ANALYSIS: The barrier beaches and high dunes which characterize this stretch 

 of shore are of special ecological and scenic value. Situated downwind from 

 the major storm paths across Lake Ontario these barrier beaches are exposed 

 to the highest storm waves reported on the Great Lakes, but because of 

 relatively low land development there are few protective structures along 

 this reach of the shore. Sand extends lakeward across a series of longshore 

 bars. There are no known rock outcrops, and there is a close balance 

 between southward and northward longshore transport. 



EVALUATION OF TERMS: 



z = 0.3 meter Proposed long-term increase in lake level. 



7.6 meters Average height of the eroding dunes above 

 mean lake level (from field surveys). 



13.4 meters Profile closure depth (from the App.). 



Z = 21.0 meters Sum of the two values obtained above. 



X = 2,414 meters Average distance of the 13.4-meter depth 



contour from shore. The vertical datum 

 should be the same as the reference level 

 below which closure depth was measured in 

 the previous step. 



R A = 1 All of the material eroded from the upper 



beach is expected to remain within the 

 bounds of the responding profile. 



zX(r^)^8 2 0.3(2,414) 1 



X = = = 34 meters (evaluating the equation) 



Z 21 



It is estimated that the higher stages would shift the equilibrium shore 

 profile an average of 34 meters inland and raise it 0.3 meter above its 

 present elevation. 



*************** EXAMPLE PROBLEM 2*************** 



GIVEN: Assume a new regulation plan is proposed to modify the inflow to Lake 

 Michigan and Lake Huron via the St. Marys River. If adopted, this plan 

 would lower the long-term mean surface elevation of Lake Michigan and Lake 

 Huron by 0.3 meter. 



FIND: The effect the lower water levels will have on shore erosion at Indiana 



Dunes National Seashore. 



ANALYSIS : The dredged channel and navigation structures at Michigan City, 

 updrift of the Indiana Dunes National Seashore, block some of the potential 

 sediment input from the east. Westward longshore transport out of the dune 

 area thus creates a sand deficit and contributes to a long-standing erosion 

 problem in the park. As lake levels fall, the shoreline withdraws and the 



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