Developing and Testing Physically Based Triggering Thresholds for Runoff‐Generated Debris Flows. Issue 15 (5th August 2019)

• Record Type: Journal Article
• Authors: Tang, Hui; McGuire, Luke A.; Rengers, Francis K.; Kean, Jason W.; Staley, Dennis M.; Smith, Joel B.
• Is Part Of: Geophysical research letters. Volume 46:Issue 15(2019)
• Page Start: 8830
• Page End: 8839
• Publication Date: 2019-08-05
• Subjects: Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1029/2019GL083623
• Languages: English
• ISSNs: 0094-8276

Abstract

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. Key Points: Slope‐dependent thresholds of dimensionless discharge and Shields stress can predict postfire debris flow initiation We propose a process‐based method for calculating rainfall intensity‐duration thresholds Rainfall intensity‐duration thresholds derived from process‐based hydrologic modeling are comparable to empirical thresholds