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UID:seminar-15391@epss.ucla.edu
DTSTAMP:20260522T193453Z
DTSTART:20260513T153000Z
DTEND:20260513T163000Z
SUMMARY:Geophysics &#038\; Geology (245/287): Alexander Koutsoukos &#8211\; Impact of Extreme Rainfall and Fire on Geomorphic Hazards of Western Transverse Ranges in Southern California
DESCRIPTION:Speaker: Alexander Koutsoukos
Affiliation: EPSS\, UCLA
Date: Wednesday\, May 13\, 2026
Time: 12:00 PM

Abstract
 Between 2010 and January 2025\, California’s western Transverse Ranges experienced 18 fires with burn areas larger than 20 km2\, the largest of which was the ~1141 km2 Thomas Fire\, which burned across Ventura and Santa Barbara Counties in December 2017. During the same period\, this area occasionally experienced unusually wet seasons with several landfalling atmospheric rivers. The most notable was the 2022-2023 atmospheric river season\, which saw significantly elevated precipitation totals relative to the 30-year average and which triggered widespread landslides and debris flows in burned hillslopes across Southern California. Terrain\, cloud cover\, and vegetation cover complicate comprehensive range-scale post-atmospheric river surface disturbance mapping and monitoring. We created a supervised threshold-based NDVI (normalized difference vegetation index) change detection to map surface disturbances. We then run a frequency ratio-based susceptibility model using confirmed landslide heads. We applied these models to the eastern Santa Ynez Mountains northwest of Ojai\, CA\, on terrain burned by the December 2017 Thomas Fire and affected by the January 9\, 2023 atmospheric river\, to better understand the relationship between local topographic factors\, landslide triggering\, and extent of downstream sedimentation. We considered eleven different parameters at 250 landslide heads in (distance to channel\, eastness\, elevation\, northness\, plan curvature\, profile curvature\, roughness\, sediment transport index\, slope\, and stream power index\, and topographic wetness index). Of these\, we found the three most statistically relevant metrics in our study area were plan curvature\, topographic wetness index\, and distance to channel.
URL:https://epss.ucla.edu/geophysics-geology-245-287-alexander-koutsoukos-impact-of-extreme-rainfall-and-fire-on-geomorphic-hazards-of-western-transverse-ranges-in-southern-california/
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