THE UPDATED LANDSLIDE MAP AND INVENTORY OF UTAH

Significant economic losses are associated with landslides, and Utah contains numerous landslides and landslide-prone geologic units. For this reason, the Utah Geological Survey (UGS) compiled a series of maps in 1989 displaying known landslide deposits in Utah. Since then, new geologic maps and landslide investigations have been completed by the UGS. With this new information, we updated the landslide maps and integrated the data into a geographic information system (GIS). The new information allowed us to refine our existing landslide boundaries and map numerous pre-existing landslides not included in the previous compilation. The resulting product consists of 47 maps (1:100,000-scale) and an accompanying geodatabase.

The maps contain more than 15,000 landslides in Utah that cover over 5% of the state, and show landslide deposits as well as landslide scarps. We classified landslide deposits primarily based on failure type and depth to the surface of rupture. Shallow landslides are classified where depth to the surface of rupture is less than 10 feet (3 m) and include mainly debris slides and debris flows. Deep-seated landslides are classified where depth to the surface of rupture is generally greater than 10 feet (3 m) and include slumps, earth flows, and complex landslides. Lateral spreads and landslides undifferentiated from other mass-movement deposits (such as talus, colluvium and glacial deposits) are also included.

The accompanying geodatabase organizes and stores specific information about each landslide, including landslide category, historical landslide events, possible causes of movement, and cost of landslide damage. The geodatabase also provides information on the original data source, where more specific information may be obtained.

Understanding landsliding in Utah is becoming more important as development continues to expand into mountainous regions of the state. The maps and accompanying geodatabase provide a way to identify the location and extent of previous landsliding and will aid in identifying potential landslide areas. This information will be useful to local jurisdictions in land-use planning, and can also be used by developers and geotechnical consultants in identifying areas where landslide investigations are needed prior to development.