IV. PREVIOUS STUDIES 



Powers' (1958) comprehensive study on Lake Michigan classified the entire 

 shoreline according to geomorphology, based on bluff type, composition, and 

 height. Powers also measured bluff recession around the lake. Of 134 meas- 

 urement stations, 124 eroded an average of 0.45 meter per year; 4 had no 

 change; and the remaining 6 accreted an average of 0.48 meter per year. 

 Forty-four of the measurement points are located within the area covered by 

 the 17 profile lines. Two locations experienced a net accretion while the 

 remaining 42 eroded. The average change for all 44 locations was -0.38 meter 

 per year. Periods of coverage varied from 20 to 127 years with some data as 

 early as 1830. Powers recognized lake level fluctuations, severe storms, and 

 manmade structures as being the primary factors affecting the recession date. 

 However, he noted that his measurements were insufficient to quantify the 

 relationship between lake level and bluff recession. Powers' report also 

 included a summary of studies conducted as early as 1864. 



Seven of Powers' eastern Lake Michigan sites were resurveyed in 1973 by 

 Buckler and Winters (1975). Of the seven sites, three had stabilized since 

 1956, while two were retreating at similar rates and two at higher rates. 

 They found no pattern between retreat rates and bluff composition and hypoth- 

 esized that other factors were more important. 



Seibel (1972) used aerial photos to examine bluff recession since 1938 at 

 four Lake Michigan and two Lake Huron locations. He also examined the 

 relationship between lake level and precipitation and between lake level, 

 storm frequency, and bluff recession. He determined linear relationships 

 between average lake level and bluff recession for each of the six sites. One 

 of the significant conclusions reached by Seibel was the importance of 

 infrequent severe storms in controlling the rate and amount of bluff 

 recession. 



Because lakeshore property values and insurance costs may be linked to 

 the recession rate in an area, there is considerable interest in predicting 

 future bluff lines for at least the mortgage life (typically 30 years) of a 

 structure. Jannereth (1974) described the State of Michigan's effort to do 

 this using 1938 and 1974 aerial photos. The results, published by the 

 Michigan Department of Natural Resources (1975), are a series of maps of the 

 Lake Michigan shoreline identifying high-risk erosion areas. A minimum set- 

 back line equal to 30 times the annual recession rate was computed for each 

 area. A recommended setback line was also determined by adding 9 meters to 

 the minimum setback value. The highest recession rate (1.9 meters per year) 

 was measured just south of South Haven, Michigan (between lines 13 and 14 in 

 Fig. 2). 



Tanner (1975) analyzed air photos of bluff recession in Berrien County 

 near the Donald C. Cook Nuclear Power Plant. He proposed an exponential 

 relationship between bluff retreat and lake level, wave characteristics, and 

 other unspecified parameters. The existence and movement of a series of 

 southward-moving "beach pads" (or rhythmic undulations in the shoreline) was 

 described. The distance between pads averaged 45 meters, and the pads moved 

 51 meters during the ice-free season. Tanner postulated that the pads serve 

 as a mechanism for offshore sand transport with material being directed 

 diagonally offshore along the edge of the pads. 



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