beach widens. Assuming lake currents and waves are not altered, they will 

 tend to reestablish the previous profile shape at a lower and more lakeward 

 position. Longshore losses to the west continue to exceed the net supply from 

 the east. However, offshore where the bottom slope is gradual, lowering of 

 the water surface brings bottom sediments into a shallower hydraulic regime. 

 This results in landward sediment transport which steepens the nearshore 

 slope, builds dunes on the widened beach, and feeds the longshore currents 

 leaving the dune area to the west. The cumulative effect of these adjustments 

 can be estimated using the equation. 



EVALUATION OF TERMS: 



z = -0.3 meter Given (negative indicates a reduction in water 

 level) . 



2.9 meters Estimated average height of dunes expected to 

 form on the widened beach lakeward of the 

 present foredune. 



11.1 meters Profile closure (mean of depths at adjacent 

 sites 28 and 29 in App.). 



Z = 14.0 meters Sum of the two values obtained above. 



X = 3,030 meters Average distance of the 11.1-meter contour 

 from shore, based on field surveys. 



R. = 1 Offshore sands are expected to move, onshore, 



and the wind is not expected to carry sand 

 inland past the present foredune. 



zX(r^)^8 ^ -0.3(3,030) 1 ^ 



X = = = -65 meters (evaluating the equation) 



Z 14 



It is thus estimated that lowering the lake level 0.3 meter will effectively 

 shift the equilihvium position 65 meters lakeward. As previously mentioned, 

 a net loss of sand will still prevail due to the predominance of transport 

 to the west. Therefore, the actual pihovelnne is not expected to advance 65 

 meters lakeward. A reasonable interpretation is that there will be a long- 

 term gain of 65 meters of beach that otherwise would have been lost by 

 erosion if the water level had not been lowered. Dividing 65 meters by the 

 average past recession rate would provide an estimate of when the avoided 

 erosion would otherwise have occurred. 



If 15 percent of the offshore sediments were thought to be too fine to 

 remain in the active shore zone, then the width of shore "saved" should be 

 reduced to (1 - 0.15) x -65 meters = -55 meters. Note that a liberal 

 estimate of future dune heights would also make the predicted savings in 

 beach width more conservative. 



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