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Open-File Report 2013–1260

Emergency Assessment of Post-Fire Debris-Flow Hazards for the 2013 Rim Fire, Stanislaus National Forest and Yosemite National Park, California

By Dennis M. Staley

Thumbnail of and link to report PDF (3.9 MB)Abstract

Wildfire can significantly alter the hydrologic response of a watershed to the extent that even modest rainstorms can produce dangerous flash floods and debris flows. In this report, empirical models are used to predict the probability and magnitude of debris-flow occurrence in response to a 10-year rainstorm for the 2013 Rim fire in Yosemite National Park and the Stanislaus National Forest, California. Overall, the models predict a relatively high probability (60–80 percent) of debris flow for 28 of the 1,238 drainage basins in the burn area in response to a 10-year recurrence interval design storm. Predictions of debris-flow volume suggest that debris flows may entrain a significant volume of material, with 901 of the 1,238 basins identified as having potential debris-flow volumes greater than 10,000 cubic meters. These results of the relative combined hazard analysis suggest there is a moderate likelihood of significant debris-flow hazard within and downstream of the burn area for nearby populations, infrastructure, 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 October 29, 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., 2013, Emergency assessment of post-fire debris-flow hazards for the 2013 Rim Fire, Stanislaus National Forest and Yosemite National Park, California: U.S. Geological Survey Open-File Report 2013–1260, 11 p., 3 plates, http://pubs.usgs.gov/of/2013/1260/.



Contents

Abstract

Introduction

Physical Setting of the Rim Fire Burn Area

Methods Used To Estimate Debris-Flow Hazards

Debris-Flow Hazard Assessment Results

Summary and Conclusions

References Cited


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