. . . . If only one line of drift exists, as when a 

 higher tide follows a lower one, the markings left by 

 the lower tide would be obliterated by the higher tide 

 and the tendency would be to delineate the line left 

 by the latter, or possibly a line slightly seaward of 

 such drift line. 



In addition to the above, the topographer, who 

 is an expert in his field, familiarizes himself with 

 the tide in the area, and notes the characteristics of 

 the beach as to the relative compactness of the sand 

 (the sand back of the high-water line is usually less 

 compact and coarser) , the difference in character and 

 color of the sun cracks on mud flats, the discolor- 

 ation of the grass on marshy areas, and the tufts of 

 grass or other vegetation likely along the high-water 

 line . 



51. Historical references are included to emphasize that it was the 

 intention of all the agency's topographic surveys to determine the line of 

 mean high water (MHW) for delineation on maps. With the exception of tidal 

 marsh areas, where in most cases the outer limit of vegetation is mapped, MHW 

 delineated on the surveys by the experienced topographer or photogrammetrist 

 was that line at the time of survev or date of photography. 



Map Production 



52. The following procedures for producing shoreline change maps are 

 identical to those used by Everts, Battley, and Gibson (1983). To make this 

 study as current as possible, USGS quadrangle maps were revised to show a 

 1982/83 MHWL. Revision was made using 1982/83 color aerial photographs flown 

 for this study. Date and time of photography were correlated with stage of 

 the tide, and a detailed stereoscopic examination of the photographs was made 

 to determine the MHW line. This process was completed by the Cartographic 

 Revision Section of the Photogrammetry Division of NOS . Their method was by 

 direct transfer of photo -interpreted lines (see paragraph 60) from 1:24,000- 

 ratioed film positives to USGS base maps. Using the ratioed photography, base 

 maps (manuscripts) were held planimetrically to local physical features. In 

 the absence of triangulation stations to position manuscripts accurately 

 against photographs, it is possible to use "hard" planimetric features, such 

 as road intersections or other permanent physical structures without great 

 relief, to assure good photographic positioning. In areas where there were 



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