gravel accumulation, heavy mineral concentrations, and drift- 

 wood or other debris. 



(d) Color slides were taken of all sites during each visit, 

 mostly from about 100 feet south of the profiles. The slides 

 recorded the overall character of the site at each visit. 



Dates of the visits to the 17 sites, spaced at approximately 4-week 

 intervals, are listed in Table 4. 



3. Data Limitations. 



An office and field analysis of the Emery (1961) method of surveying 

 (Czerniak, 1973) indicated a possibility of cumulative error that could 

 result in the seaward end of the measured profile being displaced up 

 to 1 foot vertically from the actual profile. There was also a problem 

 reestablishing some of the bench marks which had disappeared between 

 surveys. For these reasons, only gross changes could reliably be ana- 

 lyzed, and only those changes on the landward end of the profile would 

 be sufficiently accurate to quantitatively evaluate. Therefore, this 

 report is limited to an evaluation of the recession of the dune or 

 bluff, although beach change trends are discussed for particular sites. 



V. BEACH PROFILE CHANGES 



The following discussion on each of the 17 beach sites is based on the 

 profile surveys and color slides described previously. In the discussions 

 the terms terrace recession , bluff recession , and erosion refer to the 

 amount of horizontal retreat of the steep part of the profile that lies 

 landward of the active beach. The term erosion is used to denote removal 

 of sediment from the profile; accretion indicates addition of sediment to 

 the profile. Additional information, vertical and oblique photos, bench 

 mark locations, and geomorphology of the 17 profile sites are available in 

 Davis, Fingleton, and Pritchett (1975). 



1. Change at Each Location . 



a. Profile Site 1 . The beach is typically composed of much pebble 

 and cobble-gravel with imbrication common. Low-lying vegetated dunes 

 which contain numerous blowouts are adjacent to the beach. The U.S. Coast 

 Guard station at Point Betsie and associated seawalls are located about 

 one-quarter mile north of the site. 



During the first year of study there was little change in overall 

 beach configuration. A small ridgelike berm of gravel was present through 

 most of the year. The seaward face of the low-lying dunes eroded 7 feet 

 during the fall of 1970, without a corresponding change in beach position. 

 This indicates that the beach recovered from storm erosion in less than 

 the 4-week period between surveys. Erosion during July 1971 caused the 

 usual concentration of heavy minerals in the backshore area. 



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