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August 8, 2013
Emmet McGuire 520-670-6671 ext 284 emcguire@usgs.gov
Jennifer  LaVista 303-202-4764 jlavista@usgs.gov

Studying Potential Debris Flow in Yarnell Hill Burn Area

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Reporters: Want to go accompany field crews as they study a potential debris flow site? Contact Emmet McGuire.   

Scientists are surveying a potential debris flow area within the Yarnell Hill burn zone, as part of a cooperative study by the U.S. Geological Survey, the Arizona Geological Survey, and the Arizona Department of Emergency Management. 

There is an increased potential for debris flows following the recent Yarnell Hill fire event in central Arizona, especially during the summer thunderstorm season. Debris flows are slurries of water, mud, and rocks resulting from rainfall on rugged, recently burned, forested areas that can create potential hazards to people, infrastructure, and water resources. Findings will help advance the understanding of debris flows following fires in the western United States. 

"Results from this study will improve modeling of post-fire debris flows, which can be used by emergency managers to potentially help save lives and property," said USGS scientist Emmet McGuire.

Scientists are surveying a slope five miles northwest of Yarnell, Ariz., that is completely burned and has debris flow potential. Crews surveyed the slope during the week of July 15 before rainfall events occurred, and these data will be compared to future assessments after rainfall events. The slope is being studied using LiDAR imaging and GPS surveying. LiDAR, or light detection and ranging, uses lasers to measure elevations in a specific distance/area. The LiDAR data are being used to construct high-resolution three-dimensional maps. The GPS surveying is used to track debris that falls down the slope. Scientists are also measuring the amount of rainfall, and will visit the site after each major rain event.

Slopes are made up of different types of materials, and studying diverse burn areas helps improve the ability to predict debris-flow hazards. The Yarnell Hill burn area contains slopes that are made up of granite, and create a specific type of decomposed granitic rubble. Learning more about post-fire debris flows in this area will advance the understanding of other areas that contain granite slopes, including western Colorado and other areas in Arizona.

To learn more about post-fire debris flow, visit the USGS landslide hazards website

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