DEVELOPMENT OF THE ARIZONA STATEWIDE LANDSLIDE INVENTORY DATABASE; PRACTICAL AND GEOLOGICAL LESSONS LEARNED (Invited Presentation)

In 2014, the Arizona Geological Survey received funding from the Federal Emergency Management Agency’s Pre-Disaster Mitigation grant program to develop an Arizona Statewide Landslide Inventory Database (AzSLID) of previously documented landslides. New mapping was not part of this program. We initially developed the geodatabase following the National Cooperative Geologic Mapping Program (NCGMP09) structure so we could use our in-house toolbar to import data. Relational tables captured all information that might be available about landslides (e.g. type of landslide, failure mechanism and depth, event data, costs, etc.). We compiled previously documented landslide data from our archives (published and unpublished) and from other sources (e.g. USGS maps, theses, etc.). AzSLID currently contains over 6000 landslide polygon features covering approximately 2000 km², and over 2000 landslide point features representing debris flows.

Arizona encompasses three physiographic provinces with a wide variety of geologic units with diverse ages. The Colorado Plateau covers the northern third of the state and contains 57% of the landslide features in AzSLID while the Central Highlands Transition Zone contains 4%, and the Basin and Range in the southern part of the state contains 38% of landslide features. Based on mapped units, 62% of the features are within sedimentary units, 15% in plutonic and metamorphic units, 17% in volcanic units and 5% in unconsolidated surficial deposits.

The distribution of landslide features within AzSLID is, however, mainly a function of previous mapping efforts, thus large swaths of the state contain no data, or contain unmapped features we identified using Google Earth imagery. Future efforts will focus on mapping landslides in some of these areas, particularly after statewide lidar data is available, projected for 2023. Since the original geodatabase was completed in 2017, we have transitioned through several iterations of databases, simplifying the structure each time as we found the original, more complex database had too many fields that contained no data and relations between tables too complicated. AzSLID can be viewed through the Natural Hazards in Arizona viewer found at https://azgs.arizona.edu/.