1. Data Collection . 



Reference points were chosen in close proximity to each of the 17 pro- 

 file sites.' The points designated were easily recognizable features that 

 could be seen on all photos of a particular location! e.g., corners of 

 buildings, large trees, or stairways. An effort was also made to choose 

 the points as close to lake level as possible to minimize the parallactic 

 effect due to elevation. Measurements included the horizontal distance 

 from the designated points to the edge of the terrace or bluff, shoreline, 

 and the crest (lightest part) of each bar. All measurements could not be 

 performed on every photo and as mentioned previously, attempts to measure 

 the longshore bar positions proved fruitless. Measurements were scaled by 

 measuring an actual distance in the field and comparing this to the aerial 

 photo. This was accomplished by taking the photos to the coast and locat- 

 ing features that appeared on the photos . 



A Zeiss Aero Sketchmaster was used at maximum magnification to locate 

 reference points and mark points for measurement. Actual measurements were 

 made with a reticle and optical comparator, giving measurements accurate 

 to 0.05 millimeter on the photos. 



2. Lake Level During Period of Aerial Photography . 



Aerial photos obtained for the study span a fairly broad range of lake 

 level positions. However, it was not possible to obtain photos during some 

 extreme lake level conditions. Figure 8 shows changes in mean annual lake 

 level during the period of photo coverage (1938-72) . This represents es- 

 sentially a complete, but minor cycle in lake level with the photos taken 

 at periods of low level. An abrupt and extreme rise occurred between 1950 

 and 1952; 1952 had the highest levels to date in this century. There was 

 a steep decline to 1959, then a year of marked increase before falling 

 toward the alltime low level in 1964 (Fig. 8) . From this point to the 

 present there has been a rather steep and uniform rise in lake level. 



3. Aerial Photo Data . 



a. Shoreline . The change in shoreline position is one of the measure- 

 ments which show a rather predictable and marked change with respect to 

 changes in lake level. The strand-line position was measured from a common 

 reference point for all photos available. From these data, average annual 

 rates of change were calculated for the shoreline position, and plotted 

 at the midpoint between photo dates (Fig. 9). Figure 9 is divided into 

 two parts so the data can be more easily distinguished; the left half of 

 the figure showing results for profile sites 1 to 9 which are in the 

 northern half of the study area. There is some room for error in that the 

 photos were not all flown at the same time of the year. As a result, there 

 may be some effect of annual lake level fluctuations; e.g., photos flown in 

 spring before foliage is abundant are at a time of low lake level; summer- 

 time photos are flown during near-peak lake level. This effect of lake 

 level rise on shoreline position will vary with slope of the foreshore, 

 which in turn, depends on the littoral material and perhaps on wave action. 



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