14 Flash Floods, Landslides, and Debris Flows in the Midcontinent (Posters)

Monday, 18 May 2020
8:30 AM - 5:30 PM
Lake Superior Ballroom KJ

LANDSLIDE CHARACTERIZATION IN THE LOWER MINNESOTA RIVER VALLEY

Paper number: 14-3
Program: Theme Sessions
Time: 8:30 AM – 5:30 PM

Authors

Abstract

The lower Minnesota River Valley is underlain by unconsolidated glacial till interbedded with fluvial-lacustrine sediment. The valley is flanked by steep bluffs, as are the deeply incised tributary valleys that feed it. The combination of unconsolidated material and steep slopes lead to slope failure, but there are few data on the frequency and distribution of failures, triggering mechanisms, or landscape susceptibility to future failures. The creation of a landslide inventory is the initial step in understanding local landslides and developing a strategy to mitigate future damage to infrastructure and loss of life. As part of a nearly-statewide landslide mapping effort, we mapped landslides in the Minnesota River Valley between St. Peter and Chaska, using lidar topography and a DEM-derived slope map. Several areas were field-verified to validate criteria for landslide identification, to characterize geologic materials, and to make observations about the types of landslide processes at work. The project identified 1774 landslides over a ~2000 km2 area with lengths ranging between 1.4 and 792 m. Most of the landslides in the region are on the order of tens to a few hundreds of m2 in scarp area. Nearly all the identified landslides lie within glacial till and are not grounded in bedrock. Most landslides are located on slopes over 30 degrees; these may be naturally steep from ongoing stream valley incision or artificially steepened by human activities. This inventory allows preliminary assessment of relationships between geologic material and slope failure in order to gain a broader understanding of Minnesota landslides. These data will be combined with data from other landslide-prone regions in Minnesota and analyzed to create a landslide susceptibility map for the state.

Geological Society of America Abstracts with Programs. Vol. 52, No. 5

doi: 10.1130/abs/2020NC-348146

© Copyright 2020 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.