primary difference between reaches A and B is a 5 79-meter-long seawall con- 

 structed in reach B during the study period. The two reaches were conopared 

 to determine the effect of the seawall on the surrounding shoreline. 



Reaches, C, D, and E differ from A and B in that the active bluff line is 

 composed primarily of low foredunes fronting a ridge which reaches heights of 

 36 meters above the mean lake level. Reaches C and E (on opposite sides of 

 the powerplant) differ slightly in orientation and both are undeveloped; reach 

 D is developed. None of these three reaches include any major shore protection 

 structures, 



2. Available Data . 



The primary data used in this study were aerial photos taken monthly of 

 the shoreline from July 1970 to December 1974. These photos were originally 

 used to monitor the effects on the adjacent shoreline of the temporary harbor 

 and the sand-bypassing project at the powerplant. Each photo set covered about 

 18 kilometers of shoreline centered around the nuclear powerplant. Nominal 

 scale was 1:3,600 with 40 to 60 percent overlap for stereo viewing. The air 

 photo analysis procedure and its accuracy are discussed in the Appendix. 



Other data collected during the study period include (a) hourly wind meas- 

 urements at the powerplant, (b) visual observations of daily wave and wind 

 characteristics from Warren Dunes State Park (within reach E) , and (c) monthly 

 ground surveys of 17 eastern Lake Michigan profile lines (including profile 

 line 16 in reach B collected by Davis, Fingleton, and Pritchett (1975), Davis 

 (1976), and the U.S. Army Engineer District, Detroit). 



Background data for the study area are presented in Section II. Section 



III discusses the data for each reach and the changes that occurred. Section 



IV compares the results, both between reaches and to the results of other 

 Berrien County studies; speculation about the effects of lake level changes 

 and storms on the rate of bluff recession and about the effects of seawalls 

 on adjacent shorelines is also presented. A summary and recommendations for 

 future studies are given in section V. 



II. ENVIRONMENTAL CHARACTERISTICS OF THE STUDY AREA 



Many important factors influence the rate of bluff and shoreline change. 

 These factors can be divided into "shore factors" and "process factors." Shore 

 factors include the shape, composition, and orientation of the beach and bluff, 

 which are relatively easy to determine for any particular area. Process fac- 

 tors include the v/ind and wave climate, water level variations, and storm type 

 and frequency which are not so easily determined. Secondary factors, such as 

 ice cover and runoff, are also important. 



1. Lake Levels . 



The most widely discussed process factor affecting bluff recession is the 

 fluctuation in lake level. Although a high proportion of bluff recession prob- 

 ably results from individual storms, lake level appears to be a controlling 

 factor (Hough, 1958; Seibel, 1972; Maresca, 1975; Berg and Collinson, 1976). 



