UPDATE TO THE STATEWIDE LANDSLIDE INFORMATION DATABASE FOR OREGON (SLIDO) RELEASE 4.0

Landslides are one of the significant geologic hazards in Oregon. In order to reduce the risk from future landslides, a variety of measures are required, all of which need to start with an accurate and complete assessment of where landslide hazards exist. In order to make these data easy to access, the Statewide Landslide Information Database of Oregon (SLIDO) was created and published as Release 1 in 2008. The first release was a compilation of previously mapped landslides digitized from paper maps and included more than 15,000 landslide polygons. The second release (2011) included recorded landslide locations called historic points. The third release (2014) included a continuous update procedure for adding new data. Because of the wide range of SLIDO users, the reports and GIS data are available as downloadable files, streaming map services, and through an interactive web map. These previous releases contain landslide inventory data only.

After we understand what has happened in the past, the next step is to predict which areas are more or less likely to have landslides in the future, known as landslide susceptibility. To meet this need, SLIDO was updated to Release 4 in 2016. Release 4 contains a new statewide landslide susceptibility overview dataset with a published scale of 1:500,000. A matrix was developed, combining landslide density per geologic unit and slopes prone to landsliding and used to establish the susceptibility zones of low, moderate, high, and very high (mapped landslides). Release 4 also contains new detailed shallow and deep landslide susceptibility datasets with published scales of 1:8,000. Unlike the new statewide overview map, these new detailed datasets cover a small portion of the state so far.

The field (date) that holds the date information in the landslide inventory portions of SLIDO was expanded to five separate fields in Release 4 which are: year, month, day, reactivation (date), and date range. This will allow for better capture and organization of timing data. SLIDO 4 includes 41,029 landslide polygons and 12,095 historic landslide point locations compiled from 352 studies. The original studies vary widely in scale and focus which is reflected in the wide range of accuracy, and completeness with which landslides are mapped. We continue to add detailed, precise mapping of landslides in Oregon.