Slow-moving landslides near the U.S. West Coast mapped from ALOS and ALOS-2 InSAR, 2007-2019

This data set provides a polygon shapefile delineating relatively large, slow-moving (4-17 cm/year in the radar line-of-sight direction) landslides in the continental U.S. western coastal states (California, Oregon, and Washington). The polygons also are provided in a Google Earth .kmz file. Delineated landslides were identified from displacement signals captured by InSAR (Interferometric Synthetic Aperture Radar) interferograms of ALOS PALSAR (Advanced Land Observing Satellite; Phased Array type L-band Synthetic Aperture Radar) images between 2007 and 2011, and ALOS-2 PALSAR-2 images between 2015 and 2019. The ALOS PALSAR images utilized cover the three states entirely; the ALOS-2 PALSAR images utilized cover primarily the western half of the study area where 97.6% of the identified landslides are located. The Scene IDs of the used ALOS and ALOS-2 images are provided in text files. The 1/3 arc-second National Elevation Datasets from the U.S. Geological Survey (https://apps.nationalmap.gov/downloader/, last accessed November 12, 2020), and optical images available from Google Earth were utilized to assist in landslide identification.

Each polygon in the shapefile outlines the active area of a landslide. The active areas identified for a given landslide using the ALOS PALSAR and ALOS-2 PALSAR-2 interferograms differ slightly in some cases. For these, we used the larger polygon as the landslide boundary. The shapefile attribute table indicates which data were used to identify the landslide ("Comments"), and this is also indicated by the "Flag" field of the table, where values of 1, 2, and 3 indicate ALOS, ALOS2, and both datasets, respectively; a flag value of 4 was assigned for rock glaciers, which were only identified using ALOS data. The attribute table also provides areas of each polygon in square meters.

These data support a study described in:
Xu, Y., Schulz, W.H., Lu, Z., Kim, J., and Baxstrom, K., 2021, Geologic controls of slow-moving landslides near the U.S. west coast: Landslides, doi:10.1007/s10346-021-01732-3