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Open-File Report 2012–1158

Pubs Warehouse

### Prepared in cooperation with Colorado Department of Transportation

## Probability and Volume of Potential PostwildfireDebris Flows in the 2012 Waldo Canyon Burn Areanear Colorado Springs, Colorado

#### By Kristine L. Verdin, Jean A. Dupree, and John G. Elliott

| Abstract
This report presents a preliminary emergency assessment of the debris-flow hazards from drainage basins burned by the 2012 Waldo Canyon fire near Colorado Springs in El Paso County, Colorado. Empirical models derived from statistical evaluation of data collected from recently burned basins throughout the intermountain western United States were used to estimate the probability of debris-flow occurrence and potential volume of debris flows along the drainage network of the burned area and to estimate the same for 22 selected drainage basins along U.S. Highway 24 and the perimeter of the burned area. Input data for the models included topographic parameters, soil characteristics, burn severity, and rainfall totals and intensities for a (1) 2-year-recurrence, 1-hour-duration rainfall, referred to as a 2-year storm (29 millimeters); (2) 10-year-recurrence, 1-hour-duration rainfall, referred to as a 10-year storm (42 millimeters); and (3) 25-year-recurrence, 1-hour-duration rainfall, referred to as a 25-year storm (48 millimeters).

Estimated debris-flow probabilities at the pour points of the the drainage basins of interest ranged from less than 1 to 54 percent in response to the 2-year storm; from less than 1 to 74 percent in response to the 10-year storm; and from less than 1 to 82 percent in response to the 25-year storm.  Basins and drainage networks with the highest probabilities tended to be those on the southern and southeastern edge of the burn area where soils have relatively high clay contents and gradients are steep.  Nine of the 22 drainage basins of interest have greater than a 40-percent probability of producing a debris flow in response to the 10-year storm.  Estimated debris-flow volumes for all rainfalls modeled range from a low of 1,500 cubic meters to a high of greater than 100,000 cubic meters. Estimated debris-flow volumes increase with basin size and distance along the drainage network, but some smaller drainages were also predicted to produce substantial volumes of material. The predicted probabilities and some of the volumes predicted for the modeled storms indicate a potential for substantial debris-flow impacts on structures, reservoirs, roads, bridges, and culverts located both within and immediately downstream from the burned area. U.S. Highway 24, on the southern edge of the burn area,  is also susceptible to impacts from debris flows. | First posted July 30, 2012
-  **Report** PDF (1.63 MB) 
-  **Plate 1** (1.9 MB)   
-  **Plate 2** (1.3 MB) 

**For additional information contact:**Center Director, USGS Colorado Water Science Center  Box 25046, Mail Stop   415  Denver, CO 80225http://co.water.usgs.gov

Part or all of this report is presented in Portable Document Format (PDF); the latest version of Adobe Reader or similar software is required to view it. Download the latest version of Adobe Reader, free of charge. |
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### Suggested citation:

Verdin, K.L., Dupree, J.A, and Elliott, J.G., Probability and volume of potential postwildfire debris flows in the 2012 Waldo Canyon Burn Area near Colorado Springs, Colorado: U.S. Geological Survey Open-File Report 2012–1158, 8 p.

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### Contents

Abstract

Introduction

Probability and Volume of Potential Debris Flows

References Cited

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U.S. Department of the Interior |            U.S. Geological Survey           	URL: *http://pubsdata.usgs.gov/pubs/of/2012/1158/index.html*            Page Contact Information: GS Pubs Web Contact           	Page Last Modified: Monday, 07-Mar-2016 13:43:26 EST