Description:

Widespread Acceleration of Slow-Moving Landslides in California Due to Extreme Rainfall

Abstract
Episodically to continuously active slow-moving landslides are driven by precipitation. These landslides cause significant erosion and pose a major natural hazard that can damage infrastructure and threaten life. Climate change, which is altering both the frequency and magnitude of precipitation worldwide, is therefore predicted to have a major impact on landslides. Here we examine the behavior of hundreds of slow-moving landslides in northern California in response to large changes in annual precipitation that occurred between 2016 and 2018. We quantify the landslide displacement using repeat-pass radar interferometry and pixel offset tracking techniques on data from the airborne NASA/JPL Uninhabited Aerial Vehicle Synthetic Aperture Radar. We found that 312 landslides were moving due to extreme rainfall during 2017, compared to 119 during 2016, which was the final year of a historic multi-year drought. However, with a return to below average rainfall in 2018, only 146 landslides remained in motion. The increased landslide frequency during 2017 was accommodated by landslides that were smaller (area < 7 x 105 m2) than the landslides that remained active between 2016 and 2018. Furthermore, by examining a subset of 51 landslides, we found that 49 had increased velocities during 2017 when compared to 2016. Our results show that slow-moving landslides are sensitive to rapid changes in precipitation, particularly the smaller (and thinner) landslides that likely experience larger hydrologic changes. Based on future predictions of precipitation over the next century in California, we hypothesize that there will be profound changes in landslide behavior.

Bio
Alexander Handwerger is a NASA Postdoctoral Program Fellow at the Jet Propulsion Laboratory, California Institute of Technology.

Recent publication: https://earthobservatory.nasa.gov/images/144518/drought-then-deluge-turned-a-stable-landslide-into-disaster