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#           Postfire hydrologic response along the central California (USA) coast: Insights for the emergency assessment of postfire debris-flow hazards      

      July 7, 2023    

The steep, tectonically active terrain along the Central California (USA) coast is well known to produce deadly and destructive debris flows. However, the extent to which fire affects debris-flow susceptibility in this region is an open question. We documented the occurrence of postfire debris floods and flows following the landfall of a storm that delivered intense rainfall across multiple burn areas. We used this inventory to evaluate the predictive performance of the US Geological Survey M1 likelihood model, a tool that presently underlies the emergency assessment of postfire debris-flow hazards in the western USA. To test model performance, we used the threat score skill statistic and found that the rainfall thresholds estimated by the M1 model for the Central California coast performed similarly to training (Southern California) and testing (Intermountain West) data associated with the original model calibration. Model performance decreased when differentiating between “minor” and “major” postfire hydrologic response types, which weigh effects on human life and infrastructure. Our results underscore that the problem of false positives is a major challenge for developing accurate rainfall thresholds for the occurrence of postfire debris flows. As wildfire activity increases throughout the western USA, so too will the demand for the assessment of postfire debris-flow hazards. We conclude that additional collection of field-verified inventories of postfire hydrologic response will be critical to prioritize which model variables may be suitable candidates for regional calibration or replacement.

## Citation Information

## Related Content

                  -              Data           
                  -              Connect           

June 23, 2023

####                 Field-verified inventory of postfire hydrologic response for the 2020 CZU Lightning Complex, River, Camel, and Dolan Fires following a 26-29 January 2021 atmospheric river storm sequence              

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#### Matthew A Thomas

##### Research Hydrologist

Landslide Hazards Program

matthewthomas@usgs.gov

303-273-8588

#### Jason Kean

##### Research Hydrologist

Landslide Hazards Program

jwkean@usgs.gov

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#### Jaime Kostelnik

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jkostelnik@usgs.gov

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#### Francis Rengers

##### Research Geologist

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frengers@usgs.gov

303-273-8637

#### Amy East

##### Research Geologist

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aeast@usgs.gov

831-460-7533

#### Brian Collins

##### Supervisory Research Civil Engineer

Geology, Minerals, Energy, and Geophysics Science Center

bcollins@usgs.gov

650-439-2466

## Related Content

June 23, 2023

####                 Field-verified inventory of postfire hydrologic response for the 2020 CZU Lightning Complex, River, Camel, and Dolan Fires following a 26-29 January 2021 atmospheric river storm sequence              

Natural Hazards Mission Area, Landslide Hazards Program, Geologic Hazards Science Center

#### Matthew A Thomas

##### Research Hydrologist

Landslide Hazards Program

matthewthomas@usgs.gov

303-273-8588

#### Jason Kean

##### Research Hydrologist

Landslide Hazards Program

jwkean@usgs.gov

303-273-8608

#### Jaime Kostelnik

##### Geologist

Landslide Hazards Program

jkostelnik@usgs.gov

720-392-8049 

#### Francis Rengers

##### Research Geologist

Landslide Hazards Program

frengers@usgs.gov

303-273-8637

#### Amy East

##### Research Geologist

Pacific Coastal and Marine Science Center

aeast@usgs.gov

831-460-7533

#### Brian Collins

##### Supervisory Research Civil Engineer

Geology, Minerals, Energy, and Geophysics Science Center

bcollins@usgs.gov

650-439-2466

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#### Geologic Hazards Science Center

1711 Illinois St.Golden, CO80401United States

303-273-8500

####               Geology, Minerals, Energy, and Geophysics Science Center          

Building 19, 350 N. Akron Rd.P.O. Box 158Moffett Field, CA94035United States

####               Pacific Coastal and Marine Science Center          

2885 Mission StreetSanta Cruz, CA95060United States

831-460-7401

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