A SLIPPERY SLOPE: THE FIRST STEPS TO ESTABLISHING A STATEWIDE LANDSLIDE DATABASE IN MINNESOTA

Landslides have long posed a threat to human livelihood within the United States, affecting areas such as Washington, California, and even the Twin Cities metro area of Minnesota. While the Twin Cities metropolitan area is likely not the first place to come to mind when thinking of landslides, late glacial events including spillway creation and waterfall retreat have created an environment prone to slope failures. The need for a landslide database in Minnesota first became apparent about in 2014 when a landslide below the Fairview University Hospital in Minneapolis nearly knocked the hospital out of commision and cost the state untold dollars in damages. Since then, there has been a push to establish a landslide database in order to better predict and prepare for future landslides. Hennepin County, location of Minneapolis and a densely populated urban area, led the development of a historical landslide inventory. Historical records of various formats including digital records and microfiche were searched for any type of references to landslides. These references were then catalogued, with the date of each event, probable location of the slide, and a copy of the source material for the failure. Phase two of this project, to be completed by December, 2017 consists of identifying past slides in Hennepin County using LiDAR data. The methods are drawn from work in Washington and Oregon, and adjusted to suit the landscape of Minnesota. From a LiDAR DEM we identify likely past landslides, tracing an outline of the failure into a shapefile in ArcGIS. For each landslide in the shapefile, data were recorded including type of failure, material that failed, whether the slide is old (pre-settlement) or recent, and area of the scarp. With the historical landslide inventory we found that landslides usually occur from may to October, with peaks in June & August. The LiDAR based-database, has provided more locations of landslides along river corridors, the shores of Lake Minnetonka, as modified slopes such as those along roads and railways. This research with a focus on Hennepin County lays the groundwork for the future expansion of the database to a statewide level.