The rate of bluff recession decreased between April and November 1972, to 

 only 4.1 meters per year. The recession rate increased south to north with 

 the southern end and some sections behind the seawall experiencing the least 

 change. Figure 15 shows the reach between stations 35 and 13 in November 1972. 

 The seawall is composed of steel sheet pile from station 28 to the northern end. 

 From station 23 to 28 the beach is protected by the older and lower concrete 

 wall behind which is evidence of recent bluff erosion. No beach exists lake- 

 ward of the seawall. The first evidence of a beach appears at station 24; a 

 narrow beach also fronts the dune. 



The most serious erosion occurred from November 1972 to March 1973 due to 

 the intensity of the early spring storm (see Section 11,3). The average rate 

 of bluff recession during the period reached 10.1 meters per year for reach B. 

 The bluff at station 42 retreated 14 meters. The seawall, completed during 

 this period, did not fully protect the bluff behind it as evidenced by one 

 small building which toppled down the bluff causing considerable recession at 

 station 27. During this period the downdrift cut became better defined, ex- 

 tending from station 22 to about station 15. The bluff at station 22 retreated 

 11 meters. No beach was within the downdrift cut, though south of it the beach 

 widened quickly to a maximum width of 23 meters at station 13. 



Bluff recession continued at a reduced rate during the final three periods 

 of study. The rate of bluff recession was the lowest behind the seawall and 

 along the dune. However, the bluff at the downdrift cut was actively retreat- 

 ing, and the cut appeared to be lengthening (see the November 1973 photo in 

 Fig. 15). The exact effects of the seawall on the bluff downdrift are diffi- 

 cult to fully assess because of seawall construction within the cut. This 

 resulted in the formation of a second cut, to the south of the first (see the 

 November 1974 photos in Fig. 9) . 



The sequence of events described above is illustrated in Figure 16. Aver- 

 age recession rates for each area are plotted in the figure, and compared with 

 the rate for reach A since it represents the unprotected bluff recession rate. 

 Variations in lake level are also shown. The reach A recession rate increased 

 during the period of rising lake levels and then stabilized at a lower rate 

 when the lake levels stabilized in 1974 (not including the usual seasonal 

 variations). This stability may be attributed to other factors, particularly 

 to the absence of severe storms in 1974. The dune section experienced a dra- 

 matic reduction in bluff recession rate after November 1973 which followed an 

 equally dramatic period of erosion. The unstable areas were the downdrift cut 

 and CERC profile line 16 (station 13). The downdrift cut shows a decrease in 

 recession rate in November 1974, probably due to efforts to stabilize the area. 

 These same measures probably accentuated the problem at CERC profile line 16 

 and farther south. The increase in recession was verified by ground surveys 

 which measured an increase in bluff recession from 1.8 meters (Davis, 1976) 

 between August 1970 and July 1973 to 9.4 meters between October 1973 and 

 November 1974 (Birkemeier, in preparation 1980) . 



The downdrift erosion has continued; however, an October 1976 field visit 

 found the bluff slope in the cut area well vegetated and stabilized (Fig. 17) 

 and the bluff at CERC profile line 16 stabilized by the installation of a pre- 

 cast concrete seawall (Fig. 18). Measurements at CERC profile line 16 indi- 

 cated an additional 9 meters of recession since November 1974. The bluff 



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