data in Table 14 indicate that such a relationship may exist. It was deter- 

 mined that the additional volumetric loss of the bluff adjacent to the down- 

 drift end of the seawall approximately equaled the amount of material removed 

 from the sediment supply by the seawall. The length of shore affected in- 

 creased during the study and appeared to be still increasing in 1976 as 

 attempts were made to stabilize the eroding area. 



2, Further Research . 



This study has concentrated primarily on obtaining measurements of bluff and 

 shoreline changes. The aerial photos are, however, limited in' providing details 

 on bluff composition, runoff effects, and other features; therefore, the impor- 

 tance of these factors cannot be examined without detailed ground surveys. Most 

 States now have programs to determine long-term recession rates (see Great Lakes 

 Basin Commission, 1974; Michigan Department of Natural Resources, 1975; Berg and 

 Collinson, 1976; Carter, 1976). 



Further research should be directed toward obtaining a better and more com- 

 plete record of bluff recession and the conplex factors controlling it. This 

 requires a well-planned program of ground surveys coupled with aerial photos. 



Sites should be carefully chosen to include various bluff and shoreline 

 conditions and a reasonable nixmber of cultural features for reference points. 

 Although the aerial photos can easily cover long stretches of shore, only short 

 reaches need to be analyzed. Accurate ground control can be established by 

 ground surveys coi^led with contour maps compiled from aerial photos. Measure- 

 ments should be taken at minimiim intervals of 1 year and after major storms. 

 Monitoring should continue through one full lake level cycle (20 to 25 years) 

 and preferably longer. 



A conplete and consistent record of the wave energy reaching the beach is 

 also necessary. Wave hindcasting is probably the most cost-effective means 

 for obtaining this information. Accurate observations of ice cover are also 

 required along with lake level measurements. 



This type of program is necessary to fully understand the relationship 

 between lake level, storms, and bluff recession. It is particularly important 

 if attempts are made to minimize shore erosion by lake level regulation. 



The systematic long-term research program outlined above would provide con- 

 siderable insight into these long- and short-term relationships. This type of 

 effort is necessary to develop confidence in an ability to predict future Great 

 Lakes bluff and shoreline changes. 



62 



