. Changes in rates of shore retreat : Lake Michigan, 1967-76. Coast changes; Beach erosion. mean lake level remained essentially stable in 1974 (, repeated the sequence of record high monthly means set in 1973), then began dropping slowly in 1975. During the last half of 1976, precipitation in Lakes Superior and Michigan basins was down 40 and 45 percent, respectively, from their long-term averages, and Lake Michigan levels began to fall rapidly. The relationship between shore retreat and lake level changes is in- dicated in Figure 16. The ordinate value of each point is the difference bet
. Changes in rates of shore retreat : Lake Michigan, 1967-76. Coast changes; Beach erosion. mean lake level remained essentially stable in 1974 (, repeated the sequence of record high monthly means set in 1973), then began dropping slowly in 1975. During the last half of 1976, precipitation in Lakes Superior and Michigan basins was down 40 and 45 percent, respectively, from their long-term averages, and Lake Michigan levels began to fall rapidly. The relationship between shore retreat and lake level changes is in- dicated in Figure 16. The ordinate value of each point is the difference between the daily mean lake levels from one survey to the next, several years later; the abscissa is the distance the shore retreated between surveys. The general tendency of shore retreat to be proportional to the change in water level and the deviation of individual measurements from this trend are Submergence Emergence Figure 16. Submergence (the rise in water level) versus retreat (the landward migration of the shoreline). Data on emergence were obtained between 1975 and 1976, several years after the lake levels began to decline slowly. Outliers far from the evident linear trend are identified by station number. As expected, local variations in wave exposure, in the nature and orientation of the shore, in offshore topography, etc., cause the indi- vidual measurements to scatter widely about the mean predicted solely on 32. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Hands, Edward B; Coastal Engineering Research Center (U. S. ). Fort Belvoir, Va. : U. S. Army, Corps of Engineers, Coastal Engineering Research Center ; Springfield, Va. : available from National Technical Information Service
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