Debris flow initiation by runoff in a recently burned basin: Is grain-by-grain sediment bulking or en masse failure to blame?

Geophysical Research Letters
By: , and 

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Abstract

Postwildfire debris flows are frequently triggered by runoff following high-intensity rainfall, but the physical mechanisms by which water-dominated flows transition to debris flows are poorly understood relative to debris flow initiation from shallow landslides. In this study, we combined a numerical model with high-resolution hydrologic and geomorphic data sets to test two different hypotheses for debris flow initiation during a rainfall event that produced numerous debris flows within a recently burned drainage basin. Based on simulations, large volumes of sediment eroded from the hillslopes were redeposited within the channel network throughout the storm, leading to the initiation of numerous debris flows as a result of the mass failure of sediment dams that built up within the channel. More generally, results provide a quantitative framework for assessing the potential of runoff-generated debris flows based on sediment supply and hydrologic conditions.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Debris flow initiation by runoff in a recently burned basin: Is grain-by-grain sediment bulking or en masse failure to blame?
Series title Geophysical Research Letters
DOI 10.1002/2017GL074243
Volume 44
Issue 14
Year Published 2017
Language English
Publisher American Geophysical Union
Contributing office(s) Geologic Hazards Science Center
Description 10 p.
First page 7310
Last page 7319
Country United States
State California