LANDSLIDE SUSCEPTIBILITY IN MINNESOTA: INSIGHT FROM LANDSLIDE INVENTORY MAPPING AND LIDAR CHANGE DETECTION

The recently published landslide inventory for most landslide-prone areas in Minnesota provides the basis for generation of landslide susceptibility maps. These maps are derived from logistic regression analysis of mapped landslide occurrences, terrain characteristics, and Quaternary geological mapping. While the heterogenous glacial deposits that cover much of Minnesota complicate susceptibility analysis, it is apparent that (1) steep slopes adjacent to post-glacial valley networks are susceptible to landslides in areas underlain by clayey glacial till and poorly consolidated sandy outwash, (2) slopes of variable steepness are highly susceptible to landslides in areas of clay-rich deposits from former glacial lake and nearshore/deltaic environments and (3) exposed bedrock is susceptible to rock falls, particularly in southeastern Minnesota where glacial cover is thin and older river valleys are cut more deeply into layered sedimentary bedrock. Recent landslide activity in Minnesota indicates that modified slopes, altered stormwater management, and artificial fill are also susceptible to landslides. Comparison of landslide inventory mapping with landslides in northeastern Minnesota triggered by a 500-year-recurrence storm in 2012 reveal that some mapped pre-existing landslides in susceptible locations were stable. Thus, these older slides, which often have complex morphology with multiple arcuate scarps, may be relict landforms formed under different climatic or groundwater regimes, or as a response to initial post-glacial valley formation. Landslides of similar morphology are also found in other parts of Minnesota and may represent a suite of now-stable ancient landslides, complicating inventory-based susceptibility analysis. These studies, which were only possible via collaboration among many institutions and researchers using statewide airborne lidar coverage, provide a wealth of new insight into landslide hazards across the landscapes of Minnesota. This new information is being disseminated via a range of publications targeting a range of stakeholders and the scientific community.