shore. Zones of deposition of the material found offshore caused the cumula- 

 tive volume measurement made along the profiles to increase toward zero. The 

 cumulative volume curve typically crossed zero and displayed high positive 

 values before settling toward a constant value far from shore. There was no 

 tendency for imbalances on one profile to cancel opposite imbalances on 

 dire,ctly adjacent profiles. However, considering the overall region, onshore 

 losses closely matched offshore gains; there was no evidence of significant 

 exchange beyond the surveyed area. 



The general sequence of response to increased water levels includes 

 immediate inundation, gradual migration of the longshore bar sequence up the 

 beach slope, and increased shore recession (but at a rate dependent on storm 

 events). Bar migration occurs even under relatively mild wave conditions. 

 This tends to maintain constant bar depths even while the mean water elevation 

 is changing. Consequently, the barred profile becomes compressed toward 

 shore. The erosion of shore deposits and their redistribution lag behind the 

 migration of the bars. Shore recession eventually reestablishes a wider 

 separation between inner bars and the waterline. In the present instance, 

 reversal of the lake level trend occurred before all the material deposited 

 offshore was reshaped to reestablish relief on the outer bar comparable to 

 that observed at the beginning of the study. 



VII. CONCLUSION AND RECOMMENDATIONS 



Hands (1979) presented a set of shore retreat measurements made at the 

 present profile stations over various periods of water level change. The 

 average shore retreat for a given change in water level was approximately 

 proportional to the amount which the water level had risert over that period of 

 time. It was suggested that this linear dependence be used as a guide in 

 estimating the effects of future lake level changes, not at a single profile 

 station but for a reasonable stretch of similar shoreline responding to a sim- 

 ilar submergence. Qualitative guidelines suggested how the estimates should 

 be modified to reflect differences in sediment characteristics, erosional 

 forces, and the length of time considered. Because the lake level and shore- 

 line measurements referred to changes over the same time period, no allowance 

 was made for the fact that the shore was probably out-of-phase or lagging 

 behind the water level change. It was, however, pointed out that some lag was 

 inevitable and that the evidence indicated it could be on the order of a few 

 years. The time required for complete readjustment would depend on the energy 

 available for sediment redistribution. 



A more comprehensive method of estimating profile response to high water 

 is developed here using hydrographic survey data to extend the same beach pro- 

 files to depths of more than 12 meters. A simple sediment balance equation 

 predicts the amount of retreat ultimately necessary to reestablish an equilib- 

 rium profile. Remarkable agreement was found between the estimated ultimate 

 retreat and that which actually accrued 3 years after lake levels stabilized. 

 Realistically, the equilibrium model also overpredicted shore retreat for the 

 shorter periods of sustained lake level rise before stabilization. 



The choice of whether to adopt a linear relationship between retreat and 

 submergence, making the qualitative adjustments as discussed in Hands (1979), 

 or to apply the sediment balance approach presented here will depend on the 

 tiraespan of interest, the amount of site-specific data available, and the 



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