Landslide

A detailed description of the sources and methods of this database compilation can be found in Idaho Transportation Department report RP-278. Landslide inventory databases are fundamental tools for documenting and assessing slope stability hazards. They are often used by emergency managers and government agencies to catalog the location and contributing factors of landslides, and to prioritize mitigation efforts. Prior to this project, Idaho did not have a comprehensive, public landslide inventory database. The last statewide landslide inventory (IGS publication SGM-1) was published in 1991 as a static map and is not suitable for modern digital analyses. In this project, the Idaho Geological Survey produced a statewide landslide inventory database to document known slope failures. The goal of this project was to compile and update landslide data in a central database that is publicly accessible via interactive webmap or downloadable digital files. We compiled and reviewed historical landslide data from several sources and added newly mapped landslides to create a comprehensive landslide inventory. We assessed the accuracy of historical landslide data and assigned each record with a qualitative measure of spatial accuracy. Limited field verification was performed as part of this project, in which selected sites across the state were visited by IGS geologists to compare the database mapping to existing conditions in the field. The field verification suggested that most mapped landslides are real and are accurately mapped, but many landslides in the field are not included in the database. The database is also available as an ArcGIS service, which supports an interactive webmap hosted by Idaho Geological Survey. The database is designed to be updated as new data are collected.Primary data sources include:Geologic maps published by the Idaho Geological Survey.New landslides mapped on lidar basemaps.Adams, Wayne C. and Breckenridge, Roy M. 1991. “Landslides in Idaho” Idaho Geological Survey Surficial Map 1, scale 1:500,000.Dixon, Michael D., and Wasniewski, Louis W. 1998. “Summary of Landslide Inventory on the Westside of the Payette National Forest from the New Year 1997 Storm.” Payette National Forest Supervisors Office, McCall, Idaho, 26 p.Jones, Douglas, R. 1991. “Slope movement hazard evaluation along a portion of the Salmon River and Little Salmon River canyons, Idaho County, Idaho.” University of Idaho M.S. thesis, 97 p., 3 plates, scale 1:24,000.Shaub, Suzanne. 2001. “Landslides and wildfire: An example from the Boise National Forest.” Boise State University M.S. thesis, 85 p., 1 plate scale 1:24,000.