range is reduced at the head of the bay, large quantities of water do not 

 build up behind the barrier during storms, which greatly minimizes the proba- 

 bility of inlet breaching. This area is also discontinuously underlain by 

 well-developed salt-raarsh peat, which prevents surges from scouring a sub- 

 aqueous channel through the barrier. 



e. New North Beach . The New North Beach section of the Nauset Spit sys- 

 tem has developed since 1868 as a result of spit elongation (Fig. 3). Follow- 

 ing the formation of the inlet through North beach in 1846 across from Allen 

 Point, the isolated section of the inlet began to migrate landward. In 1851 

 dunes and salt marshes were still prominent on this island (Fig. 106) : a 

 total of 274.6 hectares of dune-washover and 20.7 hectares of salt marsh 

 (Table 50). The dune line along the central section does not appear to have 

 been interrupted by any washover breaches. The average barrier width was 

 458 meters along the entite island and 505 meters along the central section 

 (Table 43). The northern and southern ends of the island had begun to erode 

 rapidly and were dominated by washovers. 



All that remained of the new island by 1886 was a narrow, unvegetated 

 supratidal sandbar (Fig. 106). As a result of a major northeaster in 1868, 

 the inlet initiated in 1846 widened and deepened, becoming the major channel 

 into Pleasant Bay. Sediment transported as littoral drift was cut off from 

 the island, since the inlet intercepted or diverted eastward most of the 

 previously available sand. The island had eroded landward an average of 795 

 meters in 35 years. Dunes and salt marshes were not evident on the barrier 

 in 1886, and the average width was only 153 meters (Table 43). 



As the island eroded landward between 1851 and 1886, the inlet migrated 

 1525 meters southward at a rate of 85 meters per year. A total of 90.7 

 hectares of new supratidal surface was added at the terminus of North baach. 

 No dunes and salt marshes had developed on this section by 1886. 



The south island migrated onto the Chatham mainland during the 1890' s. As 

 the inlet continued to move southward between 1886 and 1938, an additional 

 3500 meters was added to the spit terminus at a rate of 67 meters per year. 

 This lower race of elongation was caused by the development of numerous spit 

 recurves. Spit width and back-barrier contour on New North Beach correlate 

 with mainland shore features, creating a roughly consistent distance between 

 the mainland and the barrier (McClennen, 1979). It appeared that the channel 

 between Chatham Inlet and Pleasant Bay had maintained a consistent width-to- 

 depth ratio established by the volume of water flushing from Pleasant Bay with 

 each tide. Opposite concavities in the Chatham coastline, spit recurves have 

 widened the barrier (Hayes, 1981). Between 1886 and 1938 North Beach elon- 

 gated opposite an embayment in the mainland at the Chatham Fish Pier (Fig. 

 90). In this region the barrier widened to as much as 800 meters. 



In 1938 New North Beach was 4.1 kilometers long and extremely wide, 

 averaging 626 meters (Tables 41 and 43). A total of 242.5 hectares of new 

 supratidal environment k'ss added at the spit terminus between 1886 and 1938 

 (Table 50). By 1938 broad dunes had formed on 91 hectares and salt-marsh 

 vegetation had colonized 16.8 hectares. 



Between 1938 and 1952 New North Beach rapidly extended southward as sand 

 was added to the sptt terminus across from the Chatham Light area, which arcs 



179 



V 



