landward bluff or dune recession for all sites by month and by year are 

 shown in Figure 24. 



1. Lake Level and Seasonal Effects . 



Changes observed during the 2 years of systematic monitoring of the 

 17 sites are assumed to be related to changes in lake level and seasonal 

 weather conditions. 



Mean annual lake level began to rise in 1965 (Fig. 3), and it had 

 risen about 4 feet by 1973. One author observed that, during periods of 

 low lake level (1963-64), there was considerable beach accretion and a 

 high berm developed with an overall large beach width. As lake level 

 began to rise during 1965, the accreting beach profile was slowly changed 

 to an eroding beach profile. The well-developed berm was removed and 

 beaches were eroded to a generally narrow width. These changes were the 

 combined result of a volume of sediment being removed from the beach by 

 wave action, and the drowning of the subaerial beach due to a rise in 

 lake level. 



Although this condition has prevailed for the past few years there 

 are times, during periods of low wave energy, when certain locations 

 experience temporary beach accretion, and an accretionary profile forms. 

 In the study period this was most prevalent at Little Sable Point (site 

 6). This site was the focus of converging longshore transport (Fig. 5) 

 so sediment was available. However, during the second year this site 

 was subjected to significant beach erosion. Although apparently not a 

 place of littoral convergence, there was considerable beach accretion at 

 site 5 during the second year of the study. Brief periods of beach 

 accretion were also observed at other locations, but did not exceed one 

 or two sampling periods. 



The combination of high lake level and narrow beaches without berms 

 has provided easy access, by waves, to the foredune terrace or bluffs. 

 All of the sites exhibit a pattern of erosion that can be related to 

 seasonal weather changes. There is an increase in overall erosion during 

 the fall months with the maximum rate of erosion occurring just before 

 winter ice cover. A period of less intense erosion follows ice breakup 

 in the spring. Summer is relatively free of coastal erosion. However, 

 this pattern does not conform to lake level cycles since the erosion rate 

 is highest in November and December (Fig. 24) when lake level is 

 approaching its lowest level within the annual cycle (Fig. 4). Lake level 

 varies about 1 foot during the year due to seasonal changes in precipita- 

 tion and runoff. 



On an annual basis lake level and bluff or dune erosion could be 

 related, as reported by Seibel (1972). During 1971-72, when lake levels 

 were higher than in corresponding months of 1970-71, sites 1, 3, 4, 11, 

 12, 13, and 17 showed a greater amount of erosion (Fig. 23). However, 

 sites 5, 7, 9, 10, 15, and 16 showed less erosion the second year, while 



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