WATER LEVEL FALLING 



WITHDRAWAL 

 f (Emergence) 



WATER LEVEL RISING 



ENCROACHMENT 

 f (Submergence) 



0. Verticol Chongcs b. Horizontal Chonges 



Figure 6. Terminology of vertical and horizontal shoreline changes. 



accustom the reader to viewing the data from the slightly different per- 

 spective employed here. 



The most direct way to represent retreat of the shoreline would be to 

 superimpose a set of shoreline maps. However, to depict on a page even 

 a small part of the present study area, distances normal to shore would 

 have to be exaggerated; otherwise, even where the shoreline has retreated 

 35 meters, the change would not be evident. For example, note that in 

 the aerial photo at the bottom of Figure 7, all shoreline positions for 

 the last 10 years would overlie one another and be indistinguishable at 

 this scale. Expanding the scale perpendicular to shore pulls the shore- 

 lines apart as shown above the photo. Note the expansion also greatly 

 distorts shoreline shape. Since the primary interest is in shoreline re- 

 treat, not shape, all attempts to show shoreline shape could be abandoned 

 and all shorelines referenced to their position on either the initial or - 

 the final survey. Because the year of initial surveying differs among 

 stations, shoreline positions are referenced at the top of Figure 7 to 

 their final positions (as determined in October 1976) . 



Figure 7 shows a two-step transformation of shoreline data (from map 

 view), first to exaggerated distance from base line, then to exaggerated 

 distances from the 1976 shoreline. Because the shoreline protrudes about 

 10 kilometers lakeward in the vicinity of Little Sable Point (Fig. 4), it 

 is infeasible to depict both shoreline shape and changes in shore position 

 for the entire study area on the same figure; therefore, in all the re- 

 maining plots the shoreline and contour positions are referenced to their 

 final positions as determined in the 1976 survey at each station. The 

 plots will also have the same exaggeration of scale perpendicular to shore 

 as shown at the top of Figure 7. 



Shore retreat throughout the study area is shown in Figure 8. Note 

 that two different horizontal scales are used to permit comparison of 

 the closely spaced measurements near Pentwater Harbor with measurements 

 from the more widely spaced stations elsewhere. The straight lines con- 

 necting 1967, 1969, and 1975 data points are plotted to quickly identify 



17 



