During the period from 1986 to 1995, Sector G and the area to the south 

 received perhaps 50 percent of the coarse sediment eroded from the feeder 

 beach. Therefore, this sector and the shoreline to the south experience a 

 deficit compared to the historic sediment supply. This situation, combined 

 with the depleted supply during the years prior to 1976, must have resulted in 

 decreased sediment cover in this area and may have caused an increase in 

 downcutting and shoreline recession. Comparison of the 1991 and 1995 lake 

 bed bathymetries indicates the problem of accelerated offshore lowering and 

 the related shoreline recession has extended south of Sector G. 



It would be much more effective to place the entire annual allotment of 

 beach nourishment (or at least the trucked coarse sediment) south of Lines R22 

 or R23 where it would be 100 percent effective in supplying the downdrift 

 shores. The erosion problems in the study area could be addressed with site- 

 specific solutions. With this action, the implementation of further shoreline 

 structures to the south of Line 22, to counteract the increased erosion, may be 

 avoided. 



Recommendations for Future Monitoring 



The following monitoring activities should be continued to assess the effective- 

 ness of modifications to the beach nourishment program. 



Aerial photos should be continued to monitor the level of shoreline pro- 

 tection in and south of Sectors F and G. 



Aerial photos should be regularly analyzed to monitor recession rates in 

 and south of Sections F and G to update the MDNR data. 



Lines R12 to R23 and new lines further to the south should be moni- 

 tored regularly to improve understanding of the lake bed changes in 

 these areas. 



A complete survey of the lake bed, both north and south of the harbor 

 jetties, should be completed 5 to 10 years after the 1995 SHOALS 

 survey, or after significant modification to the beach nourishment 

 program. 



88 



Chapter 5 Interpretation of Results - A Descriptive Model of Coastal Morphodynamics 



