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Open-File Report 2011–1251

Emergency Assessment of Postwildfire Debris-Flow Hazards for the 2011 Motor Fire, Sierra and Stanislaus National Forests, California

By Susan H. Cannon and John A. Michael

Thumbnail of and link to report PDF (4.07 MB) Abstract

This report presents an emergency assessment of potential debris-flow hazards from basins burned by the 2011 Motor fire in the Sierra and Stanislaus National Forests, Calif. Statistical-empirical models are used to estimate the probability and volume of debris flows that may be produced from burned drainage basins as a function of different measures of basin burned extent, gradient, and soil physical properties, and in response to a 30-minute-duration, 10-year-recurrence rainstorm. Debris-flow probability and volume estimates are then combined to form a relative hazard ranking for each basin. This assessment provides critical information for issuing warnings, locating and designing mitigation measures, and planning evacuation timing and routes within the first two years following the fire.

First posted September 30, 2011

For additional information contact:
Center Director, Geologic Hazards Science Center
U.S. Geological Survey
Box 25046, Mail Stop 966
Denver, CO 80225

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Suggested citation:

Cannon, S.H., and Michael, J.A., 2011, Emergency assessment of postwildfire debris-flow hazards for the 2011 Motor Fire, Sierra and Stanislaus National Forests, California: U.S. Geological Survey Open-File Report 2011–1251, 10 p.




Methods and Approach

Debris-Flow Probability Estimates

Debris-Flow Volume Estimates

Combined Relative Debris-Flow Hazard Rankings

Limitations of Assessment

Summary and Conclusions

References Cited

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