UPDATES TO THE U.S. LANDSLIDE INVENTORY COMPILATION AND ASSESSMENT OF NATIONAL-SCALE LANDSLIDE SUSCEPTIBILITY

In 2019 the U.S. Geological Survey (USGS) partnered with other Federal Agencies and State Geological Surveys to gather and combine many geodatabases of landslide occurrence across the U.S. and Territories. This initial step towards a national inventory identified around 300,000 landslides and landslide-related features in every U.S. State. This data compilation of points and polygons has highlighted the vast disparity in the availability, documentation, and confidence levels of landslide information across different regions of the country. It has also facilitated both qualitative and quantitative re-evaluation of previous national-scale landslide susceptibility assessments. This reveals that previous approaches that relied primarily on coarse resolution geologic information and topography may under-estimate landslide potential in relatively moderately sloping terrain. These important revelations about landslide data availability and prior susceptibility maps have motivated a recent update to ingest more landslide data, including revised, new, and newly identified inventories, totaling over 570,000 points and polygons. We have also revised our initial semi-quantitative criteria for assessing confidence in landslide information to account for differences between discrete landslides and other polygons that map landslide-related features. Although the updated database is still known to be incomplete, the USGS inventory compilation provides a centralized portal to access landslide occurrence information for land managers, emergency planners, researchers, and the public. The national landslide occurrence map has also generated increased sharing of landslide data and prompted a broader community-wide discussion about developing and adopting standards for future landslide inventories.

The national landslide map is at https://usgs.gov/maps/national-landslides-map-and-data. Please contact gs-haz_landslides_inventory@usgs.gov for more information on how to contribute to this community effort.