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Presentation Title

A Slippery Slope: Towards Better Understanding and Prediction of At-Risk Hillsides by Carrie Jennings, Minnesota Department of Natural Resources

Presentation Overview

Minnesota’s wettest recorded month in June 2014 led to widespread gravitational failure of sediment and rock in the metropolitan area of Minneapolis-St. Paul.  The failure beneath the oxygen supply for Fairview Riverside hospital was costly enough to allow the entire state to qualify for a federal disaster declaration.  Two years prior, a similarly rainy period resulted in loss of life as well as extensive property damage.  Our goal is to develop a better predictive model of when and where failures occur in order to inform hazard response plans, best management practices and to develop model ordinance language. 

We inventoried historical failures in a broad region that included the metropolitan area by searching online sources and print newspaper archives. We interviewed Minnesota Department of Transportation personnel with extensive knowledge of problematic areas in heavily engineered landscapes near roadways. Failures were mapped onto a 1m-hillshade DEM created with LiDAR data at a density ranging from 1.5 to 8 data points per square meter.  Failure scars discovered on the DEM and not through the historical archives were noted and municipalities contacted for more information on timing.  The antecedent  precipitation for two to four weeks prior to the failure  and soil moisture conditions at the time failure were extracted from climate archives for the periods identified. 

Nearly all of the slides occurred between May and October with peaks in June and August, both periods of higher incidence of convective storms in Minnesota. The earliest record of failure was in 1879.  Wet periods in the late 1890s, early 1900s, 1980s and 1990s are reflected in an increase in reporting of slides.  The increase in slides reported since 2010 may reflect the wetter climate as well as the ease of searching online records.  The failures were primarily located along the Mississippi and Minnesota River corridors.

Jennings, Carrie E.¹, Feinberg, Joshua M.¹, Kurak, Ethan¹, Meier, Rachel³, Palazzolo, Jessica¹, Schmidt, Craig², Waage, Eric⁴

¹ University of Minnesota, ²National Weather Service , ³Gustavus Adolphus College, ⁴Hennepin County Emergency Management

Speaker Biography

Carrie has been a geologist at the Department of Natural Resources for 3 and a half years.  Prior to that was a geologist for 22 years at the Minnesota Geological Survey, part of the School of Earth Sciences at the University of Minnesota.  She has mapped the surficial geology of half of the state.  She has taught at the undergraduate and graduate levels; her field-oriented glacial geology class at the U of M has been offered for the last 22 years.  Carrie has applied her understanding of glacial geology and landscape evolution to help protect surface water, explore for aggregate resources  and groundwater, and understand landslide hazards.