"Simultaneous with these studies have been similarly oriented projects 

 by Brater and Seihel (1971) and Seibel (1972) . Brater and Seibel dealt 

 with some engineering aspects of erosion sites along eastern Lake Michigan; 

 Seibel conducted a long-term aerial photo study of seven critical erosion 

 sites on Lakes Michigan and Huron. Results from these studies are sum- 

 marized in Davis, Seibel, andFox (1974) and Seibel (1974). Great Lakes 

 Basin Commission (1975) provides a later discussion of the recession rates 

 in the study area. 



II. BEACH MORPHOLOGY AND PROCESSES 



Regardless of their location, beaches have a rather typical form and 

 are subjected to similar processes. Primary differences from place to 

 place include only the rate at which processes occur and the scale of the 

 features involved. These topics have been discussed by Bascom (1964), 

 King (1972), and Shepard (1972). The discussion of beach morphology and 

 processes here is limited to eastern Lake Michigan. 



1. Morphology . 



The eastern Lake Michigan coast is characterized by sand dunes and 

 bluffs of glacial drift. Lakeward of these features a low-lying sand 

 terrace is typically developed; this feature may be absent or exist for 

 only a few years from place to place. The terrace is commonly covered by 

 grass and shrubs and is generally less than 10 feet above lake level. At 

 any given time or place the terrace may terminate lakeward in a low bluff 

 or may grade into the active beach without apparent topographic expression. 



The backshore zone (Fig. 2) may be nearly horizontal or slope gently 

 lakeward, depending upon the overall conditions at that time. During per- 

 iods of accretion the zone is approximately horizontal; it slopes lakeward 

 during periods of erosion. This variation in shape depends upon wave 

 action on the beach and on lake level. As a result, there are both sea- 

 sonal and long-term changes, with the long-term changes in lake level 

 dominating. During periods of rising lake level, erosion dominates due 

 to the combination of wave activity and encroachment of the strand line 

 to the backshore zone. As a result, both the shape and the width of the 

 beach are altered with minimal beach development during high lake level. 

 There are sites on eastern Lake Michigan which have recently had no beach 

 at all during high-energy periods of late fall when storms are common. 



The foreshore zone also changes in response to lake level and storm 

 conditions although there is only a minor change in its slope. In general, 

 the foreshore is relatively steep (3° to 10°) in comparison to the back- 

 shore (Fig. 2) . Erosion apparently steepens the slope of the foreshore 

 and displaces it landward; accretion appears to reduce the slope. During 

 prolonged periods of erosion the foreshore zone may comprise the entire 

 beach. 



Lakeward of the strand line and at the base of the foreshore slope is 

 a plunge zone or plunge step. This is a small and abrupt topographic 

 change with generally less than 1 foot of vertical relief over a horizontal 

 distance of 1 to 3 feet. This feature is formed by the last breaking of 



