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Open-File Report 2013–1249

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

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

Thumbnail of and link to report PDF (2.9 MB)Abstract

Wildfire dramatically alters the hydrologic response of a watershed such that even modest rainstorms can produce dangerous flash floods and debris flows. We use empirical models to predict the probability and magnitude of debris flow occurrence in response to a 10-year rainstorm for the 2013 Mountain fire near Palm Springs, California. Overall, the models predict a relatively high probability (60–100 percent) of debris flow for six of the drainage basins in the burn area in response to a 10-year recurrence interval design storm. Volumetric predictions suggest that debris flows that occur may entrain a significant volume of material, with 8 of the 14 basins identified as having potential debris-flow volumes greater than 100,000 cubic meters. These results suggest there is a high likelihood of significant debris-flow hazard within and downstream of the burn area for nearby 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., Gartner, J.E., Smoczyk, G.M., and Reeves, R.R., 2013, Emergency assessment of post-fire debris-flow hazards for the 2013 Mountain fire, southern California: U.S. Geological Survey Open-File Report 2013–1249, 13 p., 3 plates, http://pubs.usgs.gov/of/2013/1249/.



Contents

Abstract

Introduction

Physical Setting of the Mountain Burn Area

Methods Used To Estimate Debris-Flow Hazards

Debris-Flow Hazard Assessment

Summary and Conclusions

References Cited


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