5. American Beachgrass with 90-Centlmeter Spacing (Plot 5) . 



a. Installation, Damage, and Repair. Plot 5 was planted in 1970 with 

 American beachgrass on 90-centlmeter centers, three to five sprigs per hill. 

 Planting survival in June 1971 measured 60 to 70 percent. Bare areas were 

 replanted in October 1971. The severe storm of February 1972 deposited a 

 veneer of sand over the plantings. Areas of low survival were replanted in 

 April 1972. 



b. Short-Term Dune Growth . Sand accumulation was negligible at the end 

 of the first growing season. After two growing seasons 10 cubic meters per 

 meter had accumulated and the crest elevation was 2.9 meters, 0.9 meter above 

 the initial planting surface (Fig. 19). 



Figure 19, Plot 5 (A^merican beachgrass on 90-centimeter 

 spacing), May 1973. 



c. Long-Term Dune Growth . Figure 20 illustrates the growth of the dune 

 from 1970 to 1977. A small secondary dune ridge had formed landward of the 

 test area by 1973. After seven growing seasons, 55 cubic meters per meter had 

 accumulated and the crest elevation was 3.9 meters, about 2.0 meters above the 

 original planting surface. Most of the sand accumulation was seaward of the 

 centerline of the plot. Base width of the dune in 1977 was very broad, aver- 

 aging 96.3 meters. The landward and seaward slopes of the dune were 1 on 8.7 

 and 1 on 9.8, respectively. The bay shoreline remained relatively stable dur- 

 ing the experiment; the seaward shoreline receded approximately 28.5 meters. 



d. Performance Summary. Table 7 summarizes the growth characteristics of 



plot 5. 



27 



