few areas of moderate.