Estimate of cliff recession rates for a US highway located on a sandstone liff over lake superior
Coastal cliff erosion is a problem in many coastal regions including the Great Lakes of Canada and the United States. While data exists on the recession rates for oceanic cliffs, there is limited data for the fresh water cliff erosion. Currently, cliff recession is threatening a US highway (US-41) located on a 30 m sandstone cliff on the south shore of Lake Superior. The recession has advanced to a point where it is undercutting the guardrail system for the highway. A research program was conducted to determine the regression rate and when the highway should be relocated or if alternative methods of slope remediation can be performed allowing the scenic highway to remain in its current position. The cliff regression analysis includes investigating variations in shore platform widths, freeze thaw cycling, and other environmental factors, in addition to rock characteristics. Laboratory tests include point load testing, uniaxial compressive testing, rock quality designation (RQD), rock mass rating (RMR), and freeze-thaw durability. It was found that the following factors control the rate of the cliff regression, which was found to be about 0.15 feet/year: (1) deposition of mine waste at the base of the cliffs during the early 20th century and the subsequent removal by long shore currents; (2) rock weathering and water migration above low permeability layers accessing the cliff face; and (3) the development of the talus slope at the base of the cliff, which acts as a barrier to further regression. Copyright ASCE 2008.
Geotechnical Special Publication
Estimate of cliff recession rates for a US highway located on a sandstone liff over lake superior.
Geotechnical Special Publication(178), 491-498.
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