Recurrently, during periods of extreme shore damage, there has been 

 public pressure to increase control over lake level fluctuations. A 

 recent investigation considered the feasibility of regulating the entire 

 Great Lakes system (International Great Lakes Levels Board, 1973). Al- 

 though regulation of all five lakes is an engineering possibility, bene- 

 fits were not found to be commensurate with costs. 



Some control over lake levels already exists. Outflows from Lake 

 Superior and from Lake Ontario have been controlled since 1921 and 1958, 

 respectively (Fig. 2). However, regulation which reduces the range of 

 levels on Lake Superior tends to increase fluctuations on Lakes Huron 

 and Michigan. On the other hand, reduction of the range of levels on 

 Lake Ontario can presently be accomplished without affecting the other 

 lakes, because the major inflow is via Niagara Falls and the outflow is 

 to the St. Lawrence Seaway via a series of control structures. Conse- 

 quently, during the 1973-74 high water period, the outflow from Lake 

 Ontario was increased 46 percent above its average flow to alleviate 

 erosion and flooding problems. In spite of these improvements, both the 

 water levels and the erosion problems remained significantly above their 

 long-term average (Haras, 1975). 



Because uncontrollable natural variations in water supply are so 

 large, it is impractical to attempt to maintain a constant volume of water 

 in any of the lakes. Regulation plans, nevertheless, continue to be re- 

 viewed to determine if modifications to currently controlled flows would 

 reduce the total lake level-related damage to all concerns. Knowledge of 

 how water level fluctuations affect erosion rates is important for deter- 

 mining how changes in regulation plans will affect riparian interests. 

 Knowledge of fluctuations in lake level and their effect on rates of shore 

 retreat is also important in the design of coastal construction projects, 

 in recommending coastal setback, for planning proper beach-fill operations, 

 and in evaluating the usefulness of short-term erosion measurements as a 

 basis for extrapolating to longer periods on the lakes. 



3. Previous Erosion Reports . 



A number of previous studies related to shore erosion on the Great 

 Lakes have been published by CERC . Shore changes were measured monthly 

 from 1970 to 1974 at 17 sites widely scattered over Lake Michigan's 

 eastern shore; results of the first 3 years of this study, reported by 

 Davis, Fingleton, and Pritchett (1975) and Davis (1976) identify seasonal 

 cycles in bluff retreat related to seasonal changes in lake level and 

 storminess. Large, unexplainable spatial differences in bluff retreat 

 were noted. It was hypothesized that these large differences might re- 

 flect the influence of offshore bathymetry on shoaling waves. Well- 

 developed, multiple longshore bars dominate the eastern lake-shore bathy- 

 metry out to depths of about 6 meters (20 feet) . Bars absorb part of the 

 wave energy incident on the shore before it reaches the shore. The cross- 

 sectional geometry, areal patterns, and textural composition of the long- 

 shore bars are described in Hands (1976) . On the basis of surveys 

 spanning a 4-year period. Hands also briefly discussed gradual changes - 



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