Geologic Publications for Mount Rainier
Distinguishing between debris flows and floods from field evidence in small watersheds
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Thomas C. Pierson
Fact Sheet 2004-3142
United States Geological Survey
Post-flood indirect measurement techniques to back-calculate flood magnitude are not valid for debris flows, which commonly occur in small steep watersheds during intense rainstorms. This is because debris flows can move much faster than floods in steep channel reaches and much slower than floods in low-gradient reaches. In addition, debris-flow deposition may drastically alter channel geometry in reaches where slope-area surveys are applied. Because high-discharge flows are seldom witnessed and automated samplers are commonly plugged or destroyed, determination of flow type often must be made on the basis of field evidence preserved at the site.
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In Text Citation:
Pierson (2005) or (Pierson, 2005)
Pierson, T.C., 2005, Distinguishing between debris flows and floods from field evidence in small watersheds: Fact Sheet 2004-3142, United States Geological Survey, 4 p..