Lake Michigan Bluff Dewatering and Stabilization Study - Allegan County, Michigan
Final rept. 2001-2008
ENGINEER RESEARCH AND DEVELOPMENT CENTER VICKSBURG MS GEOTECHNICAL AND STRUCTURES LAB
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In the Great Lakes region, bluff recession is a major cause of residential, commercial, municipal, and federal property loss. The average rate of recession in Allegan County, Michigan, ranged from 1 to 2 ft per year, from 1831 to 1958, or a total of 130 to 258 ft over 127 years Powers 1958. From 1938 to 1996, a 0.1 to 1.7 ft per year recession rate was measured, for a total land loss of 5 to 100 ft over 58 years Montgomery 1998. Reports show that recession rates are not uniform along the shoreline, nor are they similar during two different time periods at a given site Chamberlin 1877 Powers 1958 Seibel 1972 Montgomery 1998 Chase et al. 2000. It is difficult to predict future rates of recession. Also, it is evident that recession has not slowed with the introduction of modern stabilization structures. The purpose of this research is to investigate the natural factors that influence lake-bluff instability and to demonstrate an innovative approach i.e., dewatering the bluff for deterring or slowing the recession rate. Three geologically distinct sites along the Lake Michigan coast in Allegan County were chosen. In 2004, measurement instrumentation was installed at each of the sites. Part of each site was dewatered using submersible pumps or gravity drains, while another part of each site was not. A total of 76 in-place inclinometers IPIs and 28 vibrating wire piezometers VWPs among 26 monitoring wells, 45 dewatering wells, and two weather stations were installed.