Evolution of a natural debris flow; in situ measurements of flow dynamics, video imagery, and terrestrial laser scanning

Many theoretical and laboratory studies have been undertaken to understand debris-flow processes and their associated hazards. However, complete and quantitative data sets from natural debris flows needed for confirmation of these results are limited. We used a novel combination of in situ measureme...

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Bibliographic Details
Published in:Geology (Boulder) 2010-08, Vol.38 (8), p.735-738
Main Authors: McCoy, Scott W, Kean, Jason W, Coe, Jeffrey A, Staley, Dennis M, Wasklewicz, Thad A, Tucker, Gregory E
Format: Article
Language:English
Subjects:
Chaffee County Colorado
Chalk Cliffs
channels
Colorado
debris flows
field studies
Fluid dynamics
fluid pressure
Geomorphology
laser methods
mass movements
Measurement
Mount Princeton
North America
observations
Rocky Mountains
Sawatch Range
Sediment transport
Sedimentation & deposition
slope stability
U. S. Rocky Mountains
United States
video methods
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Summary:Many theoretical and laboratory studies have been undertaken to understand debris-flow processes and their associated hazards. However, complete and quantitative data sets from natural debris flows needed for confirmation of these results are limited. We used a novel combination of in situ measurements of debris-flow dynamics, video imagery, and pre- and postflow 2-cm-resolution digital terrain models to study a natural debris-flow event. Our field data constrain the initial and final reach morphology and key flow dynamics. The observed event consisted of multiple surges, each with clear variation of flow properties along the length of the surge. Steep, highly resistant, surge fronts of coarse-grained material without measurable pore-fluid pressure were pushed along by relatively fine-grained and water-rich tails that had a wide range of pore-fluid pressures (some two times greater than hydrostatic). Surges with larger nonequilibrium pore-fluid pressures had longer travel distances. A wide range of travel distances from different surges of similar size indicates that dynamic flow properties are of equal or greater importance than channel properties in determining where a particular surge will stop. Progressive vertical accretion of multiple surges generated the total thickness of mapped debris-flow deposits; nevertheless, deposits had massive, vertically unstratified sedimentological textures.
ISSN:0091-7613
1943-2682
DOI:10.1130/G30928.1