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Movement of Sediment Through a Burned Landscape:Sediment Volume Observations and Model Comparisons in the San Gabriel Mountains, California, USA.
Rengers, F. K., McGuire, L. A., Kean, J. W., Staley, D. M., Dobre, M., Robichaud, P. R., & Swetnam, T. 2021.
Movement of Sediment Through a Burned Landscape:Sediment Volume Observations and Model Comparisons in the San Gabriel Mountains, California, USA..
Journal of Geophysical Research:Earth Surface 126 DOI: 10.1029/2020JF006053.
Keywords: debris flow, wildfire, seismic monitoring, natural hazard, mass wasting, sediment transport
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Abstract:
Post-wildfire changes to hydrologic and geomorphic systems can lead to widespread
sediment redistribution. Understanding how sediment moves through a watershed is crucial for assessing
hazards, developing debris flow inundation models, engineering sediment retention solutions, and
quantifying the role that disturbances play in landscape evolution. In this study, we used terrestrial and
airborne lidar to measure sediment redistribution in the 2016 Fish Fire, in the San Gabriel Mountains
in southern California, USA. The lidar areas are in two adjacent watersheds, at spatial scales of 900 m2
to 4 km2, respectively. Terrestrial lidar data were acquired prior to rainfall, and two subsequent surveys
show erosional change after rainstorms. Two airborne lidar flights occurred (1) 7 months before, and
(2) 14 months after the fire ignition, capturing the erosional effects after rainfall. We found hillslope
erosion dominated the overall sediment budget in the first rainy season after wildfire. Only 7% of the total
erosion came from the active channel bed and channel banks, and the remaining 93% of eroded sediment
was derived from hillslopes. Within the channelized portion of the watershed erosion/deposition could
be generally described with topographic metrics used in a stream power equation. Observed sediment
volumes were compared with four empirical models and one process-based model. We found that the
best predictions of sediment volume were obtained from an empirical model developed in the same
physiographic region. Moreover, this study showed that post-wildfire erosion rates in the San Gabriel
Mountains attain the same magnitude as millennial time scale bedrock erosion rates.
Moscow FSL publication no. 2021g
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