Developing and testing physically based triggering thresholds for runoff‐generated debris flows

Geophysical Research Letters
By: , and 

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Abstract

Runoff in steep channels is capable of transitioning into debris flows with hazardous implications for downstream communities and infrastructure, particularly in alpine landscapes with minimal vegetation and areas recently disturbed by wildfire. Here, we derive thresholds for the initiation of runoff‐generated debris flows based on critical values of dimensionless discharge and Shields stress. These thresholds are derived by using a numerical model to estimate the hydrodynamic conditions coinciding with the timing of debris flow activity in a recently burned basin. A benefit of hydrodynamic thresholds is that they can be used to assess debris flow likelihood based on measurable hydrologic and geomorphic parameters and therefore provide more universal criteria for quantifying the runoff‐to‐debris flow transition in landscape evolution studies and hazard assessments. We then demonstrate how hydrodynamic thresholds can be used to estimate rainfall intensity‐duration thresholds for runoff‐generated debris flows without the need for historic debris flow observations.

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Publication type Article
Publication Subtype Journal Article
Title Developing and testing physically based triggering thresholds for runoff‐generated debris flows
Series title Geophysical Research Letters
DOI 10.1029/2019GL083623
Volume 46
Issue 15
Year Published 2019
Language English
Publisher American Geophysical Union
Contributing office(s) Geologic Hazards Science Center
Description 10 p.
First page 8830
Last page 8839
Country United States
State California
Other Geospatial San Gabriel Mountains
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