The apparent shoreline position may also be affected by the amount of run- 

 up at the time of the aerial photo. 



The longest single period between photos (1938-52) represents a period 

 of modest increase and decrease in lake level. Annual rates of change at 

 the four sites where data are available show a very slight recession except 

 at site 6 where the strand line receded 14 feet per year, averaged over the 

 14-year interval (Fig. 9). 



During the period 1950 to 1955, there were rather high lake levels and 

 correspondingly every location for which data are available in the period 

 shows slight to extreme recession rates with a maximum of 25 feet per year 

 at site 14 (Fig. 9) . 



Widespread beach accretion followed during the period 1952 to 1960, 

 with all sites except 7 and 9 showing accretion. Average rates of beach 

 growth reached 28 feet per year at site 6 (Fig. 9) . It should be noted 

 that the 8 feet per year recession rate for site 8 is for a photo coverage 

 period of 1950 to 1955, similar to the trends shown on the right of Figure 

 9 for the southern profile sites. Recession rates of 2 to 3 feet per year 

 for sites 7 and 9 are anomalous. The rate for site 9 represents a mean 

 annual rate for the period 1950 to 1962. Possibly, the erosion in 1952-53 

 during high lake level was enough to offset accretion in the late 1950's, 

 thereby producing a net retreat of the shoreline. No explanation is 

 offered for recession at site 7 from 1952 to 1958. 



During the next photo period (1958 to 1965) there was a short-term 

 cycle of lake level change, although general conditions were favorable for 

 beach accretion due to the relatively low level of the lake. All locations 

 for which data are available during this period show a net accretion except 

 on profile site 2. With the exception of site 6 where the rate was 17 feet 

 per year, all rates were less than 5 feet per year. However, aerial photos 

 during essentially the same period (1960 to 1967) for the southern part of 

 the study area show more variation (Fig. 9, left). One-half of these sites 

 show a net accretion, and the other half a net recession of the strand 

 line during this 1960-67 time interval. Because the last 3 years within 

 this period of comparison were during fairly rapidly rising lake level, it 

 is likely that some of the accretion during the early 1960's was removed 

 during the rapid rise in lake level. 



All sites except 5 and 13 showed strand- line recession from 1965 to 

 1972 (Fig. 9). Rates were high, ranging about 40 feet per year. In gen- 

 eral, the rates at the southern sites were slightly greater than at the 

 northern sites (Fig. 9) . Profile site 13 showed a net accretion which was 

 undoubtly related to the shoreline irregularity alluded to previously; 

 this is typical for that site (Davis, 1972) . However, the reasons for the 

 significant beach accretion rate at that site cannot be explained. 



In general, the pattern shown by the strand-line position from the 

 photos is expected; it moves lakeward during low or decreasing lake level, 

 and landward as lake level increases. This is caused both by the changing 



48 



