Map of landslide activity in California between April 2016 and February 2018
Average line-of-sight landslide velocity between April 2016 and February 2018 observed along two UAVSAR flight paths, draped over hillshade of topography, northern California. Red and blue correspond to active landslide deformation. Black arrows indicate azimuth (along track) and look direction of UAVSAR instruments. Changes in landslide activity are based on inventories by Bennett et al. [2016]. Digital elevation models from OpenTopography and TanDEM-X. Credit: Handwerger et al. [2019], Figure 4
Source: Journal of Geophysical Research: Earth Surface

Future climate projections indicate an increasing likelihood of extreme precipitation in many regions globally. Much of the western United States saw extreme wet conditions in winter 2017, providing opportunities to study geomorphic response to a scenario likely to repeat more frequently in the future.

Building on earlier investigations of slow-moving landslides in northern California, Handwerger et al. [2019] employed a novel Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR) dataset to map hundreds of slow-moving landslides, and estimated changes in velocity inferred to have resulted from changes in rainfall over three water years (2016–2018). By tracking landslide motion from the end of a historic drought through extreme wet conditions and back to subsequent below-average rainfall, the authors found that landslide velocity and the number of active slides clearly tracked large changes in annual precipitation. Smaller, thinner landslides were especially sensitive to annual rainfall changes, as those landslides undergo larger changes in basal pore-water pressure.

These results suggest that, as California experiences more-frequent extreme wet years and more-frequent dry-to-extreme-wet transitions over the twenty-first century, there will be an overall increase in landslide activity. Moreover, such applications of rapid, high-resolution and large-spatial-domain remote-sensing techniques have the potential to revolutionize landslide studies.

Citation: Handwerger, A. L., Fielding, E. J., Huang, M.‐H., Bennett, G. L., Liang, C., & Schulz, W. H. [2019]. Widespread initiation, reactivation, and acceleration of landslides in the northern California Coast Ranges due to extreme rainfall. Journal Geophysical Research: Earth Surface, 124.

—Amy East, Editor in Chief, JGR: Earth Surface

Text © 2019. The authors. CC BY-NC-ND 3.0
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