North-Central Section - 54th Annual Meeting - 2020

Paper No. 4-5
Presentation Time: 9:20 AM

LANDSLIDES IN THE RED RIVER VALLEY, MINNESOTA


DAY, Stephanie S., Department of Geosciences, North Dakota State University, 1340 Bolley Drive, Fargo, ND 58103, NIXON Jr., Charles Idell, Environmental and Conservation Sciences, North Dakota State University, 1340 Administration Avenue, Fargo, ND 58102, JENNINGS, Carrie, The Freshwater Society, ND, GRAN, Karen B., Department of Earth and Environmental Sciences, University of Minnesota - Duluth, Duluth, ND 55812, DELONG, Stephen B., Earthquake Science Center, U.S. Geological Survey, Moffett Field, CA 94035, DELONG, Whitney M., Department of Geography, Environment & Society, University of Minnesota, Minneapolis, ND 55455, OSTRAND, Megan, School of Natural Resources, North Dakota State University, 1340 Bolley Drive, Fargo, ND 58103, MAROLT, Samuel D., Department of Geosciences, North Dakota State University, 1340 Administration Ave, Fargo, ND 58105, HALVORSON, Victoria Elizabeth, North Dakota State University, Department of Geosciences, NDSU Dept 2745, PO Box 6050, Fargo, ND 56201 and SULLIVAN, Micheal, Geosciences, North Dakota State University, P.O. Box 6050 / 2745, Fargo, ND 58108

Despite its low relief, the Red River Valley in Minnesota does experience mass wasting, including landslides. Thousands of slides, primarily along rivers or lake shores, have been identified using airborne lidar data, and a subset of these have been field-verified. The size and failure mechanism of these slides changes throughout the valley in response to west-to-east changes in the surficial geology. Along the western edge of Minnesota, near the axis of the valley, the sediment is dominated by offshore glacial Lake Agassiz deposits of clay and silt which fail slowly as shallow slides, often as a result of changes to the vegetation or overburden. Moving a few tens of kilometers east into the near-shore Lake Agassiz environment, deposits are dominated by interbedded lacustrine and fluvial sands. Rivers in this area are deeply incised and form steep bluffs that can lead to large rotational failures. Farthest to the east towards the edge of the Red River valley watershed, rivers are less incised with lower river banks, but small rotational failures still occur in glacially dominated sediments. This inventory of Red River Valley landslides is a component of a greater Minnesota landslide mapping effort and highlights the need for understanding the variety of factors that contribute to landslide hazards in the state.