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Beach Profile Changes: East Coast of Lake Michigan, 1970-72.

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Miscellaneous paper,

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The primary result of this field study of beach changes on the eastern shore of Lake Michigan concerned the movement of the bluff or the edge of the terrace marking the landward boundary of the beach. Data collected every 4 weeks from August 1970 to August 1972 indicated recession or no change at each of 17 profile sites on a 250-mile segment of the east coast of Lake Michigan. During this period, lake levels were rising from a mean of 578.9 feet above mean water level MWL in 1970 to 579.7 feet MWL in 1972. The maximum bluff erosion at any one site between monthly surveys was 20 feet at profile 4 in June 1972. Variables affecting the rate of movement of the bluff include lake level, composition of the bluff or terrace, orientation and straightness of shoreline, wave climate, manmade structures, and possibly longshore bars. There was a lack of correlation between bluff erosion at nearby stations, but each site varied seasonally with maximum erosion occurring in late fall when storm occurrence is also high. Shore ice protected the beaches in winter erosion resumed in spring at a reduced level. Beach width from the base of the bluff to the water level at the time of the survey also varied seasonally, with beaches narrow in early summer when lake level is at a maximum and wider in late fall when lake level is at a lower level. The study beaches were mostly well-sorted sand mean grain size between 0.330 to 0.189 millimeter or 1.60 and 2.40 phi units with some gravel and heavy mineral concentrations. Author

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  • Geology, Geochemistry and Mineralogy

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