Table 40. Erosion rates along glacial cliffs 

 and the Nauset Spit system (m/yr) . 



Data source 



Marlndln 

 (1889) 



Zelgler, 

 et al. (1964) 



Nauset Cliffs X =■ 1.0 X - 0.7 



(1868-86) (1868-1957) 



Catto This 

 (1979) 



1.8 



3.8 



2.1 



(1938-74) 



Nauset Splt- 

 Eastham 



Old North 

 Beach 



New North 

 Beach 



X - 0.1 X - 1.3 1 .3 X - 0.9 

 (1856-86) (1856-1957) (1938-74) (1356-1978) 



X - 1.0 



X - 2.4 

 (1868-86) 



'included with Ola North Beach. 





(1356-1952) 





X - 1.2 



(1938-78) 



2.0 



0.9 



(1938-74) 



X - 1.5 

 (1868-1978) 



X - 0.7 

 (1868-86) 





X - 1.6 

 (1933-78) 



5.1 

 5.9 



(1938-74) 



X - 5.8 

 (1938-78) 



This study is the first attempt to describe quantitatively changes in 

 physiographic features on Nauset Spit during the past 127 years. The U.S. 

 Coast Survey Maps for 1851, 1856, 1867, 1868, and 1886 and aerial photos taken 

 in 1938, 1941, 1952, 1964, and 1978 were used to map ocean and bay shoreline 

 positions and vegetative units. Aerial photos for 1938, 1952, and 1978, which 

 were taken after major storms, are used in this study. These photos bias the 

 results in favor of washovers, because in many cases dune and shallow-buried 

 salt-marsh plants may have been alive and recovering from burial, but were not 

 visible on the photos. If these photos were taken during calm periods, wash- 

 overs would be much less prominent. These photos were chosen because they 

 were complete for the spit system and showed the magnitude of overwash proc- 

 esses. Photos taken in 1941 and 1964, although of inferior quality, were used 

 to expand the data obtained from 1938, 1952, and 1978 photos. 



b. Methodology . The principles and accuracy problems of map construction 

 from historical aerial photos and coastal charts were reviewed by Anders and 

 Leatherman (1980), so only a brief summary of the methodology will be pre- 

 sented. A technique of map construction from charts and aerial photos was 

 devised with the assistance of National Ocean Survey (NOS). The first step in 

 the procedure is to locate stable control points on each chart or photo. The 

 same points are marked on corresponding NOS T sheets. Road intersections and 

 buildings are the most accurate points due to their fixed positions. Manmade 

 structures, however, are not always present on barriers or the mainland shore- 

 line. Natural features which have remained stable over the duration of the 

 mapping interval can be used as alternative points. A minimum of four control 

 points were located and plotted on each photo of the Nauset Spit system and on 

 the corresponding T sheet. 



165 



