6 Beach Nourishment Design 

 Guidelines 



Based on the findings of this investigation and the knowledge of cohesive 

 shores that has developed since the early 1980's, some general design 

 guidelines are presented for the specific circumstances of SL Joseph, and for 

 some general categories of cohesive shore situations. 



Recommendations for St. Joseph 



Lowering of the lake bed offshore of the MDOT and C&O revetment (i.e., 

 Sector E in Figure 34) is a result of both the interruption of alongshore 

 transport (particularly prior to the initiation of the Section 1 1 1 program) and 

 the stabilization of the shoreline position related to the construction of the 

 revetment. 



The present beach nourishment program does not appear to provide any 

 significant benefit to the stability of the revetment along the Sector E shoreline 

 or to the lake bed offshore of the revetment. This is despite the fact that 

 perhaps 50 percent of the beachfiU sediment is deposited permanently on the 

 lake bed in this sector, and volume losses dropped to less than one fifth their 

 former 20-year average during the 30 years after nourishment was initiated. 



Beach nourishment is definitely effective at maintaining a stable shoreline 

 position in Sector D. The coarse grain sediment is an essential component 

 which protects the tiU under the upper beach from downcutting during storms. 

 Fine-grain nourishment on its own (i.e., from dredging alone) is, however, 

 insufficient to protect the underlying till from exposure and downcutting. 



Placement of unrestricted beachfdl (i.e., without any substantial retaining 

 structures such as headlands) is probably not a cost-effective means of main- 

 taining an average stable shoreline position. A solution to retaining a 

 permanent beach at this location should be sought through the use of rock 

 headlands or breakwaters. It may be argued that this is not the intention of the 

 Section 1 1 1 program; however, it must be recognized that this has been the 



Chapter 6 Beach Nourishment Design Guidelines 



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