Lake Levels 



15. The US Corps of Engineers has supported numerous studies on lake 

 levels in the Great Lakes region (Hands 1976a, 1981, 1984). These reports 

 document the effects of rising lake levels on shore position by monitoring 

 beach profiles. Analysis of the data set indicates fluctuations in lake lev- 

 els as much as 2 m over a 10-year interval. These changes have resulted in 

 significant erosion of sandy beaches and cliffs bordering the Great Lakes. A 

 recent publication by Bowles and James (1985) discusses the rising level of 

 the Great Salt Lake and the impact on Utah's economy. The recent rise in lake 

 surface has been ascribed to high precipitation, record river flows, and low 

 evaporation in lake water level. On a long-term geological basis, cyclic 

 fluctuations have been recorded as varves or rings that indicate climate vari- 

 ations and historic climatic conditions (Dean et al. 1984). Lake varves or 

 laminae develop as sediments are deposited in still water within a year's 

 time. I • 



Engineering Implications 



16. Shoreline response to sea-level rise has been studied in detail by 

 coastal engineers during the past 25 years. Per Bruun (1962) stated that 

 under rising water conditions the beach and upper shoreface profile would 

 erode at the expense of the lower part of the shoreface profile where an equal 

 volume of sediment would be deposited. Many case studies for specific coastal 

 areas have been conducted using Bruun 's Rule: 



a. Schwartz (1965) verified Bruun 's theory using laboratory and 

 field tests. 



b. Dubois (1976) applied Bruun 's Rule to the nearshore zone at 

 Larry Andrae State Park, Wisconsin. 



c. Rosen (1978) verified the relationship of the equilibrium 

 profile along 336-km shoreline on the Virginia Chesapeake Bay. 



d. Hands (1976a, 1981, 1984) applied Bruun' s Rule to field data 

 collected along Lake Michigan shore over a 9-year period. 



e. Everts' (1987) method added a grain-size sediment component to 

 Bruun 's Rule for a specific coastal reach based on a minimal 

 20-year time period. 



Another useful source of general guidance in understanding an anticipated rise 



in sea level is a report commissioned by the National Research Council (1987). 



