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Open-File Report 2013–1248

Emergency Assessment of Post-Fire Debris-Flow Hazards for the 2013 Powerhouse Fire, Southern California

By Dennis M. Staley, Greg M. Smoczyk, and Ryan R. Reeves

Thumbnail of and link to report PDF (3.17 MB)Abstract

Wildfire dramatically alters the hydrologic response of a watershed such that even modest rainstorms can produce dangerous flash floods and debris flows. Existing empirical models were used to predict the probability and magnitude of debris-flow occurrence in response to a 10-year recurrence interval rainstorm for the 2013 Powerhouse fire near Lancaster, California. Overall, the models predict a relatively low probability for debris-flow occurrence in response to the design storm. However, volumetric predictions suggest that debris flows that occur may entrain a significant volume of material, with 44 of the 73 basins identified as having potential debris-flow volumes between 10,000 and 100,000 cubic meters. These results suggest that even though the likelihood of debris flow is relatively low, the consequences of post-fire debris-flow initiation within the burn area may be significant for downstream populations, infrastructure, and wildlife and water resources. Given these findings, we recommend that residents, emergency managers, and public works departments pay close attention to weather forecasts and National-Weather-Service-issued Debris Flow and Flash Flood Outlooks, Watches, and Warnings and that residents adhere to any evacuation orders.

First posted September 30, 2013

For additional information contact:
Director, Geologic Hazards Science Center
U.S. Geological Survey
Box 25046, MS-966
Denver, CO 80225-0046
http://geohazards.cr.usgs.gov/

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Suggested citation:

Staley, D.M., Smoczyk, G.M., and Reeves, R.R., 2013, Emergency assessment of post-fire debris-flow hazards for the 2013 Powerhouse fire, southern California: U.S. Geological Survey Open-File Report 2013–1248, 13 p., 3 plates, http://pubs.usgs.gov/of/2013/1248/.



Contents

Abstract

Introduction

Physical Setting of the Powerhouse Burn Area

Methods Used To Estimate Debris-Flow Hazards

Debris-Flow Hazard Assessment

Summary and Conclusions

References Cited


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