The entire transect was affected by overwash during the February 1973 

 storm (Fig. 11). The low backdcnes were planed off, creating a relatively 

 flat, gently sloping sand surface. The washover fan was expanded 25 meters 

 westward into the marsh. The greatest deposition occurred over the sand road 

 and on the adjacent 1972 washover fan. The beria crest was displaced approxi- 

 mately 15 to 20 meters landward. Sand plug data showed that along the tran- 

 sect through the throat area, vegetation was displaced by the overwash surges 

 (Fig. 11). The more cohesive substrate of the marsh resisted any erosion; the 

 marsh was subjected to deep burial (from to 85 centimeters). 



While approximately 1200 meters of the 2100-meter-long dune line on Nauset 

 Spit-F<asthara was eroded during the February storm, dunes at site 1 were eroded 

 only 4 to 10 meters on either side of the throat (Fig. 15). The throat sec- 

 tion through the dune line was straightened, and the washover fan was enlarged 

 in all dimensions (Fig. 16). Approximately 5000 square meters of sand was 

 added to the fan, but the feature retained the same general shape present in 

 1972. About 8000 cubic meters of sediment was added to site 1 washover in 

 February 1978. 



(a) Site 1 Thro at. Extensive erosion and redeposition took place 

 at site I throat during the February 1978 storm. Three-dimensional plots 

 from elevation data were developed for 5 and 19 February 1978 (Fig. 17). The 

 vegetated dune north of the site eroded landward, and the large, wind-shadow 

 dune couth of the throat eroded to a position outside the plot. Low areas 

 were filled and high areas were flattened. For the 149 elevation stations 

 surveyed in 1977 and resurveyed in 1978, mean net depth of burial was +0.11 

 meter (o » 0.41 meter) with an erosional range of 0.78 meter and a deposi- 

 tional range of 1.02 meters. The standard deviations of the elevation points 

 surveyed in 1977 (0.60 meter) and 1978 (0.32 meter) reflect the flattening 

 effect of overwash on a dune coizssunity. The shallowest deposition,, less than 

 25 centimeters, occurred in the seaward part of the throat where low elevation 

 was maintained with little net change. The greatest deposition occurred on 

 the marshward edge of the 1977 washover throat. 



1971 



Figure 15. Site 1 before and after February 1978 etora. 



42 



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