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Dry sediment loading of headwater channels fuels post-wildfire debris flows in bedrock landscapes

DiBiase, Roman A. and Lamb, Michael P. (2020) Dry sediment loading of headwater channels fuels post-wildfire debris flows in bedrock landscapes. Geology, 48 (2). pp. 189-193. ISSN 0091-7613.

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Landscapes following wildfire commonly have significant increases in sediment yield and debris flows that pose major hazards and are difficult to predict. Ultimately, post-wildfire sediment yield is governed by processes that deliver sediment from hillslopes to channels, but it is commonly unclear the degree to which hillslope sediment delivery is driven by wet versus dry processes, which limits the ability to predict debris-flow occurrence and response to climate change. Here we use repeat airborne lidar topography to track sediment movement following the 2009 CE Station Fire in southern California, USA, and show that post-wildfire debris flows initiated in channels filled by dry sediment transport, rather than on hillsides during rainfall as typically assumed. We found widespread patterns of 1–3 m of dry sediment loading in headwater channels immediately following wildfire and before rainfall, followed by sediment excavation during subsequent storms. In catchments where post-wildfire dry sediment loading was absent, possibly due to differences in lithology, channel scour during storms did not occur. Our results support a fire-flood model in bedrock landscapes whereby debris-flow occurrence depends on dry sediment loading rather than hillslope-runoff erosion, shallow landslides, or burn severity, indicating that sediment supply can limit debris-flow occurrence in bedrock landscapes with more-frequent fires.

Item Type:Article
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URLURL TypeDescription
DiBiase, Roman A.0000-0002-5347-8396
Lamb, Michael P.0000-0002-5701-0504
Additional Information:© 2019 The Authors. Gold Open Access: This paper is published under the terms of the CC-BY license. Manuscript received 7 August 2019; Revised manuscript received 27 October 2019; Manuscript accepted 30 October 2019. Published online 9 December 2019. We thank Drew Decker for assistance with obtaining the June 2009 lidar data set, and Lisa Woodward for help with preliminary analysis. DiBiase acknowledges funding from the National Science Foundation (grant EAR-1848321). September 2009 lidar data were collected by the National Center for Airborne Laser Mapping with funding support from Arizona State University, the California Institute of Technology, and the U.S. Geological Survey, and are available from OpenTopography ( Comments from Tom Dunne and two anonymous reviewers helped improve the paper.
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Arizona State UniversityUNSPECIFIED
Issue or Number:2
Record Number:CaltechAUTHORS:20191209-143427217
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Official Citation:Roman A. DiBiase, Michael P. Lamb; Dry sediment loading of headwater channels fuels post-wildfire debris flows in bedrock landscapes. Geology ; 48 (2): 189–193. doi:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:100246
Deposited By: Tony Diaz
Deposited On:09 Dec 2019 23:31
Last Modified:28 Jan 2020 18:33

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